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bashreadline.c
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bashreadline.c
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/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
/* Copyright (c) 2021 Facebook */
#include <argp.h>
#include <stdio.h>
#include <errno.h>
#include <signal.h>
#include <time.h>
#include <unistd.h>
#include <ctype.h>
#include <bpf/libbpf.h>
#include <bpf/bpf.h>
#include "bashreadline.h"
#include "bashreadline.skel.h"
#include "btf_helpers.h"
#include "trace_helpers.h"
#include "uprobe_helpers.h"
#define PERF_BUFFER_PAGES 16
#define PERF_POLL_TIMEOUT_MS 100
#define warn(...) fprintf(stderr, __VA_ARGS__)
static volatile sig_atomic_t exiting = 0;
const char *argp_program_version = "bashreadline 1.0";
const char *argp_program_bug_address =
"https://github.com/iovisor/bcc/tree/master/libbpf-tools";
const char argp_program_doc[] =
"Print entered bash commands from all running shells.\n"
"\n"
"USAGE: bashreadline [-s <path/to/libreadline.so>]\n"
"\n"
"EXAMPLES:\n"
" bashreadline\n"
" bashreadline -s /usr/lib/libreadline.so\n";
static const struct argp_option opts[] = {
{ "shared", 's', "PATH", 0, "the location of libreadline.so library" },
{ "verbose", 'v', NULL, 0, "Verbose debug output" },
{ NULL, 'h', NULL, OPTION_HIDDEN, "Show the full help" },
{},
};
static char *libreadline_path = NULL;
static bool verbose = false;
static error_t parse_arg(int key, char *arg, struct argp_state *state)
{
switch (key) {
case 's':
libreadline_path = strdup(arg);
if (libreadline_path == NULL)
return ARGP_ERR_UNKNOWN;
break;
case 'v':
verbose = true;
break;
case 'h':
argp_state_help(state, stderr, ARGP_HELP_STD_HELP);
break;
default:
return ARGP_ERR_UNKNOWN;
}
return 0;
}
static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
{
if (level == LIBBPF_DEBUG && !verbose)
return 0;
return vfprintf(stderr, format, args);
}
static void handle_event(void *ctx, int cpu, void *data, __u32 data_size)
{
struct str_t *e = data;
struct tm *tm;
char ts[16];
time_t t;
time(&t);
tm = localtime(&t);
strftime(ts, sizeof(ts), "%H:%m:%S", tm);
printf("%-9s %-7d %s\n", ts, e->pid, e->str);
}
static void handle_lost_events(void *ctx, int cpu, __u64 lost_cnt)
{
warn("lost %llu events on CPU #%d\n", lost_cnt, cpu);
}
static char *find_readline_so()
{
const char *bash_path = "/bin/bash";
FILE *fp;
off_t func_off;
char *line = NULL;
size_t line_sz = 0;
char path[128];
char *result = NULL;
func_off = get_elf_func_offset(bash_path, "readline");
if (func_off >= 0)
return strdup(bash_path);
/*
* Try to find libreadline.so if readline is not defined in
* bash itself.
*
* ldd will print a list of names of shared objects,
* dependencies, and their paths. The line for libreadline
* would looks like
*
* libreadline.so.8 => /usr/lib/libreadline.so.8 (0x00007b....)
*
* Here, it finds a line with libreadline.so and extracts the
* path after the arrow, '=>', symbol.
*/
fp = popen("ldd /bin/bash", "r");
if (fp == NULL)
goto cleanup;
while (getline(&line, &line_sz, fp) >= 0) {
if (sscanf(line, "%*s => %127s", path) < 1)
continue;
if (strstr(line, "/libreadline.so")) {
result = strdup(path);
break;
}
}
cleanup:
if (line)
free(line);
if (fp)
pclose(fp);
return result;
}
static void sig_int(int signo)
{
exiting = 1;
}
int main(int argc, char **argv)
{
LIBBPF_OPTS(bpf_object_open_opts, open_opts);
static const struct argp argp = {
.options = opts,
.parser = parse_arg,
.doc = argp_program_doc,
};
struct bashreadline_bpf *obj = NULL;
struct perf_buffer *pb = NULL;
char *readline_so_path;
off_t func_off;
int err;
err = argp_parse(&argp, argc, argv, 0, NULL, NULL);
if (err)
return err;
if (libreadline_path) {
readline_so_path = libreadline_path;
} else if ((readline_so_path = find_readline_so()) == NULL) {
warn("failed to find readline\n");
return 1;
}
libbpf_set_strict_mode(LIBBPF_STRICT_ALL);
libbpf_set_print(libbpf_print_fn);
err = ensure_core_btf(&open_opts);
if (err) {
warn("failed to fetch necessary BTF for CO-RE: %s\n", strerror(-err));
goto cleanup;
}
obj = bashreadline_bpf__open_opts(&open_opts);
if (!obj) {
warn("failed to open BPF object\n");
goto cleanup;
}
err = bashreadline_bpf__load(obj);
if (err) {
warn("failed to load BPF object: %d\n", err);
goto cleanup;
}
func_off = get_elf_func_offset(readline_so_path, "readline");
if (func_off < 0) {
warn("cound not find readline in %s\n", readline_so_path);
goto cleanup;
}
obj->links.printret = bpf_program__attach_uprobe(obj->progs.printret, true, -1,
readline_so_path, func_off);
if (!obj->links.printret) {
err = -errno;
warn("failed to attach readline: %d\n", err);
goto cleanup;
}
pb = perf_buffer__new(bpf_map__fd(obj->maps.events), PERF_BUFFER_PAGES,
handle_event, handle_lost_events, NULL, NULL);
if (!pb) {
err = -errno;
warn("failed to open perf buffer: %d\n", err);
goto cleanup;
}
if (signal(SIGINT, sig_int) == SIG_ERR) {
warn("can't set signal handler: %s\n", strerror(errno));
err = 1;
goto cleanup;
}
printf("%-9s %-7s %s\n", "TIME", "PID", "COMMAND");
while (!exiting) {
err = perf_buffer__poll(pb, PERF_POLL_TIMEOUT_MS);
if (err < 0 && err != -EINTR) {
warn("error polling perf buffer: %s\n", strerror(-err));
goto cleanup;
}
err = 0;
}
cleanup:
if (readline_so_path)
free(readline_so_path);
perf_buffer__free(pb);
bashreadline_bpf__destroy(obj);
cleanup_core_btf(&open_opts);
return err != 0;
}