(2012/04/11 19:30), Srikar Dronamraju wrote: > From: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> > > 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 > > Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> > --- > > Changelog (since v9) > - Handle comments from Steven Rostedt about uprobe tracer documentation. > - Disable preemption while in perf handler as suggested by Jiri Olsa. > > Changelog (since v5) > - Added uprobe tracer documentation to this patch. > > Documentation/trace/uprobetracer.txt | 95 ++++ > arch/Kconfig | 2 > kernel/trace/Kconfig | 16 + > kernel/trace/Makefile | 1 > kernel/trace/trace.h | 5 > kernel/trace/trace_kprobe.c | 2 > kernel/trace/trace_probe.c | 14 - > kernel/trace/trace_probe.h | 3 > kernel/trace/trace_uprobe.c | 788 ++++++++++++++++++++++++++++++++++ > 9 files changed, 919 insertions(+), 7 deletions(-) > create mode 100644 Documentation/trace/uprobetracer.txt > create mode 100644 kernel/trace/trace_uprobe.c > > diff --git a/Documentation/trace/uprobetracer.txt b/Documentation/trace/uprobetracer.txt > new file mode 100644 > index 0000000..eae40a0 > --- /dev/null > +++ b/Documentation/trace/uprobetracer.txt > @@ -0,0 +1,95 @@ > + Uprobe-tracer: Uprobe-based Event Tracing > + ========================================= > + Documentation written by Srikar Dronamraju > + > +Overview > +-------- > +Uprobe based trace events are similar to kprobe based trace events. > +To enable this feature, build your kernel with CONFIG_UPROBE_EVENTS=y. > + > +Similar to the kprobe-event tracer, this doesn't need to be activated via > +current_tracer. Instead of that, add probe points via > +/sys/kernel/debug/tracing/uprobe_events, and enable it via > +/sys/kernel/debug/tracing/events/uprobes/<EVENT>/enabled. > + > +However unlike kprobe-event tracer, the uprobe event interface expects the > +user to calculate the offset of the probepoint in the object > + > +Synopsis of uprobe_tracer > +------------------------- > + p[:[GRP/]EVENT] PATH:SYMBOL[+offs] [FETCHARGS] : Set a probe > + > + GRP : Group name. If omitted, use "uprobes" for it. > + EVENT : Event name. If omitted, the event name is generated > + based on SYMBOL+offs. > + PATH : path to an executable or a library. > + SYMBOL[+offs] : Symbol+offset where the probe is inserted. > + > + FETCHARGS : Arguments. Each probe can have up to 128 args. > + %REG : Fetch register REG > + > +Event Profiling > +--------------- > + You can check the total number of probe hits and probe miss-hits via > +/sys/kernel/debug/tracing/uprobe_profile. > + The first column is event name, the second is the number of probe hits, > +the third is the number of probe miss-hits. > + > +Usage examples > +-------------- > +To add a probe as a new event, write a new definition to uprobe_events > +as below. > + > + echo 'p: /bin/bash:0x4245c0' > /sys/kernel/debug/tracing/uprobe_events > + > + This sets a uprobe at an offset of 0x4245c0 in the executable /bin/bash > + > + echo > /sys/kernel/debug/tracing/uprobe_events > + > + This clears all probe points. > + > +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 > +function 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 > + > +0x46420 is the offset of zfree in object /bin/zsh that is loaded at > +0x00400000. Hence the command to probe would be : > + > + # echo 'p /bin/zsh:0x46420 %ip %ax' > uprobe_events > + > +Please note: User has to explicitly calculate the offset of the probepoint > +in the object. We can see the events that are registered by looking at the > +uprobe_events file. > + > + # cat uprobe_events > + p:uprobes/p_zsh_0x46420 /bin/zsh:0x0000000000046420 Doesn't uprobe_events show the arguments of existing events? And also, could you add an event format of above event here? Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@xxxxxxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>