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Subject[tip: x86/asm] x86/entry: Simplify entry_INT80_compat()
The following commit has been merged into the x86/asm branch of tip:

Commit-ID: d205222eb6a8e5e70c21200beb81c6e19ec211d6
Gitweb: https://git.kernel.org/tip/d205222eb6a8e5e70c21200beb81c6e19ec211d6
Author: Linus Torvalds <torvalds@linux-foundation.org>
AuthorDate: Fri, 06 May 2022 14:14:33 +02:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Fri, 06 May 2022 15:49:51 +02:00

x86/entry: Simplify entry_INT80_compat()

Instead of playing silly games with rdi, use rax for simpler and more
consistent code.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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/20220506121631.221072885@infradead.org
---
arch/x86/entry/entry_64_compat.S | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index c5aeb08..d743eaa 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -362,26 +362,25 @@ SYM_CODE_START(entry_INT80_compat)

/* switch to thread stack expects orig_ax and rdi to be pushed */
pushq %rax /* pt_regs->orig_ax */
- pushq %rdi /* pt_regs->di */

/* Need to switch before accessing the thread stack. */
- SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi
+ SWITCH_TO_KERNEL_CR3 scratch_reg=%rax

/* In the Xen PV case we already run on the thread stack. */
ALTERNATIVE "", "jmp .Lint80_keep_stack", X86_FEATURE_XENPV

- movq %rsp, %rdi
+ movq %rsp, %rax
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp

- pushq 6*8(%rdi) /* regs->ss */
- pushq 5*8(%rdi) /* regs->rsp */
- pushq 4*8(%rdi) /* regs->eflags */
- pushq 3*8(%rdi) /* regs->cs */
- pushq 2*8(%rdi) /* regs->ip */
- pushq 1*8(%rdi) /* regs->orig_ax */
- pushq (%rdi) /* pt_regs->di */
+ pushq 5*8(%rax) /* regs->ss */
+ pushq 4*8(%rax) /* regs->rsp */
+ pushq 3*8(%rax) /* regs->eflags */
+ pushq 2*8(%rax) /* regs->cs */
+ pushq 1*8(%rax) /* regs->ip */
+ 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 */
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