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authorPeter Zijlstra <peterz@infradead.org>2022-05-06 15:14:34 +0300
committerBorislav Petkov <bp@suse.de>2022-05-06 16:57:02 +0300
commit8c42819b61b8340cff0643e65b5ce6a4144ab155 (patch)
tree004465a4e2c22446f5396768f49c5f197720c71f
parentd205222eb6a8e5e70c21200beb81c6e19ec211d6 (diff)
downloadlinux-8c42819b61b8340cff0643e65b5ce6a4144ab155.tar.xz
x86/entry: Use PUSH_AND_CLEAR_REGS for compat
Since the upper regs don't exist for ia32 code, preserving them doesn't hurt and it simplifies the code. This doesn't add any attack surface that would not already be available through INT80. Notably: - 32bit SYSENTER: didn't clear si, dx, cx. - 32bit SYSCALL, INT80: *do* clear si since the C functions don't take a second argument. - 64bit: didn't clear si since the C functions take a second argument; except the error_entry path might have only one argument, so clearing si was missing here. 32b SYSENTER should be clearing all those 3 registers, nothing uses them and selftests pass. Unconditionally clear rsi since it simplifies code. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Borislav Petkov <bp@suse.de> Link: https://lore.kernel.org/r/20220506121631.293889636@infradead.org
-rw-r--r--arch/x86/entry/calling.h1
-rw-r--r--arch/x86/entry/entry_64_compat.S87
2 files changed, 4 insertions, 84 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index a4c061fb7c6e..debbe94aa3db 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -99,6 +99,7 @@ For 32-bit we have the following conventions - kernel is built with
* well before they could be put to use in a speculative execution
* gadget.
*/
+ xorl %esi, %esi /* nospec si */
xorl %edx, %edx /* nospec dx */
xorl %ecx, %ecx /* nospec cx */
xorl %r8d, %r8d /* nospec r8 */
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index d743eaa19d9b..ed2be3615b50 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -83,32 +83,7 @@ SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL)
movl %eax, %eax
pushq %rax /* pt_regs->orig_ax */
- pushq %rdi /* pt_regs->di */
- pushq %rsi /* pt_regs->si */
- pushq %rdx /* pt_regs->dx */
- pushq %rcx /* pt_regs->cx */
- pushq $-ENOSYS /* pt_regs->ax */
- pushq $0 /* pt_regs->r8 = 0 */
- xorl %r8d, %r8d /* nospec r8 */
- pushq $0 /* pt_regs->r9 = 0 */
- xorl %r9d, %r9d /* nospec r9 */
- pushq $0 /* pt_regs->r10 = 0 */
- xorl %r10d, %r10d /* nospec r10 */
- pushq $0 /* pt_regs->r11 = 0 */
- xorl %r11d, %r11d /* nospec r11 */
- pushq %rbx /* pt_regs->rbx */
- xorl %ebx, %ebx /* nospec rbx */
- pushq %rbp /* pt_regs->rbp (will be overwritten) */
- xorl %ebp, %ebp /* nospec rbp */
- pushq $0 /* pt_regs->r12 = 0 */
- xorl %r12d, %r12d /* nospec r12 */
- pushq $0 /* pt_regs->r13 = 0 */
- xorl %r13d, %r13d /* nospec r13 */
- pushq $0 /* pt_regs->r14 = 0 */
- xorl %r14d, %r14d /* nospec r14 */
- pushq $0 /* pt_regs->r15 = 0 */
- xorl %r15d, %r15d /* nospec r15 */
-
+ PUSH_AND_CLEAR_REGS rax=$-ENOSYS
UNWIND_HINT_REGS
cld
@@ -225,35 +200,7 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_safe_stack, SYM_L_GLOBAL)
SYM_INNER_LABEL(entry_SYSCALL_compat_after_hwframe, SYM_L_GLOBAL)
movl %eax, %eax /* discard orig_ax high bits */
pushq %rax /* pt_regs->orig_ax */
- pushq %rdi /* pt_regs->di */
- pushq %rsi /* pt_regs->si */
- xorl %esi, %esi /* nospec si */
- pushq %rdx /* pt_regs->dx */
- xorl %edx, %edx /* nospec dx */
- pushq %rbp /* pt_regs->cx (stashed in bp) */
- xorl %ecx, %ecx /* nospec cx */
- pushq $-ENOSYS /* pt_regs->ax */
- pushq $0 /* pt_regs->r8 = 0 */
- xorl %r8d, %r8d /* nospec r8 */
- pushq $0 /* pt_regs->r9 = 0 */
- xorl %r9d, %r9d /* nospec r9 */
- pushq $0 /* pt_regs->r10 = 0 */
- xorl %r10d, %r10d /* nospec r10 */
- pushq $0 /* pt_regs->r11 = 0 */
- xorl %r11d, %r11d /* nospec r11 */
- pushq %rbx /* pt_regs->rbx */
- xorl %ebx, %ebx /* nospec rbx */
- pushq %rbp /* pt_regs->rbp (will be overwritten) */
- xorl %ebp, %ebp /* nospec rbp */
- pushq $0 /* pt_regs->r12 = 0 */
- xorl %r12d, %r12d /* nospec r12 */
- pushq $0 /* pt_regs->r13 = 0 */
- xorl %r13d, %r13d /* nospec r13 */
- pushq $0 /* pt_regs->r14 = 0 */
- xorl %r14d, %r14d /* nospec r14 */
- pushq $0 /* pt_regs->r15 = 0 */
- xorl %r15d, %r15d /* nospec r15 */
-
+ PUSH_AND_CLEAR_REGS rax=$-ENOSYS
UNWIND_HINT_REGS
movq %rsp, %rdi
@@ -380,35 +327,7 @@ SYM_CODE_START(entry_INT80_compat)
pushq 0*8(%rax) /* regs->orig_ax */
.Lint80_keep_stack:
- pushq %rdi /* pt_regs->di */
- pushq %rsi /* pt_regs->si */
- xorl %esi, %esi /* nospec si */
- pushq %rdx /* pt_regs->dx */
- xorl %edx, %edx /* nospec dx */
- pushq %rcx /* pt_regs->cx */
- xorl %ecx, %ecx /* nospec cx */
- pushq $-ENOSYS /* pt_regs->ax */
- pushq %r8 /* pt_regs->r8 */
- xorl %r8d, %r8d /* nospec r8 */
- pushq %r9 /* pt_regs->r9 */
- xorl %r9d, %r9d /* nospec r9 */
- pushq %r10 /* pt_regs->r10*/
- xorl %r10d, %r10d /* nospec r10 */
- pushq %r11 /* pt_regs->r11 */
- xorl %r11d, %r11d /* nospec r11 */
- pushq %rbx /* pt_regs->rbx */
- xorl %ebx, %ebx /* nospec rbx */
- pushq %rbp /* pt_regs->rbp */
- xorl %ebp, %ebp /* nospec rbp */
- pushq %r12 /* pt_regs->r12 */
- xorl %r12d, %r12d /* nospec r12 */
- pushq %r13 /* pt_regs->r13 */
- xorl %r13d, %r13d /* nospec r13 */
- pushq %r14 /* pt_regs->r14 */
- xorl %r14d, %r14d /* nospec r14 */
- pushq %r15 /* pt_regs->r15 */
- xorl %r15d, %r15d /* nospec r15 */
-
+ PUSH_AND_CLEAR_REGS rax=$-ENOSYS
UNWIND_HINT_REGS
cld