On 2025-04-19 11:06:31+0200, Willy Tarreau wrote:
> On Wed, Apr 16, 2025 at 08:40:17PM +0200, Thomas Weißschuh wrote:
> > Both constructors and main() may be executed with different function
> > signatures than they are actually using.
> > This is intentional but trips up UBSAN.
> >
> > Disable the function sanitizer of UBSAN in _start_c().
> >
> > Signed-off-by: Thomas Weißschuh <li...@weissschuh.net>
> > ---
> > tools/include/nolibc/crt.h | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h
> > index
> > c4b10103bbec50f1a3a0a4562e34fdbd1b43ce6f..961cfe777c3564e705dfdd581de828b374d05b0b
> > 100644
> > --- a/tools/include/nolibc/crt.h
> > +++ b/tools/include/nolibc/crt.h
> > @@ -7,6 +7,8 @@
> > #ifndef _NOLIBC_CRT_H
> > #define _NOLIBC_CRT_H
> >
> > +#include "compiler.h"
> > +
> > char **environ __attribute__((weak));
> > const unsigned long *_auxv __attribute__((weak));
> >
> > @@ -25,6 +27,9 @@ extern void (*const __fini_array_end[])(void)
> > __attribute__((weak));
> >
> > void _start_c(long *sp);
> > __attribute__((weak,used))
> > +#if __nolibc_has_feature(undefined_behavior_sanitizer)
> > + __attribute__((no_sanitize("function")))
> > +#endif
>
> I'm wondering if it wouldn't be more reliable with:
>
> #if __nolibc_has_attribute(no_sanitize)
> __attribute__((no_sanitize("function")))
> #endif
>
> Because in the end, what you want is to always place that attribute
> whenever it's supported, no ?
That doesn't work because GCC does knows no_sanitize but not
no_sanitize("function").
Also no_sanitize is not specific to UBSAN but works for all sanitizers.
>
> > void _start_c(long *sp)
> > {
> > long argc;
>
> Willy
