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authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>2008-10-18 23:27:08 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-20 11:52:32 -0400
commite575f111dc0f27044e170580e7de50985ab3e011 (patch)
tree96021950c36cd6c537a8fc00811f4846767813b8 /Documentation/filesystems
parentd903ef9f38813e7eb268744a7e579e92f411c83a (diff)
coredump_filter: add hugepage dumping
Presently hugepage's vma has a VM_RESERVED flag in order not to be swapped. But a VM_RESERVED vma isn't core dumped because this flag is often used for some kernel vmas (e.g. vmalloc, sound related). Thus hugepages are never dumped and it can't be debugged easily. Many developers want hugepages to be included into core-dump. However, We can't read generic VM_RESERVED area because this area is often IO mapping area. then these area reading may change device state. it is definitly undesiable side-effect. So adding a hugepage specific bit to the coredump filter is better. It will be able to hugepage core dumping and doesn't cause any side-effect to any i/o devices. In additional, libhugetlb use hugetlb private mapping pages as anonymous page. Then, hugepage private mapping pages should be core dumped by default. Then, /proc/[pid]/core_dump_filter has two new bits. - bit 5 mean hugetlb private mapping pages are dumped or not. (default: yes) - bit 6 mean hugetlb shared mapping pages are dumped or not. (default: no) I tested by following method. % ulimit -c unlimited % ./crash_hugepage 50 % ./crash_hugepage 50 -p % ls -lh % gdb ./crash_hugepage core % % echo 0x43 > /proc/self/coredump_filter % ./crash_hugepage 50 % ./crash_hugepage 50 -p % ls -lh % gdb ./crash_hugepage core #include <stdlib.h> #include <stdio.h> #include <unistd.h> #include <sys/mman.h> #include <string.h> #include "hugetlbfs.h" int main(int argc, char** argv){ char* p; int ch; int mmap_flags = MAP_SHARED; int fd; int nr_pages; while((ch = getopt(argc, argv, "p")) != -1) { switch (ch) { case 'p': mmap_flags &= ~MAP_SHARED; mmap_flags |= MAP_PRIVATE; break; default: /* nothing*/ break; } } argc -= optind; argv += optind; if (argc == 0){ printf("need # of pages\n"); exit(1); } nr_pages = atoi(argv[0]); if (nr_pages < 2) { printf("nr_pages must >2\n"); exit(1); } fd = hugetlbfs_unlinked_fd(); p = mmap(NULL, nr_pages * gethugepagesize(), PROT_READ|PROT_WRITE, mmap_flags, fd, 0); sleep(2); *(p + gethugepagesize()) = 1; /* COW */ sleep(2); /* crash! */ *(int*)0 = 1; return 0; } Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Kawai Hidehiro <hidehiro.kawai.ez@hitachi.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: William Irwin <wli@holomorphy.com> Cc: Adam Litke <agl@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/proc.txt15
1 files changed, 10 insertions, 5 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index c032bf39e8b9..02cb7faeed6b 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -2412,24 +2412,29 @@ will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
2412of memory types. If a bit of the bitmask is set, memory segments of the 2412of memory types. If a bit of the bitmask is set, memory segments of the
2413corresponding memory type are dumped, otherwise they are not dumped. 2413corresponding memory type are dumped, otherwise they are not dumped.
2414 2414
2415The following 4 memory types are supported: 2415The following 7 memory types are supported:
2416 - (bit 0) anonymous private memory 2416 - (bit 0) anonymous private memory
2417 - (bit 1) anonymous shared memory 2417 - (bit 1) anonymous shared memory
2418 - (bit 2) file-backed private memory 2418 - (bit 2) file-backed private memory
2419 - (bit 3) file-backed shared memory 2419 - (bit 3) file-backed shared memory
2420 - (bit 4) ELF header pages in file-backed private memory areas (it is 2420 - (bit 4) ELF header pages in file-backed private memory areas (it is
2421 effective only if the bit 2 is cleared) 2421 effective only if the bit 2 is cleared)
2422 - (bit 5) hugetlb private memory
2423 - (bit 6) hugetlb shared memory
2422 2424
2423 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 2425 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
2424 are always dumped regardless of the bitmask status. 2426 are always dumped regardless of the bitmask status.
2425 2427
2426Default value of coredump_filter is 0x3; this means all anonymous memory 2428 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
2427segments are dumped. 2429 effected by bit 5-6.
2430
2431Default value of coredump_filter is 0x23; this means all anonymous memory
2432segments and hugetlb private memory are dumped.
2428 2433
2429If you don't want to dump all shared memory segments attached to pid 1234, 2434If you don't want to dump all shared memory segments attached to pid 1234,
2430write 1 to the process's proc file. 2435write 0x21 to the process's proc file.
2431 2436
2432 $ echo 0x1 > /proc/1234/coredump_filter 2437 $ echo 0x21 > /proc/1234/coredump_filter
2433 2438
2434When a new process is created, the process inherits the bitmask status from its 2439When a new process is created, the process inherits the bitmask status from its
2435parent. It is useful to set up coredump_filter before the program runs. 2440parent. It is useful to set up coredump_filter before the program runs.