Messages in this thread Patch in this message | | | Date | Wed, 4 Mar 2015 14:56:46 -0800 | From | tip-bot for Denys Vlasenko <> | Subject | [tip:x86/asm] x86/asm/entry/64: Simplify optimistic SYSRET |
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Commit-ID: d441c1f2b73ec742c2e55be804ebc6fee130c77f Gitweb: http://git.kernel.org/tip/d441c1f2b73ec742c2e55be804ebc6fee130c77f Author: Denys Vlasenko <dvlasenk@redhat.com> AuthorDate: Thu, 26 Feb 2015 14:40:38 -0800 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 4 Mar 2015 22:50:52 +0100
x86/asm/entry/64: Simplify optimistic SYSRET
Avoid redundant load of %r11 (it is already loaded a few instructions before).
Also simplify %rsp restoration, instead of two steps:
add $0x80, %rsp mov 0x18(%rsp), %rsp
we can do a simplified single step to restore user-space RSP:
mov 0x98(%rsp), %rsp
and get the same result.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Signed-off-by: Andy Lutomirski <luto@amacapital.net> [ Clarified the changelog. ] Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Drewry <wad@chromium.org> Link: http://lkml.kernel.org/r/1aef69b346a6db0d99cdfb0f5ba83e8c985e27d7.1424989793.git.luto@amacapital.net Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/include/asm/calling.h | 3 +++ arch/x86/kernel/entry_64.S | 6 +++--- 2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/calling.h b/arch/x86/include/asm/calling.h index 3374235..f1a962f 100644 --- a/arch/x86/include/asm/calling.h +++ b/arch/x86/include/asm/calling.h @@ -176,6 +176,9 @@ For 32-bit we have the following conventions - kernel is built with .macro RESTORE_C_REGS_EXCEPT_RCX RESTORE_C_REGS_HELPER 1,0,1,1,1 .endm + .macro RESTORE_C_REGS_EXCEPT_R11 + RESTORE_C_REGS_HELPER 1,1,0,1,1 + .endm .macro RESTORE_RSI_RDI RESTORE_C_REGS_HELPER 0,0,0,0,0 .endm diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 858e94e..bc15278 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -757,9 +757,9 @@ retint_swapgs: /* return to user-space */ */ irq_return_via_sysret: CFI_REMEMBER_STATE - RESTORE_C_REGS - REMOVE_PT_GPREGS_FROM_STACK 8 - movq (RSP-RIP)(%rsp),%rsp + /* r11 is already restored (see code above) */ + RESTORE_C_REGS_EXCEPT_R11 + movq RSP(%rsp),%rsp USERGS_SYSRET64 CFI_RESTORE_STATE
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