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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