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Re: RFC: Shadow Stack support in glibc

Szabolcs Nagy <> writes:

> that's just the first part of the jmp_buf struct,
> what matters is the size of jmp_buf which is
> struct __jmp_buf_tag
>   {
>     /* NOTE: The machine-dependent definitions of `__sigsetjmp'
>        assume that a `jmp_buf' begins with a `__jmp_buf' and that
>        `__mask_was_saved' follows it.  Do not move these members
>        or add others before it.  */
>     __jmp_buf __jmpbuf;		/* Calling environment.  */
>     int __mask_was_saved;	/* Saved the signal mask?  */
>     __sigset_t __saved_mask;	/* Saved signal mask.  */
>   };
> typedef struct __jmp_buf_tag jmp_buf[1];
> and only the first few bytes of __saved_mask is used on linux,
> there is lot of free space there, it's just not setup for
> target specific tinkering currently.

Yes, please investigate if you can make this work by stealing some
bits.  setjmp/longjmp isn't performance-critical, and if we can avoid
the ABI bump, I'd appreciate that very much.


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