Merge tag 'powerpc-6.6-6' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc...

[platform/kernel/linux-starfive.git] / arch / x86 / kernel / fpu / xstate.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * xsave/xrstor support.
 *
 * Author: Suresh Siddha <suresh.b.siddha@intel.com>
 */
#include <linux/bitops.h>
#include <linux/compat.h>
#include <linux/cpu.h>
#include <linux/mman.h>
#include <linux/nospec.h>
#include <linux/pkeys.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/vmalloc.h>

#include <asm/fpu/api.h>
#include <asm/fpu/regset.h>
#include <asm/fpu/signal.h>
#include <asm/fpu/xcr.h>

#include <asm/tlbflush.h>
#include <asm/prctl.h>
#include <asm/elf.h>

#include "context.h"
#include "internal.h"
#include "legacy.h"
#include "xstate.h"

#define for_each_extended_xfeature(bit, mask)                           \
        (bit) = FIRST_EXTENDED_XFEATURE;                                \
        for_each_set_bit_from(bit, (unsigned long *)&(mask), 8 * sizeof(mask))

/*
 * Although we spell it out in here, the Processor Trace
 * xfeature is completely unused.  We use other mechanisms
 * to save/restore PT state in Linux.
 */
static const char *xfeature_names[] =
{
        "x87 floating point registers",
        "SSE registers",
        "AVX registers",
        "MPX bounds registers",
        "MPX CSR",
        "AVX-512 opmask",
        "AVX-512 Hi256",
        "AVX-512 ZMM_Hi256",
        "Processor Trace (unused)",
        "Protection Keys User registers",
        "PASID state",
        "Control-flow User registers",
        "Control-flow Kernel registers (unused)",
        "unknown xstate feature",
        "unknown xstate feature",
        "unknown xstate feature",
        "unknown xstate feature",
        "AMX Tile config",
        "AMX Tile data",
        "unknown xstate feature",
};

static unsigned short xsave_cpuid_features[] __initdata = {
        [XFEATURE_FP]                           = X86_FEATURE_FPU,
        [XFEATURE_SSE]                          = X86_FEATURE_XMM,
        [XFEATURE_YMM]                          = X86_FEATURE_AVX,
        [XFEATURE_BNDREGS]                      = X86_FEATURE_MPX,
        [XFEATURE_BNDCSR]                       = X86_FEATURE_MPX,
        [XFEATURE_OPMASK]                       = X86_FEATURE_AVX512F,
        [XFEATURE_ZMM_Hi256]                    = X86_FEATURE_AVX512F,
        [XFEATURE_Hi16_ZMM]                     = X86_FEATURE_AVX512F,
        [XFEATURE_PT_UNIMPLEMENTED_SO_FAR]      = X86_FEATURE_INTEL_PT,
        [XFEATURE_PKRU]                         = X86_FEATURE_OSPKE,
        [XFEATURE_PASID]                        = X86_FEATURE_ENQCMD,
        [XFEATURE_CET_USER]                     = X86_FEATURE_SHSTK,
        [XFEATURE_XTILE_CFG]                    = X86_FEATURE_AMX_TILE,
        [XFEATURE_XTILE_DATA]                   = X86_FEATURE_AMX_TILE,
};

static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init =
        { [ 0 ... XFEATURE_MAX - 1] = -1};
static unsigned int xstate_sizes[XFEATURE_MAX] __ro_after_init =
        { [ 0 ... XFEATURE_MAX - 1] = -1};
static unsigned int xstate_flags[XFEATURE_MAX] __ro_after_init;

#define XSTATE_FLAG_SUPERVISOR  BIT(0)
#define XSTATE_FLAG_ALIGNED64   BIT(1)

/*
 * Return whether the system supports a given xfeature.
 *
 * Also return the name of the (most advanced) feature that the caller requested:
 */
int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
{
        u64 xfeatures_missing = xfeatures_needed & ~fpu_kernel_cfg.max_features;

        if (unlikely(feature_name)) {
                long xfeature_idx, max_idx;
                u64 xfeatures_print;
                /*
                 * So we use FLS here to be able to print the most advanced
                 * feature that was requested but is missing. So if a driver
                 * asks about "XFEATURE_MASK_SSE | XFEATURE_MASK_YMM" we'll print the
                 * missing AVX feature - this is the most informative message
                 * to users:
                 */
                if (xfeatures_missing)
                        xfeatures_print = xfeatures_missing;
                else
                        xfeatures_print = xfeatures_needed;

                xfeature_idx = fls64(xfeatures_print)-1;
                max_idx = ARRAY_SIZE(xfeature_names)-1;
                xfeature_idx = min(xfeature_idx, max_idx);

                *feature_name = xfeature_names[xfeature_idx];
        }

        if (xfeatures_missing)
                return 0;

        return 1;
}
EXPORT_SYMBOL_GPL(cpu_has_xfeatures);

static bool xfeature_is_aligned64(int xfeature_nr)
{
        return xstate_flags[xfeature_nr] & XSTATE_FLAG_ALIGNED64;
}

static bool xfeature_is_supervisor(int xfeature_nr)
{
        return xstate_flags[xfeature_nr] & XSTATE_FLAG_SUPERVISOR;
}

static unsigned int xfeature_get_offset(u64 xcomp_bv, int xfeature)
{
        unsigned int offs, i;

        /*
         * Non-compacted format and legacy features use the cached fixed
         * offsets.
         */
        if (!cpu_feature_enabled(X86_FEATURE_XCOMPACTED) ||
            xfeature <= XFEATURE_SSE)
                return xstate_offsets[xfeature];

        /*
         * Compacted format offsets depend on the actual content of the
         * compacted xsave area which is determined by the xcomp_bv header
         * field.
         */
        offs = FXSAVE_SIZE + XSAVE_HDR_SIZE;
        for_each_extended_xfeature(i, xcomp_bv) {
                if (xfeature_is_aligned64(i))
                        offs = ALIGN(offs, 64);
                if (i == xfeature)
                        break;
                offs += xstate_sizes[i];
        }
        return offs;
}

/*
 * Enable the extended processor state save/restore feature.
 * Called once per CPU onlining.
 */
void fpu__init_cpu_xstate(void)
{
        if (!boot_cpu_has(X86_FEATURE_XSAVE) || !fpu_kernel_cfg.max_features)
                return;

        cr4_set_bits(X86_CR4_OSXSAVE);

        /*
         * Must happen after CR4 setup and before xsetbv() to allow KVM
         * lazy passthrough.  Write independent of the dynamic state static
         * key as that does not work on the boot CPU. This also ensures
         * that any stale state is wiped out from XFD.
         */
        if (cpu_feature_enabled(X86_FEATURE_XFD))
                wrmsrl(MSR_IA32_XFD, init_fpstate.xfd);

        /*
         * XCR_XFEATURE_ENABLED_MASK (aka. XCR0) sets user features
         * managed by XSAVE{C, OPT, S} and XRSTOR{S}.  Only XSAVE user
         * states can be set here.
         */
        xsetbv(XCR_XFEATURE_ENABLED_MASK, fpu_user_cfg.max_features);

        /*
         * MSR_IA32_XSS sets supervisor states managed by XSAVES.
         */
        if (boot_cpu_has(X86_FEATURE_XSAVES)) {
                wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor() |
                                     xfeatures_mask_independent());
        }
}

static bool xfeature_enabled(enum xfeature xfeature)
{
        return fpu_kernel_cfg.max_features & BIT_ULL(xfeature);
}

/*
 * Record the offsets and sizes of various xstates contained
 * in the XSAVE state memory layout.
 */
static void __init setup_xstate_cache(void)
{
        u32 eax, ebx, ecx, edx, i;
        /* start at the beginning of the "extended state" */
        unsigned int last_good_offset = offsetof(struct xregs_state,
                                                 extended_state_area);
        /*
         * The FP xstates and SSE xstates are legacy states. They are always
         * in the fixed offsets in the xsave area in either compacted form
         * or standard form.
         */
        xstate_offsets[XFEATURE_FP]     = 0;
        xstate_sizes[XFEATURE_FP]       = offsetof(struct fxregs_state,
                                                   xmm_space);

        xstate_offsets[XFEATURE_SSE]    = xstate_sizes[XFEATURE_FP];
        xstate_sizes[XFEATURE_SSE]      = sizeof_field(struct fxregs_state,
                                                       xmm_space);

        for_each_extended_xfeature(i, fpu_kernel_cfg.max_features) {
                cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);

                xstate_sizes[i] = eax;
                xstate_flags[i] = ecx;

                /*
                 * If an xfeature is supervisor state, the offset in EBX is
                 * invalid, leave it to -1.
                 */
                if (xfeature_is_supervisor(i))
                        continue;

                xstate_offsets[i] = ebx;

                /*
                 * In our xstate size checks, we assume that the highest-numbered
                 * xstate feature has the highest offset in the buffer.  Ensure
                 * it does.
                 */
                WARN_ONCE(last_good_offset > xstate_offsets[i],
                          "x86/fpu: misordered xstate at %d\n", last_good_offset);

                last_good_offset = xstate_offsets[i];
        }
}

static void __init print_xstate_feature(u64 xstate_mask)
{
        const char *feature_name;

        if (cpu_has_xfeatures(xstate_mask, &feature_name))
                pr_info("x86/fpu: Supporting XSAVE feature 0x%03Lx: '%s'\n", xstate_mask, feature_name);
}

/*
 * Print out all the supported xstate features:
 */
static void __init print_xstate_features(void)
{
        print_xstate_feature(XFEATURE_MASK_FP);
        print_xstate_feature(XFEATURE_MASK_SSE);
        print_xstate_feature(XFEATURE_MASK_YMM);
        print_xstate_feature(XFEATURE_MASK_BNDREGS);
        print_xstate_feature(XFEATURE_MASK_BNDCSR);
        print_xstate_feature(XFEATURE_MASK_OPMASK);
        print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
        print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
        print_xstate_feature(XFEATURE_MASK_PKRU);
        print_xstate_feature(XFEATURE_MASK_PASID);
        print_xstate_feature(XFEATURE_MASK_CET_USER);
        print_xstate_feature(XFEATURE_MASK_XTILE_CFG);
        print_xstate_feature(XFEATURE_MASK_XTILE_DATA);
}

/*
 * This check is important because it is easy to get XSTATE_*
 * confused with XSTATE_BIT_*.
 */
#define CHECK_XFEATURE(nr) do {         \
        WARN_ON(nr < FIRST_EXTENDED_XFEATURE);  \
        WARN_ON(nr >= XFEATURE_MAX);    \
} while (0)

/*
 * Print out xstate component offsets and sizes
 */
static void __init print_xstate_offset_size(void)
{
        int i;

        for_each_extended_xfeature(i, fpu_kernel_cfg.max_features) {
                pr_info("x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n",
                        i, xfeature_get_offset(fpu_kernel_cfg.max_features, i),
                        i, xstate_sizes[i]);
        }
}

/*
 * This function is called only during boot time when x86 caps are not set
 * up and alternative can not be used yet.
 */
static __init void os_xrstor_booting(struct xregs_state *xstate)
{
        u64 mask = fpu_kernel_cfg.max_features & XFEATURE_MASK_FPSTATE;
        u32 lmask = mask;
        u32 hmask = mask >> 32;
        int err;

        if (cpu_feature_enabled(X86_FEATURE_XSAVES))
                XSTATE_OP(XRSTORS, xstate, lmask, hmask, err);
        else
                XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);

        /*
         * We should never fault when copying from a kernel buffer, and the FPU
         * state we set at boot time should be valid.
         */
        WARN_ON_FPU(err);
}

/*
 * All supported features have either init state all zeros or are
 * handled in setup_init_fpu() individually. This is an explicit
 * feature list and does not use XFEATURE_MASK*SUPPORTED to catch
 * newly added supported features at build time and make people
 * actually look at the init state for the new feature.
 */
#define XFEATURES_INIT_FPSTATE_HANDLED          \
        (XFEATURE_MASK_FP |                     \
         XFEATURE_MASK_SSE |                    \
         XFEATURE_MASK_YMM |                    \
         XFEATURE_MASK_OPMASK |                 \
         XFEATURE_MASK_ZMM_Hi256 |              \
         XFEATURE_MASK_Hi16_ZMM  |              \
         XFEATURE_MASK_PKRU |                   \
         XFEATURE_MASK_BNDREGS |                \
         XFEATURE_MASK_BNDCSR |                 \
         XFEATURE_MASK_PASID |                  \
         XFEATURE_MASK_CET_USER |               \
         XFEATURE_MASK_XTILE)

/*
 * setup the xstate image representing the init state
 */
static void __init setup_init_fpu_buf(void)
{
        BUILD_BUG_ON((XFEATURE_MASK_USER_SUPPORTED |
                      XFEATURE_MASK_SUPERVISOR_SUPPORTED) !=
                     XFEATURES_INIT_FPSTATE_HANDLED);

        if (!boot_cpu_has(X86_FEATURE_XSAVE))
                return;

        print_xstate_features();

        xstate_init_xcomp_bv(&init_fpstate.regs.xsave, init_fpstate.xfeatures);

        /*
         * Init all the features state with header.xfeatures being 0x0
         */
        os_xrstor_booting(&init_fpstate.regs.xsave);

        /*
         * All components are now in init state. Read the state back so
         * that init_fpstate contains all non-zero init state. This only
         * works with XSAVE, but not with XSAVEOPT and XSAVEC/S because
         * those use the init optimization which skips writing data for
         * components in init state.
         *
         * XSAVE could be used, but that would require to reshuffle the
         * data when XSAVEC/S is available because XSAVEC/S uses xstate
         * compaction. But doing so is a pointless exercise because most
         * components have an all zeros init state except for the legacy
         * ones (FP and SSE). Those can be saved with FXSAVE into the
         * legacy area. Adding new features requires to ensure that init
         * state is all zeroes or if not to add the necessary handling
         * here.
         */
        fxsave(&init_fpstate.regs.fxsave);
}

int xfeature_size(int xfeature_nr)
{
        u32 eax, ebx, ecx, edx;

        CHECK_XFEATURE(xfeature_nr);
        cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
        return eax;
}

/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */
static int validate_user_xstate_header(const struct xstate_header *hdr,
                                       struct fpstate *fpstate)
{
        /* No unknown or supervisor features may be set */
        if (hdr->xfeatures & ~fpstate->user_xfeatures)
                return -EINVAL;

        /* Userspace must use the uncompacted format */
        if (hdr->xcomp_bv)
                return -EINVAL;

        /*
         * If 'reserved' is shrunken to add a new field, make sure to validate
         * that new field here!
         */
        BUILD_BUG_ON(sizeof(hdr->reserved) != 48);

        /* No reserved bits may be set */
        if (memchr_inv(hdr->reserved, 0, sizeof(hdr->reserved)))
                return -EINVAL;

        return 0;
}

static void __init __xstate_dump_leaves(void)
{
        int i;
        u32 eax, ebx, ecx, edx;
        static int should_dump = 1;

        if (!should_dump)
                return;
        should_dump = 0;
        /*
         * Dump out a few leaves past the ones that we support
         * just in case there are some goodies up there
         */
        for (i = 0; i < XFEATURE_MAX + 10; i++) {
                cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
                pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
                        XSTATE_CPUID, i, eax, ebx, ecx, edx);
        }
}

#define XSTATE_WARN_ON(x, fmt, ...) do {                                        \
        if (WARN_ONCE(x, "XSAVE consistency problem: " fmt, ##__VA_ARGS__)) {   \
                __xstate_dump_leaves();                                         \
        }                                                                       \
} while (0)

#define XCHECK_SZ(sz, nr, __struct) ({                                  \
        if (WARN_ONCE(sz != sizeof(__struct),                           \
            "[%s]: struct is %zu bytes, cpu state %d bytes\n",          \
            xfeature_names[nr], sizeof(__struct), sz)) {                \
                __xstate_dump_leaves();                                 \
        }                                                               \
        true;                                                           \
})


/**
 * check_xtile_data_against_struct - Check tile data state size.
 *
 * Calculate the state size by multiplying the single tile size which is
 * recorded in a C struct, and the number of tiles that the CPU informs.
 * Compare the provided size with the calculation.
 *
 * @size:       The tile data state size
 *
 * Returns:     0 on success, -EINVAL on mismatch.
 */
static int __init check_xtile_data_against_struct(int size)
{
        u32 max_palid, palid, state_size;
        u32 eax, ebx, ecx, edx;
        u16 max_tile;

        /*
         * Check the maximum palette id:
         *   eax: the highest numbered palette subleaf.
         */
        cpuid_count(TILE_CPUID, 0, &max_palid, &ebx, &ecx, &edx);

        /*
         * Cross-check each tile size and find the maximum number of
         * supported tiles.
         */
        for (palid = 1, max_tile = 0; palid <= max_palid; palid++) {
                u16 tile_size, max;

                /*
                 * Check the tile size info:
                 *   eax[31:16]:  bytes per title
                 *   ebx[31:16]:  the max names (or max number of tiles)
                 */
                cpuid_count(TILE_CPUID, palid, &eax, &ebx, &edx, &edx);
                tile_size = eax >> 16;
                max = ebx >> 16;

                if (tile_size != sizeof(struct xtile_data)) {
                        pr_err("%s: struct is %zu bytes, cpu xtile %d bytes\n",
                               __stringify(XFEATURE_XTILE_DATA),
                               sizeof(struct xtile_data), tile_size);
                        __xstate_dump_leaves();
                        return -EINVAL;
                }

                if (max > max_tile)
                        max_tile = max;
        }

        state_size = sizeof(struct xtile_data) * max_tile;
        if (size != state_size) {
                pr_err("%s: calculated size is %u bytes, cpu state %d bytes\n",
                       __stringify(XFEATURE_XTILE_DATA), state_size, size);
                __xstate_dump_leaves();
                return -EINVAL;
        }
        return 0;
}

/*
 * We have a C struct for each 'xstate'.  We need to ensure
 * that our software representation matches what the CPU
 * tells us about the state's size.
 */
static bool __init check_xstate_against_struct(int nr)
{
        /*
         * Ask the CPU for the size of the state.
         */
        int sz = xfeature_size(nr);

        /*
         * Match each CPU state with the corresponding software
         * structure.
         */
        switch (nr) {
        case XFEATURE_YMM:        return XCHECK_SZ(sz, nr, struct ymmh_struct);
        case XFEATURE_BNDREGS:    return XCHECK_SZ(sz, nr, struct mpx_bndreg_state);
        case XFEATURE_BNDCSR:     return XCHECK_SZ(sz, nr, struct mpx_bndcsr_state);
        case XFEATURE_OPMASK:     return XCHECK_SZ(sz, nr, struct avx_512_opmask_state);
        case XFEATURE_ZMM_Hi256:  return XCHECK_SZ(sz, nr, struct avx_512_zmm_uppers_state);
        case XFEATURE_Hi16_ZMM:   return XCHECK_SZ(sz, nr, struct avx_512_hi16_state);
        case XFEATURE_PKRU:       return XCHECK_SZ(sz, nr, struct pkru_state);
        case XFEATURE_PASID:      return XCHECK_SZ(sz, nr, struct ia32_pasid_state);
        case XFEATURE_XTILE_CFG:  return XCHECK_SZ(sz, nr, struct xtile_cfg);
        case XFEATURE_CET_USER:   return XCHECK_SZ(sz, nr, struct cet_user_state);
        case XFEATURE_XTILE_DATA: check_xtile_data_against_struct(sz); return true;
        default:
                XSTATE_WARN_ON(1, "No structure for xstate: %d\n", nr);
                return false;
        }

        return true;
}

static unsigned int xstate_calculate_size(u64 xfeatures, bool compacted)
{
        unsigned int topmost = fls64(xfeatures) -  1;
        unsigned int offset = xstate_offsets[topmost];

        if (topmost <= XFEATURE_SSE)
                return sizeof(struct xregs_state);

        if (compacted)
                offset = xfeature_get_offset(xfeatures, topmost);
        return offset + xstate_sizes[topmost];
}

/*
 * This essentially double-checks what the cpu told us about
 * how large the XSAVE buffer needs to be.  We are recalculating
 * it to be safe.
 *
 * Independent XSAVE features allocate their own buffers and are not
 * covered by these checks. Only the size of the buffer for task->fpu
 * is checked here.
 */
static bool __init paranoid_xstate_size_valid(unsigned int kernel_size)
{
        bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED);
        bool xsaves = cpu_feature_enabled(X86_FEATURE_XSAVES);
        unsigned int size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
        int i;

        for_each_extended_xfeature(i, fpu_kernel_cfg.max_features) {
                if (!check_xstate_against_struct(i))
                        return false;
                /*
                 * Supervisor state components can be managed only by
                 * XSAVES.
                 */
                if (!xsaves && xfeature_is_supervisor(i)) {
                        XSTATE_WARN_ON(1, "Got supervisor feature %d, but XSAVES not advertised\n", i);
                        return false;
                }
        }
        size = xstate_calculate_size(fpu_kernel_cfg.max_features, compacted);
        XSTATE_WARN_ON(size != kernel_size,
                       "size %u != kernel_size %u\n", size, kernel_size);
        return size == kernel_size;
}

/*
 * Get total size of enabled xstates in XCR0 | IA32_XSS.
 *
 * Note the SDM's wording here.  "sub-function 0" only enumerates
 * the size of the *user* states.  If we use it to size a buffer
 * that we use 'XSAVES' on, we could potentially overflow the
 * buffer because 'XSAVES' saves system states too.
 *
 * This also takes compaction into account. So this works for
 * XSAVEC as well.
 */
static unsigned int __init get_compacted_size(void)
{
        unsigned int eax, ebx, ecx, edx;
        /*
         * - CPUID function 0DH, sub-function 1:
         *    EBX enumerates the size (in bytes) required by
         *    the XSAVES instruction for an XSAVE area
         *    containing all the state components
         *    corresponding to bits currently set in
         *    XCR0 | IA32_XSS.
         *
         * When XSAVES is not available but XSAVEC is (virt), then there
         * are no supervisor states, but XSAVEC still uses compacted
         * format.
         */
        cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
        return ebx;
}

/*
 * Get the total size of the enabled xstates without the independent supervisor
 * features.
 */
static unsigned int __init get_xsave_compacted_size(void)
{
        u64 mask = xfeatures_mask_independent();
        unsigned int size;

        if (!mask)
                return get_compacted_size();

        /* Disable independent features. */
        wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor());

        /*
         * Ask the hardware what size is required of the buffer.
         * This is the size required for the task->fpu buffer.
         */
        size = get_compacted_size();

        /* Re-enable independent features so XSAVES will work on them again. */
        wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor() | mask);

        return size;
}

static unsigned int __init get_xsave_size_user(void)
{
        unsigned int eax, ebx, ecx, edx;
        /*
         * - CPUID function 0DH, sub-function 0:
         *    EBX enumerates the size (in bytes) required by
         *    the XSAVE instruction for an XSAVE area
         *    containing all the *user* state components
         *    corresponding to bits currently set in XCR0.
         */
        cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
        return ebx;
}

static int __init init_xstate_size(void)
{
        /* Recompute the context size for enabled features: */
        unsigned int user_size, kernel_size, kernel_default_size;
        bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED);

        /* Uncompacted user space size */
        user_size = get_xsave_size_user();

        /*
         * XSAVES kernel size includes supervisor states and uses compacted
         * format. XSAVEC uses compacted format, but does not save
         * supervisor states.
         *
         * XSAVE[OPT] do not support supervisor states so kernel and user
         * size is identical.
         */
        if (compacted)
                kernel_size = get_xsave_compacted_size();
        else
                kernel_size = user_size;

        kernel_default_size =
                xstate_calculate_size(fpu_kernel_cfg.default_features, compacted);

        if (!paranoid_xstate_size_valid(kernel_size))
                return -EINVAL;

        fpu_kernel_cfg.max_size = kernel_size;
        fpu_user_cfg.max_size = user_size;

        fpu_kernel_cfg.default_size = kernel_default_size;
        fpu_user_cfg.default_size =
                xstate_calculate_size(fpu_user_cfg.default_features, false);

        return 0;
}

/*
 * We enabled the XSAVE hardware, but something went wrong and
 * we can not use it.  Disable it.
 */
static void __init fpu__init_disable_system_xstate(unsigned int legacy_size)
{
        fpu_kernel_cfg.max_features = 0;
        cr4_clear_bits(X86_CR4_OSXSAVE);
        setup_clear_cpu_cap(X86_FEATURE_XSAVE);

        /* Restore the legacy size.*/
        fpu_kernel_cfg.max_size = legacy_size;
        fpu_kernel_cfg.default_size = legacy_size;
        fpu_user_cfg.max_size = legacy_size;
        fpu_user_cfg.default_size = legacy_size;

        /*
         * Prevent enabling the static branch which enables writes to the
         * XFD MSR.
         */
        init_fpstate.xfd = 0;

        fpstate_reset(&current->thread.fpu);
}

/*
 * Enable and initialize the xsave feature.
 * Called once per system bootup.
 */
void __init fpu__init_system_xstate(unsigned int legacy_size)
{
        unsigned int eax, ebx, ecx, edx;
        u64 xfeatures;
        int err;
        int i;

        if (!boot_cpu_has(X86_FEATURE_FPU)) {
                pr_info("x86/fpu: No FPU detected\n");
                return;
        }

        if (!boot_cpu_has(X86_FEATURE_XSAVE)) {
                pr_info("x86/fpu: x87 FPU will use %s\n",
                        boot_cpu_has(X86_FEATURE_FXSR) ? "FXSAVE" : "FSAVE");
                return;
        }

        if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
                WARN_ON_FPU(1);
                return;
        }

        /*
         * Find user xstates supported by the processor.
         */
        cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
        fpu_kernel_cfg.max_features = eax + ((u64)edx << 32);

        /*
         * Find supervisor xstates supported by the processor.
         */
        cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
        fpu_kernel_cfg.max_features |= ecx + ((u64)edx << 32);

        if ((fpu_kernel_cfg.max_features & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
                /*
                 * This indicates that something really unexpected happened
                 * with the enumeration.  Disable XSAVE and try to continue
                 * booting without it.  This is too early to BUG().
                 */
                pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n",
                       fpu_kernel_cfg.max_features);
                goto out_disable;
        }

        /*
         * Clear XSAVE features that are disabled in the normal CPUID.
         */
        for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) {
                unsigned short cid = xsave_cpuid_features[i];

                /* Careful: X86_FEATURE_FPU is 0! */
                if ((i != XFEATURE_FP && !cid) || !boot_cpu_has(cid))
                        fpu_kernel_cfg.max_features &= ~BIT_ULL(i);
        }

        if (!cpu_feature_enabled(X86_FEATURE_XFD))
                fpu_kernel_cfg.max_features &= ~XFEATURE_MASK_USER_DYNAMIC;

        if (!cpu_feature_enabled(X86_FEATURE_XSAVES))
                fpu_kernel_cfg.max_features &= XFEATURE_MASK_USER_SUPPORTED;
        else
                fpu_kernel_cfg.max_features &= XFEATURE_MASK_USER_SUPPORTED |
                                        XFEATURE_MASK_SUPERVISOR_SUPPORTED;

        fpu_user_cfg.max_features = fpu_kernel_cfg.max_features;
        fpu_user_cfg.max_features &= XFEATURE_MASK_USER_SUPPORTED;

        /* Clean out dynamic features from default */
        fpu_kernel_cfg.default_features = fpu_kernel_cfg.max_features;
        fpu_kernel_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC;

        fpu_user_cfg.default_features = fpu_user_cfg.max_features;
        fpu_user_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC;

        /* Store it for paranoia check at the end */
        xfeatures = fpu_kernel_cfg.max_features;

        /*
         * Initialize the default XFD state in initfp_state and enable the
         * dynamic sizing mechanism if dynamic states are available.  The
         * static key cannot be enabled here because this runs before
         * jump_label_init(). This is delayed to an initcall.
         */
        init_fpstate.xfd = fpu_user_cfg.max_features & XFEATURE_MASK_USER_DYNAMIC;

        /* Set up compaction feature bit */
        if (cpu_feature_enabled(X86_FEATURE_XSAVEC) ||
            cpu_feature_enabled(X86_FEATURE_XSAVES))
                setup_force_cpu_cap(X86_FEATURE_XCOMPACTED);

        /* Enable xstate instructions to be able to continue with initialization: */
        fpu__init_cpu_xstate();

        /* Cache size, offset and flags for initialization */
        setup_xstate_cache();

        err = init_xstate_size();
        if (err)
                goto out_disable;

        /* Reset the state for the current task */
        fpstate_reset(&current->thread.fpu);

        /*
         * Update info used for ptrace frames; use standard-format size and no
         * supervisor xstates:
         */
        update_regset_xstate_info(fpu_user_cfg.max_size,
                                  fpu_user_cfg.max_features);

        /*
         * init_fpstate excludes dynamic states as they are large but init
         * state is zero.
         */
        init_fpstate.size               = fpu_kernel_cfg.default_size;
        init_fpstate.xfeatures          = fpu_kernel_cfg.default_features;

        if (init_fpstate.size > sizeof(init_fpstate.regs)) {
                pr_warn("x86/fpu: init_fpstate buffer too small (%zu < %d), disabling XSAVE\n",
                        sizeof(init_fpstate.regs), init_fpstate.size);
                goto out_disable;
        }

        setup_init_fpu_buf();

        /*
         * Paranoia check whether something in the setup modified the
         * xfeatures mask.
         */
        if (xfeatures != fpu_kernel_cfg.max_features) {
                pr_err("x86/fpu: xfeatures modified from 0x%016llx to 0x%016llx during init, disabling XSAVE\n",
                       xfeatures, fpu_kernel_cfg.max_features);
                goto out_disable;
        }

        /*
         * CPU capabilities initialization runs before FPU init. So
         * X86_FEATURE_OSXSAVE is not set. Now that XSAVE is completely
         * functional, set the feature bit so depending code works.
         */
        setup_force_cpu_cap(X86_FEATURE_OSXSAVE);

        print_xstate_offset_size();
        pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
                fpu_kernel_cfg.max_features,
                fpu_kernel_cfg.max_size,
                boot_cpu_has(X86_FEATURE_XCOMPACTED) ? "compacted" : "standard");
        return;

out_disable:
        /* something went wrong, try to boot without any XSAVE support */
        fpu__init_disable_system_xstate(legacy_size);
}

/*
 * Restore minimal FPU state after suspend:
 */
void fpu__resume_cpu(void)
{
        /*
         * Restore XCR0 on xsave capable CPUs:
         */
        if (cpu_feature_enabled(X86_FEATURE_XSAVE))
                xsetbv(XCR_XFEATURE_ENABLED_MASK, fpu_user_cfg.max_features);

        /*
         * Restore IA32_XSS. The same CPUID bit enumerates support
         * of XSAVES and MSR_IA32_XSS.
         */
        if (cpu_feature_enabled(X86_FEATURE_XSAVES)) {
                wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor()  |
                                     xfeatures_mask_independent());
        }

        if (fpu_state_size_dynamic())
                wrmsrl(MSR_IA32_XFD, current->thread.fpu.fpstate->xfd);
}

/*
 * Given an xstate feature nr, calculate where in the xsave
 * buffer the state is.  Callers should ensure that the buffer
 * is valid.
 */
static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
{
        u64 xcomp_bv = xsave->header.xcomp_bv;

        if (WARN_ON_ONCE(!xfeature_enabled(xfeature_nr)))
                return NULL;

        if (cpu_feature_enabled(X86_FEATURE_XCOMPACTED)) {
                if (WARN_ON_ONCE(!(xcomp_bv & BIT_ULL(xfeature_nr))))
                        return NULL;
        }

        return (void *)xsave + xfeature_get_offset(xcomp_bv, xfeature_nr);
}

/*
 * Given the xsave area and a state inside, this function returns the
 * address of the state.
 *
 * This is the API that is called to get xstate address in either
 * standard format or compacted format of xsave area.
 *
 * Note that if there is no data for the field in the xsave buffer
 * this will return NULL.
 *
 * Inputs:
 *      xstate: the thread's storage area for all FPU data
 *      xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP,
 *      XFEATURE_SSE, etc...)
 * Output:
 *      address of the state in the xsave area, or NULL if the
 *      field is not present in the xsave buffer.
 */
void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
{
        /*
         * Do we even *have* xsave state?
         */
        if (!boot_cpu_has(X86_FEATURE_XSAVE))
                return NULL;

        /*
         * We should not ever be requesting features that we
         * have not enabled.
         */
        if (WARN_ON_ONCE(!xfeature_enabled(xfeature_nr)))
                return NULL;

        /*
         * This assumes the last 'xsave*' instruction to
         * have requested that 'xfeature_nr' be saved.
         * If it did not, we might be seeing and old value
         * of the field in the buffer.
         *
         * This can happen because the last 'xsave' did not
         * request that this feature be saved (unlikely)
         * or because the "init optimization" caused it
         * to not be saved.
         */
        if (!(xsave->header.xfeatures & BIT_ULL(xfeature_nr)))
                return NULL;

        return __raw_xsave_addr(xsave, xfeature_nr);
}

#ifdef CONFIG_ARCH_HAS_PKEYS

/*
 * This will go out and modify PKRU register to set the access
 * rights for @pkey to @init_val.
 */
int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
                              unsigned long init_val)
{
        u32 old_pkru, new_pkru_bits = 0;
        int pkey_shift;

        /*
         * This check implies XSAVE support.  OSPKE only gets
         * set if we enable XSAVE and we enable PKU in XCR0.
         */
        if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
                return -EINVAL;

        /*
         * This code should only be called with valid 'pkey'
         * values originating from in-kernel users.  Complain
         * if a bad value is observed.
         */
        if (WARN_ON_ONCE(pkey >= arch_max_pkey()))
                return -EINVAL;

        /* Set the bits we need in PKRU:  */
        if (init_val & PKEY_DISABLE_ACCESS)
                new_pkru_bits |= PKRU_AD_BIT;
        if (init_val & PKEY_DISABLE_WRITE)
                new_pkru_bits |= PKRU_WD_BIT;

        /* Shift the bits in to the correct place in PKRU for pkey: */
        pkey_shift = pkey * PKRU_BITS_PER_PKEY;
        new_pkru_bits <<= pkey_shift;

        /* Get old PKRU and mask off any old bits in place: */
        old_pkru = read_pkru();
        old_pkru &= ~((PKRU_AD_BIT|PKRU_WD_BIT) << pkey_shift);

        /* Write old part along with new part: */
        write_pkru(old_pkru | new_pkru_bits);

        return 0;
}
#endif /* ! CONFIG_ARCH_HAS_PKEYS */

static void copy_feature(bool from_xstate, struct membuf *to, void *xstate,
                         void *init_xstate, unsigned int size)
{
        membuf_write(to, from_xstate ? xstate : init_xstate, size);
}

/**
 * __copy_xstate_to_uabi_buf - Copy kernel saved xstate to a UABI buffer
 * @to:         membuf descriptor
 * @fpstate:    The fpstate buffer from which to copy
 * @xfeatures:  The mask of xfeatures to save (XSAVE mode only)
 * @pkru_val:   The PKRU value to store in the PKRU component
 * @copy_mode:  The requested copy mode
 *
 * Converts from kernel XSAVE or XSAVES compacted format to UABI conforming
 * format, i.e. from the kernel internal hardware dependent storage format
 * to the requested @mode. UABI XSTATE is always uncompacted!
 *
 * It supports partial copy but @to.pos always starts from zero.
 */
void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
                               u64 xfeatures, u32 pkru_val,
                               enum xstate_copy_mode copy_mode)
{
        const unsigned int off_mxcsr = offsetof(struct fxregs_state, mxcsr);
        struct xregs_state *xinit = &init_fpstate.regs.xsave;
        struct xregs_state *xsave = &fpstate->regs.xsave;
        struct xstate_header header;
        unsigned int zerofrom;
        u64 mask;
        int i;

        memset(&header, 0, sizeof(header));
        header.xfeatures = xsave->header.xfeatures;

        /* Mask out the feature bits depending on copy mode */
        switch (copy_mode) {
        case XSTATE_COPY_FP:
                header.xfeatures &= XFEATURE_MASK_FP;
                break;

        case XSTATE_COPY_FX:
                header.xfeatures &= XFEATURE_MASK_FP | XFEATURE_MASK_SSE;
                break;

        case XSTATE_COPY_XSAVE:
                header.xfeatures &= fpstate->user_xfeatures & xfeatures;
                break;
        }

        /* Copy FP state up to MXCSR */
        copy_feature(header.xfeatures & XFEATURE_MASK_FP, &to, &xsave->i387,
                     &xinit->i387, off_mxcsr);

        /* Copy MXCSR when SSE or YMM are set in the feature mask */
        copy_feature(header.xfeatures & (XFEATURE_MASK_SSE | XFEATURE_MASK_YMM),
                     &to, &xsave->i387.mxcsr, &xinit->i387.mxcsr,
                     MXCSR_AND_FLAGS_SIZE);

        /* Copy the remaining FP state */
        copy_feature(header.xfeatures & XFEATURE_MASK_FP,
                     &to, &xsave->i387.st_space, &xinit->i387.st_space,
                     sizeof(xsave->i387.st_space));

        /* Copy the SSE state - shared with YMM, but independently managed */
        copy_feature(header.xfeatures & XFEATURE_MASK_SSE,
                     &to, &xsave->i387.xmm_space, &xinit->i387.xmm_space,
                     sizeof(xsave->i387.xmm_space));

        if (copy_mode != XSTATE_COPY_XSAVE)
                goto out;

        /* Zero the padding area */
        membuf_zero(&to, sizeof(xsave->i387.padding));

        /* Copy xsave->i387.sw_reserved */
        membuf_write(&to, xstate_fx_sw_bytes, sizeof(xsave->i387.sw_reserved));

        /* Copy the user space relevant state of @xsave->header */
        membuf_write(&to, &header, sizeof(header));

        zerofrom = offsetof(struct xregs_state, extended_state_area);

        /*
         * This 'mask' indicates which states to copy from fpstate.
         * Those extended states that are not present in fpstate are
         * either disabled or initialized:
         *
         * In non-compacted format, disabled features still occupy
         * state space but there is no state to copy from in the
         * compacted init_fpstate. The gap tracking will zero these
         * states.
         *
         * The extended features have an all zeroes init state. Thus,
         * remove them from 'mask' to zero those features in the user
         * buffer instead of retrieving them from init_fpstate.
         */
        mask = header.xfeatures;

        for_each_extended_xfeature(i, mask) {
                /*
                 * If there was a feature or alignment gap, zero the space
                 * in the destination buffer.
                 */
                if (zerofrom < xstate_offsets[i])
                        membuf_zero(&to, xstate_offsets[i] - zerofrom);

                if (i == XFEATURE_PKRU) {
                        struct pkru_state pkru = {0};
                        /*
                         * PKRU is not necessarily up to date in the
                         * XSAVE buffer. Use the provided value.
                         */
                        pkru.pkru = pkru_val;
                        membuf_write(&to, &pkru, sizeof(pkru));
                } else {
                        membuf_write(&to,
                                     __raw_xsave_addr(xsave, i),
                                     xstate_sizes[i]);
                }
                /*
                 * Keep track of the last copied state in the non-compacted
                 * target buffer for gap zeroing.
                 */
                zerofrom = xstate_offsets[i] + xstate_sizes[i];
        }

out:
        if (to.left)
                membuf_zero(&to, to.left);
}

/**
 * copy_xstate_to_uabi_buf - Copy kernel saved xstate to a UABI buffer
 * @to:         membuf descriptor
 * @tsk:        The task from which to copy the saved xstate
 * @copy_mode:  The requested copy mode
 *
 * Converts from kernel XSAVE or XSAVES compacted format to UABI conforming
 * format, i.e. from the kernel internal hardware dependent storage format
 * to the requested @mode. UABI XSTATE is always uncompacted!
 *
 * It supports partial copy but @to.pos always starts from zero.
 */
void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
                             enum xstate_copy_mode copy_mode)
{
        __copy_xstate_to_uabi_buf(to, tsk->thread.fpu.fpstate,
                                  tsk->thread.fpu.fpstate->user_xfeatures,
                                  tsk->thread.pkru, copy_mode);
}

static int copy_from_buffer(void *dst, unsigned int offset, unsigned int size,
                            const void *kbuf, const void __user *ubuf)
{
        if (kbuf) {
                memcpy(dst, kbuf + offset, size);
        } else {
                if (copy_from_user(dst, ubuf + offset, size))
                        return -EFAULT;
        }
        return 0;
}


/**
 * copy_uabi_to_xstate - Copy a UABI format buffer to the kernel xstate
 * @fpstate:    The fpstate buffer to copy to
 * @kbuf:       The UABI format buffer, if it comes from the kernel
 * @ubuf:       The UABI format buffer, if it comes from userspace
 * @pkru:       The location to write the PKRU value to
 *
 * Converts from the UABI format into the kernel internal hardware
 * dependent format.
 *
 * This function ultimately has three different callers with distinct PKRU
 * behavior.
 * 1.   When called from sigreturn the PKRU register will be restored from
 *      @fpstate via an XRSTOR. Correctly copying the UABI format buffer to
 *      @fpstate is sufficient to cover this case, but the caller will also
 *      pass a pointer to the thread_struct's pkru field in @pkru and updating
 *      it is harmless.
 * 2.   When called from ptrace the PKRU register will be restored from the
 *      thread_struct's pkru field. A pointer to that is passed in @pkru.
 *      The kernel will restore it manually, so the XRSTOR behavior that resets
 *      the PKRU register to the hardware init value (0) if the corresponding
 *      xfeatures bit is not set is emulated here.
 * 3.   When called from KVM the PKRU register will be restored from the vcpu's
 *      pkru field. A pointer to that is passed in @pkru. KVM hasn't used
 *      XRSTOR and hasn't had the PKRU resetting behavior described above. To
 *      preserve that KVM behavior, it passes NULL for @pkru if the xfeatures
 *      bit is not set.
 */
static int copy_uabi_to_xstate(struct fpstate *fpstate, const void *kbuf,
                               const void __user *ubuf, u32 *pkru)
{
        struct xregs_state *xsave = &fpstate->regs.xsave;
        unsigned int offset, size;
        struct xstate_header hdr;
        u64 mask;
        int i;

        offset = offsetof(struct xregs_state, header);
        if (copy_from_buffer(&hdr, offset, sizeof(hdr), kbuf, ubuf))
                return -EFAULT;

        if (validate_user_xstate_header(&hdr, fpstate))
                return -EINVAL;

        /* Validate MXCSR when any of the related features is in use */
        mask = XFEATURE_MASK_FP | XFEATURE_MASK_SSE | XFEATURE_MASK_YMM;
        if (hdr.xfeatures & mask) {
                u32 mxcsr[2];

                offset = offsetof(struct fxregs_state, mxcsr);
                if (copy_from_buffer(mxcsr, offset, sizeof(mxcsr), kbuf, ubuf))
                        return -EFAULT;

                /* Reserved bits in MXCSR must be zero. */
                if (mxcsr[0] & ~mxcsr_feature_mask)
                        return -EINVAL;

                /* SSE and YMM require MXCSR even when FP is not in use. */
                if (!(hdr.xfeatures & XFEATURE_MASK_FP)) {
                        xsave->i387.mxcsr = mxcsr[0];
                        xsave->i387.mxcsr_mask = mxcsr[1];
                }
        }

        for (i = 0; i < XFEATURE_MAX; i++) {
                mask = BIT_ULL(i);

                if (hdr.xfeatures & mask) {
                        void *dst = __raw_xsave_addr(xsave, i);

                        offset = xstate_offsets[i];
                        size = xstate_sizes[i];

                        if (copy_from_buffer(dst, offset, size, kbuf, ubuf))
                                return -EFAULT;
                }
        }

        if (hdr.xfeatures & XFEATURE_MASK_PKRU) {
                struct pkru_state *xpkru;

                xpkru = __raw_xsave_addr(xsave, XFEATURE_PKRU);
                *pkru = xpkru->pkru;
        } else {
                /*
                 * KVM may pass NULL here to indicate that it does not need
                 * PKRU updated.
                 */
                if (pkru)
                        *pkru = 0;
        }

        /*
         * The state that came in from userspace was user-state only.
         * Mask all the user states out of 'xfeatures':
         */
        xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR_ALL;

        /*
         * Add back in the features that came in from userspace:
         */
        xsave->header.xfeatures |= hdr.xfeatures;

        return 0;
}

/*
 * Convert from a ptrace standard-format kernel buffer to kernel XSAVE[S]
 * format and copy to the target thread. Used by ptrace and KVM.
 */
int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf, u32 *pkru)
{
        return copy_uabi_to_xstate(fpstate, kbuf, NULL, pkru);
}

/*
 * Convert from a sigreturn standard-format user-space buffer to kernel
 * XSAVE[S] format and copy to the target thread. This is called from the
 * sigreturn() and rt_sigreturn() system calls.
 */
int copy_sigframe_from_user_to_xstate(struct task_struct *tsk,
                                      const void __user *ubuf)
{
        return copy_uabi_to_xstate(tsk->thread.fpu.fpstate, NULL, ubuf, &tsk->thread.pkru);
}

static bool validate_independent_components(u64 mask)
{
        u64 xchk;

        if (WARN_ON_FPU(!cpu_feature_enabled(X86_FEATURE_XSAVES)))
                return false;

        xchk = ~xfeatures_mask_independent();

        if (WARN_ON_ONCE(!mask || mask & xchk))
                return false;

        return true;
}

/**
 * xsaves - Save selected components to a kernel xstate buffer
 * @xstate:     Pointer to the buffer
 * @mask:       Feature mask to select the components to save
 *
 * The @xstate buffer must be 64 byte aligned and correctly initialized as
 * XSAVES does not write the full xstate header. Before first use the
 * buffer should be zeroed otherwise a consecutive XRSTORS from that buffer
 * can #GP.
 *
 * The feature mask must be a subset of the independent features.
 */
void xsaves(struct xregs_state *xstate, u64 mask)
{
        int err;

        if (!validate_independent_components(mask))
                return;

        XSTATE_OP(XSAVES, xstate, (u32)mask, (u32)(mask >> 32), err);
        WARN_ON_ONCE(err);
}

/**
 * xrstors - Restore selected components from a kernel xstate buffer
 * @xstate:     Pointer to the buffer
 * @mask:       Feature mask to select the components to restore
 *
 * The @xstate buffer must be 64 byte aligned and correctly initialized
 * otherwise XRSTORS from that buffer can #GP.
 *
 * Proper usage is to restore the state which was saved with
 * xsaves() into @xstate.
 *
 * The feature mask must be a subset of the independent features.
 */
void xrstors(struct xregs_state *xstate, u64 mask)
{
        int err;

        if (!validate_independent_components(mask))
                return;

        XSTATE_OP(XRSTORS, xstate, (u32)mask, (u32)(mask >> 32), err);
        WARN_ON_ONCE(err);
}

#if IS_ENABLED(CONFIG_KVM)
void fpstate_clear_xstate_component(struct fpstate *fps, unsigned int xfeature)
{
        void *addr = get_xsave_addr(&fps->regs.xsave, xfeature);

        if (addr)
                memset(addr, 0, xstate_sizes[xfeature]);
}
EXPORT_SYMBOL_GPL(fpstate_clear_xstate_component);
#endif

#ifdef CONFIG_X86_64

#ifdef CONFIG_X86_DEBUG_FPU
/*
 * Ensure that a subsequent XSAVE* or XRSTOR* instruction with RFBM=@mask
 * can safely operate on the @fpstate buffer.
 */
static bool xstate_op_valid(struct fpstate *fpstate, u64 mask, bool rstor)
{
        u64 xfd = __this_cpu_read(xfd_state);

        if (fpstate->xfd == xfd)
                return true;

         /*
          * The XFD MSR does not match fpstate->xfd. That's invalid when
          * the passed in fpstate is current's fpstate.
          */
        if (fpstate->xfd == current->thread.fpu.fpstate->xfd)
                return false;

        /*
         * XRSTOR(S) from init_fpstate are always correct as it will just
         * bring all components into init state and not read from the
         * buffer. XSAVE(S) raises #PF after init.
         */
        if (fpstate == &init_fpstate)
                return rstor;

        /*
         * XSAVE(S): clone(), fpu_swap_kvm_fpu()
         * XRSTORS(S): fpu_swap_kvm_fpu()
         */

        /*
         * No XSAVE/XRSTOR instructions (except XSAVE itself) touch
         * the buffer area for XFD-disabled state components.
         */
        mask &= ~xfd;

        /*
         * Remove features which are valid in fpstate. They
         * have space allocated in fpstate.
         */
        mask &= ~fpstate->xfeatures;

        /*
         * Any remaining state components in 'mask' might be written
         * by XSAVE/XRSTOR. Fail validation it found.
         */
        return !mask;
}

void xfd_validate_state(struct fpstate *fpstate, u64 mask, bool rstor)
{
        WARN_ON_ONCE(!xstate_op_valid(fpstate, mask, rstor));
}
#endif /* CONFIG_X86_DEBUG_FPU */

static int __init xfd_update_static_branch(void)
{
        /*
         * If init_fpstate.xfd has bits set then dynamic features are
         * available and the dynamic sizing must be enabled.
         */
        if (init_fpstate.xfd)
                static_branch_enable(&__fpu_state_size_dynamic);
        return 0;
}
arch_initcall(xfd_update_static_branch)

void fpstate_free(struct fpu *fpu)
{
        if (fpu->fpstate && fpu->fpstate != &fpu->__fpstate)
                vfree(fpu->fpstate);
}

/**
 * fpstate_realloc - Reallocate struct fpstate for the requested new features
 *
 * @xfeatures:  A bitmap of xstate features which extend the enabled features
 *              of that task
 * @ksize:      The required size for the kernel buffer
 * @usize:      The required size for user space buffers
 * @guest_fpu:  Pointer to a guest FPU container. NULL for host allocations
 *
 * Note vs. vmalloc(): If the task with a vzalloc()-allocated buffer
 * terminates quickly, vfree()-induced IPIs may be a concern, but tasks
 * with large states are likely to live longer.
 *
 * Returns: 0 on success, -ENOMEM on allocation error.
 */
static int fpstate_realloc(u64 xfeatures, unsigned int ksize,
                           unsigned int usize, struct fpu_guest *guest_fpu)
{
        struct fpu *fpu = &current->thread.fpu;
        struct fpstate *curfps, *newfps = NULL;
        unsigned int fpsize;
        bool in_use;

        fpsize = ksize + ALIGN(offsetof(struct fpstate, regs), 64);

        newfps = vzalloc(fpsize);
        if (!newfps)
                return -ENOMEM;
        newfps->size = ksize;
        newfps->user_size = usize;
        newfps->is_valloc = true;

        /*
         * When a guest FPU is supplied, use @guest_fpu->fpstate
         * as reference independent whether it is in use or not.
         */
        curfps = guest_fpu ? guest_fpu->fpstate : fpu->fpstate;

        /* Determine whether @curfps is the active fpstate */
        in_use = fpu->fpstate == curfps;

        if (guest_fpu) {
                newfps->is_guest = true;
                newfps->is_confidential = curfps->is_confidential;
                newfps->in_use = curfps->in_use;
                guest_fpu->xfeatures |= xfeatures;
                guest_fpu->uabi_size = usize;
        }

        fpregs_lock();
        /*
         * If @curfps is in use, ensure that the current state is in the
         * registers before swapping fpstate as that might invalidate it
         * due to layout changes.
         */
        if (in_use && test_thread_flag(TIF_NEED_FPU_LOAD))
                fpregs_restore_userregs();

        newfps->xfeatures = curfps->xfeatures | xfeatures;
        newfps->user_xfeatures = curfps->user_xfeatures | xfeatures;
        newfps->xfd = curfps->xfd & ~xfeatures;

        /* Do the final updates within the locked region */
        xstate_init_xcomp_bv(&newfps->regs.xsave, newfps->xfeatures);

        if (guest_fpu) {
                guest_fpu->fpstate = newfps;
                /* If curfps is active, update the FPU fpstate pointer */
                if (in_use)
                        fpu->fpstate = newfps;
        } else {
                fpu->fpstate = newfps;
        }

        if (in_use)
                xfd_update_state(fpu->fpstate);
        fpregs_unlock();

        /* Only free valloc'ed state */
        if (curfps && curfps->is_valloc)
                vfree(curfps);

        return 0;
}

static int validate_sigaltstack(unsigned int usize)
{
        struct task_struct *thread, *leader = current->group_leader;
        unsigned long framesize = get_sigframe_size();

        lockdep_assert_held(&current->sighand->siglock);

        /* get_sigframe_size() is based on fpu_user_cfg.max_size */
        framesize -= fpu_user_cfg.max_size;
        framesize += usize;
        for_each_thread(leader, thread) {
                if (thread->sas_ss_size && thread->sas_ss_size < framesize)
                        return -ENOSPC;
        }
        return 0;
}

static int __xstate_request_perm(u64 permitted, u64 requested, bool guest)
{
        /*
         * This deliberately does not exclude !XSAVES as we still might
         * decide to optionally context switch XCR0 or talk the silicon
         * vendors into extending XFD for the pre AMX states, especially
         * AVX512.
         */
        bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED);
        struct fpu *fpu = &current->group_leader->thread.fpu;
        struct fpu_state_perm *perm;
        unsigned int ksize, usize;
        u64 mask;
        int ret = 0;

        /* Check whether fully enabled */
        if ((permitted & requested) == requested)
                return 0;

        /* Calculate the resulting kernel state size */
        mask = permitted | requested;
        /* Take supervisor states into account on the host */
        if (!guest)
                mask |= xfeatures_mask_supervisor();
        ksize = xstate_calculate_size(mask, compacted);

        /* Calculate the resulting user state size */
        mask &= XFEATURE_MASK_USER_SUPPORTED;
        usize = xstate_calculate_size(mask, false);

        if (!guest) {
                ret = validate_sigaltstack(usize);
                if (ret)
                        return ret;
        }

        perm = guest ? &fpu->guest_perm : &fpu->perm;
        /* Pairs with the READ_ONCE() in xstate_get_group_perm() */
        WRITE_ONCE(perm->__state_perm, mask);
        /* Protected by sighand lock */
        perm->__state_size = ksize;
        perm->__user_state_size = usize;
        return ret;
}

/*
 * Permissions array to map facilities with more than one component
 */
static const u64 xstate_prctl_req[XFEATURE_MAX] = {
        [XFEATURE_XTILE_DATA] = XFEATURE_MASK_XTILE_DATA,
};

static int xstate_request_perm(unsigned long idx, bool guest)
{
        u64 permitted, requested;
        int ret;

        if (idx >= XFEATURE_MAX)
                return -EINVAL;

        /*
         * Look up the facility mask which can require more than
         * one xstate component.
         */
        idx = array_index_nospec(idx, ARRAY_SIZE(xstate_prctl_req));
        requested = xstate_prctl_req[idx];
        if (!requested)
                return -EOPNOTSUPP;

        if ((fpu_user_cfg.max_features & requested) != requested)
                return -EOPNOTSUPP;

        /* Lockless quick check */
        permitted = xstate_get_group_perm(guest);
        if ((permitted & requested) == requested)
                return 0;

        /* Protect against concurrent modifications */
        spin_lock_irq(&current->sighand->siglock);
        permitted = xstate_get_group_perm(guest);

        /* First vCPU allocation locks the permissions. */
        if (guest && (permitted & FPU_GUEST_PERM_LOCKED))
                ret = -EBUSY;
        else
                ret = __xstate_request_perm(permitted, requested, guest);
        spin_unlock_irq(&current->sighand->siglock);
        return ret;
}

int __xfd_enable_feature(u64 xfd_err, struct fpu_guest *guest_fpu)
{
        u64 xfd_event = xfd_err & XFEATURE_MASK_USER_DYNAMIC;
        struct fpu_state_perm *perm;
        unsigned int ksize, usize;
        struct fpu *fpu;

        if (!xfd_event) {
                if (!guest_fpu)
                        pr_err_once("XFD: Invalid xfd error: %016llx\n", xfd_err);
                return 0;
        }

        /* Protect against concurrent modifications */
        spin_lock_irq(&current->sighand->siglock);

        /* If not permitted let it die */
        if ((xstate_get_group_perm(!!guest_fpu) & xfd_event) != xfd_event) {
                spin_unlock_irq(&current->sighand->siglock);
                return -EPERM;
        }

        fpu = &current->group_leader->thread.fpu;
        perm = guest_fpu ? &fpu->guest_perm : &fpu->perm;
        ksize = perm->__state_size;
        usize = perm->__user_state_size;

        /*
         * The feature is permitted. State size is sufficient.  Dropping
         * the lock is safe here even if more features are added from
         * another task, the retrieved buffer sizes are valid for the
         * currently requested feature(s).
         */
        spin_unlock_irq(&current->sighand->siglock);

        /*
         * Try to allocate a new fpstate. If that fails there is no way
         * out.
         */
        if (fpstate_realloc(xfd_event, ksize, usize, guest_fpu))
                return -EFAULT;
        return 0;
}

int xfd_enable_feature(u64 xfd_err)
{
        return __xfd_enable_feature(xfd_err, NULL);
}

#else /* CONFIG_X86_64 */
static inline int xstate_request_perm(unsigned long idx, bool guest)
{
        return -EPERM;
}
#endif  /* !CONFIG_X86_64 */

u64 xstate_get_guest_group_perm(void)
{
        return xstate_get_group_perm(true);
}
EXPORT_SYMBOL_GPL(xstate_get_guest_group_perm);

/**
 * fpu_xstate_prctl - xstate permission operations
 * @tsk:        Redundant pointer to current
 * @option:     A subfunction of arch_prctl()
 * @arg2:       option argument
 * Return:      0 if successful; otherwise, an error code
 *
 * Option arguments:
 *
 * ARCH_GET_XCOMP_SUPP: Pointer to user space u64 to store the info
 * ARCH_GET_XCOMP_PERM: Pointer to user space u64 to store the info
 * ARCH_REQ_XCOMP_PERM: Facility number requested
 *
 * For facilities which require more than one XSTATE component, the request
 * must be the highest state component number related to that facility,
 * e.g. for AMX which requires XFEATURE_XTILE_CFG(17) and
 * XFEATURE_XTILE_DATA(18) this would be XFEATURE_XTILE_DATA(18).
 */
long fpu_xstate_prctl(int option, unsigned long arg2)
{
        u64 __user *uptr = (u64 __user *)arg2;
        u64 permitted, supported;
        unsigned long idx = arg2;
        bool guest = false;

        switch (option) {
        case ARCH_GET_XCOMP_SUPP:
                supported = fpu_user_cfg.max_features | fpu_user_cfg.legacy_features;
                return put_user(supported, uptr);

        case ARCH_GET_XCOMP_PERM:
                /*
                 * Lockless snapshot as it can also change right after the
                 * dropping the lock.
                 */
                permitted = xstate_get_host_group_perm();
                permitted &= XFEATURE_MASK_USER_SUPPORTED;
                return put_user(permitted, uptr);

        case ARCH_GET_XCOMP_GUEST_PERM:
                permitted = xstate_get_guest_group_perm();
                permitted &= XFEATURE_MASK_USER_SUPPORTED;
                return put_user(permitted, uptr);

        case ARCH_REQ_XCOMP_GUEST_PERM:
                guest = true;
                fallthrough;

        case ARCH_REQ_XCOMP_PERM:
                if (!IS_ENABLED(CONFIG_X86_64))
                        return -EOPNOTSUPP;

                return xstate_request_perm(idx, guest);

        default:
                return -EINVAL;
        }
}

#ifdef CONFIG_PROC_PID_ARCH_STATUS
/*
 * Report the amount of time elapsed in millisecond since last AVX512
 * use in the task.
 */
static void avx512_status(struct seq_file *m, struct task_struct *task)
{
        unsigned long timestamp = READ_ONCE(task->thread.fpu.avx512_timestamp);
        long delta;

        if (!timestamp) {
                /*
                 * Report -1 if no AVX512 usage
                 */
                delta = -1;
        } else {
                delta = (long)(jiffies - timestamp);
                /*
                 * Cap to LONG_MAX if time difference > LONG_MAX
                 */
                if (delta < 0)
                        delta = LONG_MAX;
                delta = jiffies_to_msecs(delta);
        }

        seq_put_decimal_ll(m, "AVX512_elapsed_ms:\t", delta);
        seq_putc(m, '\n');
}

/*
 * Report architecture specific information
 */
int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns,
                        struct pid *pid, struct task_struct *task)
{
        /*
         * Report AVX512 state if the processor and build option supported.
         */
        if (cpu_feature_enabled(X86_FEATURE_AVX512F))
                avx512_status(m, task);

        return 0;
}
#endif /* CONFIG_PROC_PID_ARCH_STATUS */