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authorRoss Zwisler <ross.zwisler@linux.intel.com>2015-10-06 00:33:36 +0200
committerDan Williams <dan.j.williams@intel.com>2015-11-09 19:29:54 +0100
commit5037835c1f3eabf4f22163fc0278dd87165f8957 (patch)
tree6cfa915dabfa9512ade4d974eb36635293c02447 /Documentation/filesystems
parentMerge branch 'for-4.4/hotplug' into libnvdimm-for-next (diff)
downloadlinux-5037835c1f3eabf4f22163fc0278dd87165f8957.tar.xz
linux-5037835c1f3eabf4f22163fc0278dd87165f8957.zip
coredump: add DAX filtering for ELF coredumps
Add two new flags to the existing coredump mechanism for ELF files to allow us to explicitly filter DAX mappings. This is desirable because DAX mappings, like hugetlb mappings, have the potential to be very large. Update the coredump_filter documentation in Documentation/filesystems/proc.txt so that it addresses the new DAX coredump flags. Also update the documented default value of coredump_filter to be consistent with the core(5) man page. The documentation being updated talks about bit 4, Dump ELF headers, which is enabled if CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS is turned on in the kernel config. This kernel config option defaults to "y" if both ELF binaries and coredump are enabled. Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Acked-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/proc.txt22
1 files changed, 12 insertions, 10 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index d411ca63c8b6..6f887cf873a1 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1598,16 +1598,16 @@ Documentation/accounting.
---------------------------------------------------------------
When a process is dumped, all anonymous memory is written to a core file as
long as the size of the core file isn't limited. But sometimes we don't want
-to dump some memory segments, for example, huge shared memory. Conversely,
-sometimes we want to save file-backed memory segments into a core file, not
-only the individual files.
+to dump some memory segments, for example, huge shared memory or DAX.
+Conversely, sometimes we want to save file-backed memory segments into a core
+file, not only the individual files.
/proc/<pid>/coredump_filter allows you to customize which memory segments
will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
of memory types. If a bit of the bitmask is set, memory segments of the
corresponding memory type are dumped, otherwise they are not dumped.
-The following 7 memory types are supported:
+The following 9 memory types are supported:
- (bit 0) anonymous private memory
- (bit 1) anonymous shared memory
- (bit 2) file-backed private memory
@@ -1616,20 +1616,22 @@ The following 7 memory types are supported:
effective only if the bit 2 is cleared)
- (bit 5) hugetlb private memory
- (bit 6) hugetlb shared memory
+ - (bit 7) DAX private memory
+ - (bit 8) DAX shared memory
Note that MMIO pages such as frame buffer are never dumped and vDSO pages
are always dumped regardless of the bitmask status.
- Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
- effected by bit 5-6.
+ Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
+ only affected by bit 5-6, and DAX is only affected by bits 7-8.
-Default value of coredump_filter is 0x23; this means all anonymous memory
-segments and hugetlb private memory are dumped.
+The default value of coredump_filter is 0x33; this means all anonymous memory
+segments, ELF header pages and hugetlb private memory are dumped.
If you don't want to dump all shared memory segments attached to pid 1234,
-write 0x21 to the process's proc file.
+write 0x31 to the process's proc file.
- $ echo 0x21 > /proc/1234/coredump_filter
+ $ echo 0x31 > /proc/1234/coredump_filter
When a new process is created, the process inherits the bitmask status from its
parent. It is useful to set up coredump_filter before the program runs.