lkml.org 
[lkml]   [2020]   [Apr]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 5/7] x86/speculation: Annotate intra-function calls

On 4/3/20 6:16 PM, Josh Poimboeuf wrote:
> On Fri, Apr 03, 2020 at 11:05:38AM -0500, Josh Poimboeuf wrote:
>> On Thu, Apr 02, 2020 at 10:22:18AM +0200, Alexandre Chartre wrote:
>>> .macro RETPOLINE_JMP reg:req
>>> - call .Ldo_rop_\@
>>> + INTRA_FUNCTION_CALL .Ldo_rop_\@
>>> .Lspec_trap_\@:
>>> pause
>>> lfence
>>> @@ -102,7 +116,7 @@
>>> .Ldo_retpoline_jmp_\@:
>>> RETPOLINE_JMP \reg
>>> .Ldo_call_\@:
>>> - call .Ldo_retpoline_jmp_\@
>>> + INTRA_FUNCTION_CALL .Ldo_retpoline_jmp_\@
>>> .endm
>>
>> There's a catch: this is part of an alternative. Which means if
>> X86_FEATURE_RETPOLINE isn't set at runtime, then the retpoline won't be
>> there and the ORC data will be wrong.
>>
>> In fact objtool should probably be made smart enough to warn about this
>> situation, when an alternative changes the stack state.
>>
>> The only way I can think of to fix this is to have ORC alternatives :-/

So that means that any alternative that does a stack manipulation isn't
currently supported?

alex.

> Or they could be converted to use static branches instead of
> alternatives.
>

\
 
 \ /
  Last update: 2020-04-03 19:14    [W:0.123 / U:0.752 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site