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#! /usr/bin/python3
# @lint-avoid-python-3-compatibility-imports
#
# shmsnoop Trace shm*() syscalls.
# For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: shmsnoop [-h] [-T] [-x] [-p PID] [-d DURATION] [-t TID] [-n NAME]
#
# Copyright (c) 2018 Jiri Olsa.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 08-Oct-2018 Jiri Olsa Created this.
from __future__ import print_function
from bcc import ArgString, BPF
import argparse
from datetime import datetime, timedelta
# arguments
examples = """examples:
./shmsnoop # trace all shm*() syscalls
./shmsnoop -T # include timestamps
./shmsnoop -p 181 # only trace PID 181
./shmsnoop -t 123 # only trace TID 123
./shmsnoop -d 10 # trace for 10 seconds only
./shmsnoop -n main # only print process names containing "main"
"""
parser = argparse.ArgumentParser(
description="Trace shm*() syscalls",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-T", "--timestamp", action="store_true",
help="include timestamp on output")
parser.add_argument("-p", "--pid",
help="trace this PID only")
parser.add_argument("-t", "--tid",
help="trace this TID only")
parser.add_argument("-d", "--duration",
help="total duration of trace in seconds")
parser.add_argument("-n", "--name",
type=ArgString,
help="only print process names containing this name")
parser.add_argument("--ebpf", action="store_true",
help=argparse.SUPPRESS)
args = parser.parse_args()
debug = 0
if args.duration:
args.duration = timedelta(seconds=int(args.duration))
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <uapi/linux/limits.h>
#include <linux/sched.h>
struct val_t {
u64 id;
u64 ts;
int sys;
unsigned long key;
unsigned long size;
unsigned long shmflg;
unsigned long shmid;
unsigned long cmd;
unsigned long buf;
unsigned long shmaddr;
unsigned long ret;
char comm[TASK_COMM_LEN];
};
BPF_HASH(infotmp, u64, struct val_t);
BPF_PERF_OUTPUT(events);
enum {
SYS_SHMGET,
SYS_SHMAT,
SYS_SHMDT,
SYS_SHMCTL,
};
static int enter(struct val_t *val)
{
u64 id = bpf_get_current_pid_tgid();
u32 pid = id >> 32; // PID is higher part
u32 tid = id; // Cast and get the lower part
FILTER
val->id = id;
infotmp.update(&id, val);
return 0;
}
int trace_return(struct pt_regs *ctx)
{
u64 id = bpf_get_current_pid_tgid();
u64 tsp = bpf_ktime_get_ns();
struct val_t *val;
val = infotmp.lookup(&id);
if (val == 0)
return 0;
if (bpf_get_current_comm(&val->comm, sizeof(val->comm)) != 0)
goto out;
val->ts = tsp / 1000;
val->ret = PT_REGS_RC(ctx);
events.perf_submit(ctx, val, sizeof(*val));
out:
infotmp.delete(&id);
return 0;
}
int syscall__shmget(struct pt_regs *ctx, u64 key, u64 size, u64 shmflg)
{
struct val_t val = {
.sys = SYS_SHMGET,
};
val.key = key;
val.size = size;
val.shmflg = shmflg;
return enter(&val);
};
int syscall__shmat(struct pt_regs *ctx, u64 shmid, u64 shmaddr, u64 shmflg)
{
struct val_t val = {
.sys = SYS_SHMAT,
};
val.shmid = shmid;
val.shmaddr = shmaddr;
val.shmflg = shmflg;
return enter(&val);
};
int syscall__shmdt(struct pt_regs *ctx, u64 shmaddr)
{
struct val_t val = {
.sys = SYS_SHMDT,
};
val.shmaddr = shmaddr;
return enter(&val);
};
int syscall__shmctl(struct pt_regs *ctx, u64 shmid, u64 cmd, u64 buf)
{
struct val_t val = {
.sys = SYS_SHMCTL,
};
val.shmid = shmid;
val.cmd = cmd;
val.buf = buf;
return enter(&val);
};
"""
if args.tid: # TID trumps PID
bpf_text = bpf_text.replace('FILTER',
'if (tid != %s) { return 0; }' % args.tid)
elif args.pid:
bpf_text = bpf_text.replace('FILTER',
'if (pid != %s) { return 0; }' % args.pid)
else:
bpf_text = bpf_text.replace('FILTER', '')
if debug or args.ebpf:
print(bpf_text)
if args.ebpf:
exit()
# initialize BPF
b = BPF(text=bpf_text)
syscall_fnname = b.get_syscall_fnname("shmget")
if BPF.ksymname(syscall_fnname) != -1:
b.attach_kprobe(event=syscall_fnname, fn_name="syscall__shmget")
b.attach_kretprobe(event=syscall_fnname, fn_name="trace_return")
syscall_fnname = b.get_syscall_fnname("shmat")
if BPF.ksymname(syscall_fnname) != -1:
b.attach_kprobe(event=syscall_fnname, fn_name="syscall__shmat")
b.attach_kretprobe(event=syscall_fnname, fn_name="trace_return")
syscall_fnname = b.get_syscall_fnname("shmdt")
if BPF.ksymname(syscall_fnname) != -1:
b.attach_kprobe(event=syscall_fnname, fn_name="syscall__shmdt")
b.attach_kretprobe(event=syscall_fnname, fn_name="trace_return")
syscall_fnname = b.get_syscall_fnname("shmctl")
if BPF.ksymname(syscall_fnname) != -1:
b.attach_kprobe(event=syscall_fnname, fn_name="syscall__shmctl")
b.attach_kretprobe(event=syscall_fnname, fn_name="trace_return")
TASK_COMM_LEN = 16 # linux/sched.h
SYS_SHMGET = 0
SYS_SHMAT = 1
SYS_SHMDT = 2
SYS_SHMCTL = 3
initial_ts = 0
# header
if args.timestamp:
print("%-14s" % ("TIME(s)"), end="")
print("%-6s %-16s %6s %16s ARGs" %
("TID" if args.tid else "PID", "COMM", "SYS", "RET"))
def sys_name(sys):
switcher = {
SYS_SHMGET: "SHMGET",
SYS_SHMAT: "SHMAT",
SYS_SHMDT: "SHMDT",
SYS_SHMCTL: "SHMCTL",
}
return switcher.get(sys, "N/A")
shmget_flags = [
{ 'name' : 'IPC_CREAT', 'value' : 0o1000 },
{ 'name' : 'IPC_EXCL', 'value' : 0o2000 },
{ 'name' : 'SHM_HUGETLB', 'value' : 0o4000 },
{ 'name' : 'SHM_HUGE_2MB', 'value' : 21 << 26 },
{ 'name' : 'SHM_HUGE_1GB', 'value' : 30 << 26 },
{ 'name' : 'SHM_NORESERVE', 'value' : 0o10000 },
{ 'name' : 'SHM_EXEC', 'value' : 0o100000 }
]
shmat_flags = [
{ 'name' : 'SHM_RDONLY', 'value' : 0o10000 },
{ 'name' : 'SHM_RND', 'value' : 0o20000 },
{ 'name' : 'SHM_REMAP', 'value' : 0o40000 },
{ 'name' : 'SHM_EXEC', 'value' : 0o100000 },
]
def shmflg_str(val, flags):
cur = filter(lambda x : x['value'] & val, flags)
str = "0x%x" % val
if (not val):
return str
str += " ("
cnt = 0
for x in cur:
if cnt:
str += "|"
str += x['name']
val &= ~x['value']
cnt += 1
if val != 0 or not cnt:
if cnt:
str += "|"
str += "0%o" % val
str += ")"
return str
# process event
def print_event(cpu, data, size):
event = b["events"].event(data)
global initial_ts
if not initial_ts:
initial_ts = event.ts
if args.name and bytes(args.name) not in event.comm:
return
if args.timestamp:
delta = event.ts - initial_ts
print("%-14.9f" % (float(delta) / 1000000), end="")
print("%-6d %-16s %6s %16lx " %
(event.id & 0xffffffff if args.tid else event.id >> 32,
event.comm.decode(), sys_name(event.sys), event.ret), end = '')
if event.sys == SYS_SHMGET:
print("key: 0x%lx, size: %lu, shmflg: %s" %
(event.key, event.size, shmflg_str(event.shmflg, shmget_flags)))
if event.sys == SYS_SHMAT:
print("shmid: 0x%lx, shmaddr: 0x%lx, shmflg: %s" %
(event.shmid, event.shmaddr, shmflg_str(event.shmflg, shmat_flags)))
if event.sys == SYS_SHMDT:
print("shmaddr: 0x%lx" % (event.shmaddr))
if event.sys == SYS_SHMCTL:
print("shmid: 0x%lx, cmd: %lu, buf: 0x%x" % (event.shmid, event.cmd, event.buf))
# loop with callback to print_event
b["events"].open_perf_buffer(print_event, page_cnt=64)
start_time = datetime.now()
while not args.duration or datetime.now() - start_time < args.duration:
try:
b.perf_buffer_poll(timeout=1000)
except KeyboardInterrupt:
exit()
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