[PATCHSET 00/12] tracing/uprobes: Add support for more fetch methods

Namhyung Kim
2013-07-03T12:35:52Z

Hello,

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
address.

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

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

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 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 perf.data (~33 samples) ]

# perf script | grep -v ^#
foo 2008 [002 2199.867154: probe_foo:foo (4004c3)
glob=4294967295 str="hello uprobe." bit=5 argc=1 local=1234

Note that 4294967295 is 0xffffffff.

Obviously, the perf tools also need to be improved. I'll work on that
later.

This patchset is based on the current tip/perf/core. I also put this
on my 'uprobe/fetch-v1' 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@hitachi.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>

Hyeoncheol Lee (2):
tracing/kprobes: Move fetch functions to trace_kprobe.c
tracing/kprobes: Add fetch{,_size} member into symbol and deref fetch
method

Namhyung Kim (10):
tracing/kprobes: Make stack and memory fetch functions static
tracing/kprobes: Factor out struct trace_probe
tracing/uprobes: Convert to struct trace_probe
tracing/kprobes: Move common functions to trace_probe.c
tracing/kprobes: Remove duplicate set_print_fmt()
tracing/uprobes: Fetch args before reserving a ring buffer
tracing/uprobes: Fix a comment for uprobe registration syntax
tracing/kprobes: Add priv argument to fetch functions
tracing/uprobes: Add more fetch functions
tracing/uprobes: Add support for full argument access methods

kernel/trace/trace_kprobe.c | 529 ++++++++++++++++++++++----------------------
kernel/trace/trace_probe.c | 451 ++++++++++++++++++-------------------
kernel/trace/trace_probe.h | 154 ++++++++++++-
kernel/trace/trace_uprobe.c | 429 ++++++++++++++++++++++++-----------
4 files changed, 926 insertions(+), 637 deletions(-)

--
1.7.11.7