diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index f67dce2af802..a510d8ed716f 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -75,5 +75,6 @@ enum libbpf_tristate { }; #define __kconfig __attribute__((section(".kconfig"))) +#define __ksym __attribute__((section(".ksyms"))) #endif diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index 70c1b7ec2bd0..06cd1731c154 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h @@ -168,6 +168,11 @@ static inline bool btf_kflag(const struct btf_type *t) return BTF_INFO_KFLAG(t->info); } +static inline bool btf_is_void(const struct btf_type *t) +{ + return btf_kind(t) == BTF_KIND_UNKN; +} + static inline bool btf_is_int(const struct btf_type *t) { return btf_kind(t) == BTF_KIND_INT; diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index ffccb5af32a5..18461deb1b19 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -285,6 +285,7 @@ struct bpf_struct_ops { #define BSS_SEC ".bss" #define RODATA_SEC ".rodata" #define KCONFIG_SEC ".kconfig" +#define KSYMS_SEC ".ksyms" #define STRUCT_OPS_SEC ".struct_ops" enum libbpf_map_type { @@ -331,6 +332,7 @@ struct bpf_map { enum extern_type { EXT_UNKNOWN, EXT_KCFG, + EXT_KSYM, }; enum kcfg_type { @@ -358,6 +360,9 @@ struct extern_desc { int data_off; bool is_signed; } kcfg; + struct { + unsigned long long addr; + } ksym; }; }; @@ -2817,9 +2822,25 @@ static int cmp_externs(const void *_a, const void *_b) return strcmp(a->name, b->name); } +static int find_int_btf_id(const struct btf *btf) +{ + const struct btf_type *t; + int i, n; + + n = btf__get_nr_types(btf); + for (i = 1; i <= n; i++) { + t = btf__type_by_id(btf, i); + + if (btf_is_int(t) && btf_int_bits(t) == 32) + return i; + } + + return 0; +} + static int bpf_object__collect_externs(struct bpf_object *obj) { - struct btf_type *sec, *kcfg_sec = NULL; + struct btf_type *sec, *kcfg_sec = NULL, *ksym_sec = NULL; const struct btf_type *t; struct extern_desc *ext; int i, n, off; @@ -2900,6 +2921,17 @@ static int bpf_object__collect_externs(struct bpf_object *obj) pr_warn("extern (kcfg) '%s' type is unsupported\n", ext_name); return -ENOTSUP; } + } else if (strcmp(sec_name, KSYMS_SEC) == 0) { + const struct btf_type *vt; + + ksym_sec = sec; + ext->type = EXT_KSYM; + + vt = skip_mods_and_typedefs(obj->btf, t->type, NULL); + if (!btf_is_void(vt)) { + pr_warn("extern (ksym) '%s' is not typeless (void)\n", ext_name); + return -ENOTSUP; + } } else { pr_warn("unrecognized extern section '%s'\n", sec_name); return -ENOTSUP; @@ -2913,6 +2945,46 @@ static int bpf_object__collect_externs(struct bpf_object *obj) /* sort externs by type, for kcfg ones also by (align, size, name) */ qsort(obj->externs, obj->nr_extern, sizeof(*ext), cmp_externs); + /* for .ksyms section, we need to turn all externs into allocated + * variables in BTF to pass kernel verification; we do this by + * pretending that each extern is a 8-byte variable + */ + if (ksym_sec) { + /* find existing 4-byte integer type in BTF to use for fake + * extern variables in DATASEC + */ + int int_btf_id = find_int_btf_id(obj->btf); + + for (i = 0; i < obj->nr_extern; i++) { + ext = &obj->externs[i]; + if (ext->type != EXT_KSYM) + continue; + pr_debug("extern (ksym) #%d: symbol %d, name %s\n", + i, ext->sym_idx, ext->name); + } + + sec = ksym_sec; + n = btf_vlen(sec); + for (i = 0, off = 0; i < n; i++, off += sizeof(int)) { + struct btf_var_secinfo *vs = btf_var_secinfos(sec) + i; + struct btf_type *vt; + + vt = (void *)btf__type_by_id(obj->btf, vs->type); + ext_name = btf__name_by_offset(obj->btf, vt->name_off); + ext = find_extern_by_name(obj, ext_name); + if (!ext) { + pr_warn("failed to find extern definition for BTF var '%s'\n", + ext_name); + return -ESRCH; + } + btf_var(vt)->linkage = BTF_VAR_GLOBAL_ALLOCATED; + vt->type = int_btf_id; + vs->offset = off; + vs->size = sizeof(int); + } + sec->size = off; + } + if (kcfg_sec) { sec = kcfg_sec; /* for kcfg externs calculate their offsets within a .kconfig map */ @@ -2924,7 +2996,7 @@ static int bpf_object__collect_externs(struct bpf_object *obj) ext->kcfg.data_off = roundup(off, ext->kcfg.align); off = ext->kcfg.data_off + ext->kcfg.sz; - pr_debug("extern #%d (kcfg): symbol %d, off %u, name %s\n", + pr_debug("extern (kcfg) #%d: symbol %d, off %u, name %s\n", i, ext->sym_idx, ext->kcfg.data_off, ext->name); } sec->size = off; @@ -5022,9 +5094,14 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj) break; case RELO_EXTERN: ext = &obj->externs[relo->sym_off]; - insn[0].src_reg = BPF_PSEUDO_MAP_VALUE; - insn[0].imm = obj->maps[obj->kconfig_map_idx].fd; - insn[1].imm = ext->kcfg.data_off; + if (ext->type == EXT_KCFG) { + insn[0].src_reg = BPF_PSEUDO_MAP_VALUE; + insn[0].imm = obj->maps[obj->kconfig_map_idx].fd; + insn[1].imm = ext->kcfg.data_off; + } else /* EXT_KSYM */ { + insn[0].imm = (__u32)ext->ksym.addr; + insn[1].imm = ext->ksym.addr >> 32; + } break; case RELO_CALL: err = bpf_program__reloc_text(prog, obj, relo); @@ -5643,10 +5720,58 @@ static int bpf_object__sanitize_maps(struct bpf_object *obj) return 0; } +static int bpf_object__read_kallsyms_file(struct bpf_object *obj) +{ + char sym_type, sym_name[500]; + unsigned long long sym_addr; + struct extern_desc *ext; + int ret, err = 0; + FILE *f; + + f = fopen("/proc/kallsyms", "r"); + if (!f) { + err = -errno; + pr_warn("failed to open /proc/kallsyms: %d\n", err); + return err; + } + + while (true) { + ret = fscanf(f, "%llx %c %499s%*[^\n]\n", + &sym_addr, &sym_type, sym_name); + if (ret == EOF && feof(f)) + break; + if (ret != 3) { + pr_warn("failed to read kallasyms entry: %d\n", ret); + err = -EINVAL; + goto out; + } + + ext = find_extern_by_name(obj, sym_name); + if (!ext || ext->type != EXT_KSYM) + continue; + + if (ext->is_set && ext->ksym.addr != sym_addr) { + pr_warn("extern (ksym) '%s' resolution is ambiguous: 0x%llx or 0x%llx\n", + sym_name, ext->ksym.addr, sym_addr); + err = -EINVAL; + goto out; + } + if (!ext->is_set) { + ext->is_set = true; + ext->ksym.addr = sym_addr; + pr_debug("extern (ksym) %s=0x%llx\n", sym_name, sym_addr); + } + } + +out: + fclose(f); + return err; +} + static int bpf_object__resolve_externs(struct bpf_object *obj, const char *extra_kconfig) { - bool need_config = false; + bool need_config = false, need_kallsyms = false; struct extern_desc *ext; void *kcfg_data = NULL; int err, i; @@ -5676,6 +5801,8 @@ static int bpf_object__resolve_externs(struct bpf_object *obj, } else if (ext->type == EXT_KCFG && strncmp(ext->name, "CONFIG_", 7) == 0) { need_config = true; + } else if (ext->type == EXT_KSYM) { + need_kallsyms = true; } else { pr_warn("unrecognized extern '%s'\n", ext->name); return -EINVAL; @@ -5699,6 +5826,11 @@ static int bpf_object__resolve_externs(struct bpf_object *obj, if (err) return -EINVAL; } + if (need_kallsyms) { + err = bpf_object__read_kallsyms_file(obj); + if (err) + return -EINVAL; + } for (i = 0; i < obj->nr_extern; i++) { ext = &obj->externs[i];