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Commit 4cd70632 authored by Sasha Goldshtein's avatar Sasha Goldshtein
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Implemented histogram functionality, including strings; added examples

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tools/gentrace.py
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......@@ -3,116 +3,204 @@
# gentrace.py Trace a function and display a histogram or summary of its
# parameter values.
#
# USAGE: TODO
# USAGE: gentrace.py [-h] [-p PID] [-z STRING_SIZE]
# [-s SPECIFIER [SPECIFIER ...]]
# [interval] [count]
#
# Copyright (C) 2016 Sasha Goldshtein.
from bcc import BPF
from time import sleep
from time import sleep, strftime
import argparse
class Specifier(object):
text = """
DATA_DECL
int PROBENAME(struct pt_regs *ctx, SIGNATURE)
int PROBENAME(struct pt_regs *ctx SIGNATURE)
{
EXPR_TYPE __key = EXPR;
KEY_EXPR
if (!(FILTER)) return 0;
COLLECT
return 0;
}
"""
def __init__(self, specifier, library):
# <raw|hist>:lib:function(signature)[:type:expr[:filter]]
def __init__(self, specifier, pid):
self.raw_spec = specifier
parts = specifier.strip().split(':')
if len(parts) < 4 or len(parts) > 5:
if len(parts) < 3 or len(parts) > 6:
raise ValueError("invalid specifier format")
self.type = parts[0] # hist or raw
if self.type != "hist" and self.type != "raw":
raise ValueError("unrecognized probe type")
fparts = parts[1].split('(')
self.library = parts[1]
fparts = parts[2].split('(')
if len(fparts) != 2:
raise ValueError("invalid specifier format")
self.function = fparts[0]
self.signature = fparts[1][:-1]
self.expr_type = parts[2]
self.expr = parts[3]
self.filter = None if len(parts) != 5 else parts[4]
self.library = library
if len(parts) >= 5:
self.expr_type = parts[3]
self.expr = parts[4]
else:
self.expr_type = "u64"
self.expr = "1"
self.filter = None if len(parts) != 6 else parts[5]
self.pid = pid
self.probe_func_name = self.function + "_probe"
self.probe_hash_name = self.function + "_hash"
def generate_text(self):
# TODO Need special treatment of strings (char *) expressions
def _is_string_probe(self):
return self.expr_type == "char*" or self.expr_type == "char *"
def generate_text(self, string_size):
program = self.text.replace("PROBENAME", self.probe_func_name)
program = program.replace("SIGNATURE", self.signature)
if self.type == "raw":
signature = "" if len(self.signature) == 0 \
else "," + self.signature
program = program.replace("SIGNATURE", signature)
if self._is_string_probe():
decl = """
struct %s_key_t { char key[%d]; };
BPF_HASH(%s, struct %s_key_t, u64);
""" \
% (self.function, string_size,
self.probe_hash_name, self.function)
collect = "%s.increment(__key);" % self.probe_hash_name
key_expr = """
struct %s_key_t __key = {0};
bpf_probe_read(&__key.key, sizeof(__key.key), %s);
""" \
% (self.function, self.expr)
elif self.type == "raw":
decl = "BPF_HASH(%s, %s, u64);" % \
(self.probe_hash_name, self.expr_type)
collect = "u64 zero = 0, *val; val = %s.lookup_or_init(&__key, &zero); (*val)++;" % self.probe_hash_name
collect = "%s.increment(__key);" % self.probe_hash_name
key_expr = "%s __key = %s;" % \
(self.expr_type, self.expr)
elif self.type == "hist":
pass # TODO
decl = "BPF_HISTOGRAM(%s, %s);" % \
(self.probe_hash_name, self.expr_type)
collect = "%s.increment(bpf_log2l(__key));" % \
self.probe_hash_name
key_expr = "%s __key = %s;" % \
(self.expr_type, self.expr)
program = program.replace("DATA_DECL", decl)
program = program.replace("EXPR_TYPE", self.expr_type)
program = program.replace("EXPR", self.expr)
program = program.replace("KEY_EXPR", key_expr)
program = program.replace("FILTER", self.filter or "1")
program = program.replace("COLLECT", collect)
return program
def attach(self, bpf):
self.bpf = bpf
if self.library is not None:
if len(self.library) > 0:
bpf.attach_uprobe(name=self.library,
sym=self.function,
fn_name=self.probe_func_name)
fn_name=self.probe_func_name,
pid=self.pid or -1)
else:
bpf.attach_kprobe(event=self.function,
fn_name=self.probe_func_name)
def display(self):
print(self.raw_spec)
data = self.bpf.get_table(self.probe_hash_name)
if self.type == "raw":
for key, value in sorted(data.items(), key=lambda kv: kv[1].value):
print("%20s = %-20s count = %s" % (self.expr, str(key.value), str(value.value)))
print("\t%-10s %s" % ("COUNT", "EVENT"))
for key, value in sorted(data.items(),
key=lambda kv: kv[1].value):
if self._is_string_probe():
key_str = key.key
else:
key_str = str(key.value)
print("\t%-10s %s = %s" %
(str(value.value), self.expr, key_str))
elif self.type == "hist":
pass # TODO
data.print_log2_hist(val_type=self.expr)
examples = """
Probe specifier syntax:
<raw|hist>:[library]:function(signature)[:type:expr[:filter]]
Where:
<raw|hist> -- collect raw data or a histogram of values
library -- the library that contains the function
(leave empty for kernel functions)
function -- the function name to trace
signature -- the function's parameters, as in the C header
type -- the type of the expression to collect
expr -- the expression to collect
filter -- a filter that is applied to collected values
EXAMPLES:
TODO
"""
# probe specifier syntax:
# <hist|raw>:<function name>(<signature>):<type>:<expr>[:filter]
# hist:malloc(size_t size):size_t:size:size>16
# hist:fwrite(FILE* f, size_t count):size_t:count
# raw:printf(char * format):char:format[0]
# hist:fwrite(FILE* file):int:file->fd:file->fd==2
gentrace.py -s "hist::__kmalloc(u64 size):u64:size"
Print a histogram of allocation sizes passed to kmalloc
gentrace.py -p 1005 -s "raw:c:malloc(size_t size):size_t:size:size==16"
Print a raw count of how many times process 1005 called malloc with
an allocation size of 16 bytes
gentrace.py -p 1005 -s "raw:c:write(int fd):int:fd"
Print raw counts of how many times writes were issued to a particular
file descriptor number, in process 1005
gentrace.py -s "hist:c:write(int fd, const void *buf, size_t count):size_t:count:fd==1"
Print a histogram of buffer sizes passed to write() across all
processes, where the file descriptor was 1 (STDOUT)
gentrace.py -s "raw:c:fork"
Count fork() calls in libc across all processes
Can also use funccount.py, which is easier and more flexible
gentrace.py -s \\
"hist:c:sleep(u32 seconds):u32:seconds" \\
"hist:c:nanosleep(struct timespec { time_t tv_sec; long tv_nsec; } *req):long:req->tv_nsec"
Print histograms of sleep() and nanosleep() parameter values
gentrace.py -p 2780 -s -z 120 "raw:c:write(int fd, char* buf, size_t len):char*:buf:fd==1"
Spy on writes to STDOUT performed by process 2780, up to a string size
of 120 characters
"""
parser = argparse.ArgumentParser(description=
"Trace a function and display a summary of its parameter values.",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-l", "--library",
help="the library which contains the function to trace")
parser.add_argument("-s", "--specifier", nargs="+", dest="specifiers",
help="the probe specifier")
parser.add_argument("interval", nargs="?", default=1,
parser.add_argument("-p", "--pid", type=int,
help="id of the process to trace (optional)")
parser.add_argument("-z", "--string-size", default=80, type=int,
help="maximum string size to read from char* arguments")
parser.add_argument("interval", nargs="?", default=1, type=int,
help="output interval, in seconds")
parser.add_argument("count", nargs="?",
parser.add_argument("count", nargs="?", type=int,
help="number of outputs")
parser.add_argument("-s", "--specifier", nargs="+", dest="specifiers",
help="the probe specifiers (see examples below)")
args = parser.parse_args()
specifiers = []
for specifier in args.specifiers:
specifiers.append(Specifier(specifier, args.library))
specifiers.append(Specifier(specifier, args.pid))
bpf_source = "#include <uapi/linux/ptrace.h>\n"
for specifier in specifiers:
bpf_source += specifier.generate_text()
bpf_source += specifier.generate_text(args.string_size)
bpf = BPF(text=bpf_source)
for specifier in specifiers:
specifier.attach(bpf)
count_so_far = 0
while True:
print("COLLECTED DATA:")
try:
sleep(args.interval)
except KeyboardInterrupt:
exit()
print("[%s]" % strftime("%H:%M:%S"))
for specifier in specifiers:
specifier.display()
sleep(args.interval)
count_so_far += 1
if args.count is not None and count_so_far >= args.count:
exit()
tools/gentrace_examples.txt 0 → 100644
View file @ 4cd70632
Demonstrations of gentrace.
gentrace probes functions you specify and collects parameter values into a
histogram or a counting table. This can be used to understand the distribution
of values a certain parameter takes, filter and print interesting parameters
without attaching a debugger, and getting general execution statistics on
various functions.
For example, suppose you want to find what allocation sizes are common in
your application:
# ./gentrace.py -p 2420 -s "raw:c:malloc(size_t size):size_t:size"
[01:42:29]
raw:c:malloc(size_t size):size_t:size
COUNT EVENT
[01:42:30]
raw:c:malloc(size_t size):size_t:size
COUNT EVENT
[01:42:31]
raw:c:malloc(size_t size):size_t:size
COUNT EVENT
1 size = 16
[01:42:32]
raw:c:malloc(size_t size):size_t:size
COUNT EVENT
2 size = 16
[01:42:33]
raw:c:malloc(size_t size):size_t:size
COUNT EVENT
3 size = 16
[01:42:34]
raw:c:malloc(size_t size):size_t:size
COUNT EVENT
4 size = 16
^C
It seems that the application is allocating blocks of size 16. The COUNT
column contains the number of occurrences of a particular event, and the
EVENT column describes the event. In this case, the "size" parameter was
probed and its value was 16, repeatedly.
Now, suppose you wanted a histogram of buffer sizes passed to the write()
function across the system:
# ./gentrace.py -s "hist:c:write(int fd, void *buf, size_t len):size_t:len"
[01:45:22]
hist:c:write(int fd, void *buf, size_t len):size_t:len
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 2 |************* |
4 -> 7 : 0 | |
8 -> 15 : 2 |************* |
16 -> 31 : 0 | |
32 -> 63 : 6 |****************************************|
[01:45:23]
hist:c:write(int fd, void *buf, size_t len):size_t:len
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 11 |*************** |
4 -> 7 : 0 | |
8 -> 15 : 4 |***** |
16 -> 31 : 0 | |
32 -> 63 : 28 |****************************************|
64 -> 127 : 12 |***************** |
[01:45:24]
hist:c:write(int fd, void *buf, size_t len):size_t:len
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 21 |**************** |
4 -> 7 : 0 | |
8 -> 15 : 6 |**** |
16 -> 31 : 0 | |
32 -> 63 : 52 |****************************************|
64 -> 127 : 26 |******************** |
^C
It seems that most writes fall into three buckets: very small writes of 2-3
bytes, medium writes of 32-63 bytes, and larger writes of 64-127 bytes.
But these are writes across the board -- what if you wanted to focus on writes
to STDOUT?
# ./gentrace.py -s "hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1"
[01:47:17]
hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 1 |****************************************|
16 -> 31 : 0 | |
32 -> 63 : 1 |****************************************|
[01:47:18]
hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 2 |************* |
16 -> 31 : 0 | |
32 -> 63 : 3 |******************** |
64 -> 127 : 6 |****************************************|
[01:47:19]
hist:c:write(int fd, void *buf, size_t len):size_t:len:fd==1
len : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 3 |********* |
16 -> 31 : 0 | |
32 -> 63 : 5 |*************** |
64 -> 127 : 13 |****************************************|
^C
The "fd==1" part is a filter that is applied to every invocation of write().
Only if the filter condition is true, the value is recorded.
You can also use gentrace to trace kernel functions. For example, suppose you
wanted a histogram of kernel allocation (kmalloc) sizes across the system,
printed twice with 3 second intervals:
# ./gentrace.py 3 2 -s "hist::__kmalloc(size_t size):size_t:size"
[01:50:00]
hist::__kmalloc(size_t size):size_t:size
size : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 6 |****************************************|
[01:50:03]
hist::__kmalloc(size_t size):size_t:size
size : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 22 |****************************************|
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 5 |********* |
128 -> 255 : 2 |*** |
Occasionally, numeric information isn't enough and you want to capture strings.
What are the strings printed by puts() across the system?
# ./gentrace.py 10 1 -s "raw:c:puts(char *str):char*:str"
[01:53:54]
raw:c:puts(char *str):char*:str
COUNT EVENT
2 str = Press ENTER to start.
It looks like the message "Press ENTER to start." was printed twice during the
10 seconds we were tracing.
USAGE message:
# ./gentrace.py -h
usage: gentrace.py [-h] [-p PID] [-z STRING_SIZE]
[-s SPECIFIERS [SPECIFIERS ...]]
[interval] [count]
Trace a function and display a summary of its parameter values.
positional arguments:
interval output interval, in seconds
count number of outputs
optional arguments:
-h, --help show this help message and exit
-p PID, --pid PID id of the process to trace (optional)
-z STRING_SIZE, --string-size STRING_SIZE
maximum string size to read from char* arguments
-s SPECIFIERS [SPECIFIERS ...], --specifier SPECIFIERS [SPECIFIERS ...]
the probe specifiers (see examples below)
Probe specifier syntax:
<raw|hist>:[library]:function(signature)[:type:expr[:filter]]
Where:
<raw|hist> -- collect raw data or a histogram of values
library -- the library that contains the function
(leave empty for kernel functions)
function -- the function name to trace
signature -- the function's parameters, as in the C header
type -- the type of the expression to collect
expr -- the expression to collect
filter -- a filter that is applied to collected values
EXAMPLES:
gentrace.py -s "hist::__kmalloc(u64 size):u64:size"
Print a histogram of allocation sizes passed to kmalloc
gentrace.py -p 1005 -s "raw:c:malloc(size_t size):size_t:size:size==16"
Print a raw count of how many times process 1005 called malloc with
an allocation size of 16 bytes
gentrace.py -p 1005 -s "raw:c:write(int fd):int:fd"
Print raw counts of how many times writes were issued to a particular
file descriptor number, in process 1005
gentrace.py -s "hist:c:write(int fd, const void *buf, size_t count):size_t:count:fd==1"
Print a histogram of buffer sizes passed to write() across all
processes, where the file descriptor was 1 (STDOUT)
gentrace.py -s "raw:c:fork"
Count fork() calls in libc across all processes
Can also use funccount.py, which is easier and more flexible
gentrace.py -s \
"hist:c:sleep(u32 seconds):u32:seconds" \
"hist:c:nanosleep(struct timespec { time_t tv_sec; long tv_nsec; } *req):long:req->tv_nsec"
Print histograms of sleep() and nanosleep() parameter values
gentrace.py -p 2780 -s -z 120 "raw:c:write(int fd, char* buf, size_t len):char*:buf:fd==1"
Spy on writes to STDOUT performed by process 2780, up to a string size
of 120 characters
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