From 9dbe6015636c19f929a7f7b742f27f303ff6069d Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Sat, 2 Oct 2021 06:47:54 +0530 Subject: libbpf: Support kernel module function calls This patch adds libbpf support for kernel module function call support. The fd_array parameter is used during BPF program load to pass module BTFs referenced by the program. insn->off is set to index into this array, but starts from 1, because insn->off as 0 is reserved for btf_vmlinux. We try to use existing insn->off for a module, since the kernel limits the maximum distinct module BTFs for kfuncs to 256, and also because index must never exceed the maximum allowed value that can fit in insn->off (INT16_MAX). In the future, if kernel interprets signed offset as unsigned for kfunc calls, this limit can be increased to UINT16_MAX. Also introduce a btf__find_by_name_kind_own helper to start searching from module BTF's start id when we know that the BTF ID is not present in vmlinux BTF (in find_ksym_btf_id). Signed-off-by: Kumar Kartikeya Dwivedi Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20211002011757.311265-7-memxor@gmail.com --- tools/lib/bpf/bpf.c | 1 + tools/lib/bpf/btf.c | 18 ++++++++-- tools/lib/bpf/libbpf.c | 74 +++++++++++++++++++++++++++++------------ tools/lib/bpf/libbpf_internal.h | 3 ++ 4 files changed, 72 insertions(+), 24 deletions(-) (limited to 'tools/lib') diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 2401fad090c5..7d1741ceaa32 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -264,6 +264,7 @@ int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr) attr.line_info_rec_size = load_attr->line_info_rec_size; attr.line_info_cnt = load_attr->line_info_cnt; attr.line_info = ptr_to_u64(load_attr->line_info); + attr.fd_array = ptr_to_u64(load_attr->fd_array); if (load_attr->name) memcpy(attr.prog_name, load_attr->name, diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 6ad63e4d418a..7774f99afa6e 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -695,15 +695,15 @@ __s32 btf__find_by_name(const struct btf *btf, const char *type_name) return libbpf_err(-ENOENT); } -__s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name, - __u32 kind) +static __s32 btf_find_by_name_kind(const struct btf *btf, int start_id, + const char *type_name, __u32 kind) { __u32 i, nr_types = btf__get_nr_types(btf); if (kind == BTF_KIND_UNKN || !strcmp(type_name, "void")) return 0; - for (i = 1; i <= nr_types; i++) { + for (i = start_id; i <= nr_types; i++) { const struct btf_type *t = btf__type_by_id(btf, i); const char *name; @@ -717,6 +717,18 @@ __s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name, return libbpf_err(-ENOENT); } +__s32 btf__find_by_name_kind_own(const struct btf *btf, const char *type_name, + __u32 kind) +{ + return btf_find_by_name_kind(btf, btf->start_id, type_name, kind); +} + +__s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name, + __u32 kind) +{ + return btf_find_by_name_kind(btf, 1, type_name, kind); +} + static bool btf_is_modifiable(const struct btf *btf) { return (void *)btf->hdr != btf->raw_data; diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index e23f1b6b9402..ea1c51dbc0f3 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -443,6 +443,11 @@ struct extern_desc { /* local btf_id of the ksym extern's type. */ __u32 type_id; + /* BTF fd index to be patched in for insn->off, this is + * 0 for vmlinux BTF, index in obj->fd_array for module + * BTF + */ + __s16 btf_fd_idx; } ksym; }; }; @@ -454,6 +459,7 @@ struct module_btf { char *name; __u32 id; int fd; + int fd_array_idx; }; struct bpf_object { @@ -539,6 +545,10 @@ struct bpf_object { void *priv; bpf_object_clear_priv_t clear_priv; + int *fd_array; + size_t fd_array_cap; + size_t fd_array_cnt; + char path[]; }; #define obj_elf_valid(o) ((o)->efile.elf) @@ -5407,6 +5417,7 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog) ext = &obj->externs[relo->sym_off]; insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL; insn[0].imm = ext->ksym.kernel_btf_id; + insn[0].off = ext->ksym.btf_fd_idx; break; case RELO_SUBPROG_ADDR: if (insn[0].src_reg != BPF_PSEUDO_FUNC) { @@ -6236,6 +6247,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, } load_attr.log_level = prog->log_level; load_attr.prog_flags = prog->prog_flags; + load_attr.fd_array = prog->obj->fd_array; /* adjust load_attr if sec_def provides custom preload callback */ if (prog->sec_def && prog->sec_def->preload_fn) { @@ -6752,13 +6764,14 @@ out: static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name, __u16 kind, struct btf **res_btf, - int *res_btf_fd) + struct module_btf **res_mod_btf) { - int i, id, btf_fd, err; + struct module_btf *mod_btf; struct btf *btf; + int i, id, err; btf = obj->btf_vmlinux; - btf_fd = 0; + mod_btf = NULL; id = btf__find_by_name_kind(btf, ksym_name, kind); if (id == -ENOENT) { @@ -6767,10 +6780,10 @@ static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name, return err; for (i = 0; i < obj->btf_module_cnt; i++) { - btf = obj->btf_modules[i].btf; - /* we assume module BTF FD is always >0 */ - btf_fd = obj->btf_modules[i].fd; - id = btf__find_by_name_kind(btf, ksym_name, kind); + /* we assume module_btf's BTF FD is always >0 */ + mod_btf = &obj->btf_modules[i]; + btf = mod_btf->btf; + id = btf__find_by_name_kind_own(btf, ksym_name, kind); if (id != -ENOENT) break; } @@ -6779,7 +6792,7 @@ static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name, return -ESRCH; *res_btf = btf; - *res_btf_fd = btf_fd; + *res_mod_btf = mod_btf; return id; } @@ -6788,11 +6801,12 @@ static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj, { const struct btf_type *targ_var, *targ_type; __u32 targ_type_id, local_type_id; + struct module_btf *mod_btf = NULL; const char *targ_var_name; - int id, btf_fd = 0, err; struct btf *btf = NULL; + int id, err; - id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &btf_fd); + id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &mod_btf); if (id == -ESRCH && ext->is_weak) { return 0; } else if (id < 0) { @@ -6827,7 +6841,7 @@ static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj, } ext->is_set = true; - ext->ksym.kernel_btf_obj_fd = btf_fd; + ext->ksym.kernel_btf_obj_fd = mod_btf ? mod_btf->fd : 0; ext->ksym.kernel_btf_id = id; pr_debug("extern (var ksym) '%s': resolved to [%d] %s %s\n", ext->name, id, btf_kind_str(targ_var), targ_var_name); @@ -6839,26 +6853,20 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj, struct extern_desc *ext) { int local_func_proto_id, kfunc_proto_id, kfunc_id; + struct module_btf *mod_btf = NULL; const struct btf_type *kern_func; struct btf *kern_btf = NULL; - int ret, kern_btf_fd = 0; + int ret; local_func_proto_id = ext->ksym.type_id; - kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC, - &kern_btf, &kern_btf_fd); + kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC, &kern_btf, &mod_btf); if (kfunc_id < 0) { pr_warn("extern (func ksym) '%s': not found in kernel BTF\n", ext->name); return kfunc_id; } - if (kern_btf != obj->btf_vmlinux) { - pr_warn("extern (func ksym) '%s': function in kernel module is not supported\n", - ext->name); - return -ENOTSUP; - } - kern_func = btf__type_by_id(kern_btf, kfunc_id); kfunc_proto_id = kern_func->type; @@ -6870,9 +6878,30 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj, return -EINVAL; } + /* set index for module BTF fd in fd_array, if unset */ + if (mod_btf && !mod_btf->fd_array_idx) { + /* insn->off is s16 */ + if (obj->fd_array_cnt == INT16_MAX) { + pr_warn("extern (func ksym) '%s': module BTF fd index %d too big to fit in bpf_insn offset\n", + ext->name, mod_btf->fd_array_idx); + return -E2BIG; + } + /* Cannot use index 0 for module BTF fd */ + if (!obj->fd_array_cnt) + obj->fd_array_cnt = 1; + + ret = libbpf_ensure_mem((void **)&obj->fd_array, &obj->fd_array_cap, sizeof(int), + obj->fd_array_cnt + 1); + if (ret) + return ret; + mod_btf->fd_array_idx = obj->fd_array_cnt; + /* we assume module BTF FD is always >0 */ + obj->fd_array[obj->fd_array_cnt++] = mod_btf->fd; + } + ext->is_set = true; - ext->ksym.kernel_btf_obj_fd = kern_btf_fd; ext->ksym.kernel_btf_id = kfunc_id; + ext->ksym.btf_fd_idx = mod_btf ? mod_btf->fd_array_idx : 0; pr_debug("extern (func ksym) '%s': resolved to kernel [%d]\n", ext->name, kfunc_id); @@ -7031,6 +7060,9 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr) err = bpf_gen__finish(obj->gen_loader); } + /* clean up fd_array */ + zfree(&obj->fd_array); + /* clean up module BTFs */ for (i = 0; i < obj->btf_module_cnt; i++) { close(obj->btf_modules[i].fd); diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index ec79400517d4..f7fd3944d46d 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -298,6 +298,7 @@ struct bpf_prog_load_params { __u32 log_level; char *log_buf; size_t log_buf_sz; + int *fd_array; }; int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr); @@ -408,6 +409,8 @@ int btf_type_visit_type_ids(struct btf_type *t, type_id_visit_fn visit, void *ct int btf_type_visit_str_offs(struct btf_type *t, str_off_visit_fn visit, void *ctx); int btf_ext_visit_type_ids(struct btf_ext *btf_ext, type_id_visit_fn visit, void *ctx); int btf_ext_visit_str_offs(struct btf_ext *btf_ext, str_off_visit_fn visit, void *ctx); +__s32 btf__find_by_name_kind_own(const struct btf *btf, const char *type_name, + __u32 kind); extern enum libbpf_strict_mode libbpf_mode; -- cgit v1.2.3