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Commit d9c4a30e authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

uprobes: Move BUG_ON(UPROBE_SWBP_INSN_SIZE) from write_opcode() to install_breakpoint() 



write_opcode() ensures that UPROBE_SWBP_INSN doesn't cross the
page boundary. This looks a bit confusing, the check does not
depend on vaddr and it is enough to do it only once right after
install_breakpoint()->arch_uprobe_analyze_insn().

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: default avatarAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154350.GA9611@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent eb2bf57b

kernel/events/uprobes.c

+5 −6
Original line number Diff line number Diff line
@@ -210,7 +210,6 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, 
	void *vaddr_old, *vaddr_new;

	struct vm_area_struct *vma;

	struct uprobe *uprobe;

	unsigned long pgoff;

	int ret;

retry:

	/* Read the page with vaddr into memory */
@@ -251,11 +250,7 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, 
	vaddr_new = kmap_atomic(new_page);



	memcpy(vaddr_new, vaddr_old, PAGE_SIZE);



	/* poke the new insn in, ASSUMES we don't cross page boundary */

	pgoff = (vaddr & ~PAGE_MASK);

	BUG_ON(pgoff + UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);

	memcpy(vaddr_new + pgoff, &opcode, UPROBE_SWBP_INSN_SIZE);

	memcpy(vaddr_new + (vaddr & ~PAGE_MASK), &opcode, UPROBE_SWBP_INSN_SIZE);



	kunmap_atomic(vaddr_new);

	kunmap_atomic(vaddr_old);
@@ -699,6 +694,10 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, 
		if (ret)

			return ret;



		/* write_opcode() assumes we don't cross page boundary */

		BUG_ON((uprobe->offset & ~PAGE_MASK) +

				UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);



		uprobe->flags |= UPROBE_COPY_INSN;

	}