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inwardvesselAlexei Starovoitov
inwardvessel
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Alexei Starovoitov
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bpf/selftests: coverage for bpf_map_ops errors
These tests expose the issue of being unable to properly check for errors returned from inlined bpf map helpers that make calls to the bpf_map_ops functions. At best, a check for zero or non-zero can be done but these tests show it is not possible to check for a negative value or for a specific error value. Signed-off-by: JP Kobryn <[email protected]> Tested-by: Eduard Zingerman <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>
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‎tools/testing/selftests/bpf/prog_tests/map_ops.c

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// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
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#include <errno.h>
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#include <sys/syscall.h>
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#include <unistd.h>
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#include "test_map_ops.skel.h"
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#include "test_progs.h"
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static void map_update(void)
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{
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(void)syscall(__NR_getpid);
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}
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static void map_delete(void)
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{
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(void)syscall(__NR_getppid);
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}
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static void map_push(void)
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{
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(void)syscall(__NR_getuid);
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}
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static void map_pop(void)
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{
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(void)syscall(__NR_geteuid);
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}
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static void map_peek(void)
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{
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(void)syscall(__NR_getgid);
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}
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static void map_for_each_pass(void)
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{
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(void)syscall(__NR_gettid);
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}
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static void map_for_each_fail(void)
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{
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(void)syscall(__NR_getpgid);
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}
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static int setup(struct test_map_ops **skel)
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{
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int err = 0;
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if (!skel)
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return -1;
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*skel = test_map_ops__open();
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if (!ASSERT_OK_PTR(*skel, "test_map_ops__open"))
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return -1;
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(*skel)->rodata->pid = getpid();
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err = test_map_ops__load(*skel);
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if (!ASSERT_OK(err, "test_map_ops__load"))
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return err;
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err = test_map_ops__attach(*skel);
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if (!ASSERT_OK(err, "test_map_ops__attach"))
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return err;
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return err;
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}
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static void teardown(struct test_map_ops **skel)
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{
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if (skel && *skel)
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test_map_ops__destroy(*skel);
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}
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static void map_ops_update_delete_subtest(void)
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{
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struct test_map_ops *skel;
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if (setup(&skel))
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goto teardown;
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map_update();
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ASSERT_OK(skel->bss->err, "map_update_initial");
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map_update();
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ASSERT_LT(skel->bss->err, 0, "map_update_existing");
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ASSERT_EQ(skel->bss->err, -EEXIST, "map_update_existing");
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map_delete();
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ASSERT_OK(skel->bss->err, "map_delete_existing");
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map_delete();
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ASSERT_LT(skel->bss->err, 0, "map_delete_non_existing");
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ASSERT_EQ(skel->bss->err, -ENOENT, "map_delete_non_existing");
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teardown:
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teardown(&skel);
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}
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static void map_ops_push_peek_pop_subtest(void)
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{
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struct test_map_ops *skel;
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if (setup(&skel))
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goto teardown;
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map_push();
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ASSERT_OK(skel->bss->err, "map_push_initial");
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map_push();
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ASSERT_LT(skel->bss->err, 0, "map_push_when_full");
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ASSERT_EQ(skel->bss->err, -E2BIG, "map_push_when_full");
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map_peek();
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ASSERT_OK(skel->bss->err, "map_peek");
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map_pop();
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ASSERT_OK(skel->bss->err, "map_pop");
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map_peek();
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ASSERT_LT(skel->bss->err, 0, "map_peek_when_empty");
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ASSERT_EQ(skel->bss->err, -ENOENT, "map_peek_when_empty");
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map_pop();
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ASSERT_LT(skel->bss->err, 0, "map_pop_when_empty");
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ASSERT_EQ(skel->bss->err, -ENOENT, "map_pop_when_empty");
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teardown:
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teardown(&skel);
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}
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static void map_ops_for_each_subtest(void)
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{
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struct test_map_ops *skel;
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if (setup(&skel))
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goto teardown;
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map_for_each_pass();
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/* expect to iterate over 1 element */
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ASSERT_EQ(skel->bss->err, 1, "map_for_each_no_flags");
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map_for_each_fail();
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ASSERT_LT(skel->bss->err, 0, "map_for_each_with_flags");
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ASSERT_EQ(skel->bss->err, -EINVAL, "map_for_each_with_flags");
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teardown:
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teardown(&skel);
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}
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void test_map_ops(void)
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{
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if (test__start_subtest("map_ops_update_delete"))
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map_ops_update_delete_subtest();
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if (test__start_subtest("map_ops_push_peek_pop"))
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map_ops_push_peek_pop_subtest();
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if (test__start_subtest("map_ops_for_each"))
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map_ops_for_each_subtest();
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}

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

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// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
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#include "vmlinux.h"
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#include <bpf/bpf_helpers.h>
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char _license[] SEC("license") = "GPL";
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, 1);
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__type(key, int);
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__type(value, int);
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} hash_map SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_STACK);
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__uint(max_entries, 1);
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__type(value, int);
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} stack_map SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_ARRAY);
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__uint(max_entries, 1);
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__type(key, int);
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__type(value, int);
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} array_map SEC(".maps");
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const volatile pid_t pid;
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long err = 0;
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static u64 callback(u64 map, u64 key, u64 val, u64 ctx, u64 flags)
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{
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return 0;
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}
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SEC("tp/syscalls/sys_enter_getpid")
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int map_update(void *ctx)
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{
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const int key = 0;
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const int val = 1;
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if (pid != (bpf_get_current_pid_tgid() >> 32))
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return 0;
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err = bpf_map_update_elem(&hash_map, &key, &val, BPF_NOEXIST);
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return 0;
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}
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SEC("tp/syscalls/sys_enter_getppid")
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int map_delete(void *ctx)
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{
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const int key = 0;
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if (pid != (bpf_get_current_pid_tgid() >> 32))
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return 0;
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err = bpf_map_delete_elem(&hash_map, &key);
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return 0;
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}
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SEC("tp/syscalls/sys_enter_getuid")
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int map_push(void *ctx)
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{
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const int val = 1;
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if (pid != (bpf_get_current_pid_tgid() >> 32))
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return 0;
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err = bpf_map_push_elem(&stack_map, &val, 0);
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return 0;
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}
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SEC("tp/syscalls/sys_enter_geteuid")
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int map_pop(void *ctx)
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{
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int val;
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if (pid != (bpf_get_current_pid_tgid() >> 32))
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return 0;
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err = bpf_map_pop_elem(&stack_map, &val);
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return 0;
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}
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SEC("tp/syscalls/sys_enter_getgid")
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int map_peek(void *ctx)
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{
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int val;
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if (pid != (bpf_get_current_pid_tgid() >> 32))
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return 0;
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err = bpf_map_peek_elem(&stack_map, &val);
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return 0;
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}
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SEC("tp/syscalls/sys_enter_gettid")
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int map_for_each_pass(void *ctx)
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{
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const int key = 0;
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const int val = 1;
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const u64 flags = 0;
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int callback_ctx;
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if (pid != (bpf_get_current_pid_tgid() >> 32))
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return 0;
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bpf_map_update_elem(&array_map, &key, &val, flags);
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err = bpf_for_each_map_elem(&array_map, callback, &callback_ctx, flags);
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return 0;
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}
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SEC("tp/syscalls/sys_enter_getpgid")
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int map_for_each_fail(void *ctx)
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{
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const int key = 0;
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const int val = 1;
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const u64 flags = BPF_NOEXIST;
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int callback_ctx;
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if (pid != (bpf_get_current_pid_tgid() >> 32))
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return 0;
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bpf_map_update_elem(&array_map, &key, &val, flags);
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/* calling for_each with non-zero flags will return error */
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err = bpf_for_each_map_elem(&array_map, callback, &callback_ctx, flags);
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return 0;
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}

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