diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2012-05-29 21:29:47 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2012-06-06 17:22:03 +0200 |
| commit | 56bb4cf6475d702d2fb00fc641aa6441097c0330 (patch) | |
| tree | 0be90e9cdb9d998e9ca795f12eb530b397435844 /kernel/events | |
| parent | 77fc4af1b59d12ab3b1467adf0a5204806853123 (diff) | |
uprobes: Teach handle_swbp() to rely on "is_swbp" rather than uprobes_srcu
Currently handle_swbp() assumes that it can't race with
unregister, so it roughly does:
if (find_uprobe(vaddr))
process_uprobe();
else
send_sig(SIGTRAP);
This relies on the not-really-working uprobes_srcu code we are
going to remove, see the next patch.
With this patch we rely on the result of
is_swbp_at_addr(bp_vaddr) if find_uprobe() fails.
If is_swbp == 1, then we hit the normal int3, we should send
SIGTRAP.
If is_swbp == 0, we raced with uprobe_unregister(), we simply
restart this insn again.
The "difficult" case is is_swbp == -EFAULT, when we can't read
this memory. In this case I think we should restart too, and
this is more correct compared to the current code which sends
SIGTRAP.
Ignoring ENOMEM/etc from get_user_pages(), this can only happen
if another thread unmaps this memory before find_active_uprobe()
takes mmap_sem. It would be better to pretend it was unmapped
before this insn was executed, restart, and get SIGSEGV.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529192947.GF8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/uprobes.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index a2ed82b4808..1f02e3bbfc1 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1530,14 +1530,26 @@ static void handle_swbp(struct pt_regs *regs) struct uprobe_task *utask; struct uprobe *uprobe; unsigned long bp_vaddr; - int is_swbp; + int uninitialized_var(is_swbp); bp_vaddr = uprobe_get_swbp_addr(regs); uprobe = find_active_uprobe(bp_vaddr, &is_swbp); if (!uprobe) { - /* No matching uprobe; signal SIGTRAP. */ - send_sig(SIGTRAP, current, 0); + if (is_swbp > 0) { + /* No matching uprobe; signal SIGTRAP. */ + send_sig(SIGTRAP, current, 0); + } else { + /* + * Either we raced with uprobe_unregister() or we can't + * access this memory. The latter is only possible if + * another thread plays with our ->mm. In both cases + * we can simply restart. If this vma was unmapped we + * can pretend this insn was not executed yet and get + * the (correct) SIGSEGV after restart. + */ + instruction_pointer_set(regs, bp_vaddr); + } return; } |