Messages in this thread Patch in this message | | | From | Andy Lutomirski <> | Subject | [PATCH 15/16] x86: entry.S: simplify optimistic SYSRET | Date | Thu, 26 Feb 2015 14:40:38 -0800 |
| |
From: Denys Vlasenko <dvlasenk@redhat.com>
Avoid redundant load of %r11 (it is already loaded a few instructions before). Do not needlessly increment %rsp - we are going to return to userspace via SYSRET, this insn doesn't use stack for return.
Changes since v1: added a comment
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> CC: Linus Torvalds <torvalds@linux-foundation.org> CC: Steven Rostedt <rostedt@goodmis.org> CC: Ingo Molnar <mingo@kernel.org> CC: Borislav Petkov <bp@alien8.de> CC: "H. Peter Anvin" <hpa@zytor.com> CC: Andy Lutomirski <luto@amacapital.net> CC: Oleg Nesterov <oleg@redhat.com> CC: Frederic Weisbecker <fweisbec@gmail.com> CC: Alexei Starovoitov <ast@plumgrid.com> CC: Will Drewry <wad@chromium.org> CC: Kees Cook <keescook@chromium.org> CC: x86@kernel.org CC: linux-kernel@vger.kernel.org Message-Id: <1424824222-10856-1-git-send-email-dvlasenk@redhat.com> Signed-off-by: Andy Lutomirski <luto@amacapital.net> --- 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 337423590b08..f1a962ff7ddf 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 6fcf5d1e36c9..4670fcdb5150 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 -- 2.1.0
| |