Messages in this thread | | | Date | Fri, 26 Jan 2007 17:58:47 +0100 | From | Pavel Machek <> | Subject | Re: [Fwd: [PATCH 4/4] coredump: documentation for proc and sysctl] |
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Hi!
> This patch adds the documentation for the following parameters: > /proc/<pid>/core_flags > /proc/sys/kernel/core_flags_enable
Sysctl seems really strange to me. Either the feature is safe to use, or it is not. Users can already ulimit -c 0, and we do not have "/proc/sys/kernel/allow_users_to_disable_their_core_dumps".
Plus, this is pretty analogical to ulimit -c, so I believe it should be implemented like that one. You'll need less locking that way.
> +2.14 /proc/<pid>/core_flags - Core dump control flags > +--------------------------------------------------------------------- > +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. > + > +The /proc/<pid>/core_flags file enables you to omit some anonymous memory from > +a core file when it is generated. The content of the proc file is bitmask of > +memory segment types you don't want to dump. When the <pid> process is dumped, > +the core dump routine decides whether a given memory segment should be dumped > +into a core file or not, based on the type of the memory segment and bitmask. > + > +Currently, only valid bit is bit 0. If bit 0 is set, anonymous `shared' memory > +segments are not dumped. There are three types of anonymous shared memory: > + > + - IPC shared memory > + - the memory segments created by mmap(2) with MAP_ANONYMOUS and MAP_SHARED > + flags > + - the memory segments created by mmap(2) with MAP_SHARED flag, and the > + mapped file has already been unlinked > + > +Because current core dump routine doesn't distinguish these segments, you can > +only choose either dumping all anonymous shared memory segments or not. > + > +If you don't want to dump all shared memory segments attached to pid 1234, set > +the bit 0 of the process's core_flags to 1: > + > + $ echo 1 > /proc/1234/core_flags > + > +Additionally, you can check its hexadecimal value by reading the file: > + > + $ cat /proc/1234/core_flags > + 00000001 > + > +When a new process is created, the process inherits the core_flags setting > +from its parent. It is useful to set the core_flags before the program runs. > +For example: > + > + $ echo 1 > /proc/self/core_flags > + $ ./some_program > +
Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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