From dankwiki
Revision as of 22:25, 16 June 2011 by Dank (talk | contribs)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search
  • Produce a corefile for a running process with gcore(1)
  • The RLIMIT_CORE rlimit specifies the maximum size of a corefile
    • Use 0 to disable corefile generation, and "unlimited" for no explicit restriction on coredump size.
    • pam might be setting a hard limit at login time. Check /etc/security/limits.conf.


  • sysctl kern.corefile controls naming mechanisms. See the core(5) man page.
  • sysctl kern.sugid_coredump controls whether processes with different effective and real U/GIDs produce corefiles
  • See savecore(8) and crashinfo(8) for further FreeBSD-specific capabilities


  • /proc/sys/kernel/core_pattern allows core naming to be configured (since Linux 2.6 and 2.4.21), and corefiles to be piped to programs. See the core(5) man page.
  • /proc/sys/kernel/core_uses_pid controls whether the PID is appended to the corefile's name
  • The prctl flag PR_SET_DUMPABLE allows process-specific coredump generation settings
  • /proc/sys/fs/suid_dumpable
  • /proc/PID/coredump_filter allows memory map-specific coredump generation settings


(largely taken from the Valgrind FAQ)

If they're not detailed enough, make sure you are compiling with -g to add debug information. And don't strip symbol tables (programs should be unstripped unless you run 'strip' on them; some libraries ship stripped). Also, -fomit-frame-pointer and -fstack-check can make stack traces worse. Some example sub-traces:

  • With debug information and unstripped (best):
Invalid write of size 1
       at 0x80483BF: really (malloc1.c:20)
       by 0x8048370: main (malloc1.c:9)
  • With no debug information, unstripped:
Invalid write of size 1
       at 0x80483BF: really (in /auto/homes/njn25/grind/head5/a.out)
       by 0x8048370: main (in /auto/homes/njn25/grind/head5/a.out)
  • With no debug information, stripped:
Invalid write of size 1
       at 0x80483BF: (within /auto/homes/njn25/grind/head5/a.out)
       by 0x8048370: (within /auto/homes/njn25/grind/head5/a.out)
       by 0x42015703: __libc_start_main (in /lib/tls/
       by 0x80482CC: (within /auto/homes/njn25/grind/head5/a.out)
  • With debug information and -fomit-frame-pointer:
Invalid write of size 1
       at 0x80483C4: really (malloc1.c:20)
       by 0x42015703: __libc_start_main (in /lib/tls/
       by 0x80482CC: ??? (start.S:81)
  • A leak error message involving an unloaded shared object:
84 bytes in 1 blocks are possibly lost in loss record 488 of 713
       at 0x1B9036DA: operator new(unsigned) (vg_replace_malloc.c:132)
       by 0x1DB63EEB: ???
       by 0x1DB4B800: ???
       by 0x1D65E007: ???
       by 0x8049EE6: main (main.cpp:24)