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

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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: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Ananth 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Oleg Nesterov 2012-06-15 17:43:50 +02:00 committed by Ingo Molnar
parent eb2bf57bee
commit d9c4a30e82
1 changed files with 5 additions and 6 deletions
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11
kernel/events/uprobes.c
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@ -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 @@ retry:
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;
}