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selftests/bpf: Isolate fmod_ret hooks by pid

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modify_return's fmod_ret programs can override bpf_modify_return_test()'s
return value, which conflicts with get_func_ip_test when selftests run in
parallel.

Store current tgid in BSS and make modify_return hooks act only for that
tgid. For other tasks, fentry/fexit become no-ops and fmod_ret returns the
original ret.

Drop the serial-only restriction and remove the TODO comment.

Tested:
  sudo ./test_progs -t modify_return
  sudo ./test_progs -t get_func_ip_test
  sudo ./test_progs -j$(nproc) -t modify_return
  sudo ./test_progs -j$(nproc) -t get_func_ip_test

Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
Link: https://lore.kernel.org/r/20260313034540.255805-1-sun.jian.kdev@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Sun Jian 2026-03-13 11:45:40 +08:00 committed by Alexei Starovoitov
parent 888329ba6c
commit 4a4fedb8a5
2 changed files with 18 additions and 3 deletions
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8
tools/testing/selftests/bpf/prog_tests/modify_return.c
View File

@ -5,6 +5,7 @@
*/
#include <test_progs.h>
#include <unistd.h>
#include "modify_return.skel.h"
#define LOWER(x) ((x) & 0xffff)
@ -23,11 +24,13 @@ static void run_test(__u32 input_retval, __u16 want_side_effect, __s16 want_ret)
if (!ASSERT_OK_PTR(skel, "skel_load"))
goto cleanup;
skel->bss->input_retval = input_retval;
skel->bss->test_pid = getpid();
err = modify_return__attach(skel);
if (!ASSERT_OK(err, "modify_return__attach failed"))
goto cleanup;
skel->bss->input_retval = input_retval;
prog_fd = bpf_program__fd(skel->progs.fmod_ret_test);
err = bpf_prog_test_run_opts(prog_fd, &topts);
ASSERT_OK(err, "test_run");
@ -49,8 +52,7 @@ static void run_test(__u32 input_retval, __u16 want_side_effect, __s16 want_ret)
modify_return__destroy(skel);
}
/* TODO: conflict with get_func_ip_test */
void serial_test_modify_return(void)
void test_modify_return(void)
{
run_test(0 /* input_retval */,
2 /* want_side_effect */,

13
tools/testing/selftests/bpf/progs/modify_return.c
View File

@ -12,11 +12,14 @@ char _license[] SEC("license") = "GPL";
static int sequence = 0;
__s32 input_retval = 0;
__u32 test_pid = 0;
__u64 fentry_result = 0;
SEC("fentry/bpf_modify_return_test")
int BPF_PROG(fentry_test, int a, __u64 b)
{
if (bpf_get_current_pid_tgid() >> 32 != test_pid)
return 0;
sequence++;
fentry_result = (sequence == 1);
return 0;
@ -26,6 +29,8 @@ __u64 fmod_ret_result = 0;
SEC("fmod_ret/bpf_modify_return_test")
int BPF_PROG(fmod_ret_test, int a, int *b, int ret)
{
if (bpf_get_current_pid_tgid() >> 32 != test_pid)
return ret;
sequence++;
/* This is the first fmod_ret program, the ret passed should be 0 */
fmod_ret_result = (sequence == 2 && ret == 0);
@ -36,6 +41,8 @@ __u64 fexit_result = 0;
SEC("fexit/bpf_modify_return_test")
int BPF_PROG(fexit_test, int a, __u64 b, int ret)
{
if (bpf_get_current_pid_tgid() >> 32 != test_pid)
return 0;
sequence++;
/* If the input_reval is non-zero a successful modification should have
* occurred.
@ -55,6 +62,8 @@ SEC("fentry/bpf_modify_return_test2")
int BPF_PROG(fentry_test2, int a, int *b, short c, int d, void *e, char f,
int g)
{
if (bpf_get_current_pid_tgid() >> 32 != test_pid)
return 0;
sequence2++;
fentry_result2 = (sequence2 == 1);
return 0;
@ -65,6 +74,8 @@ SEC("fmod_ret/bpf_modify_return_test2")
int BPF_PROG(fmod_ret_test2, int a, int *b, short c, int d, void *e, char f,
int g, int ret)
{
if (bpf_get_current_pid_tgid() >> 32 != test_pid)
return ret;
sequence2++;
/* This is the first fmod_ret program, the ret passed should be 0 */
fmod_ret_result2 = (sequence2 == 2 && ret == 0);
@ -76,6 +87,8 @@ SEC("fexit/bpf_modify_return_test2")
int BPF_PROG(fexit_test2, int a, int *b, short c, int d, void *e, char f,
int g, int ret)
{
if (bpf_get_current_pid_tgid() >> 32 != test_pid)
return 0;
sequence2++;
/* If the input_reval is non-zero a successful modification should have
* occurred.