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olsajiriAlexei Starovoitov
olsajiri
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Alexei Starovoitov
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selftests/bpf: Add test for d_path helper
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 <[email protected]> Signed-off-by: Jiri Olsa <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
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‎tools/testing/selftests/bpf/prog_tests/d_path.c

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

‎tools/testing/selftests/bpf/progs/test_d_path.c

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

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