Commit a8dd9c4d authored Aug 21, 2018 by Omar Sandoval Committed by Linus Torvalds Aug 22, 2018

proc/kcore: don't grab lock for kclist_add()

Patch series "/proc/kcore improvements", v4.

This series makes a few improvements to /proc/kcore.  It fixes a couple of
small issues in v3 but is otherwise the same.  Patches 1, 2, and 3 are
prep patches.  Patch 4 is a fix/cleanup.  Patch 5 is another prep patch.
Patches 6 and 7 are optimizations to ->read().  Patch 8 makes it possible
to enable CRASH_CORE on any architecture, which is needed for patch 9.
Patch 9 adds vmcoreinfo to /proc/kcore.

This patch (of 9):

kclist_add() is only called at init time, so there's no point in grabbing
any locks.  We're also going to replace the rwlock with a rwsem, which we
don't want to try grabbing during early boot.

While we're here, mark kclist_add() with __init so that we'll get a
warning if it's called from non-init code.

Link: http://lkml.kernel.org/r/98208db1faf167aa8b08eebfa968d95c70527739.1531953780.git.osandov@fb.com


Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Bhupesh Sharma <bhsharma@redhat.com>
Tested-by: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: James Morse <james.morse@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent df865e83

fs/proc/kcore.c

+3 −4

Original line number	Diff line number	Diff line
		@@ -62,16 +62,15 @@ static LIST_HEAD(kclist_head);
		static DEFINE_RWLOCK(kclist_lock);
		static int kcore_need_update = 1;

		void
		kclist_add(struct kcore_list new, void addr, size_t size, int type)
		/* This doesn't grab kclist_lock, so it should only be used at init time. */
		void __init kclist_add(struct kcore_list new, void addr, size_t size,
		int type)
		{
		new->addr = (unsigned long)addr;
		new->size = size;
		new->type = type;

		write_lock(&kclist_lock);
		list_add_tail(&new->list, &kclist_head);
		write_unlock(&kclist_lock);
		}

		static size_t get_kcore_size(int nphdr, size_t elf_buflen)

include/linux/kcore.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -35,7 +35,7 @@ struct vmcoredd_node {
		};

		#ifdef CONFIG_PROC_KCORE
		extern void kclist_add(struct kcore_list , void , size_t, int type);
		void __init kclist_add(struct kcore_list , void , size_t, int type);
		#else
		static inline
		void kclist_add(struct kcore_list new, void addr, size_t size, int type)

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