Hello all, I have successfully acessed(read and write) to 0x00000000(NULL) address. I had to make certain changes in .config file and recompile it.
Thank you all. Regards Ravi Teja On Sat, Sep 21, 2013 at 8:00 PM, anish singh <[email protected]>wrote: > > On Sep 21, 2013 7:35 PM, "Ravi Teja" <[email protected]> wrote: > > > > Hello Ratheesh, > > > > I have intentionally used MAP_FIXED flag as I am interested in mapping > to 0x00000000. > AFAICS in linux generally mapping to null address is not allowed as this > decision helps in debugging null dereference errors. > > > > > Even after setting the mmap_min_addr in /proc/sys/vm to 0 (which was > previously 4096), I am getting this error. > > > > Is there anything wrong that I am doing? > > > > > > On Sat, Sep 21, 2013 at 7:17 PM, ratheesh kannoth < > [email protected]> wrote: > >> > >> MAP_FIXED could be trying to get a map from 0. > >> > >> > >> Pls remove this flag and try. > >> > >> > >> On Sat, Sep 21, 2013 at 6:55 PM, Ravi Teja <[email protected]> wrote: > >>> > >>> Hello all, > >>> > >>> I tried mmap'ing to address zero after setting > /proc/sys/vm/mmap_min_addr to 0, but mmap is giving Permission Denied error. > >>> > >>> My C code is as below - > >>> > >>> #include <stdio.h> > >>> #include <stdlib.h> > >>> #include <sys/mman.h> > >>> > >>> int main(void) > >>> { > >>> int *ptr = NULL; > >>> ptr = > mmap(0,4096,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,-1,0); > >>> if(ptr == MAP_FAILED) > >>> { > >>> perror("Error in mapping\n"); > >>> exit(1); > >>> } > >>> printf("After mmap\n"); > >>> *ptr = 16; > >>> printf("Contents of address 0x%x is :: %d\n",ptr,*ptr); > >>> return 0; > >>> } > >>> > >>> Am I doing anything wrong here? > >>> > >>> Thank you in advance. > >>> > >>> Regards, > >>> Ravi Teja > >>> > >>> _______________________________________________ > >>> Kernelnewbies mailing list > >>> [email protected] > >>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > >>> > >> > > > > > > _______________________________________________ > > Kernelnewbies mailing list > > [email protected] > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > >
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