| 1 | // SPDX-License-Identifier: GPL-2.0 |
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| 2 | |
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| 3 | #include "vmlinux.h" |
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| 4 | #include <bpf/bpf_helpers.h> |
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| 5 | #include "bpf_misc.h" |
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| 6 | |
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| 7 | char _license[] SEC("license" ) = "GPL" ; |
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| 8 | |
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| 9 | struct { |
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| 10 | __uint(type, BPF_MAP_TYPE_HASH); |
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| 11 | __uint(max_entries, 1); |
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| 12 | __type(key, u64); |
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| 13 | __type(value, u64); |
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| 14 | } m_hash SEC(".maps" ); |
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| 15 | |
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| 16 | SEC("?raw_tp" ) |
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| 17 | __failure __msg("R8 invalid mem access 'map_value_or_null" ) |
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| 18 | int jeq_infer_not_null_ptr_to_btfid(void *ctx) |
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| 19 | { |
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| 20 | struct bpf_map *map = (struct bpf_map *)&m_hash; |
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| 21 | struct bpf_map *inner_map = map->inner_map_meta; |
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| 22 | u64 key = 0, ret = 0, *val; |
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| 23 | |
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| 24 | val = bpf_map_lookup_elem(map, &key); |
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| 25 | /* Do not mark ptr as non-null if one of them is |
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| 26 | * PTR_TO_BTF_ID (R9), reject because of invalid |
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| 27 | * access to map value (R8). |
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| 28 | * |
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| 29 | * Here, we need to inline those insns to access |
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| 30 | * R8 directly, since compiler may use other reg |
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| 31 | * once it figures out val==inner_map. |
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| 32 | */ |
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| 33 | asm volatile("r8 = %[val];\n" |
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| 34 | "r9 = %[inner_map];\n" |
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| 35 | "if r8 != r9 goto +1;\n" |
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| 36 | "%[ret] = *(u64 *)(r8 +0);\n" |
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| 37 | : [ret] "+r" (ret) |
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| 38 | : [inner_map] "r" (inner_map), [val] "r" (val) |
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| 39 | : "r8" , "r9" ); |
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| 40 | |
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| 41 | return ret; |
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| 42 | } |
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| 43 | |
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