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linux/tools/testing/selftests/bpf/progs/tailcall_poke.c
Jiri Olsa ffed24eff9 selftests/bpf: Add test for early update in prog_array_map_poke_run
Adding test that tries to trigger the BUG_IN during early map update
in prog_array_map_poke_run function.

The idea is to share prog array map between thread that constantly
updates it and another one loading a program that uses that prog
array.

Eventually we will hit a place where the program is ok to be updated
(poke->tailcall_target_stable check) but the address is still not
registered in kallsyms, so the bpf_arch_text_poke returns -EINVAL
and cause imbalance for the next tail call update check, which will
fail with -EBUSY in bpf_arch_text_poke as described in previous fix.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/bpf/20231206083041.1306660-3-jolsa@kernel.org
2023-12-06 22:40:43 +01:00

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C

// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
char _license[] SEC("license") = "GPL";
struct {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__uint(max_entries, 1);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u32));
} jmp_table SEC(".maps");
SEC("?fentry/bpf_fentry_test1")
int BPF_PROG(test, int a)
{
bpf_tail_call_static(ctx, &jmp_table, 0);
return 0;
}
SEC("fentry/bpf_fentry_test1")
int BPF_PROG(call1, int a)
{
return 0;
}
SEC("fentry/bpf_fentry_test1")
int BPF_PROG(call2, int a)
{
return 0;
}