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selftests/bpf: validate async callback return value check correctness

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Adjust timer/timer_ret_1 test to validate more carefully verifier logic
of enforcing async callback return value. This test will pass only if
return result is marked precise and read.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231202175705.885270-10-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-12-02 09:57:03 -08:00 committed by Alexei Starovoitov
parent eabe518de5
commit e02dea158d
1 changed files with 28 additions and 8 deletions
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36
tools/testing/selftests/bpf/progs/timer_failure.c
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@ -21,17 +21,37 @@ struct {
__type(value, struct elem);
} timer_map SEC(".maps");
static int timer_cb_ret1(void *map, int *key, struct bpf_timer *timer)
__naked __noinline __used
static unsigned long timer_cb_ret_bad()
{
if (bpf_get_smp_processor_id() % 2)
return 1;
else
return 0;
asm volatile (
"call %[bpf_get_prandom_u32];"
"if r0 s> 1000 goto 1f;"
"r0 = 0;"
"1:"
"goto +0;" /* checkpoint */
/* async callback is expected to return 0, so branch above
* skipping r0 = 0; should lead to a failure, but if exit
* instruction doesn't enforce r0's precision, this callback
* will be successfully verified
*/
"exit;"
:
: __imm(bpf_get_prandom_u32)
: __clobber_common
);
}
SEC("fentry/bpf_fentry_test1")
__failure __msg("should have been in [0, 0]")
int BPF_PROG2(test_ret_1, int, a)
__log_level(2)
__flag(BPF_F_TEST_STATE_FREQ)
__failure
/* check that fallthrough code path marks r0 as precise */
__msg("mark_precise: frame0: regs=r0 stack= before 22: (b7) r0 = 0")
/* check that branch code path marks r0 as precise */
__msg("mark_precise: frame0: regs=r0 stack= before 24: (85) call bpf_get_prandom_u32#7")
__msg("should have been in [0, 0]")
long BPF_PROG2(test_bad_ret, int, a)
{
int key = 0;
struct bpf_timer *timer;
@ -39,7 +59,7 @@ int BPF_PROG2(test_ret_1, int, a)
timer = bpf_map_lookup_elem(&timer_map, &key);
if (timer) {
bpf_timer_init(timer, &timer_map, CLOCK_BOOTTIME);
bpf_timer_set_callback(timer, timer_cb_ret1);
bpf_timer_set_callback(timer, timer_cb_ret_bad);
bpf_timer_start(timer, 1000, 0);
}