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-rw-r--r--tools/lib/bpf/libbpf.c170
1 files changed, 124 insertions, 46 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 894d388094e3..0276cf85d763 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4616,14 +4616,25 @@ static int bpf_core_calc_field_relo(const struct bpf_program *prog,
const struct bpf_core_spec *spec,
__u32 *val, bool *validate)
{
- const struct bpf_core_accessor *acc = &spec->spec[spec->len - 1];
- const struct btf_type *t = btf__type_by_id(spec->btf, acc->type_id);
+ const struct bpf_core_accessor *acc;
+ const struct btf_type *t;
__u32 byte_off, byte_sz, bit_off, bit_sz;
const struct btf_member *m;
const struct btf_type *mt;
bool bitfield;
__s64 sz;
+ if (relo->kind == BPF_FIELD_EXISTS) {
+ *val = spec ? 1 : 0;
+ return 0;
+ }
+
+ if (!spec)
+ return -EUCLEAN; /* request instruction poisoning */
+
+ acc = &spec->spec[spec->len - 1];
+ t = btf__type_by_id(spec->btf, acc->type_id);
+
/* a[n] accessor needs special handling */
if (!acc->name) {
if (relo->kind == BPF_FIELD_BYTE_OFFSET) {
@@ -4709,21 +4720,88 @@ static int bpf_core_calc_field_relo(const struct bpf_program *prog,
break;
case BPF_FIELD_EXISTS:
default:
- pr_warn("prog '%s': unknown relo %d at insn #%d\n",
- bpf_program__title(prog, false),
- relo->kind, relo->insn_off / 8);
- return -EINVAL;
+ return -EOPNOTSUPP;
}
return 0;
}
+struct bpf_core_relo_res
+{
+ /* expected value in the instruction, unless validate == false */
+ __u32 orig_val;
+ /* new value that needs to be patched up to */
+ __u32 new_val;
+ /* relocation unsuccessful, poison instruction, but don't fail load */
+ bool poison;
+ /* some relocations can't be validated against orig_val */
+ bool validate;
+};
+
+/* Calculate original and target relocation values, given local and target
+ * specs and relocation kind. These values are calculated for each candidate.
+ * If there are multiple candidates, resulting values should all be consistent
+ * with each other. Otherwise, libbpf will refuse to proceed due to ambiguity.
+ * If instruction has to be poisoned, *poison will be set to true.
+ */
+static int bpf_core_calc_relo(const struct bpf_program *prog,
+ const struct bpf_core_relo *relo,
+ int relo_idx,
+ const struct bpf_core_spec *local_spec,
+ const struct bpf_core_spec *targ_spec,
+ struct bpf_core_relo_res *res)
+{
+ int err = -EOPNOTSUPP;
+
+ res->orig_val = 0;
+ res->new_val = 0;
+ res->poison = false;
+ res->validate = true;
+
+ if (core_relo_is_field_based(relo->kind)) {
+ err = bpf_core_calc_field_relo(prog, relo, local_spec, &res->orig_val, &res->validate);
+ err = err ?: bpf_core_calc_field_relo(prog, relo, targ_spec, &res->new_val, NULL);
+ }
+
+ if (err == -EUCLEAN) {
+ /* EUCLEAN is used to signal instruction poisoning request */
+ res->poison = true;
+ err = 0;
+ } else if (err == -EOPNOTSUPP) {
+ /* EOPNOTSUPP means unknown/unsupported relocation */
+ pr_warn("prog '%s': relo #%d: unrecognized CO-RE relocation %s (%d) at insn #%d\n",
+ bpf_program__title(prog, false), relo_idx,
+ core_relo_kind_str(relo->kind), relo->kind, relo->insn_off / 8);
+ }
+
+ return err;
+}
+
+/*
+ * Turn instruction for which CO_RE relocation failed into invalid one with
+ * distinct signature.
+ */
+static void bpf_core_poison_insn(struct bpf_program *prog, int relo_idx,
+ int insn_idx, struct bpf_insn *insn)
+{
+ pr_debug("prog '%s': relo #%d: substituting insn #%d w/ invalid insn\n",
+ bpf_program__title(prog, false), relo_idx, insn_idx);
+ insn->code = BPF_JMP | BPF_CALL;
+ insn->dst_reg = 0;
+ insn->src_reg = 0;
+ insn->off = 0;
+ /* if this instruction is reachable (not a dead code),
+ * verifier will complain with the following message:
+ * invalid func unknown#195896080
+ */
+ insn->imm = 195896080; /* => 0xbad2310 => "bad relo" */
+}
+
/*
* Patch relocatable BPF instruction.
*
* Patched value is determined by relocation kind and target specification.
- * For field existence relocation target spec will be NULL if field is not
- * found.
+ * For existence relocations target spec will be NULL if field/type is not found.
* Expected insn->imm value is determined using relocation kind and local
* spec, and is checked before patching instruction. If actual insn->imm value
* is wrong, bail out with error.
@@ -4732,16 +4810,14 @@ static int bpf_core_calc_field_relo(const struct bpf_program *prog,
* 1. rX = <imm> (assignment with immediate operand);
* 2. rX += <imm> (arithmetic operations with immediate operand);
*/
-static int bpf_core_reloc_insn(struct bpf_program *prog,
+static int bpf_core_patch_insn(struct bpf_program *prog,
const struct bpf_core_relo *relo,
int relo_idx,
- const struct bpf_core_spec *local_spec,
- const struct bpf_core_spec *targ_spec)
+ const struct bpf_core_relo_res *res)
{
__u32 orig_val, new_val;
struct bpf_insn *insn;
- bool validate = true;
- int insn_idx, err;
+ int insn_idx;
__u8 class;
if (relo->insn_off % sizeof(struct bpf_insn))
@@ -4750,39 +4826,20 @@ static int bpf_core_reloc_insn(struct bpf_program *prog,
insn = &prog->insns[insn_idx];
class = BPF_CLASS(insn->code);
- if (relo->kind == BPF_FIELD_EXISTS) {
- orig_val = 1; /* can't generate EXISTS relo w/o local field */
- new_val = targ_spec ? 1 : 0;
- } else if (!targ_spec) {
- pr_debug("prog '%s': relo #%d: substituting insn #%d w/ invalid insn\n",
- bpf_program__title(prog, false), relo_idx, insn_idx);
- insn->code = BPF_JMP | BPF_CALL;
- insn->dst_reg = 0;
- insn->src_reg = 0;
- insn->off = 0;
- /* if this instruction is reachable (not a dead code),
- * verifier will complain with the following message:
- * invalid func unknown#195896080
- */
- insn->imm = 195896080; /* => 0xbad2310 => "bad relo" */
+ if (res->poison) {
+ bpf_core_poison_insn(prog, relo_idx, insn_idx, insn);
return 0;
- } else {
- err = bpf_core_calc_field_relo(prog, relo, local_spec,
- &orig_val, &validate);
- if (err)
- return err;
- err = bpf_core_calc_field_relo(prog, relo, targ_spec,
- &new_val, NULL);
- if (err)
- return err;
}
+ orig_val = res->orig_val;
+ new_val = res->new_val;
+
switch (class) {
case BPF_ALU:
case BPF_ALU64:
if (BPF_SRC(insn->code) != BPF_K)
return -EINVAL;
- if (validate && insn->imm != orig_val) {
+ if (res->validate && insn->imm != orig_val) {
pr_warn("prog '%s': relo #%d: unexpected insn #%d (ALU/ALU64) value: got %u, exp %u -> %u\n",
bpf_program__title(prog, false), relo_idx,
insn_idx, insn->imm, orig_val, new_val);
@@ -4797,7 +4854,7 @@ static int bpf_core_reloc_insn(struct bpf_program *prog,
case BPF_LDX:
case BPF_ST:
case BPF_STX:
- if (validate && insn->off != orig_val) {
+ if (res->validate && insn->off != orig_val) {
pr_warn("prog '%s': relo #%d: unexpected insn #%d (LD/LDX/ST/STX) value: got %u, exp %u -> %u\n",
bpf_program__title(prog, false), relo_idx,
insn_idx, insn->off, orig_val, new_val);
@@ -4938,6 +4995,7 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
const char *prog_name = bpf_program__title(prog, false);
struct bpf_core_spec local_spec, cand_spec, targ_spec;
const void *type_key = u32_as_hash_key(relo->type_id);
+ struct bpf_core_relo_res cand_res, targ_res;
const struct btf_type *local_type;
const char *local_name;
struct ids_vec *cand_ids;
@@ -5005,16 +5063,31 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
if (err == 0)
continue;
+ err = bpf_core_calc_relo(prog, relo, relo_idx, &local_spec, &cand_spec, &cand_res);
+ if (err)
+ return err;
+
if (j == 0) {
+ targ_res = cand_res;
targ_spec = cand_spec;
} else if (cand_spec.bit_offset != targ_spec.bit_offset) {
- /* if there are many candidates, they should all
- * resolve to the same bit offset
+ /* if there are many field relo candidates, they
+ * should all resolve to the same bit offset
*/
- pr_warn("prog '%s': relo #%d: offset ambiguity: %u != %u\n",
+ pr_warn("prog '%s': relo #%d: field offset ambiguity: %u != %u\n",
prog_name, relo_idx, cand_spec.bit_offset,
targ_spec.bit_offset);
return -EINVAL;
+ } else if (cand_res.poison != targ_res.poison || cand_res.new_val != targ_res.new_val) {
+ /* all candidates should result in the same relocation
+ * decision and value, otherwise it's dangerous to
+ * proceed due to ambiguity
+ */
+ pr_warn("prog '%s': relo #%d: relocation decision ambiguity: %s %u != %s %u\n",
+ prog_name, relo_idx,
+ cand_res.poison ? "failure" : "success", cand_res.new_val,
+ targ_res.poison ? "failure" : "success", targ_res.new_val);
+ return -EINVAL;
}
cand_ids->data[j++] = cand_spec.spec[0].type_id;
@@ -5042,13 +5115,18 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
* verifier. If it was an error, then verifier will complain and point
* to a specific instruction number in its log.
*/
- if (j == 0)
+ if (j == 0) {
pr_debug("prog '%s': relo #%d: no matching targets found\n",
prog_name, relo_idx);
- /* bpf_core_reloc_insn should know how to handle missing targ_spec */
- err = bpf_core_reloc_insn(prog, relo, relo_idx, &local_spec,
- j ? &targ_spec : NULL);
+ /* calculate single target relo result explicitly */
+ err = bpf_core_calc_relo(prog, relo, relo_idx, &local_spec, NULL, &targ_res);
+ if (err)
+ return err;
+ }
+
+ /* bpf_core_patch_insn() should know how to handle missing targ_spec */
+ err = bpf_core_patch_insn(prog, relo, relo_idx, &targ_res);
if (err) {
pr_warn("prog '%s': relo #%d: failed to patch insn at offset %d: %d\n",
prog_name, relo_idx, relo->insn_off, err);
generated by cgit (git 2.34.1) at 2025-06-02 05:16:26 +0000