From: Alexei Starovoitov Date: Fri, 3 Dec 2021 18:28:36 +0000 (-0800) Subject: libbpf: Reduce bpf_core_apply_relo_insn() stack usage. X-Git-Tag: v6.1-rc5~2306^2~228^2~15 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=78c1f8d0634cc35da613d844eda7c849fc50f643;p=platform%2Fkernel%2Flinux-starfive.git libbpf: Reduce bpf_core_apply_relo_insn() stack usage. 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 Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20211203182836.16646-1-alexei.starovoitov@gmail.com --- diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index ed4258c..2a902a9 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -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); diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index de260c9..6db0b5e 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -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 diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c index d194fb9..32464f0 100644 --- a/tools/lib/bpf/relo_core.c +++ b/tools/lib/bpf/relo_core.c @@ -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; } diff --git a/tools/lib/bpf/relo_core.h b/tools/lib/bpf/relo_core.h index 4f864b8..1779981 100644 --- a/tools/lib/bpf/relo_core.h +++ b/tools/lib/bpf/relo_core.h @@ -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);