Re: [Valgrind-users] running dynamically generated code

[Madhan S. <mad...@gm...>]

Tom gave a super fast patch and it fixes the issue. Please refer to.
https://bugs.kde.org/show_bug.cgi?id=210322

Thanks,
Madhan.

On Mon, Oct 12, 2009 at 7:08 PM, Madhan Sadasivam <mad...@gm...> wrote:
> I am sorry, I did not give a gist of what happens in the program. Was
> looking at the problem for a while, so I was getting too cozy with it.
>
> The intention is to generate and copy executable code into a shared
> memory segment and run it during program execution. To capture the
> idea, the given sample program copies the code of a local function to
> a newly created shared memory segment and jumps to it.
>
> The program works find without Valgrind, but with Valgrind 3.5.0 the
> given error appears.
>
> Thanks,
> Madhan
>
> On Mon, Oct 5, 2009 at 10:47 PM, Madhan Sadasivam <mad...@gm...> wrote:
>> Hello,
>>
>> The program below captures the essence of running dynamically generated code
>> in my application. It causes the following with --trace-signals=yes enabled.
>>  --smc-check=all, doesn't help. Is there a known workaround.
>>
>> --4416-- translations not allowed here (0x400b000) - throwing SEGV
>> --4416-- delivering signal 11 (SIGSEGV):2 to thread 1
>> --4416-- delivering 11 (code 2) to default handler; action: terminate+core
>> ==4416==
>> ==4416== Process terminating with default action of signal 11 (SIGSEGV)
>> ==4416==  Bad permissions for mapped region at address 0x400B000
>> ==4416==    at 0x400B000: ???
>> ==4416==    by 0x748DF2: (below main) (in /lib/tls/libc-2.3.4.so)
>>
>> Thanks,
>> Madhan.
>>
>> #include <stdio.h>
>> #include <sys/mman.h>
>> #include <sys/shm.h>
>> #include <assert.h>
>>
>> int f1(int c)
>> {
>>  int i;
>>  int res = 0;
>>
>>  for( i = 0; i < c; ++i )
>>  {
>>   res += i*i;
>>  }
>>  return res;
>> }
>>
>> int f2()
>> {
>>  return 0;
>> }
>>
>> typedef int (*f_t)(int);
>>
>> int main()
>> {
>>  key_t key;
>>  int   smid;
>>  int   rc;
>>  void *smad;
>>  int   sz;
>>  f_t f = f1;
>>
>>  struct shmid_ds buf;
>>
>>  key = ftok("/dev/zero",13);
>>  if ( key == (key_t)(-1) ) perror("ftok");
>>
>>  smid = shmget( key, 8192, 0777 | IPC_CREAT );
>>  if ( smid < 0 ) perror("shmget");
>>
>>  smad = shmat( smid, 0, 0 );
>>
>>  if ( smad == (void*)(-1) ) perror("shmat");
>>
>>  rc = mprotect( smad, 8192, PROT_READ | PROT_WRITE | PROT_EXEC );
>>
>>  if ( rc < 0 ) perror("mprotect");
>>
>>  sz = (char*)&f2 - (char*)&f1;
>>
>>  assert( sz > 0 && sz < 8192 );
>>
>>  memcpy( smad, &f1, sz );
>>
>>  printf("SoS(10)=%d, a=%p\n", f(10), f);
>>
>>  f = (f_t)smad;
>>
>>  printf("SoS(10)=%d, a=%p\n", f(10), f);
>>
>>  shmctl( smid, IPC_RMID, 0 );
>>
>>  return 0;
>> }
>>
>