Re: [PATCH 1/2 v2] x86/asm/entry/64: better label name, fix comments

[Borislav Petkov]

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@xxxxxxxxxx>
> CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
> CC: Ingo Molnar <mingo@xxxxxxxxxx>
> CC: Borislav Petkov <bp@xxxxxxxxx>
> CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
> CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> CC: Oleg Nesterov <oleg@xxxxxxxxxx>
> CC: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> CC: Alexei Starovoitov <ast@xxxxxxxxxxxx>
> CC: Will Drewry <wad@xxxxxxxxxxxx>
> CC: Kees Cook <keescook@xxxxxxxxxxxx>
> CC: x86@xxxxxxxxxx
> CC: linux-kernel@xxxxxxxxxxxxxxx
> ---
> 
> 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@xxxxxxx>

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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