linux/arch/x86
Denys Vlasenko 29722cd4ef x86/asm/entry/64: Save R11 into pt_regs->flags on SYSCALL64 fastpath
Before this patch, R11 was saved in pt_regs->r11.

Which looks natural, but requires messy shuffling to/from iret
frame whenever ptrace or e.g. sys_iopl() wants to modify flags -
because that's how this register is used by SYSCALL/SYSRET.

This patch saves R11 in pt_regs->flags, and uses that value for
the SYSRET64 instruction. Shuffling is eliminated.

FIXUP/RESTORE_TOP_OF_STACK are simplified.

stub_iopl is no longer needed: pt_regs->flags needs no fixing up.

Testing shows that syscall fast path is ~54.3 ns before
and after the patch (on 2.7 GHz Sandy Bridge CPU).

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
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: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1425926364-9526-2-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-10 13:56:10 +01:00
..
boot Linux 4.0-rc2 2015-03-04 06:35:43 +01:00
configs x86/kconfig/defconfig: Enable CONFIG_FHANDLE=y 2014-12-08 12:04:17 +01:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2015-02-14 09:47:01 -08:00
ia32 x86/asm/entry: Rename 'init_tss' to 'cpu_tss' 2015-03-06 08:32:58 +01:00
include x86/asm/entry/64: Save R11 into pt_regs->flags on SYSCALL64 fastpath 2015-03-10 13:56:10 +01:00
kernel x86/asm/entry/64: Save R11 into pt_regs->flags on SYSCALL64 fastpath 2015-03-10 13:56:10 +01:00
kvm Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-02-16 14:58:12 -08:00
lguest x86/asm/entry: Add this_cpu_sp0() to read sp0 for the current cpu 2015-03-06 08:32:57 +01:00
lib x86/asm: Optimize unnecessarily wide TEST instructions 2015-03-07 11:12:43 +01:00
math-emu
mm Linux 4.0-rc2 2015-03-04 06:35:43 +01:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-12-10 15:48:20 -05:00
oprofile percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t 2014-08-28 08:58:57 -04:00
pci ACPI and power management updates for v3.20-rc1 2015-02-10 15:09:41 -08:00
platform Merge branch 'linus' into x86/urgent, to merge dependent patch 2015-02-28 08:03:10 +01:00
power x86/asm/entry: Rename 'init_tss' to 'cpu_tss' 2015-03-06 08:32:58 +01:00
purgatory Merge branches 'x86-build-for-linus', 'x86-cleanups-for-linus' and 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-10 12:35:46 -08:00
realmode Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-02-16 14:58:12 -08:00
syscalls x86/compat: Remove sys32_vm86_warning 2015-03-04 06:16:21 +01:00
tools x86, build: replace Perl script with Shell script 2015-01-26 13:37:18 -08:00
um x86/asm: Use alternative_2() in rdtsc_barrier() 2015-02-23 13:44:17 +01:00
vdso x86_64: add KASan support 2015-02-13 21:21:41 -08:00
video
xen x86/asm/entry: Add this_cpu_sp0() to read sp0 for the current cpu 2015-03-06 08:32:57 +01:00
.gitignore x86/build: Add arch/x86/purgatory/ make generated files to gitignore 2014-10-09 09:29:46 +02:00
Kbuild kexec: create a new config option CONFIG_KEXEC_FILE for new syscall 2014-08-29 16:28:16 -07:00
Kconfig Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-02-21 11:12:07 -08:00
Kconfig.cpu
Kconfig.debug x86/intel/quark: Add Isolated Memory Regions for Quark X1000 2015-02-18 23:22:47 +01:00
Makefile x86/raid6: correctly check for assembler capabilities 2015-02-04 08:35:51 +11:00
Makefile.um kbuild: do not add $(call ...) to invoke cc-version or cc-fullversion 2015-01-09 17:25:44 +01:00
Makefile_32.cpu