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

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 13/02/24 09:13, Florian Weimer wrote:
> * 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.

Maybe something like:

diff --git a/include/stdio.h b/include/stdio.h
index 364f4d22a1..0fda47cf82 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -24,7 +24,7 @@
     directly alias them to their internal name.  */
 # if __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI == 1 && IS_IN (libc)
 #  define stdio_hidden_ldbl_proto(p, f) \
-  extern __typeof (p ## f) p ## f __asm (__ASMNAME ("___ieee128_" #f));
+  libc_hidden_proto_alias (p ## f, ___ieee128_ ## p ## f)
 # elif __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI == 1
 #  define stdio_hidden_ldbl_proto(p,f) __LDBL_REDIR1_DECL (p ## f, p ## f ## ieee128)
 # else
diff --git a/sysdeps/ieee754/ldbl-128ibm-compat/ieee128-snprintf_chk.c b/sysdeps/ieee754/ldbl-128ibm-compat/ieee128-snprintf_chk.c
index d5bd6aa25f..566f525a9c 100644
--- a/sysdeps/ieee754/ldbl-128ibm-compat/ieee128-snprintf_chk.c
+++ b/sysdeps/ieee754/ldbl-128ibm-compat/ieee128-snprintf_chk.c
@@ -40,3 +40,4 @@ ___ieee128___snprintf_chk (char *s, size_t maxlen, int flag, size_t slen,
   return done;
 }
 strong_alias (___ieee128___snprintf_chk, __snprintf_chkieee128)
+libc_hidden_ver (__snprintf_chkieee128, ___ieee128___snprintf_chk)