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libbpf: Reduce bpf_core_apply_relo_insn() stack usage.

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Reduce bpf_core_apply_relo_insn() stack usage and bump
BPF_CORE_SPEC_MAX_LEN limit back to 64.

Fixes: 29db4bea1d10 ("bpf: Prepare relo_core.c for kernel duty.")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211203182836.16646-1-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov
2021-12-03 10:28:36 -08:00
committed by Andrii Nakryiko
parent b633ace366
commit c3c540b402
3 changed files with 51 additions and 45 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
src/libbpf.c
View File

@@ -5515,6 +5515,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
const struct btf *local_btf, const struct btf *local_btf,
struct hashmap *cand_cache) struct hashmap *cand_cache)
{ {
struct bpf_core_spec specs_scratch[3] = {};
const void *type_key = u32_as_hash_key(relo->type_id); const void *type_key = u32_as_hash_key(relo->type_id);
struct bpf_core_cand_list *cands = NULL; struct bpf_core_cand_list *cands = NULL;
const char *prog_name = prog->name; const char *prog_name = prog->name;
@@ -5569,7 +5570,8 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
} }
} }
return bpf_core_apply_relo_insn(prog_name, insn, insn_idx, relo, relo_idx, local_btf, cands); return bpf_core_apply_relo_insn(prog_name, insn, insn_idx, relo,
relo_idx, local_btf, cands, specs_scratch);
} }
static int static int

62
src/relo_core.c
View File

@@ -68,33 +68,6 @@ enum libbpf_print_level {
#include "libbpf_internal.h" #include "libbpf_internal.h"
#endif #endif
#define BPF_CORE_SPEC_MAX_LEN 32
/* represents BPF CO-RE field or array element accessor */
struct bpf_core_accessor {
__u32 type_id; /* struct/union type or array element type */
__u32 idx; /* field index or array index */
const char *name; /* field name or NULL for array accessor */
};
struct bpf_core_spec {
const struct btf *btf;
/* high-level spec: named fields and array indices only */
struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
/* original unresolved (no skip_mods_or_typedefs) root type ID */
__u32 root_type_id;
/* CO-RE relocation kind */
enum bpf_core_relo_kind relo_kind;
/* high-level spec length */
int len;
/* raw, low-level spec: 1-to-1 with accessor spec string */
int raw_spec[BPF_CORE_SPEC_MAX_LEN];
/* raw spec length */
int raw_len;
/* field bit offset represented by spec */
__u32 bit_offset;
};
static bool is_flex_arr(const struct btf *btf, static bool is_flex_arr(const struct btf *btf,
const struct bpf_core_accessor *acc, const struct bpf_core_accessor *acc,
const struct btf_array *arr) const struct btf_array *arr)
@@ -1200,9 +1173,12 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
const struct bpf_core_relo *relo, const struct bpf_core_relo *relo,
int relo_idx, int relo_idx,
const struct btf *local_btf, const struct btf *local_btf,
struct bpf_core_cand_list *cands) struct bpf_core_cand_list *cands,
struct bpf_core_spec *specs_scratch)
{ {
struct bpf_core_spec local_spec, cand_spec, targ_spec = {}; struct bpf_core_spec *local_spec = &specs_scratch[0];
struct bpf_core_spec *cand_spec = &specs_scratch[1];
struct bpf_core_spec *targ_spec = &specs_scratch[2];
struct bpf_core_relo_res cand_res, targ_res; struct bpf_core_relo_res cand_res, targ_res;
const struct btf_type *local_type; const struct btf_type *local_type;
const char *local_name; const char *local_name;
@@ -1221,7 +1197,7 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
return -EINVAL; return -EINVAL;
err = bpf_core_parse_spec(prog_name, local_btf, local_id, spec_str, err = bpf_core_parse_spec(prog_name, local_btf, local_id, spec_str,
relo->kind, &local_spec); relo->kind, local_spec);
if (err) { if (err) {
pr_warn("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n", pr_warn("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n",
prog_name, relo_idx, local_id, btf_kind_str(local_type), prog_name, relo_idx, local_id, btf_kind_str(local_type),
@@ -1232,15 +1208,15 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog_name, pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog_name,
relo_idx, core_relo_kind_str(relo->kind), relo->kind); relo_idx, core_relo_kind_str(relo->kind), relo->kind);
bpf_core_dump_spec(prog_name, LIBBPF_DEBUG, &local_spec); bpf_core_dump_spec(prog_name, LIBBPF_DEBUG, local_spec);
libbpf_print(LIBBPF_DEBUG, "\n"); libbpf_print(LIBBPF_DEBUG, "\n");
/* TYPE_ID_LOCAL relo is special and doesn't need candidate search */ /* TYPE_ID_LOCAL relo is special and doesn't need candidate search */
if (relo->kind == BPF_CORE_TYPE_ID_LOCAL) { if (relo->kind == BPF_CORE_TYPE_ID_LOCAL) {
targ_res.validate = true; targ_res.validate = true;
targ_res.poison = false; targ_res.poison = false;
targ_res.orig_val = local_spec.root_type_id; targ_res.orig_val = local_spec->root_type_id;
targ_res.new_val = local_spec.root_type_id; targ_res.new_val = local_spec->root_type_id;
goto patch_insn; goto patch_insn;
} }
@@ -1253,38 +1229,38 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
for (i = 0, j = 0; i < cands->len; i++) { for (i = 0, j = 0; i < cands->len; i++) {
err = bpf_core_spec_match(&local_spec, cands->cands[i].btf, err = bpf_core_spec_match(local_spec, cands->cands[i].btf,
cands->cands[i].id, &cand_spec); cands->cands[i].id, cand_spec);
if (err < 0) { if (err < 0) {
pr_warn("prog '%s': relo #%d: error matching candidate #%d ", pr_warn("prog '%s': relo #%d: error matching candidate #%d ",
prog_name, relo_idx, i); prog_name, relo_idx, i);
bpf_core_dump_spec(prog_name, LIBBPF_WARN, &cand_spec); bpf_core_dump_spec(prog_name, LIBBPF_WARN, cand_spec);
libbpf_print(LIBBPF_WARN, ": %d\n", err); libbpf_print(LIBBPF_WARN, ": %d\n", err);
return err; return err;
} }
pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name, pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name,
relo_idx, err == 0 ? "non-matching" : "matching", i); relo_idx, err == 0 ? "non-matching" : "matching", i);
bpf_core_dump_spec(prog_name, LIBBPF_DEBUG, &cand_spec); bpf_core_dump_spec(prog_name, LIBBPF_DEBUG, cand_spec);
libbpf_print(LIBBPF_DEBUG, "\n"); libbpf_print(LIBBPF_DEBUG, "\n");
if (err == 0) if (err == 0)
continue; continue;
err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, &cand_spec, &cand_res); err = bpf_core_calc_relo(prog_name, relo, relo_idx, local_spec, cand_spec, &cand_res);
if (err) if (err)
return err; return err;
if (j == 0) { if (j == 0) {
targ_res = cand_res; targ_res = cand_res;
targ_spec = cand_spec; *targ_spec = *cand_spec;
} else if (cand_spec.bit_offset != targ_spec.bit_offset) { } else if (cand_spec->bit_offset != targ_spec->bit_offset) {
/* if there are many field relo candidates, they /* if there are many field relo candidates, they
* should all resolve to the same bit offset * should all resolve to the same bit offset
*/ */
pr_warn("prog '%s': relo #%d: field 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, prog_name, relo_idx, cand_spec->bit_offset,
targ_spec.bit_offset); targ_spec->bit_offset);
return -EINVAL; return -EINVAL;
} else if (cand_res.poison != targ_res.poison || cand_res.new_val != targ_res.new_val) { } else if (cand_res.poison != targ_res.poison || cand_res.new_val != targ_res.new_val) {
/* all candidates should result in the same relocation /* all candidates should result in the same relocation
@@ -1328,7 +1304,7 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
prog_name, relo_idx); prog_name, relo_idx);
/* calculate single target relo result explicitly */ /* calculate single target relo result explicitly */
err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, NULL, &targ_res); err = bpf_core_calc_relo(prog_name, relo, relo_idx, local_spec, NULL, &targ_res);
if (err) if (err)
return err; return err;
} }

30
src/relo_core.h
View File

@@ -17,11 +17,39 @@ struct bpf_core_cand_list {
int len; int len;
}; };
#define BPF_CORE_SPEC_MAX_LEN 64
/* represents BPF CO-RE field or array element accessor */
struct bpf_core_accessor {
__u32 type_id; /* struct/union type or array element type */
__u32 idx; /* field index or array index */
const char *name; /* field name or NULL for array accessor */
};
struct bpf_core_spec {
const struct btf *btf;
/* high-level spec: named fields and array indices only */
struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
/* original unresolved (no skip_mods_or_typedefs) root type ID */
__u32 root_type_id;
/* CO-RE relocation kind */
enum bpf_core_relo_kind relo_kind;
/* high-level spec length */
int len;
/* raw, low-level spec: 1-to-1 with accessor spec string */
int raw_spec[BPF_CORE_SPEC_MAX_LEN];
/* raw spec length */
int raw_len;
/* field bit offset represented by spec */
__u32 bit_offset;
};
int bpf_core_apply_relo_insn(const char *prog_name, int bpf_core_apply_relo_insn(const char *prog_name,
struct bpf_insn *insn, int insn_idx, struct bpf_insn *insn, int insn_idx,
const struct bpf_core_relo *relo, int relo_idx, const struct bpf_core_relo *relo, int relo_idx,
const struct btf *local_btf, const struct btf *local_btf,
struct bpf_core_cand_list *cands); struct bpf_core_cand_list *cands,
struct bpf_core_spec *specs_scratch);
int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id, int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
const struct btf *targ_btf, __u32 targ_id); const struct btf *targ_btf, __u32 targ_id);