On Tue, Jan 10, 2012 at 05:19:43PM +0530, Srikar Dronamraju wrote:
>
> Implements trace_event support for uprobes. In its current form it can
> be used to put probes at a specified offset in a file and dump the
> required registers when the code flow reaches the probed address.
>
> The following example shows how to dump the instruction pointer and %ax
> a register at the probed text address. Here we are trying to probe
> zfree in /bin/zsh
>
> # cd /sys/kernel/debug/tracing/
> # cat /proc/`pgrep zsh`/maps | grep /bin/zsh | grep r-xp
> 00400000-0048a000 r-xp 00000000 08:03 130904 /bin/zsh
> # objdump -T /bin/zsh | grep -w zfree
> 0000000000446420 g DF .text 0000000000000012 Base zfree
> # echo 'p /bin/zsh:0x46420 %ip %ax' > uprobe_events
> # cat uprobe_events
> p:uprobes/p_zsh_0x46420 /bin/zsh:0x0000000000046420
> # echo 1 > events/uprobes/enable
> # sleep 20
> # echo 0 > events/uprobes/enable
> # cat trace
> # tracer: nop
> #
> # TASK-PID CPU# TIMESTAMP FUNCTION
> # | | | | |
> zsh-24842 [006] 258544.995456: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
> zsh-24842 [007] 258545.000270: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
> zsh-24842 [002] 258545.043929: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
> zsh-24842 [004] 258547.046129: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
>
> TODO: Connect a filter to a consumer.
hi,
It looks to me the perf/trace filtering is already working
with the small fix attached.
In another email discussion I think you suggested to use
the 'filter property of uprobe consumer' for the perf/trace
filtering. The current code does the filtering in the handler
itself, and it's same for other perf/trace based events.
I discussed the 'filter property of uprobe consumer' with Oleg,
and he is not sure why it was added.. was it only for the perf/trace
filtering?
I've tested following event:
echo "p:probe_libc/free /lib64/libc-2.13.so:0x7a4f0 %ax" > ./uprobe_events
and commands like:
perf record -a -e probe_libc:free --filter "common_pid == 1127"
perf record -e probe_libc:free --filter "arg1 == 0xa" ls
got me proper results.
thanks,
jirka
---
The preemption needs to be disabled when submitting data into perf.
---
kernel/trace/trace_uprobe.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index af29368..4d3857c 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -653,9 +653,11 @@ static void uprobe_perf_func(struct trace_uprobe *tp, struct pt_regs *regs)
"profile buffer not large enough"))
return;
+ preempt_disable();
+
entry = perf_trace_buf_prepare(size, call->event.type, regs, &rctx);
if (!entry)
- return;
+ goto out;
entry->ip = get_uprobe_bkpt_addr(task_pt_regs(current));
data = (u8 *)&entry[1];
@@ -665,6 +667,8 @@ static void uprobe_perf_func(struct trace_uprobe *tp, struct pt_regs *regs)
head = this_cpu_ptr(call->perf_events);
perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, regs, head);
+ out:
+ preempt_enable();
}
#endif /* CONFIG_PERF_EVENTS */
--
1.7.1
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