Re: [PATCH 1/3] x86/shstk: ban ia32 sigreturn when shadow stack is enabled

[Edgecombe, Rick P]

On Thu, 2026-10-08 at 20:16 +0000, Richard Patel wrote:
> When returning from a signal via x32 or x64 rt_sigreturn, the
> shadow-stack-restore token is validated, but ia32 (rt_)sigreturn
> do not call restore_signal_shadow_stack().
> 
> With IA32_EMULATION, 'int $0x80' allows ia32 sigreturn in 64-bit
> mode, which could defeat sigreturn protection.
> 
> Refuse ia32 sigreturn by forcing a SIGSEGV instead.

How can it defeat protection? If doesn't process the shadow stack sigframe at
all, leaving the SSP where ever it was originally. What am I missing?