Messages in this thread | | | Date | Thu, 26 Mar 2015 12:45:39 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH 1/2 v2] x86/asm/entry/64: better label name, fix comments |
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On Wed, Mar 25, 2015 at 07:20:28PM +0100, Denys Vlasenko wrote: > A named label "ret_from_sys_call" implies that there are jumps > to this location from elsewhere, as happens with many other labels > in this file. > But this label is used only by the JMP a few insns above. > To make that obvious, use local numeric label instead. > > Do the same in the second copy of the syscall table dispatch code, > it has a similar JMP which skips the CALL. > > Improve comments: > > "and return regs->ax" isn't too informative. We always return regs->ax. > > The comment suggesting that it'd be cool to use rip relative addressing for CALL > is deleted. It's unclear why that would be an improvement - we aren't striving > to use position-independent code here. PIC code here would require something like > LEA sys_call_table(%rip),reg + CALL *(reg,%rax*8)... > > "iret frame is also incomplete" is no longer true, fix that too. > > 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 > --- > > Changes in v2: gave "jmp 1f" treatment to the second jump. > > arch/x86/kernel/entry_64.S | 15 ++++++++------- > 1 file changed, 8 insertions(+), 7 deletions(-)
Acked-by: Borislav Petkov <bp@suse.de>
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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