Re: [Valgrind-users] [HELP] I run the valgrind in the unreleased android version(arm32), I am confused by function stack. Can you show me why?

[John R. <jr...@bi...>]

>              Why I call the strcmp, but function stack show that the strcat is  called not the strcmp, but the file is belong to the function strcmp
>              Can you show the how to replace the strcmp with “STRCMP(VG_Z_LIBC_SONAME,          strcmp)”, and then  I can follow the code to find out why.
> 
>              I can find the code you set the LD_PRELOAD ,  but symbol name  is not match,  I do not know how you replace the strcmp with STRCMP(VG_Z_LIBC_SONAME,          strcmp).
>              Can  you help to point out the function do the job replace the strcmp with STRCMP(VG_Z_LIBC_SONAME,          strcmp)”,
> 
> Valgrind 3.12.
> CPU:arm

#include <errno.h>
#include <limits.h>
#include <stdatomic.h>
#include <string.h>
#include <sys/cdefs.h>
#include <sys/mman.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

_Atomic(unsigned int ) g_status;

#define __unused /*empty*/
#define __predict_true /*empty*/

int main(int argc __unused , char ** argv __unused ) {
         unsigned int init = 1;
         int flag = 1;
         unsigned int expect = random();
         unsigned int value = 2;
         atomic_init(&g_status, init);

         if (__predict_true(atomic_compare_exchange_strong_explicit(&g_status, &expect,
                              value, memory_order_acquire, memory_order_relaxed))) {
             flag = 0;
         }

         printf("Done  flag:%d cmp:%d \n", flag, strcmp("aaaa", "cccc") );
         return  1;
}


The compiler name and version were not specified.  I used:
	gcc (GCC) 8.0.1 20180324 (Red Hat 8.0.1-0.20)
As shown, I had to #define the symbols __unused and __predict_true.


> Valgrind show me output :
> ==30141== Invalid write of size 4
> ==30141== at 0x4C27CAE: strcat(strcmp.c:3)
> ==30141==    by 0x108871: main (testClang.c:27)
> ==30141==  Address 0xfeb445bc is on thread 1's stack
> ==30141==  12 bytes below stack pointer

Using valgrind-3.13 on Fedora 28 beta for armv7l (armhfp; 32-bit ARM):
$ valgrind ./predict
==2012== Memcheck, a memory error detector
==2012== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==2012== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==2012== Command: ./predict
==2012==
Done  flag:1 cmp:-1
==2012==
==2012== HEAP SUMMARY:
==2012==     in use at exit: 0 bytes in 0 blocks
==2012==   total heap usage: 1 allocs, 1 frees, 1,024 bytes allocated
==2012==
==2012== All heap blocks were freed -- no leaks are possible
==2012==
==2012== For counts of detected and suppressed errors, rerun with: -v
==2012== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)