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selftests/bpf: Add uprobe_regs_equal test

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Changing uretprobe_regs_trigger to allow the test for both
uprobe and uretprobe and renaming it to uprobe_regs_equal.

We check that both uprobe and uretprobe probes (bpf programs)
see expected registers with few exceptions.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20250720112133.244369-19-jolsa@kernel.org
This commit is contained in:
Jiri Olsa 2025-07-20 13:21:28 +02:00 committed by Peter Zijlstra
parent 875e1705ad
commit 275eae6789
2 changed files with 44 additions and 16 deletions
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56
tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
View File

@ -22,15 +22,17 @@
#pragma GCC diagnostic ignored "-Wattributes"
__naked unsigned long uretprobe_regs_trigger(void)
__attribute__((aligned(16)))
__nocf_check __weak __naked unsigned long uprobe_regs_trigger(void)
{
asm volatile (
".byte 0x0f, 0x1f, 0x44, 0x00, 0x00\n" /* nop5 */
"movq $0xdeadbeef, %rax\n"
"ret\n"
);
}
__naked void uretprobe_regs(struct pt_regs *before, struct pt_regs *after)
__naked void uprobe_regs(struct pt_regs *before, struct pt_regs *after)
{
asm volatile (
"movq %r15, 0(%rdi)\n"
@ -51,15 +53,17 @@ __naked void uretprobe_regs(struct pt_regs *before, struct pt_regs *after)
"movq $0, 120(%rdi)\n" /* orig_rax */
"movq $0, 128(%rdi)\n" /* rip */
"movq $0, 136(%rdi)\n" /* cs */
"pushq %rax\n"
"pushf\n"
"pop %rax\n"
"movq %rax, 144(%rdi)\n" /* eflags */
"pop %rax\n"
"movq %rsp, 152(%rdi)\n" /* rsp */
"movq $0, 160(%rdi)\n" /* ss */
/* save 2nd argument */
"pushq %rsi\n"
"call uretprobe_regs_trigger\n"
"call uprobe_regs_trigger\n"
/* save return value and load 2nd argument pointer to rax */
"pushq %rax\n"
@ -99,25 +103,37 @@ __naked void uretprobe_regs(struct pt_regs *before, struct pt_regs *after)
);
}
static void test_uretprobe_regs_equal(void)
static void test_uprobe_regs_equal(bool retprobe)
{
LIBBPF_OPTS(bpf_uprobe_opts, opts,
.retprobe = retprobe,
);
struct uprobe_syscall *skel = NULL;
struct pt_regs before = {}, after = {};
unsigned long *pb = (unsigned long *) &before;
unsigned long *pa = (unsigned long *) &after;
unsigned long *pp;
unsigned long offset;
unsigned int i, cnt;
int err;
offset = get_uprobe_offset(&uprobe_regs_trigger);
if (!ASSERT_GE(offset, 0, "get_uprobe_offset"))
return;
skel = uprobe_syscall__open_and_load();
if (!ASSERT_OK_PTR(skel, "uprobe_syscall__open_and_load"))
goto cleanup;
err = uprobe_syscall__attach(skel);
if (!ASSERT_OK(err, "uprobe_syscall__attach"))
skel->links.probe = bpf_program__attach_uprobe_opts(skel->progs.probe,
0, "/proc/self/exe", offset, &opts);
if (!ASSERT_OK_PTR(skel->links.probe, "bpf_program__attach_uprobe_opts"))
goto cleanup;
uretprobe_regs(&before, &after);
/* make sure uprobe gets optimized */
if (!retprobe)
uprobe_regs_trigger();
uprobe_regs(&before, &after);
pp = (unsigned long *) &skel->bss->regs;
cnt = sizeof(before)/sizeof(*pb);
@ -126,7 +142,7 @@ static void test_uretprobe_regs_equal(void)
unsigned int offset = i * sizeof(unsigned long);
/*
* Check register before and after uretprobe_regs_trigger call
* Check register before and after uprobe_regs_trigger call
* that triggers the uretprobe.
*/
switch (offset) {
@ -140,7 +156,7 @@ static void test_uretprobe_regs_equal(void)
/*
* Check register seen from bpf program and register after
* uretprobe_regs_trigger call
* uprobe_regs_trigger call (with rax exception, check below).
*/
switch (offset) {
/*
@ -153,6 +169,15 @@ static void test_uretprobe_regs_equal(void)
case offsetof(struct pt_regs, rsp):
case offsetof(struct pt_regs, ss):
break;
/*
* uprobe does not see return value in rax, it needs to see the
* original (before) rax value
*/
case offsetof(struct pt_regs, rax):
if (!retprobe) {
ASSERT_EQ(pp[i], pb[i], "uprobe rax prog-before value check");
break;
}
default:
if (!ASSERT_EQ(pp[i], pa[i], "register prog-after value check"))
fprintf(stdout, "failed register offset %u\n", offset);
@ -190,13 +215,13 @@ static void test_uretprobe_regs_change(void)
unsigned long cnt = sizeof(before)/sizeof(*pb);
unsigned int i, err, offset;
offset = get_uprobe_offset(uretprobe_regs_trigger);
offset = get_uprobe_offset(uprobe_regs_trigger);
err = write_bpf_testmod_uprobe(offset);
if (!ASSERT_OK(err, "register_uprobe"))
return;
uretprobe_regs(&before, &after);
uprobe_regs(&before, &after);
err = write_bpf_testmod_uprobe(0);
if (!ASSERT_OK(err, "unregister_uprobe"))
@ -616,7 +641,8 @@ static void test_uretprobe_shadow_stack(void)
/* Run all the tests with shadow stack in place. */
shstk_is_enabled = true;
test_uretprobe_regs_equal();
test_uprobe_regs_equal(false);
test_uprobe_regs_equal(true);
test_uretprobe_regs_change();
test_uretprobe_syscall_call();
@ -772,7 +798,7 @@ static void test_uprobe_sigill(void)
static void __test_uprobe_syscall(void)
{
if (test__start_subtest("uretprobe_regs_equal"))
test_uretprobe_regs_equal();
test_uprobe_regs_equal(true);
if (test__start_subtest("uretprobe_regs_change"))
test_uretprobe_regs_change();
if (test__start_subtest("uretprobe_syscall_call"))
@ -791,6 +817,8 @@ static void __test_uprobe_syscall(void)
test_uprobe_race();
if (test__start_subtest("uprobe_sigill"))
test_uprobe_sigill();
if (test__start_subtest("uprobe_regs_equal"))
test_uprobe_regs_equal(false);
}
#else
static void __test_uprobe_syscall(void)

4
tools/testing/selftests/bpf/progs/uprobe_syscall.c
View File

@ -7,8 +7,8 @@ struct pt_regs regs;
char _license[] SEC("license") = "GPL";
SEC("uretprobe//proc/self/exe:uretprobe_regs_trigger")
int uretprobe(struct pt_regs *ctx)
SEC("uprobe")
int probe(struct pt_regs *ctx)
{
__builtin_memcpy(&regs, ctx, sizeof(regs));
return 0;