Re: [PATCH] Add _FORTIFY_SOURCE implementation documentation [BZ #28998]

[Florian Weimer <fweimer@redhat.com>]

* Siddhesh Poyarekar:

> +The @code{_FORTIFY_SOURCE} macro may be defined by users to control
> +hardening of calls into some functions in @theglibc{}.  This feature
> +needs a compiler that supports either the @code{__builtin_object_size}
> +or the @code{__builtin_dynamic_object_size} builtin functions.  When the
> +macro is defined, it enables code that validates access to buffers that
> +are passed to some functions in @theglibc to determine if they
> +are safe.  If the compiler is able to deduce the size of the buffer
> +passed to the function call but the call cannot be determined as safe,
> +it is replaced by a call to its hardened variant that does the access
> +validation at runtime.  At runtime, if the access validation check for
> +the buffer fails, the program will terminate with a @code{SIGABRT}
> +signal.

This doesn't really cover %n checks and the open checks, so it's
slightly misleading.

> +The following functions are fortified in @theglibc{}:
> +
> +@itemize @bullet
> +@item @code{asprintf}: Replaced with @code{__asprintf_chk}.
> +
> +@item @code{confstr}: Replaced with @code{__confstr_chk}.

Can we auto-generate this?

It is incomplete.  __open_2, __open64_2 and the *at variants are
missing.  FD_SET, FD_CLR, FD_ISSET, too.

Thanks,
Florian