i386: Make patching more robust, fix paravirt issue

Commit 19d36ccdc34f5ed444f8a6af0cbfdb6790eb1177 "x86: Fix alternatives
and kprobes to remap write-protected kernel text" uses code which is
being patched for patching.

In particular, paravirt_ops does patching in two stages: first it
calls paravirt_ops.patch, then it fills any remaining instructions
with nop_out().  nop_out calls text_poke() which calls
lookup_address() which calls pgd_val() (aka paravirt_ops.pgd_val):
that call site is one of the places we patch.

If we always do patching as one single call to text_poke(), we only
need make sure we're not patching the memcpy in text_poke itself.
This means the prototype to paravirt_ops.patch needs to change, to
marshal the new code into a buffer rather than patching in place as it
does now.  It also means all patching goes through text_poke(), which
is known to be safe (apply_alternatives is also changed to make a
single patch).

AK: fix compilation on x86-64 (bad rusty!)
AK: fix boot on x86-64 (sigh)
AK: merged with other patches

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/i386/kernel/alternative.c b/arch/i386/kernel/alternative.c
index c85598a..27a6b0c 100644 (file)
--- a/arch/i386/kernel/alternative.c
+++ b/arch/i386/kernel/alternative.c
@@ -11,6 +11,8 @@
 #include <asm/mce.h>
 #include <asm/nmi.h>
 
+#define MAX_PATCH_LEN (255-1)
+
 #ifdef CONFIG_HOTPLUG_CPU
 static int smp_alt_once;
 
@@ -148,7 +150,8 @@ static unsigned char** find_nop_table(void)
 
 #endif /* CONFIG_X86_64 */
 
-static void nop_out(void *insns, unsigned int len)
+/* Use this to add nops to a buffer, then text_poke the whole buffer. */
+static void add_nops(void *insns, unsigned int len)
 {
        unsigned char **noptable = find_nop_table();
 
@@ -156,7 +159,7 @@ static void nop_out(void *insns, unsigned int len)
                unsigned int noplen = len;
                if (noplen > ASM_NOP_MAX)
                        noplen = ASM_NOP_MAX;
-               text_poke(insns, noptable[noplen], noplen);
+               memcpy(insns, noptable[noplen], noplen);
                insns += noplen;
                len -= noplen;
        }
@@ -174,15 +177,15 @@ extern u8 *__smp_locks[], *__smp_locks_end[];
 void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
 {
        struct alt_instr *a;
-       u8 *instr;
-       int diff;
+       char insnbuf[MAX_PATCH_LEN];
 
        DPRINTK("%s: alt table %p -> %p\n", __FUNCTION__, start, end);
        for (a = start; a < end; a++) {
+               u8 *instr = a->instr;
                BUG_ON(a->replacementlen > a->instrlen);
+               BUG_ON(a->instrlen > sizeof(insnbuf));
                if (!boot_cpu_has(a->cpuid))
                        continue;
-               instr = a->instr;
 #ifdef CONFIG_X86_64
                /* vsyscall code is not mapped yet. resolve it manually. */
                if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) {
@@ -191,9 +194,10 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
                                __FUNCTION__, a->instr, instr);
                }
 #endif
-               memcpy(instr, a->replacement, a->replacementlen);
-               diff = a->instrlen - a->replacementlen;
-               nop_out(instr + a->replacementlen, diff);
+               memcpy(insnbuf, a->replacement, a->replacementlen);
+               add_nops(insnbuf + a->replacementlen,
+                        a->instrlen - a->replacementlen);
+               text_poke(instr, insnbuf, a->instrlen);
        }
 }
 
@@ -215,16 +219,18 @@ static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
 static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end)
 {
        u8 **ptr;
+       char insn[1];
 
        if (noreplace_smp)
                return;
 
+       add_nops(insn, 1);
        for (ptr = start; ptr < end; ptr++) {
                if (*ptr < text)
                        continue;
                if (*ptr > text_end)
                        continue;
-               nop_out(*ptr, 1);
+               text_poke(*ptr, insn, 1);
        };
 }
 
@@ -351,6 +357,7 @@ void apply_paravirt(struct paravirt_patch_site *start,
                    struct paravirt_patch_site *end)
 {
        struct paravirt_patch_site *p;
+       char insnbuf[MAX_PATCH_LEN];
 
        if (noreplace_paravirt)
                return;
@@ -358,13 +365,15 @@ void apply_paravirt(struct paravirt_patch_site *start,
        for (p = start; p < end; p++) {
                unsigned int used;
 
-               used = paravirt_ops.patch(p->instrtype, p->clobbers, p->instr,
-                                         p->len);
+               BUG_ON(p->len > MAX_PATCH_LEN);
+               used = paravirt_ops.patch(p->instrtype, p->clobbers, insnbuf,
+                                         (unsigned long)p->instr, p->len);
 
                BUG_ON(used > p->len);
 
                /* Pad the rest with nops */
-               nop_out(p->instr + used, p->len - used);
+               add_nops(insnbuf + used, p->len - used);
+               text_poke(p->instr, insnbuf, p->len);
        }
 }
 extern struct paravirt_patch_site __start_parainstructions[],

diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index ea962c0..739cfb2 100644 (file)
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -69,7 +69,8 @@ DEF_NATIVE(read_tsc, "rdtsc");
 
 DEF_NATIVE(ud2a, "ud2a");
 
-static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len)
+static unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
+                            unsigned long addr, unsigned len)
 {
        const unsigned char *start, *end;
        unsigned ret;
@@ -90,7 +91,7 @@ static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len)
 #undef SITE
 
        patch_site:
-               ret = paravirt_patch_insns(insns, len, start, end);
+               ret = paravirt_patch_insns(ibuf, len, start, end);
                break;
 
        case PARAVIRT_PATCH(make_pgd):
@@ -107,7 +108,7 @@ static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len)
                break;
 
        default:
-               ret = paravirt_patch_default(type, clobbers, insns, len);
+               ret = paravirt_patch_default(type, clobbers, ibuf, addr, len);
                break;
        }
 
@@ -129,68 +130,67 @@ struct branch {
        u32 delta;
 } __attribute__((packed));
 
-unsigned paravirt_patch_call(void *target, u16 tgt_clobbers,
-                            void *site, u16 site_clobbers,
+unsigned paravirt_patch_call(void *insnbuf,
+                            const void *target, u16 tgt_clobbers,
+                            unsigned long addr, u16 site_clobbers,
                             unsigned len)
 {
-       unsigned char *call = site;
-       unsigned long delta = (unsigned long)target - (unsigned long)(call+5);
-       struct branch b;
+       struct branch *b = insnbuf;
+       unsigned long delta = (unsigned long)target - (addr+5);
 
        if (tgt_clobbers & ~site_clobbers)
                return len;     /* target would clobber too much for this site */
        if (len < 5)
                return len;     /* call too long for patch site */
 
-       b.opcode = 0xe8; /* call */
-       b.delta = delta;
-       BUILD_BUG_ON(sizeof(b) != 5);
-       text_poke(call, (unsigned char *)&b, 5);
+       b->opcode = 0xe8; /* call */
+       b->delta = delta;
+       BUILD_BUG_ON(sizeof(*b) != 5);
 
        return 5;
 }
 
-unsigned paravirt_patch_jmp(void *target, void *site, unsigned len)
+unsigned paravirt_patch_jmp(const void *target, void *insnbuf,
+                           unsigned long addr, unsigned len)
 {
-       unsigned char *jmp = site;
-       unsigned long delta = (unsigned long)target - (unsigned long)(jmp+5);
-       struct branch b;
+       struct branch *b = insnbuf;
+       unsigned long delta = (unsigned long)target - (addr+5);
 
        if (len < 5)
                return len;     /* call too long for patch site */
 
-       b.opcode = 0xe9;        /* jmp */
-       b.delta = delta;
-       text_poke(jmp, (unsigned char *)&b, 5);
+       b->opcode = 0xe9;       /* jmp */
+       b->delta = delta;
 
        return 5;
 }
 
-unsigned paravirt_patch_default(u8 type, u16 clobbers, void *site, unsigned len)
+unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf,
+                               unsigned long addr, unsigned len)
 {
        void *opfunc = *((void **)&paravirt_ops + type);
        unsigned ret;
 
        if (opfunc == NULL)
                /* If there's no function, patch it with a ud2a (BUG) */
-               ret = paravirt_patch_insns(site, len, start_ud2a, end_ud2a);
+               ret = paravirt_patch_insns(insnbuf, len, start_ud2a, end_ud2a);
        else if (opfunc == paravirt_nop)
                /* If the operation is a nop, then nop the callsite */
                ret = paravirt_patch_nop();
        else if (type == PARAVIRT_PATCH(iret) ||
                 type == PARAVIRT_PATCH(irq_enable_sysexit))
                /* If operation requires a jmp, then jmp */
-               ret = paravirt_patch_jmp(opfunc, site, len);
+               ret = paravirt_patch_jmp(opfunc, insnbuf, addr, len);
        else
                /* Otherwise call the function; assume target could
                   clobber any caller-save reg */
-               ret = paravirt_patch_call(opfunc, CLBR_ANY,
-                                         site, clobbers, len);
+               ret = paravirt_patch_call(insnbuf, opfunc, CLBR_ANY,
+                                         addr, clobbers, len);
 
        return ret;
 }
 
-unsigned paravirt_patch_insns(void *site, unsigned len,
+unsigned paravirt_patch_insns(void *insnbuf, unsigned len,
                              const char *start, const char *end)
 {
        unsigned insn_len = end - start;
@@ -198,7 +198,7 @@ unsigned paravirt_patch_insns(void *site, unsigned len,
        if (insn_len > len || start == NULL)
                insn_len = len;
        else
-               memcpy(site, start, insn_len);
+               memcpy(insnbuf, start, insn_len);
 
        return insn_len;
 }

diff --git a/arch/i386/kernel/vmi.c b/arch/i386/kernel/vmi.c
index 72042bb..18673e0 100644 (file)
--- a/arch/i386/kernel/vmi.c
+++ b/arch/i386/kernel/vmi.c
@@ -87,12 +87,14 @@ struct vmi_timer_ops vmi_timer_ops;
 #define IRQ_PATCH_INT_MASK 0
 #define IRQ_PATCH_DISABLE  5
 
-static inline void patch_offset(unsigned char *eip, unsigned char *dest)
+static inline void patch_offset(void *insnbuf,
+                               unsigned long eip, unsigned long dest)
 {
-        *(unsigned long *)(eip+1) = dest-eip-5;
+        *(unsigned long *)(insnbuf+1) = dest-eip-5;
 }
 
-static unsigned patch_internal(int call, unsigned len, void *insns)
+static unsigned patch_internal(int call, unsigned len, void *insnbuf,
+                              unsigned long eip)
 {
        u64 reloc;
        struct vmi_relocation_info *const rel = (struct vmi_relocation_info *)&reloc;
@@ -100,14 +102,14 @@ static unsigned patch_internal(int call, unsigned len, void *insns)
        switch(rel->type) {
                case VMI_RELOCATION_CALL_REL:
                        BUG_ON(len < 5);
-                       *(char *)insns = MNEM_CALL;
-                       patch_offset(insns, rel->eip);
+                       *(char *)insnbuf = MNEM_CALL;
+                       patch_offset(insnbuf, eip, (unsigned long)rel->eip);
                        return 5;
 
                case VMI_RELOCATION_JUMP_REL:
                        BUG_ON(len < 5);
-                       *(char *)insns = MNEM_JMP;
-                       patch_offset(insns, rel->eip);
+                       *(char *)insnbuf = MNEM_JMP;
+                       patch_offset(insnbuf, eip, (unsigned long)rel->eip);
                        return 5;
 
                case VMI_RELOCATION_NOP:
@@ -128,21 +130,26 @@ static unsigned patch_internal(int call, unsigned len, void *insns)
  * Apply patch if appropriate, return length of new instruction
  * sequence.  The callee does nop padding for us.
  */
-static unsigned vmi_patch(u8 type, u16 clobbers, void *insns, unsigned len)
+static unsigned vmi_patch(u8 type, u16 clobbers, void *insns,
+                         unsigned long eip, unsigned len)
 {
        switch (type) {
                case PARAVIRT_PATCH(irq_disable):
-                       return patch_internal(VMI_CALL_DisableInterrupts, len, insns);
+                       return patch_internal(VMI_CALL_DisableInterrupts, len,
+                                             insns, eip);
                case PARAVIRT_PATCH(irq_enable):
-                       return patch_internal(VMI_CALL_EnableInterrupts, len, insns);
+                       return patch_internal(VMI_CALL_EnableInterrupts, len,
+                                             insns, eip);
                case PARAVIRT_PATCH(restore_fl):
-                       return patch_internal(VMI_CALL_SetInterruptMask, len, insns);
+                       return patch_internal(VMI_CALL_SetInterruptMask, len,
+                                             insns, eip);
                case PARAVIRT_PATCH(save_fl):
-                       return patch_internal(VMI_CALL_GetInterruptMask, len, insns);
+                       return patch_internal(VMI_CALL_GetInterruptMask, len,
+                                             insns, eip);
                case PARAVIRT_PATCH(iret):
-                       return patch_internal(VMI_CALL_IRET, len, insns);
+                       return patch_internal(VMI_CALL_IRET, len, insns, eip);
                case PARAVIRT_PATCH(irq_enable_sysexit):
-                       return patch_internal(VMI_CALL_SYSEXIT, len, insns);
+                       return patch_internal(VMI_CALL_SYSEXIT, len, insns, eip);
                default:
                        break;
        }

diff --git a/arch/i386/xen/enlighten.c b/arch/i386/xen/enlighten.c
index 9a8c118..f0c3751 100644 (file)
--- a/arch/i386/xen/enlighten.c
+++ b/arch/i386/xen/enlighten.c
@@ -842,7 +842,8 @@ void __init xen_setup_vcpu_info_placement(void)
        }
 }
 
-static unsigned xen_patch(u8 type, u16 clobbers, void *insns, unsigned len)
+static unsigned xen_patch(u8 type, u16 clobbers, void *insnbuf,
+                         unsigned long addr, unsigned len)
 {
        char *start, *end, *reloc;
        unsigned ret;
@@ -869,7 +870,7 @@ static unsigned xen_patch(u8 type, u16 clobbers, void *insns, unsigned len)
                if (start == NULL || (end-start) > len)
                        goto default_patch;
 
-               ret = paravirt_patch_insns(insns, len, start, end);
+               ret = paravirt_patch_insns(insnbuf, len, start, end);
 
                /* Note: because reloc is assigned from something that
                   appears to be an array, gcc assumes it's non-null,
@@ -877,8 +878,8 @@ static unsigned xen_patch(u8 type, u16 clobbers, void *insns, unsigned len)
                   end. */
                if (reloc > start && reloc < end) {
                        int reloc_off = reloc - start;
-                       long *relocp = (long *)(insns + reloc_off);
-                       long delta = start - (char *)insns;
+                       long *relocp = (long *)(insnbuf + reloc_off);
+                       long delta = start - (char *)addr;
 
                        *relocp += delta;
                }
@@ -886,7 +887,8 @@ static unsigned xen_patch(u8 type, u16 clobbers, void *insns, unsigned len)
 
        default_patch:
        default:
-               ret = paravirt_patch_default(type, clobbers, insns, len);
+               ret = paravirt_patch_default(type, clobbers, insnbuf,
+                                            addr, len);
                break;
        }
 

diff --git a/drivers/lguest/lguest.c b/drivers/lguest/lguest.c
index 524beea..6e135ac 100644 (file)
--- a/drivers/lguest/lguest.c
+++ b/drivers/lguest/lguest.c
@@ -936,23 +936,24 @@ static const struct lguest_insns
 /* Now our patch routine is fairly simple (based on the native one in
  * paravirt.c).  If we have a replacement, we copy it in and return how much of
  * the available space we used. */
-static unsigned lguest_patch(u8 type, u16 clobber, void *insns, unsigned len)
+static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
+                            unsigned long addr, unsigned len)
 {
        unsigned int insn_len;
 
        /* Don't do anything special if we don't have a replacement */
        if (type >= ARRAY_SIZE(lguest_insns) || !lguest_insns[type].start)
-               return paravirt_patch_default(type, clobber, insns, len);
+               return paravirt_patch_default(type, clobber, ibuf, addr, len);
 
        insn_len = lguest_insns[type].end - lguest_insns[type].start;
 
        /* Similarly if we can't fit replacement (shouldn't happen, but let's
         * be thorough). */
        if (len < insn_len)
-               return paravirt_patch_default(type, clobber, insns, len);
+               return paravirt_patch_default(type, clobber, ibuf, addr, len);
 
        /* Copy in our instructions. */
-       memcpy(insns, lguest_insns[type].start, insn_len);
+       memcpy(ibuf, lguest_insns[type].start, insn_len);
        return insn_len;
 }
 

diff --git a/include/asm-i386/paravirt.h b/include/asm-i386/paravirt.h
index 7df88be..9fa3fa9 100644 (file)
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -47,7 +47,8 @@ struct paravirt_ops
         * The patch function should return the number of bytes of code
         * generated, as we nop pad the rest in generic code.
         */
-       unsigned (*patch)(u8 type, u16 clobber, void *firstinsn, unsigned len);
+       unsigned (*patch)(u8 type, u16 clobber, void *insnbuf,
+                         unsigned long addr, unsigned len);
 
        /* Basic arch-specific setup */
        void (*arch_setup)(void);
@@ -253,13 +254,16 @@ extern struct paravirt_ops paravirt_ops;
 
 unsigned paravirt_patch_nop(void);
 unsigned paravirt_patch_ignore(unsigned len);
-unsigned paravirt_patch_call(void *target, u16 tgt_clobbers,
-                            void *site, u16 site_clobbers,
+unsigned paravirt_patch_call(void *insnbuf,
+                            const void *target, u16 tgt_clobbers,
+                            unsigned long addr, u16 site_clobbers,
                             unsigned len);
-unsigned paravirt_patch_jmp(void *target, void *site, unsigned len);
-unsigned paravirt_patch_default(u8 type, u16 clobbers, void *site, unsigned len);
+unsigned paravirt_patch_jmp(const void *target, void *insnbuf,
+                           unsigned long addr, unsigned len);
+unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf,
+                               unsigned long addr, unsigned len);
 
-unsigned paravirt_patch_insns(void *site, unsigned len,
+unsigned paravirt_patch_insns(void *insnbuf, unsigned len,
                              const char *start, const char *end);
 
 int paravirt_disable_iospace(void);