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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: 29db4bea1d ("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 0bf40542c0
commit 78c1f8d063
4 changed files with 61 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
kernel/bpf/btf.c
View File

@ -6742,8 +6742,16 @@ int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo,
{
bool need_cands = relo->kind != BPF_CORE_TYPE_ID_LOCAL;
struct bpf_core_cand_list cands = {};
struct bpf_core_spec *specs;
int err;
/* ~4k of temp memory necessary to convert LLVM spec like "0:1:0:5"
* into arrays of btf_ids of struct fields and array indices.
*/
specs = kcalloc(3, sizeof(*specs), GFP_KERNEL);
if (!specs)
return -ENOMEM;
if (need_cands) {
struct bpf_cand_cache *cc;
int i;
@ -6779,8 +6787,9 @@ int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo,
}
err = bpf_core_apply_relo_insn((void *)ctx->log, insn, relo->insn_off / 8,
relo, relo_idx, ctx->btf, &cands);
relo, relo_idx, ctx->btf, &cands, specs);
out:
kfree(specs);
if (need_cands) {
kfree(cands.cands);
mutex_unlock(&cand_cache_mutex);

4
tools/lib/bpf/libbpf.c
View File

@ -5515,6 +5515,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
const struct btf *local_btf,
struct hashmap *cand_cache)
{
struct bpf_core_spec specs_scratch[3] = {};
const void *type_key = u32_as_hash_key(relo->type_id);
struct bpf_core_cand_list *cands = NULL;
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

62
tools/lib/bpf/relo_core.c
View File

@ -68,33 +68,6 @@ enum libbpf_print_level {
#include "libbpf_internal.h"
#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,
const struct bpf_core_accessor *acc,
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,
int relo_idx,
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;
const struct btf_type *local_type;
const char *local_name;
@ -1221,7 +1197,7 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
return -EINVAL;
err = bpf_core_parse_spec(prog_name, local_btf, local_id, spec_str,
relo->kind, &local_spec);
relo->kind, local_spec);
if (err) {
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),
@ -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,
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");
/* TYPE_ID_LOCAL relo is special and doesn't need candidate search */
if (relo->kind == BPF_CORE_TYPE_ID_LOCAL) {
targ_res.validate = true;
targ_res.poison = false;
targ_res.orig_val = local_spec.root_type_id;
targ_res.new_val = local_spec.root_type_id;
targ_res.orig_val = local_spec->root_type_id;
targ_res.new_val = local_spec->root_type_id;
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++) {
err = bpf_core_spec_match(&local_spec, cands->cands[i].btf,
cands->cands[i].id, &cand_spec);
err = bpf_core_spec_match(local_spec, cands->cands[i].btf,
cands->cands[i].id, cand_spec);
if (err < 0) {
pr_warn("prog '%s': relo #%d: error matching candidate #%d ",
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);
return err;
}
pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name,
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");
if (err == 0)
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)
return err;
if (j == 0) {
targ_res = cand_res;
targ_spec = cand_spec;
} else if (cand_spec.bit_offset != targ_spec.bit_offset) {
*targ_spec = *cand_spec;
} else if (cand_spec->bit_offset != targ_spec->bit_offset) {
/* if there are many field relo candidates, they
* should all resolve to the same bit offset
*/
pr_warn("prog '%s': relo #%d: field offset ambiguity: %u != %u\n",
prog_name, relo_idx, cand_spec.bit_offset,
targ_spec.bit_offset);
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
@ -1328,7 +1304,7 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
prog_name, relo_idx);
/* 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)
return err;
}

30
tools/lib/bpf/relo_core.h
View File

@ -17,11 +17,39 @@ struct bpf_core_cand_list {
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,
struct bpf_insn *insn, int insn_idx,
const struct bpf_core_relo *relo, int relo_idx,
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,
const struct btf *targ_btf, __u32 targ_id);