From: Peter Zijlstra peterz@infradead.org
commit 1b331eeea7b8676fc5dbdf80d0a07e41be226177 upstream.
Yes, r11 and rcx have been restored previously, but since they're being popped anyway (into rsi) might as well pop them into their own regs -- setting them to the value they already are.
Less magical code.
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Borislav Petkov bp@suse.de Link: https://lore.kernel.org/r/20220506121631.365070674@infradead.org [bwh: Backported to 5.10: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/entry/calling.h | 10 +--------- arch/x86/entry/entry_64.S | 3 +-- 2 files changed, 2 insertions(+), 11 deletions(-)
--- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -146,27 +146,19 @@ For 32-bit we have the following convent
.endm
-.macro POP_REGS pop_rdi=1 skip_r11rcx=0 +.macro POP_REGS pop_rdi=1 popq %r15 popq %r14 popq %r13 popq %r12 popq %rbp popq %rbx - .if \skip_r11rcx - popq %rsi - .else popq %r11 - .endif popq %r10 popq %r9 popq %r8 popq %rax - .if \skip_r11rcx - popq %rsi - .else popq %rcx - .endif popq %rdx popq %rsi .if \pop_rdi --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -191,8 +191,7 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_h * perf profiles. Nothing jumps here. */ syscall_return_via_sysret: - /* rcx and r11 are already restored (see code above) */ - POP_REGS pop_rdi=0 skip_r11rcx=1 + POP_REGS pop_rdi=0
/* * Now all regs are restored except RSP and RDI.