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On my Ubuntu 16.04, 64 bit the default stack size is 8192 bytes. If I set it to unlimited, seems like the vdso is remapped to a completely different memory region.

$ ulimit -s
8192

$ cat /proc/`pgrep ascii`/maps
08048000-080ed000 r-xp 00000000 08:03 7736874                            /home/sherlock/ascii                                                                           
080ed000-080ef000 rw-p 000a5000 08:03 7736874                            /home/sherlock/ascii                                                                           
080ef000-080f1000 rw-p 00000000 00:00 0
09803000-09825000 rw-p 00000000 00:00 0                                  [heap]
80000000-80001000 rwxp 00000000 00:00 0
f7f74000-f7f76000 rw-p 00000000 00:00 0
f7f76000-f7f79000 r--p 00000000 00:00 0                                  [vvar]
f7f79000-f7f7b000 r-xp 00000000 00:00 0                                  [vdso]
ff86f000-ff891000 rw-p 00000000 00:00 0                                  [stack]

$ ulimit -s unlimited

$ ulimit -s                                                                                                                                          
unlimited

$ cat /proc/`pgrep ascii`/maps
08048000-080ed000 r-xp 00000000 08:03 7736874                            /home/sherlock/ascii                                                                           
080ed000-080ef000 rw-p 000a5000 08:03 7736874                            /home/sherlock/ascii                                                                           
080ef000-080f1000 rw-p 00000000 00:00 0
0988a000-098ac000 rw-p 00000000 00:00 0                                  [heap]
2aa35000-2aa37000 rw-p 00000000 00:00 0
2aa37000-2aa3a000 r--p 00000000 00:00 0                                  [vvar]
2aa3a000-2aa3c000 r-xp 00000000 00:00 0                                  [vdso]
80000000-80001000 rwxp 00000000 00:00 0
ffed3000-ffef5000 rw-p 00000000 00:00 0                                  [stack]

Can anyone explain this behavior?

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