lkml.org 
[lkml]   [2017]   [Aug]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [tip:x86/asm] objtool: Handle GCC stack pointer adjustment bug
From
Date
On 08/30/17 02:43, tip-bot for Josh Poimboeuf wrote:
>
> Those warnings are caused by an unusual GCC non-optimization where it
> uses an intermediate register to adjust the stack pointer. It does:
>
> lea 0x8(%rsp), %rcx
> ...
> mov %rcx, %rsp
>
> Instead of the obvious:
>
> add $0x8, %rsp
>
> It makes no sense to use an intermediate register, so I opened a GCC bug
> to track it:
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81813
>
> But it's not exactly a high-priority bug and it looks like we'll be
> stuck with this issue for a while. So for now we have to track register
> values when they're loaded with stack pointer offsets.
>

This seems like a good reason to try to extract this information from
the DWARF data *if available*?

-hpa

\
 
 \ /
  Last update: 2017-08-30 21:32    [W:0.065 / U:0.276 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site