RE: segv at strcmp

From: umut aymakoglu <umutaymak_at_yahoo.com>
Date: 2004-01-06 11:04:02
Ok - I have a small repro that segvs.



#include <stdio.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <string.h>
#include <stdlib.h>


#define SHMBASE 0x200000000
#define AL (1024*1024)
#define MAXSEGMENTS  1


#ifndef SHM_R
#define SHM_R        0400
#endif
#ifndef SHM_W
#define SHM_W        0660
#endif

#define SHM_MODE     ( SHM_R | SHM_W | IPC_CREAT )
#define KEY2SUCKS    0x52435200

unsigned long     sizes[MAXSEGMENTS] ={720896};

main()
{

    int  shmid[MAXSEGMENTS];
    char *shmptr[MAXSEGMENTS];
    long addr,mykey,loop,addr_save,attempts=0;
    int i;
    char *name;


    addr = SHMBASE;
    mykey  = KEY2SUCKS;
    attempts = 0;

for( loop=0;loop<MAXSEGMENTS;loop++ )
{

shmid[loop]=shmget((key_t)mykey,sizes[loop],SHM_MODE);
 shmptr[loop]=(char
*)shmat(shmid[loop],(void*)addr,0);

 /* ALign the size on SHMLBA(16K) */
sizes[loop]=(sizes[loop] + SHMLBA - 1) & ~(SHMLBA -1);
addr=shmptr[attempts]+(unsigned long)sizes[loop];
addr_save = addr;
   printf("addr1 = %p\n",addr);

 /* aLign the Address on 1MB */
addr=(char *)(((unsigned long)addr + AL-1) & ~(AL-1));
   
   printf("addr2 = %p\n",addr);
   attempts++;
   mykey++;
}

 name = ((unsigned long)addr_save - 16);
 printf("%p\n",name);
 strcpy(name, "sqlexec");
 ret = strcmp(name,"aaaaaaaaaaaaaaaaaaaaaaaa");


 for( loop=0;loop<attempts;loop++ )
       shmctl( shmid[loop],IPC_RMID,0 );

  printf( "\n\tRemoved All Segments ... \n\n");
  exit( 0 );
}

%gcc -O -o x x.c
%./x


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Received on Mon Jan 5 19:11:10 2004

This archive was generated by hypermail 2.1.8 : 2005-08-02 09:20:21 EST