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libbpf: sanitize VAR to conservative 1-byte INT

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If VAR in non-sanitized BTF was size less than 4, converting such VAR
into an INT with size=4 will cause BTF validation failure due to
violationg of STRUCT (into which DATASEC was converted) member size.
Fix by conservatively using size=1.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2019-07-19 12:46:03 -07:00 committed by Alexei Starovoitov
parent 04efe5911f
commit 1d4126c4e1
1 changed files with 7 additions and 2 deletions
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9
tools/lib/bpf/libbpf.c
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@ -1377,8 +1377,13 @@ static void bpf_object__sanitize_btf(struct bpf_object *obj)
if (!has_datasec && kind == BTF_KIND_VAR) { if (!has_datasec && kind == BTF_KIND_VAR) {
/* replace VAR with INT */ /* replace VAR with INT */
t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0); t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0);
t->size = sizeof(int); /*
*(int *)(t+1) = BTF_INT_ENC(0, 0, 32); * using size = 1 is the safest choice, 4 will be too
* big and cause kernel BTF validation failure if
* original variable took less than 4 bytes
*/
t->size = 1;
*(int *)(t+1) = BTF_INT_ENC(0, 0, 8);
} else if (!has_datasec && kind == BTF_KIND_DATASEC) { } else if (!has_datasec && kind == BTF_KIND_DATASEC) {
/* replace DATASEC with STRUCT */ /* replace DATASEC with STRUCT */
struct btf_var_secinfo *v = (void *)(t + 1); struct btf_var_secinfo *v = (void *)(t + 1);