Commit-ID: e7d6eefaaa443130079d73cd05039d90b3db7a4a Gitweb: http://git.kernel.org/tip/e7d6eefaaa443130079d73cd05039d90b3db7a4a Author: Denys Vlasenko <dvlas...@redhat.com> AuthorDate: Fri, 27 Mar 2015 11:48:17 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Tue, 31 Mar 2015 10:45:15 +0200
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 <dvlas...@redhat.com> [ Removed unnecessary comment. ] Signed-off-by: Andy Lutomirski <l...@kernel.org> Cc: Alexei Starovoitov <a...@plumgrid.com> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Borislav Petkov <b...@alien8.de> Cc: Frederic Weisbecker <fweis...@gmail.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Kees Cook <keesc...@chromium.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Oleg Nesterov <o...@redhat.com> Cc: Steven Rostedt <rost...@goodmis.org> Cc: Will Drewry <w...@chromium.org> Link: http://lkml.kernel.org/r/63da6d778f69fd0f1345d9287f6764d58be519fa.1427482099.git.l...@kernel.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/vdso/vdso32/syscall.S | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/x86/vdso/vdso32/syscall.S b/arch/x86/vdso/vdso32/syscall.S index 5415b56..6b286bb 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: -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
