From: Joerg Roedel Date: Wed, 18 Jul 2018 09:40:49 +0000 (+0200) Subject: x86/entry/32: Add PTI cr3 switch to non-NMI entry/exit points X-Git-Tag: v4.19~463^2~42 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=e464fb9f241ddf46815b31ca594af96f2699a78e;p=platform%2Fkernel%2Flinux-rpi.git x86/entry/32: Add PTI cr3 switch to non-NMI entry/exit points Add unconditional cr3 switches between user and kernel cr3 to all non-NMI entry and exit points. Signed-off-by: Joerg Roedel Signed-off-by: Thomas Gleixner Tested-by: Pavel Machek Cc: "H . Peter Anvin" Cc: linux-mm@kvack.org Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Dave Hansen Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Jiri Kosina Cc: Boris Ostrovsky Cc: Brian Gerst Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Cc: Andrea Arcangeli Cc: Waiman Long Cc: "David H . Gutteridge" Cc: joro@8bytes.org Link: https://lkml.kernel.org/r/1531906876-13451-13-git-send-email-joro@8bytes.org --- diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index dbf7d61..60b28df 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -77,6 +77,8 @@ #endif .endm +#define PTI_SWITCH_MASK (1 << PAGE_SHIFT) + /* * User gs save/restore * @@ -154,6 +156,33 @@ #endif /* CONFIG_X86_32_LAZY_GS */ +/* Unconditionally switch to user cr3 */ +.macro SWITCH_TO_USER_CR3 scratch_reg:req + ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI + + movl %cr3, \scratch_reg + orl $PTI_SWITCH_MASK, \scratch_reg + movl \scratch_reg, %cr3 +.Lend_\@: +.endm + +/* + * Switch to kernel cr3 if not already loaded and return current cr3 in + * \scratch_reg + */ +.macro SWITCH_TO_KERNEL_CR3 scratch_reg:req + ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI + movl %cr3, \scratch_reg + /* Test if we are already on kernel CR3 */ + testl $PTI_SWITCH_MASK, \scratch_reg + jz .Lend_\@ + andl $(~PTI_SWITCH_MASK), \scratch_reg + movl \scratch_reg, %cr3 + /* Return original CR3 in \scratch_reg */ + orl $PTI_SWITCH_MASK, \scratch_reg +.Lend_\@: +.endm + .macro SAVE_ALL pt_regs_ax=%eax switch_stacks=0 cld PUSH_GS @@ -283,7 +312,6 @@ #endif /* CONFIG_X86_ESPFIX32 */ .endm - /* * Called with pt_regs fully populated and kernel segments loaded, * so we can access PER_CPU and use the integer registers. @@ -296,11 +324,19 @@ */ #define CS_FROM_ENTRY_STACK (1 << 31) +#define CS_FROM_USER_CR3 (1 << 30) .macro SWITCH_TO_KERNEL_STACK ALTERNATIVE "", "jmp .Lend_\@", X86_FEATURE_XENPV + SWITCH_TO_KERNEL_CR3 scratch_reg=%eax + + /* + * %eax now contains the entry cr3 and we carry it forward in + * that register for the time this macro runs + */ + /* Are we on the entry stack? Bail out if not! */ movl PER_CPU_VAR(cpu_entry_area), %ecx addl $CPU_ENTRY_AREA_entry_stack + SIZEOF_entry_stack, %ecx @@ -370,7 +406,8 @@ * but switch back to the entry-stack again when we approach * iret and return to the interrupted code-path. This usually * happens when we hit an exception while restoring user-space - * segment registers on the way back to user-space. + * segment registers on the way back to user-space or when the + * sysenter handler runs with eflags.tf set. * * When we switch to the task-stack here, we can't trust the * contents of the entry-stack anymore, as the exception handler @@ -387,6 +424,7 @@ * * %esi: Entry-Stack pointer (same as %esp) * %edi: Top of the task stack + * %eax: CR3 on kernel entry */ /* Calculate number of bytes on the entry stack in %ecx */ @@ -403,6 +441,14 @@ orl $CS_FROM_ENTRY_STACK, PT_CS(%esp) /* + * Test the cr3 used to enter the kernel and add a marker + * so that we can switch back to it before iret. + */ + testl $PTI_SWITCH_MASK, %eax + jz .Lcopy_pt_regs_\@ + orl $CS_FROM_USER_CR3, PT_CS(%esp) + + /* * %esi and %edi are unchanged, %ecx contains the number of * bytes to copy. The code at .Lcopy_pt_regs_\@ will allocate * the stack-frame on task-stack and copy everything over @@ -468,7 +514,7 @@ /* * This macro handles the case when we return to kernel-mode on the iret - * path and have to switch back to the entry stack. + * path and have to switch back to the entry stack and/or user-cr3 * * See the comments below the .Lentry_from_kernel_\@ label in the * SWITCH_TO_KERNEL_STACK macro for more details. @@ -514,6 +560,18 @@ /* Safe to switch to entry-stack now */ movl %ebx, %esp + /* + * We came from entry-stack and need to check if we also need to + * switch back to user cr3. + */ + testl $CS_FROM_USER_CR3, PT_CS(%esp) + jz .Lend_\@ + + /* Clear marker from stack-frame */ + andl $(~CS_FROM_USER_CR3), PT_CS(%esp) + + SWITCH_TO_USER_CR3 scratch_reg=%eax + .Lend_\@: .endm /* @@ -707,7 +765,20 @@ ENTRY(xen_sysenter_target) * 0(%ebp) arg6 */ ENTRY(entry_SYSENTER_32) + /* + * On entry-stack with all userspace-regs live - save and + * restore eflags and %eax to use it as scratch-reg for the cr3 + * switch. + */ + pushfl + pushl %eax + SWITCH_TO_KERNEL_CR3 scratch_reg=%eax + popl %eax + popfl + + /* Stack empty again, switch to task stack */ movl TSS_entry2task_stack(%esp), %esp + .Lsysenter_past_esp: pushl $__USER_DS /* pt_regs->ss */ pushl %ebp /* pt_regs->sp (stashed in bp) */ @@ -786,6 +857,9 @@ ENTRY(entry_SYSENTER_32) /* Switch to entry stack */ movl %eax, %esp + /* Now ready to switch the cr3 */ + SWITCH_TO_USER_CR3 scratch_reg=%eax + /* * Restore all flags except IF. (We restore IF separately because * STI gives a one-instruction window in which we won't be interrupted, @@ -866,7 +940,11 @@ restore_all: .Lrestore_all_notrace: CHECK_AND_APPLY_ESPFIX .Lrestore_nocheck: - RESTORE_REGS 4 # skip orig_eax/error_code + /* Switch back to user CR3 */ + SWITCH_TO_USER_CR3 scratch_reg=%eax + + /* Restore user state */ + RESTORE_REGS pop=4 # skip orig_eax/error_code .Lirq_return: /* * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on IRET core serialization