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Subject[PATCH 2/9] uprobes: allow ignoring of probe hits
Date
From: Rabin Vincent <rabin@rab.in>

Allow arches to decided to ignore a probe hit. ARM will use this to
only call handlers if the conditions to execute a conditionally executed
instruction are satisfied.

Upleveled for v3.10-rc7.

Signed-off-by: David A. Long <dave.long@linaro.org>
---
include/linux/uprobes.h | 1 +
kernel/events/uprobes.c | 17 ++++++++++++-----
2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 4e3b847..7a7c035 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -133,6 +133,7 @@ extern int arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs);
extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
extern int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
+extern bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs);
#else /* !CONFIG_UPROBES */
struct uprobes_state {
};
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index f356974..2f3a4cb 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1734,9 +1734,6 @@ static void handle_swbp(struct pt_regs *regs)
return;
}

- /* change it in advance for ->handler() and restart */
- instruction_pointer_set(regs, bp_vaddr);
-
/*
* TODO: move copy_insn/etc into _register and remove this hack.
* After we hit the bp, _unregister + _register can install the
@@ -1744,16 +1741,26 @@ static void handle_swbp(struct pt_regs *regs)
*/
smp_rmb(); /* pairs with wmb() in install_breakpoint() */
if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
- goto out;
+ goto restart;

handler_chain(uprobe, regs);
+
+ if (arch_uprobe_ignore(&uprobe->arch, regs))
+ goto out;
+
if (can_skip_sstep(uprobe, regs))
goto out;

if (!pre_ssout(uprobe, regs, bp_vaddr))
return;

- /* can_skip_sstep() succeeded, or restart if can't singlestep */
+restart:
+ /*
+ * cannot singlestep; cannot skip instruction;
+ * re-execute the instruction.
+ */
+ instruction_pointer_set(regs, bp_vaddr);
+
out:
put_uprobe(uprobe);
}
--
1.8.1.2


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