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Subject[PATCHSET 00/13] tracing/uprobes: Add support for more fetch methods (v6)

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.

The patch 1-2 are bug fixes and can be applied independently.

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.

* v6 changes:
- add more Ack's from Masami
- fix ref count of uprobe_cpu_buffer (thanks to Jovi)

* v5 changes:
- use user_stack_pointer() instead of GET_USP()
- fix a bug in 'stack' fetch method of uprobes

* 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!)


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=@0x8a8:s32 \
> str=@0x8ac:string bit=@0x8bc:b10@2/32 argc=%di local=-0x8(%bp)'
Added new event:
probe_foo:foo (on 0x4c3 with glob=@0x8a8:s32 str=@0x8ac:string
bit=@0x8bc:b10@2/32 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 (~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-v6'
branch in my tree:


Any comments are welcome, thanks.

Cc: Masami Hiramatsu <>
Cc: Srikar Dronamraju <>
Cc: Oleg Nesterov <>
Cc: zhangwei(Jovi) <>
Cc: Arnaldo Carvalho de Melo <>
Cc: Hemant Kumar <>

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 | 453 +++++++++---------------
kernel/trace/trace_probe.h | 202 ++++++++++-
kernel/trace/trace_uprobe.c | 458 +++++++++++++++++--------
5 files changed, 1063 insertions(+), 727 deletions(-)


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