Re: [patch 00/38] x86/retbleed: Call depth tracking mitigation

[Peter Zijlstra]

On Wed, Jul 20, 2022 at 10:09:37AM -0700, Linus Torvalds wrote:
> On Wed, Jul 20, 2022 at 9:57 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> >
> > [    2.488712] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:558 apply_returns+0xa3/0x1ec
> 
> That warning is kind of annoying, in how it doesn't actually give any
> information about where the problem is.
> 
> I do note that we only fix up JMP32_INSN_OPCODE, and I wonder if we
> have a "jmp __x86_return_thunk" that is close enough to the return
> thunk that it actually uses a byte offset?
> 
> But that WARN_ON_ONCE() should probably be changed to actually give
> some information about where the problem is.

There's a patch for that:

  https://lkml.kernel.org/r/20220713213819.460771-1-keescook@xxxxxxxxxxxx

it seems to have gotten lost, let me go queue that.