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authorAndrii Nakryiko <andrii@kernel.org>2021-12-13 04:07:06 +0300
committerAlexei Starovoitov <ast@kernel.org>2021-12-13 04:26:24 +0300
commit4b443bc1785f28df56fdbd6a107dc68ef7d5aa8e (patch)
tree2c6e46dbfaff8bce7a0c22d5f067aac442f70480 /tools/lib
parentf12468828c28ff90d20c99b234a94223401f7924 (diff)
downloadlinux-4b443bc1785f28df56fdbd6a107dc68ef7d5aa8e.tar.xz
libbpf: Don't validate TYPE_ID relo's original imm value
During linking, type IDs in the resulting linked BPF object file can change, and so ldimm64 instructions corresponding to BPF_CORE_TYPE_ID_TARGET and BPF_CORE_TYPE_ID_LOCAL CO-RE relos can get their imm value out of sync with actual CO-RE relocation information that's updated by BPF linker properly during linking process. We could teach BPF linker to adjust such instructions, but it feels a bit too much for linker to re-implement good chunk of bpf_core_patch_insns logic just for this. This is a redundant safety check for TYPE_ID relocations, as the real validation is in matching CO-RE specs, so if that works fine, it's very unlikely that there is something wrong with the instruction itself. So, instead, teach libbpf (and kernel) to ignore insn->imm for BPF_CORE_TYPE_ID_TARGET and BPF_CORE_TYPE_ID_LOCAL relos. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211213010706.100231-1-andrii@kernel.org
Diffstat (limited to 'tools/lib')
-rw-r--r--tools/lib/bpf/relo_core.c19
1 files changed, 14 insertions, 5 deletions
diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c
index 32464f0ab4b1..c770483b4c36 100644
--- a/tools/lib/bpf/relo_core.c
+++ b/tools/lib/bpf/relo_core.c
@@ -709,10 +709,14 @@ static int bpf_core_calc_field_relo(const char *prog_name,
static int bpf_core_calc_type_relo(const struct bpf_core_relo *relo,
const struct bpf_core_spec *spec,
- __u32 *val)
+ __u32 *val, bool *validate)
{
__s64 sz;
+ /* by default, always check expected value in bpf_insn */
+ if (validate)
+ *validate = true;
+
/* type-based relos return zero when target type is not found */
if (!spec) {
*val = 0;
@@ -722,6 +726,11 @@ static int bpf_core_calc_type_relo(const struct bpf_core_relo *relo,
switch (relo->kind) {
case BPF_CORE_TYPE_ID_TARGET:
*val = spec->root_type_id;
+ /* type ID, embedded in bpf_insn, might change during linking,
+ * so enforcing it is pointless
+ */
+ if (validate)
+ *validate = false;
break;
case BPF_CORE_TYPE_EXISTS:
*val = 1;
@@ -861,8 +870,8 @@ static int bpf_core_calc_relo(const char *prog_name,
res->fail_memsz_adjust = true;
}
} else if (core_relo_is_type_based(relo->kind)) {
- err = bpf_core_calc_type_relo(relo, local_spec, &res->orig_val);
- err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val);
+ err = bpf_core_calc_type_relo(relo, local_spec, &res->orig_val, &res->validate);
+ err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val, NULL);
} else if (core_relo_is_enumval_based(relo->kind)) {
err = bpf_core_calc_enumval_relo(relo, local_spec, &res->orig_val);
err = err ?: bpf_core_calc_enumval_relo(relo, targ_spec, &res->new_val);
@@ -1213,7 +1222,8 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
/* TYPE_ID_LOCAL relo is special and doesn't need candidate search */
if (relo->kind == BPF_CORE_TYPE_ID_LOCAL) {
- targ_res.validate = true;
+ /* bpf_insn's imm value could get out of sync during linking */
+ targ_res.validate = false;
targ_res.poison = false;
targ_res.orig_val = local_spec->root_type_id;
targ_res.new_val = local_spec->root_type_id;
@@ -1227,7 +1237,6 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
return -EOPNOTSUPP;
}
-
for (i = 0, j = 0; i < cands->len; i++) {
err = bpf_core_spec_match(local_spec, cands->cands[i].btf,
cands->cands[i].id, cand_spec);