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590699d858
Since commit 31158ad02d ("rqspinlock: Add deadlock detection
and recovery") the updated path on re-entrancy now reports deadlock
via -EDEADLK instead of the previous -EBUSY.
Also, the way reentrancy was exercised (via fentry/lookup_elem_raw)
has been fragile because lookup_elem_raw may be inlined
(find_kernel_btf_id() will return -ESRCH).
To fix this fentry is attached to bpf_obj_free_fields() instead of
lookup_elem_raw() and:
- The htab map is made to use a BTF-described struct val with a
struct bpf_timer so that check_and_free_fields() reliably calls
bpf_obj_free_fields() on element replacement.
- The selftest is updated to do two updates to the same key (insert +
replace) in prog_test.
- The selftest is updated to align with expected errno with the
kernel’s current behavior.
Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Link: https://lore.kernel.org/r/20251117060752.129648-1-skb99@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
37 lines
763 B
C
37 lines
763 B
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (C) 2022. Huawei Technologies Co., Ltd */
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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char _license[] SEC("license") = "GPL";
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/* Map value type: has BTF-managed field (bpf_timer) */
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struct val {
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struct bpf_timer t;
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__u64 payload;
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};
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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, __u32);
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__type(value, struct val);
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} htab SEC(".maps");
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int pid = 0;
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int update_err = 0;
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SEC("?fentry/bpf_obj_free_fields")
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int bpf_obj_free_fields(void *ctx)
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{
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__u32 key = 0;
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struct val value = { .payload = 1 };
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if ((bpf_get_current_pid_tgid() >> 32) != pid)
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return 0;
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update_err = bpf_map_update_elem(&htab, &key, &value, BPF_ANY);
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return 0;
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}
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