2.6.28.2 + gcc-4.3.2-7 works. 2.6.28.4 + gcc-4.4.0-0.16 does not work. I run x86_64 SMP kernel. # strace ./a.out ntp 12:10:14.780726 mmap(NULL, 2147624, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = -1 EFAULT (Bad address) <0.000038> 12:10:14.780809 close(3) = 0 <0.000012> 12:10:14.780856 munmap(0x7f3476e0d000, 421232) = 0 <0.000145> 12:10:14.781054 write(2, "./a.out: getpwnam failed: Success\n"..., 34./a.out: getpwnam failed: Success ) = 34 <0.000015> I can do malloc(3000000), then mmap call is 12:50:20.694207 mmap(NULL, 3002368, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f8a8d16b000 <0.003078> -- "When playing Russian roulette, the fact that the first shot got off safely is little comfort for the next." - Richard Feynman