Messages in this thread | ![/](/images/icornerl.gif) | | From | Andy Lutomirski <> | Date | Mon, 23 Mar 2015 13:38:37 -0700 | Subject | Re: [PATCH] x86: vdso32/syscall.S: do not load __USER32_DS to %ss |
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On Mon, Mar 23, 2015 at 12:37 PM, Andy Lutomirski <luto@amacapital.net> wrote: > On Mon, Mar 23, 2015 at 9:47 AM, Denys Vlasenko <dvlasenk@redhat.com> wrote: >> This vDSO code only gets used by 64-bit kernel, >> not 32-bit. In 64-bit kernels, data segment is the same >> for 32-bit and 64-bit userspace, and SYSRET insn does load %ss >> with its selector. No need to repeat it by hand. Segment loads >> are somewhat expensive: tens of cycles. >> >> 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 >> --- >> >> Patch was run-tested. > > Applied, thanks.
Actually, I want to remove the added comment in the code. I don't see why we should have a specific comment about SS and not about, say, CS, ESP, or anything else. OK?
> > --Andy
-- Andy Lutomirski AMA Capital Management, LLC
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