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selftests/bpf: Add test for d_path helper

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Adding test for d_path helper which is pretty much
copied from Wenbo Zhang's test for bpf_get_fd_path,
which never made it in.

The test is doing fstat/close on several fd types,
and verifies we got the d_path helper working on
kernel probes for vfs_getattr/filp_close functions.

Original-patch-by: Wenbo Zhang <ethercflow@gmail.com>

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200825192124.710397-14-jolsa@kernel.org
This commit is contained in:
Jiri Olsa 2020-08-25 21:21:23 +02:00 committed by Alexei Starovoitov
parent 762f851568
commit e4d1af4b16
2 changed files with 205 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

147
tools/testing/selftests/bpf/prog_tests/d_path.c Normal file
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// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <test_progs.h>
#include <sys/stat.h>
#include <linux/sched.h>
#include <sys/syscall.h>
#define MAX_PATH_LEN 128
#define MAX_FILES 7
#include "test_d_path.skel.h"
static int duration;
static struct {
__u32 cnt;
char paths[MAX_FILES][MAX_PATH_LEN];
} src;
static int set_pathname(int fd, pid_t pid)
{
char buf[MAX_PATH_LEN];
snprintf(buf, MAX_PATH_LEN, "/proc/%d/fd/%d", pid, fd);
return readlink(buf, src.paths[src.cnt++], MAX_PATH_LEN);
}
static int trigger_fstat_events(pid_t pid)
{
int sockfd = -1, procfd = -1, devfd = -1;
int localfd = -1, indicatorfd = -1;
int pipefd[2] = { -1, -1 };
struct stat fileStat;
int ret = -1;
/* unmountable pseudo-filesystems */
if (CHECK(pipe(pipefd) < 0, "trigger", "pipe failed\n"))
return ret;
/* unmountable pseudo-filesystems */
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (CHECK(sockfd < 0, "trigger", "scoket failed\n"))
goto out_close;
/* mountable pseudo-filesystems */
procfd = open("/proc/self/comm", O_RDONLY);
if (CHECK(procfd < 0, "trigger", "open /proc/self/comm failed\n"))
goto out_close;
devfd = open("/dev/urandom", O_RDONLY);
if (CHECK(devfd < 0, "trigger", "open /dev/urandom failed\n"))
goto out_close;
localfd = open("/tmp/d_path_loadgen.txt", O_CREAT | O_RDONLY);
if (CHECK(localfd < 0, "trigger", "open /tmp/d_path_loadgen.txt failed\n"))
goto out_close;
/* bpf_d_path will return path with (deleted) */
remove("/tmp/d_path_loadgen.txt");
indicatorfd = open("/tmp/", O_PATH);
if (CHECK(indicatorfd < 0, "trigger", "open /tmp/ failed\n"))
goto out_close;
ret = set_pathname(pipefd[0], pid);
if (CHECK(ret < 0, "trigger", "set_pathname failed for pipe[0]\n"))
goto out_close;
ret = set_pathname(pipefd[1], pid);
if (CHECK(ret < 0, "trigger", "set_pathname failed for pipe[1]\n"))
goto out_close;
ret = set_pathname(sockfd, pid);
if (CHECK(ret < 0, "trigger", "set_pathname failed for socket\n"))
goto out_close;
ret = set_pathname(procfd, pid);
if (CHECK(ret < 0, "trigger", "set_pathname failed for proc\n"))
goto out_close;
ret = set_pathname(devfd, pid);
if (CHECK(ret < 0, "trigger", "set_pathname failed for dev\n"))
goto out_close;
ret = set_pathname(localfd, pid);
if (CHECK(ret < 0, "trigger", "set_pathname failed for file\n"))
goto out_close;
ret = set_pathname(indicatorfd, pid);
if (CHECK(ret < 0, "trigger", "set_pathname failed for dir\n"))
goto out_close;
/* triggers vfs_getattr */
fstat(pipefd[0], &fileStat);
fstat(pipefd[1], &fileStat);
fstat(sockfd, &fileStat);
fstat(procfd, &fileStat);
fstat(devfd, &fileStat);
fstat(localfd, &fileStat);
fstat(indicatorfd, &fileStat);
out_close:
/* triggers filp_close */
close(pipefd[0]);
close(pipefd[1]);
close(sockfd);
close(procfd);
close(devfd);
close(localfd);
close(indicatorfd);
return ret;
}
void test_d_path(void)
{
struct test_d_path__bss *bss;
struct test_d_path *skel;
int err;
skel = test_d_path__open_and_load();
if (CHECK(!skel, "setup", "d_path skeleton failed\n"))
goto cleanup;
err = test_d_path__attach(skel);
if (CHECK(err, "setup", "attach failed: %d\n", err))
goto cleanup;
bss = skel->bss;
bss->my_pid = getpid();
err = trigger_fstat_events(bss->my_pid);
if (err < 0)
goto cleanup;
for (int i = 0; i < MAX_FILES; i++) {
CHECK(strncmp(src.paths[i], bss->paths_stat[i], MAX_PATH_LEN),
"check",
"failed to get stat path[%d]: %s vs %s\n",
i, src.paths[i], bss->paths_stat[i]);
CHECK(strncmp(src.paths[i], bss->paths_close[i], MAX_PATH_LEN),
"check",
"failed to get close path[%d]: %s vs %s\n",
i, src.paths[i], bss->paths_close[i]);
/* The d_path helper returns size plus NUL char, hence + 1 */
CHECK(bss->rets_stat[i] != strlen(bss->paths_stat[i]) + 1,
"check",
"failed to match stat return [%d]: %d vs %zd [%s]\n",
i, bss->rets_stat[i], strlen(bss->paths_stat[i]) + 1,
bss->paths_stat[i]);
CHECK(bss->rets_close[i] != strlen(bss->paths_stat[i]) + 1,
"check",
"failed to match stat return [%d]: %d vs %zd [%s]\n",
i, bss->rets_close[i], strlen(bss->paths_close[i]) + 1,
bss->paths_stat[i]);
}
cleanup:
test_d_path__destroy(skel);
}

58
tools/testing/selftests/bpf/progs/test_d_path.c Normal file
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// SPDX-License-Identifier: GPL-2.0
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#define MAX_PATH_LEN 128
#define MAX_FILES 7
pid_t my_pid = 0;
__u32 cnt_stat = 0;
__u32 cnt_close = 0;
char paths_stat[MAX_FILES][MAX_PATH_LEN] = {};
char paths_close[MAX_FILES][MAX_PATH_LEN] = {};
int rets_stat[MAX_FILES] = {};
int rets_close[MAX_FILES] = {};
SEC("fentry/vfs_getattr")
int BPF_PROG(prog_stat, struct path *path, struct kstat *stat,
__u32 request_mask, unsigned int query_flags)
{
pid_t pid = bpf_get_current_pid_tgid() >> 32;
__u32 cnt = cnt_stat;
int ret;
if (pid != my_pid)
return 0;
if (cnt >= MAX_FILES)
return 0;
ret = bpf_d_path(path, paths_stat[cnt], MAX_PATH_LEN);
rets_stat[cnt] = ret;
cnt_stat++;
return 0;
}
SEC("fentry/filp_close")
int BPF_PROG(prog_close, struct file *file, void *id)
{
pid_t pid = bpf_get_current_pid_tgid() >> 32;
__u32 cnt = cnt_close;
int ret;
if (pid != my_pid)
return 0;
if (cnt >= MAX_FILES)
return 0;
ret = bpf_d_path(&file->f_path,
paths_close[cnt], MAX_PATH_LEN);
rets_close[cnt] = ret;
cnt_close++;
return 0;
}
char _license[] SEC("license") = "GPL";