[PATCHSET 00/17] tracing/uprobes: Add support for more fetch methods (v9)

From: Namhyung Kim
Date: Sun Dec 15 2013 - 23:36:50 EST

Hello,

This patchset implements memory (address), stack[N], deference,
bitfield, retval (it needs uretprobe tho) and file_offset 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. The symbol and file_offset fetch
methods are only available to kprobes and uprobes, respectively.
Other fetch methods are shared.

For the file_offset method, it translates the offset argument to a
virtual address in a process. To do that, it calculates base mapping
address using probe address (utask->vaddr) and probe offset
(tu->offset) and then adds the argument offset. Those info are
carried via utask and a new fetch parameter.

The syntax is '@+offset' where offset are relative address to the base
address. For shared libraries, it'd be simply the st_value of symbol
in ELF format. But for executable, it needs to subtract base load
address (e.g. 0x40000 for x86_64) from the symbol value. Please see
previous discussion for an example [2] - Note that the syntax changed
to '@+' from plain '@'. The plain '@addr' syntax is used for
accessing absolute memory address if you already know the exact address.

Many thanks to Oleg who provides valuable feedbacks and suggestions.

The patch 1-2 are bug fixes and can be applied independently.
The patch 16 is a preparation for patch 17 which implements the
file_offset fetch method.


* v9 changes:
- [ku]probes_fetch_type_table have NULL terminator (Masami)
- make symbol fetch methods static inline for !CONFIG_KPROBE_EVENT (Masami)
- add more Ack's from Masami

* v8 changes:
- rename tk, tu and tp more consistently (Srikar)
- change prefix format specifier: %#x -> 0x%x (Masami)
- convert file_offset_param to uprobe_dispatch_data (Oleg)
- add more Ack's from Srikar and Masami

* v7 changes:
- restructure patches not to break build with !CONFIG_[KU]PROBE_EVENT
- print 0x prefix for unsigned types
- add @+file_offset fetch method (Oleg)
- get rid of uprobe_buffer_mutex (Oleg)
- pass 'is_return' to uprobes argument parser


[1] https://lkml.org/lkml/2012/11/14/84
[2] https://lkml.org/lkml/2013/11/5/25

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 '<main>'
00000000004004b0 <main>:
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 glob=@0x6008a8:s32 \
> str=@+0x2008ac:string bit=@+0x2008bc:b10@2/32 argc=%di:s32 local=-0x8(%bp)'
Added new event:
probe_foo:foo (on 0x4c3 with glob=@0x6008a8:s32 str=@+0x2008ac:string
bit=@+0x2008bc:b10@2/32 argc=%di:s32 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=0x5 argc=1 local=0x1234


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-v9'
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 <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: zhangwei(Jovi) <jovi.zhangwei@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: Hemant Kumar <hkshaw@xxxxxxxxxxxxxxxxxx>


Hyeoncheol Lee (1):
tracing/probes: Add fetch{,_size} member into deref fetch method

Namhyung Kim (15):
tracing/uprobes: Fix documentation of uprobe registration syntax
tracing/probes: Fix basic print type 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/probes: Integrate duplicate set_print_fmt()
tracing/probes: Move fetch function helpers to trace_probe.h
tracing/probes: Split [ku]probes_fetch_type_table
tracing/probes: Implement 'stack' fetch method for uprobes
tracing/probes: Move 'symbol' fetch method to kprobes
tracing/probes: Implement 'memory' fetch method for uprobes
tracing/uprobes: Pass 'is_return' to traceprobe_parse_probe_arg()
tracing/uprobes: Fetch args before reserving a ring buffer
tracing/uprobes: Add support for full argument access methods
tracing/uprobes: Add @+file_offset fetch method

Oleg Nesterov (1):
uprobes: Allocate ->utask before handler_chain() for tracing handlers

Documentation/trace/uprobetracer.txt | 36 +-
kernel/events/uprobes.c | 4 +
kernel/trace/trace_kprobe.c | 812 +++++++++++++++++++----------------
kernel/trace/trace_probe.c | 440 +++++++------------
kernel/trace/trace_probe.h | 216 ++++++++++
kernel/trace/trace_uprobe.c | 495 +++++++++++++++------
6 files changed, 1208 insertions(+), 795 deletions(-)

--
1.7.11.7

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