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Message-ID: <20220408223827.GR2731@worktop.programming.kicks-ass.net>
Date: Sat, 9 Apr 2022 00:38:27 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: x86@...nel.org, Lai Jiangshan <jiangshanlai@...il.com>,
Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Andrew Cooper <Andrew.Cooper3@...rix.com>,
linux-kernel@...r.kernel.org
Subject: [RFC][PATCH] x86: PUSH_AND_CLEAR_REGS_COMPAT
How insane?
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
arch/x86/entry/calling.h | 25 ++++++++----
arch/x86/entry/entry_64_compat.S | 87 ++--------------------------------------
2 files changed, 21 insertions(+), 91 deletions(-)
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index a4c061fb7c6e..7f938704da59 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -63,13 +63,15 @@ For 32-bit we have the following conventions - kernel is built with
* for assembly code:
*/
-.macro PUSH_REGS rdx=%rdx rax=%rax save_ret=0
+.macro PUSH_REGS rdx=%rdx rax=%rax save_ret=0 save_rdi=1
.if \save_ret
pushq %rsi /* pt_regs->si */
movq 8(%rsp), %rsi /* temporarily store the return address in %rsi */
movq %rdi, 8(%rsp) /* pt_regs->di (overwriting original return address) */
.else
+ .if \save_rdi
pushq %rdi /* pt_regs->di */
+ .endif
pushq %rsi /* pt_regs->si */
.endif
pushq \rdx /* pt_regs->dx */
@@ -92,7 +94,7 @@ For 32-bit we have the following conventions - kernel is built with
.endif
.endm
-.macro CLEAR_REGS
+.macro CLEAR_REGS_lo
/*
* Sanitize registers of values that a speculation attack might
* otherwise want to exploit. The lower registers are likely clobbered
@@ -101,22 +103,31 @@ For 32-bit we have the following conventions - kernel is built with
*/
xorl %edx, %edx /* nospec dx */
xorl %ecx, %ecx /* nospec cx */
+ xorl %ebx, %ebx /* nospec rbx */
+ xorl %ebp, %ebp /* nospec rbp */
+.endm
+
+.macro CLEAR_REGS_hi
xorl %r8d, %r8d /* nospec r8 */
xorl %r9d, %r9d /* nospec r9 */
xorl %r10d, %r10d /* nospec r10 */
xorl %r11d, %r11d /* nospec r11 */
- xorl %ebx, %ebx /* nospec rbx */
- xorl %ebp, %ebp /* nospec rbp */
xorl %r12d, %r12d /* nospec r12 */
xorl %r13d, %r13d /* nospec r13 */
xorl %r14d, %r14d /* nospec r14 */
xorl %r15d, %r15d /* nospec r15 */
+.endm
+.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0 save_rdi=1
+ PUSH_REGS rdx=\rdx, rax=\rax, save_ret=\save_ret save_rdi=\save_rdi
+ CLEAR_REGS_lo
+ CLEAR_REGS_hi
.endm
-.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0
- PUSH_REGS rdx=\rdx, rax=\rax, save_ret=\save_ret
- CLEAR_REGS
+.macro PUSH_AND_CLEAR_REGS_COMPAT rdx=%rdx rax=%rax save_ret=0 save_rdi=1
+ CLEAR_REGS_hi
+ PUSH_REGS rdx=\rdx, rax=\rax, save_ret=\save_ret save_rdi=\save_rdi
+ CLEAR_REGS_lo
.endm
.macro POP_REGS pop_rdi=1 skip_r11rcx=0
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 4fdb007cddbd..44a3eaf15de6 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 $0 /* pt_regs->r15 = 0 */
- xorl %r15d, %r15d /* nospec r15 */
-
+ PUSH_AND_CLEAR_REGS_COMPAT rax=$-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 $0 /* pt_regs->r15 = 0 */
- xorl %r15d, %r15d /* nospec r15 */
-
+ PUSH_AND_CLEAR_REGS_COMPAT rax=$-ENOSYS
UNWIND_HINT_REGS
movq %rsp, %rdi
@@ -381,35 +328,7 @@ SYM_CODE_START(entry_INT80_compat)
pushq 1*8(%rdi) /* regs->orig_ax */
pushq (%rdi) /* pt_regs->di */
.Lint80_keep_stack:
-
- 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 save_rdi=0
UNWIND_HINT_REGS
cld
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