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From: Namhyung Kim <namhyung <at> kernel.org>
Subject: [PATCHSET 00/13] tracing/uprobes: Add support for more fetch methods (v4)
Newsgroups: gmane.linux.kernel
Date: Tuesday 27th August 2013 08:48:43 UTC (over 3 years ago)

This patchset implements memory (address), stack[N], deference,
bitfield and retval (it needs uretprobe tho) fetch methods for
uprobes.  It's based on the previous work [1] done by Hyeoncheol Lee.

Now kprobes and uprobes have their own fetch_type_tables and, in turn,
memory and stack access methods.  Other fetch methods are shared.

For the dereference method, I added a new argument to fetch functions.
It's because for uprobes it needs to know whether the given address is
a file offset or a virtual address in an user process.  For instance,
in case of fetching from a memory directly (like @offset) it should
convert the address (offset) to a virtual address of the process, but
if it's a dereferencing, the given address already has the virtual

To determine this in a fetch function, I passed a pointer to
trace_uprobe for direct fetch, and passed NULL for dereference.

Please look at patch 10 that uses per-cpu buffer for accessing user
memory as suggested by Steven.  While I tried hard not to mess things
up there might be a chance I did something horrible.  It'd be great if
you guys take a look and give comments.

 * v4 changes:
  - add Ack's from Masami
  - rearrange patches to make it easy for simple fixes to be applied
  - update documentation
  - use per-cpu buffer for storing args (thanks to Steve!)

[1] https://lkml.org/lkml/2012/11/14/84

A simple example:

  # cat foo.c
  int glob = -1;
  char str[] = "hello uprobe.";

  struct foo {
    unsigned int unused: 2;
    unsigned int foo: 20;
    unsigned int bar: 10;
  } foo = {
    .foo = 5,

  int main(int argc, char *argv[])
    long local = 0x1234;

    return 127;

  # gcc -o foo -g foo.c

  # objdump -d foo | grep -A9 -F '
' 00000000004004b0
: 4004b0: 55 push %rbp 4004b1: 48 89 e5 mov %rsp,%rbp 4004b4: 89 7d ec mov %edi,-0x14(%rbp) 4004b7: 48 89 75 e0 mov %rsi,-0x20(%rbp) 4004bb: 48 c7 45 f8 34 12 00 movq $0x1234,-0x8(%rbp) 4004c2: 00 4004c3: b8 7f 00 00 00 mov $0x7f,%eax 4004c8: 5d pop %rbp 4004c9: c3 retq # nm foo | grep -e glob$ -e str -e foo 00000000006008bc D foo 00000000006008a8 D glob 00000000006008ac D str # perf probe -x /home/namhyung/tmp/foo -a 'foo=main+0x13 [email protected]:s32 \ > [email protected]:string [email protected]:[email protected]/32 argc=%di local=-0x8(%bp)' Added new event: probe_foo:foo (on 0x4c3 with [email protected]:s32 [email protected]:string [email protected]:[email protected]/32 argc=%di local=-0x8(%bp)) You can now use it in all perf tools, such as: perf record -e probe_foo:foo -aR sleep 1 # perf record -e probe_foo:foo ./foo [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.001 MB perf.data (~33 samples) ] # perf script | grep -v ^# foo 2008 [002 2199.867154: probe_foo:foo (4004c3) glob=-1 str="hello uprobe." bit=5 argc=1 local=1234 This patchset is based on the current for-next branch of the Steven Rostedt's linux-trace tree. I also put this on my 'uprobe/fetch-v4' branch in my tree: git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git Any comments are welcome, thanks. Namhyung Cc: Masami Hiramatsu Cc: Srikar Dronamraju Cc: Oleg Nesterov Cc: zhangwei(Jovi) <[email protected]> Cc: Arnaldo Carvalho de Melo Hyeoncheol Lee (2): tracing/kprobes: Move fetch functions to trace_kprobe.c tracing/kprobes: Add fetch{,_size} member into deref fetch method Namhyung Kim (11): tracing/uprobes: Fix documentation of uprobe registration syntax tracing/probes: Fix basic print type functions tracing/kprobes: Staticize stack and memory fetch functions tracing/kprobes: Factor out struct trace_probe tracing/uprobes: Convert to struct trace_probe tracing/kprobes: Move common functions to trace_probe.h tracing/kprobes: Integrate duplicate set_print_fmt() tracing/uprobes: Fetch args before reserving a ring buffer tracing/kprobes: Add priv argument to fetch functions tracing/uprobes: Add more fetch functions tracing/uprobes: Add support for full argument access methods Documentation/trace/uprobetracer.txt | 35 +- kernel/trace/trace_kprobe.c | 642 +++++++++++++++++++---------------- kernel/trace/trace_probe.c | 451 +++++++++--------------- kernel/trace/trace_probe.h | 202 ++++++++++- kernel/trace/trace_uprobe.c | 457 +++++++++++++++++-------- 5 files changed, 1059 insertions(+), 728 deletions(-) --
CD: 19ms