Re: [PATCH v3 14/16] libio/bits/stdio2-decl.h: Avoid PLT entries with _FORTIFY_SOURCE

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 2023-06-30 11:38, Frederic Berat wrote:
> 
> 
> On Fri, Jun 30, 2023 at 5:30 PM Siddhesh Poyarekar <siddhesh@gotplt.org 
> <mailto:siddhesh@gotplt.org>> wrote:
> 
> 
> 
>     On 2023-06-28 04:42, Frédéric Bérat wrote:
>      > The change is meant to avoid unwanted PLT entry for the
>     fgets_unlocked
>      > routine when _FORTIFY_SOURCE is set.
>      > ---
>      >   libio/bits/stdio2-decl.h | 2 +-
>      >   1 file changed, 1 insertion(+), 1 deletion(-)
>      >
>      > diff --git a/libio/bits/stdio2-decl.h b/libio/bits/stdio2-decl.h
>      > index 114b06d24b..d7ef7283d6 100644
>      > --- a/libio/bits/stdio2-decl.h
>      > +++ b/libio/bits/stdio2-decl.h
>      > @@ -122,7 +122,7 @@ extern size_t __fread_chk (void *__restrict
>     __ptr, size_t __ptrlen,
>      >                          FILE *__restrict __stream) __wur;
>      >
>      >   #ifdef __USE_GNU
>      > -extern char *__REDIRECT (__fgets_unlocked_alias,
>      > +extern char *__REDIRECT_FORTIFY (__fgets_unlocked_alias,
>      >                        (char *__restrict __s, int __n,
>      >                         FILE *__restrict __stream), fgets_unlocked)
>      >       __wur __attr_access ((__write_only__, 1, 2));
> 
>     Why not the same for all the others?
> 
> 
> I tend to avoid modifying things that are not strictly necessary. If 
> that happens to be needed on other aliases, then everything is ready for 
> it, but it seems I didn't stumbled upon a case where it was ...
> When you look at it, the same way I didn't create libc_hidden_def/proto 
> for all the routines here (like e.g. __fread_chk) if that wasn't needed.

So there's a slight difference; the __REDIRECT_FORTIFY is essentially an 
assurance that whenever there's an internal use of this function, the 
alias will redirect to that internal alias.  The hidden_def adds an 
alias, which is unnecessary until there's an actual internal use and the 
hidden_proto is only a complement to the hidden_def.

In that sense, I think the __REDIRECT_FORTIFY should be for all function 
aliases, not just the ones that are currently being used.

Sid