Re: [tip:x86/asm] objtool: Handle GCC stack pointer adjustment bug

2017-08-30 Thread Josh Poimboeuf
On Wed, Aug 30, 2017 at 04:39:42PM -0700, H. Peter Anvin wrote: > On 08/30/17 13:14, Josh Poimboeuf wrote: > > On Wed, Aug 30, 2017 at 12:23:24PM -0700, H. Peter Anvin wrote: > >> On 08/30/17 02:43, tip-bot for Josh Poimboeuf wrote: > >>> > >>> Those warnings are caused by an unusual GCC non-optimi

Re: [tip:x86/asm] objtool: Handle GCC stack pointer adjustment bug

2017-08-30 Thread H. Peter Anvin
On 08/30/17 13:14, Josh Poimboeuf wrote: > On Wed, Aug 30, 2017 at 12:23:24PM -0700, H. Peter Anvin wrote: >> 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 poin

Re: [tip:x86/asm] objtool: Handle GCC stack pointer adjustment bug

2017-08-30 Thread Josh Poimboeuf
On Wed, Aug 30, 2017 at 12:23:24PM -0700, H. Peter Anvin wrote: > 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: > > > > lea0x8(%rsp),

Re: [tip:x86/asm] objtool: Handle GCC stack pointer adjustment bug

2017-08-30 Thread H. Peter Anvin
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: > > lea0x8(%rsp), %rcx > ... > mov%rcx, %rsp > > Instead of the obvious: > > add