From: Denys Vlasenko <[email protected]> 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 <[email protected]> CC: Linus Torvalds <[email protected]> CC: Steven Rostedt <[email protected]> CC: Ingo Molnar <[email protected]> CC: Borislav Petkov <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: Andy Lutomirski <[email protected]> CC: Oleg Nesterov <[email protected]> CC: Frederic Weisbecker <[email protected]> CC: Alexei Starovoitov <[email protected]> CC: Will Drewry <[email protected]> CC: Kees Cook <[email protected]> CC: [email protected] CC: [email protected] Message-Id: <[email protected]> Signed-off-by: Andy Lutomirski <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
