From: Omar Sandoval <osandov@xxxxxx>
Hi,
Someone here reported that they were getting truncated core dumps even
when RLIMIT_CORE was larger than the physical memory of the machine. It
looks some cleanup patches back in v3.13 [1] changed the behaviour of
the limit to also charge for sparse areas of a file. Here's an example
in 4.5-rc4, where a.out is:
----
#include <signal.h>
int main(int argc, char **argv)
{
raise(SIGQUIT);
return 0;
}
----
Make sure that your sysctl kernel.core_pattern isn't piping anywhere,
and be aware that there's some stupidity about the units used for ulimit
-c in different shells (bash uses 1024-byte blocks, same as what's shown
by du by default).
----
# ulimit -c unlimited
# ./a.out
Quit (core dumped)
# du core.248
88 core.248
# du --apparent-size core.248
232 core.248
# ulimit -c 128
# ./a.out
Quit (core dumped)
# du core.252
64 core.252
# du --apparent-size core.252
72 core.252
----
These 2 patches restore the original behavior:
----
# ulimit -c 128
# ./a.out
Quit (core dumped)
# du core.245
88 core.245
# du --apparent-size core.245
232 core.245
----
Patch 1 gets rid of cprm->written, since as far as I could tell, it's
always going to be equal to cprm->file->f_pos. Patch 2 reintroduces
cprm->written as the number of bytes actually written to the file, not
including what we seek over.
This series is based on 4.5-rc4. Al, could you apply these?
Thanks!
1: http://lkml.iu.edu/hypermail/linux/kernel/1310.1/00758.html
Appendix A: a quick sanity test with the patches applied
----
# ulimit -c unlimited
# python -c 'import os, signal; l = [0] * 1024 * 1024; os.kill(os.getpid(), signal.SIGQUIT)'
Quit (core dumped)
# du core.262
12268 core.262
# du --apparent-size core.262
12628 core.262
# ulimit -c 1024
# python -c 'import os, signal; l = [0] * 1024 * 1024; os.kill(os.getpid(), signal.SIGQUIT)'
Quit (core dumped)
# du core.266
1024 core.266
# du --apparent-size core.266
1024 core.266
----
Omar Sandoval (2):
coredump: get rid of coredump_params->written
coredump: only charge written data against RLIMIT_CORE
arch/powerpc/platforms/cell/spufs/coredump.c | 5 +++--
fs/binfmt_elf.c | 2 +-
fs/binfmt_elf_fdpic.c | 2 +-
fs/coredump.c | 7 ++-----
4 files changed, 7 insertions(+), 9 deletions(-)
--
2.7.1
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