Re: [PATCH 03/11] libio: Add fortify wrapper for internal __snprintf

[Florian Weimer <fweimer@redhat.com>]

* Adhemerval Zanella Netto:

> On 09/02/24 12:25, Florian Weimer wrote:
>> ---
>>  debug/snprintf_chk.c  | 1 +
>>  include/bits/stdio2.h | 9 +++++++++
>>  include/stdio.h       | 1 +
>>  3 files changed, 11 insertions(+)
>> 
>> diff --git a/debug/snprintf_chk.c b/debug/snprintf_chk.c
>> index 995d805f5d..ea02efec3e 100644
>> --- a/debug/snprintf_chk.c
>> +++ b/debug/snprintf_chk.c
>> @@ -40,4 +40,5 @@ ___snprintf_chk (char *s, size_t maxlen, int flag, size_t slen,
>>  
>>    return ret;
>>  }
>> +ldbl_hidden_def (___snprintf_chk, __snprintf_chk)
>>  ldbl_strong_alias (___snprintf_chk, __snprintf_chk)
>
> I am seeing a build failure on powerpc64le with config options 
> --enable-stack-protector=all --enable-tunables=yes --enable-bind-now=yes 
> --enable-profile=yes --enable-fortify-source=2 --enable-hardcoded-path-in-tests:
>
> powerpc64le-glibc-linux-gnu-gcc gconv_conf.c -c -std=gnu11 -fgnu89-inline  -g -O2 -Wall -Wwrite-strings -Wundef -Werror -fmerge-all-constants -frounding-math -fstack-protector-all -fno-common -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=2 -Wstrict-prototypes -Wold-style-definition -fmath-errno  -mabi=ieeelongdouble -Wno-psabi -mno-gnu-attribute -mlong-double-128  -fPIE [....]
> In file included from gconv_conf.c:26:
> ../include/stdio.h:65:1: error: ‘asm’ declaration ignored due to conflict with previous rename [-Werror=pragmas]
>    65 | stdio_hidden_ldbl_proto (__, snprintf_chk)
>       | ^~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
>
> All other ABIs build fine.

The issue seems to be that libio/bits/stdio-ldbl.h wants to alias
__snprintf_chk to __snprintf_chkieee128, and stdio_hidden_ldbl_proto
wants to create an alias to ___ieee128_snprintf_chk.

I don't know how to solve this properly.  It seems that so far, few of
the fortified variants in the printf function family have hidden aliases
for PLT avoidance.

Thanks,
Florian