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| author | Denys Vlasenko <dvlasenk@redhat.com> | 2015-03-27 11:48:17 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-03-31 10:45:15 +0200 |
| commit | e7d6eefaaa443130079d73cd05039d90b3db7a4a (patch) | |
| tree | a4d3bc5bb4690e7d40a26fd4c113c60e1a4bf1ce /arch/x86/vdso | |
| parent | 0a4f59d6e09ef16fbb7d213cfa1bf472c7845fda (diff) | |
| download | blackbird-op-linux-e7d6eefaaa443130079d73cd05039d90b3db7a4a.tar.gz blackbird-op-linux-e7d6eefaaa443130079d73cd05039d90b3db7a4a.zip | |
x86/vdso32/syscall.S: Do not load __USER32_DS to %ss
This vDSO code only gets used by 64-bit kernels, not 32-bit ones.
On 64-bit kernels, the data segment is the same for 32-bit and
64-bit userspace, and the SYSRET instruction loads %ss with its
selector.
So there's no need to repeat it by hand. Segment loads are somewhat
expensive: tens of cycles.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
[ Removed unnecessary comment. ]
Signed-off-by: Andy Lutomirski <luto@kernel.org>
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/63da6d778f69fd0f1345d9287f6764d58be519fa.1427482099.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/vdso')
| -rw-r--r-- | arch/x86/vdso/vdso32/syscall.S | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/arch/x86/vdso/vdso32/syscall.S b/arch/x86/vdso/vdso32/syscall.S index 5415b5613d55..6b286bb5251c 100644 --- a/arch/x86/vdso/vdso32/syscall.S +++ b/arch/x86/vdso/vdso32/syscall.S @@ -19,8 +19,6 @@ __kernel_vsyscall: .Lpush_ebp: movl %ecx, %ebp syscall - movl $__USER32_DS, %ecx - movl %ecx, %ss movl %ebp, %ecx popl %ebp .Lpop_ebp: |
