From c00b275043adc14d668f36266b890f0c53d46640 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 29 May 2012 21:27:44 +0200 Subject: [PATCH] uprobes: Optimize is_swbp_at_addr() for current->mm Change is_swbp_at_addr() to try to avoid the costly read_opcode() if mm == current->mm, __copy_from_user_inatomic() should succeed in the likely case. Currently this optimization is not important, but we are going to add more is_swbp_at_addr(current->mm) callers. Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju Cc: Ananth N Mavinakayanahalli Cc: Anton Arapov Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20120529192744.GA8057@redhat.com Signed-off-by: Ingo Molnar --- kernel/events/uprobes.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 985be4d80fe8..d0f5ec0dcdea 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -333,10 +333,20 @@ static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr) uprobe_opcode_t opcode; int result; + if (current->mm == mm) { + pagefault_disable(); + result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr, + sizeof(opcode)); + pagefault_enable(); + + if (likely(result == 0)) + goto out; + } + result = read_opcode(mm, vaddr, &opcode); if (result) return result; - +out: if (is_swbp_insn(&opcode)) return 1;