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-rw-r--r--tools/lib/bpf/libbpf.c95
-rw-r--r--tools/lib/bpf/libbpf.h6
2 files changed, 61 insertions, 40 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ae34b681ae82..39f1b7633a7c 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -345,7 +345,6 @@ struct bpf_object {
bool loaded;
bool has_pseudo_calls;
- bool relaxed_core_relocs;
/*
* Information when doing elf related work. Only valid if fd
@@ -4238,25 +4237,38 @@ static int bpf_core_calc_field_relo(const struct bpf_program *prog,
*/
static int bpf_core_reloc_insn(struct bpf_program *prog,
const struct bpf_field_reloc *relo,
+ int relo_idx,
const struct bpf_core_spec *local_spec,
const struct bpf_core_spec *targ_spec)
{
- bool failed = false, validate = true;
__u32 orig_val, new_val;
struct bpf_insn *insn;
+ bool validate = true;
int insn_idx, err;
__u8 class;
if (relo->insn_off % sizeof(struct bpf_insn))
return -EINVAL;
insn_idx = relo->insn_off / sizeof(struct bpf_insn);
+ 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) {
- failed = true;
- new_val = (__u32)-1;
+ 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" */
+ return 0;
} else {
err = bpf_core_calc_field_relo(prog, relo, local_spec,
&orig_val, &validate);
@@ -4268,50 +4280,47 @@ static int bpf_core_reloc_insn(struct bpf_program *prog,
return err;
}
- insn = &prog->insns[insn_idx];
- class = BPF_CLASS(insn->code);
-
switch (class) {
case BPF_ALU:
case BPF_ALU64:
if (BPF_SRC(insn->code) != BPF_K)
return -EINVAL;
- if (!failed && validate && insn->imm != orig_val) {
- pr_warn("prog '%s': unexpected insn #%d (ALU/ALU64) value: got %u, exp %u -> %u\n",
- bpf_program__title(prog, false), insn_idx,
- insn->imm, orig_val, new_val);
+ if (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);
return -EINVAL;
}
orig_val = insn->imm;
insn->imm = new_val;
- pr_debug("prog '%s': patched insn #%d (ALU/ALU64)%s imm %u -> %u\n",
- bpf_program__title(prog, false), insn_idx,
- failed ? " w/ failed reloc" : "", orig_val, new_val);
+ pr_debug("prog '%s': relo #%d: patched insn #%d (ALU/ALU64) imm %u -> %u\n",
+ bpf_program__title(prog, false), relo_idx, insn_idx,
+ orig_val, new_val);
break;
case BPF_LDX:
case BPF_ST:
case BPF_STX:
- if (!failed && validate && insn->off != orig_val) {
- pr_warn("prog '%s': unexpected insn #%d (LD/LDX/ST/STX) value: got %u, exp %u -> %u\n",
- bpf_program__title(prog, false), insn_idx,
- insn->off, orig_val, new_val);
+ if (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);
return -EINVAL;
}
if (new_val > SHRT_MAX) {
- pr_warn("prog '%s': insn #%d (LD/LDX/ST/STX) value too big: %u\n",
- bpf_program__title(prog, false), insn_idx,
- new_val);
+ pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) value too big: %u\n",
+ bpf_program__title(prog, false), relo_idx,
+ insn_idx, new_val);
return -ERANGE;
}
orig_val = insn->off;
insn->off = new_val;
- pr_debug("prog '%s': patched insn #%d (LD/LDX/ST/STX)%s off %u -> %u\n",
- bpf_program__title(prog, false), insn_idx,
- failed ? " w/ failed reloc" : "", orig_val, new_val);
+ pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) off %u -> %u\n",
+ bpf_program__title(prog, false), relo_idx, insn_idx,
+ orig_val, new_val);
break;
default:
- pr_warn("prog '%s': trying to relocate unrecognized insn #%d, code:%x, src:%x, dst:%x, off:%x, imm:%x\n",
- bpf_program__title(prog, false),
+ pr_warn("prog '%s': relo #%d: trying to relocate unrecognized insn #%d, code:%x, src:%x, dst:%x, off:%x, imm:%x\n",
+ bpf_program__title(prog, false), relo_idx,
insn_idx, insn->code, insn->src_reg, insn->dst_reg,
insn->off, insn->imm);
return -EINVAL;
@@ -4510,24 +4519,33 @@ static int bpf_core_reloc_field(struct bpf_program *prog,
}
/*
- * For BPF_FIELD_EXISTS relo or when relaxed CO-RE reloc mode is
- * requested, it's expected that we might not find any candidates.
- * In this case, if field wasn't found in any candidate, the list of
- * candidates shouldn't change at all, we'll just handle relocating
- * appropriately, depending on relo's kind.
+ * For BPF_FIELD_EXISTS relo or when used BPF program has field
+ * existence checks or kernel version/config checks, it's expected
+ * that we might not find any candidates. In this case, if field
+ * wasn't found in any candidate, the list of candidates shouldn't
+ * change at all, we'll just handle relocating appropriately,
+ * depending on relo's kind.
*/
if (j > 0)
cand_ids->len = j;
- if (j == 0 && !prog->obj->relaxed_core_relocs &&
- relo->kind != BPF_FIELD_EXISTS) {
- pr_warn("prog '%s': relo #%d: no matching targets found for [%d] %s + %s\n",
- prog_name, relo_idx, local_id, local_name, spec_str);
- return -ESRCH;
- }
+ /*
+ * If no candidates were found, it might be both a programmer error,
+ * as well as expected case, depending whether instruction w/
+ * relocation is guarded in some way that makes it unreachable (dead
+ * code) if relocation can't be resolved. This is handled in
+ * bpf_core_reloc_insn() uniformly by replacing that instruction with
+ * BPF helper call insn (using invalid helper ID). If that instruction
+ * is indeed unreachable, then it will be ignored and eliminated by
+ * verifier. If it was an error, then verifier will complain and point
+ * to a specific instruction number in its log.
+ */
+ if (j == 0)
+ pr_debug("prog '%s': relo #%d: no matching targets found for [%d] %s + %s\n",
+ prog_name, relo_idx, local_id, local_name, spec_str);
/* bpf_core_reloc_insn should know how to handle missing targ_spec */
- err = bpf_core_reloc_insn(prog, relo, &local_spec,
+ err = bpf_core_reloc_insn(prog, relo, relo_idx, &local_spec,
j ? &targ_spec : NULL);
if (err) {
pr_warn("prog '%s': relo #%d: failed to patch insn at offset %d: %d\n",
@@ -5057,7 +5075,6 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
if (IS_ERR(obj))
return obj;
- obj->relaxed_core_relocs = OPTS_GET(opts, relaxed_core_relocs, false);
kconfig = OPTS_GET(opts, kconfig, NULL);
if (kconfig) {
obj->kconfig = strdup(kconfig);
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 2a5e3b087002..3fe12c9d1f92 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -77,7 +77,11 @@ struct bpf_object_open_opts {
const char *object_name;
/* parse map definitions non-strictly, allowing extra attributes/data */
bool relaxed_maps;
- /* process CO-RE relocations non-strictly, allowing them to fail */
+ /* DEPRECATED: handle CO-RE relocations non-strictly, allowing failures.
+ * Value is ignored. Relocations always are processed non-strictly.
+ * Non-relocatable instructions are replaced with invalid ones to
+ * prevent accidental errors.
+ * */
bool relaxed_core_relocs;
/* maps that set the 'pinning' attribute in their definition will have
* their pin_path attribute set to a file in this directory, and be