From: Andrii Nakryiko andrii@kernel.org
mainline inclusion from mainline-5.13-rc1 commit aea28a602fa19fb4fe66374030ab7e2c8ddf643e category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
-------------------------------------------------
Define __hidden helper macro in bpf_helpers.h, which is a short-hand for __attribute__((visibility("hidden"))). Add libbpf support to mark BPF subprograms marked with __hidden as static in BTF information to enforce BPF verifier's static function validation algorithm, which takes more information (caller's context) into account during a subprogram validation.
Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Acked-by: Yonghong Song yhs@fb.com Link: https://lore.kernel.org/bpf/20210423181348.1801389-5-andrii@kernel.org (cherry picked from commit aea28a602fa19fb4fe66374030ab7e2c8ddf643e) Signed-off-by: Wang Yufen wangyufen@huawei.com --- tools/lib/bpf/bpf_helpers.h | 8 ++++++ tools/lib/bpf/btf.c | 5 ---- tools/lib/bpf/libbpf.c | 45 ++++++++++++++++++++++++++++++++- tools/lib/bpf/libbpf_internal.h | 6 +++++ 4 files changed, 58 insertions(+), 6 deletions(-)
diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index 75c7581b304c..9720dc0b4605 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -47,6 +47,14 @@ #define __weak __attribute__((weak)) #endif
+/* + * Use __hidden attribute to mark a non-static BPF subprogram effectively + * static for BPF verifier's verification algorithm purposes, allowing more + * extensive and permissive BPF verification process, taking into account + * subprogram's caller context. + */ +#define __hidden __attribute__((visibility("hidden"))) + /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include * any system-level headers (such as stddef.h, linux/version.h, etc), and * commonly-used macros like NULL and KERNEL_VERSION aren't available through diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 4c0dd20c0ec9..9be6b87f8d52 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -1611,11 +1611,6 @@ static void *btf_add_type_mem(struct btf *btf, size_t add_sz) btf->hdr->type_len, UINT_MAX, add_sz); }
-static __u32 btf_type_info(int kind, int vlen, int kflag) -{ - return (kflag << 31) | (kind << 24) | vlen; -} - static void btf_type_inc_vlen(struct btf_type *t) { t->info = btf_type_info(btf_kind(t), btf_vlen(t) + 1, btf_kflag(t)); diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index cad6b9bd13ba..f2c667482ce6 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -71,6 +71,7 @@ static struct bpf_map *bpf_object__add_map(struct bpf_object *obj); static const struct btf_type * skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id); +static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog);
static int __base_pr(enum libbpf_print_level level, const char *format, va_list args) @@ -274,6 +275,7 @@ struct bpf_program { bpf_program_clear_priv_t clear_priv;
bool load; + bool mark_btf_static; enum bpf_prog_type type; enum bpf_attach_type expected_attach_type; int prog_ifindex; @@ -698,6 +700,15 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data, if (err) return err;
+ /* if function is a global/weak symbol, but has hidden + * visibility (STV_HIDDEN), mark its BTF FUNC as static to + * enable more permissive BPF verification mode with more + * outside context available to BPF verifier + */ + if (GELF_ST_BIND(sym.st_info) != STB_LOCAL + && GELF_ST_VISIBILITY(sym.st_other) == STV_HIDDEN) + prog->mark_btf_static = true; + nr_progs++; obj->nr_programs = nr_progs;
@@ -2619,7 +2630,7 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj) { struct btf *kern_btf = obj->btf; bool btf_mandatory, sanitize; - int err = 0; + int i, err = 0;
if (!obj->btf) return 0; @@ -2633,6 +2644,38 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj) return 0; }
+ /* Even though some subprogs are global/weak, user might prefer more + * permissive BPF verification process that BPF verifier performs for + * static functions, taking into account more context from the caller + * functions. In such case, they need to mark such subprogs with + * __attribute__((visibility("hidden"))) and libbpf will adjust + * corresponding FUNC BTF type to be marked as static and trigger more + * involved BPF verification process. + */ + for (i = 0; i < obj->nr_programs; i++) { + struct bpf_program *prog = &obj->programs[i]; + struct btf_type *t; + const char *name; + int j, n; + + if (!prog->mark_btf_static || !prog_is_subprog(obj, prog)) + continue; + + n = btf__get_nr_types(obj->btf); + for (j = 1; j <= n; j++) { + t = btf_type_by_id(obj->btf, j); + if (!btf_is_func(t) || btf_func_linkage(t) != BTF_FUNC_GLOBAL) + continue; + + name = btf__str_by_offset(obj->btf, t->name_off); + if (strcmp(name, prog->name) != 0) + continue; + + t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_STATIC, 0); + break; + } + } + sanitize = btf_needs_sanitization(obj); if (sanitize) { const void *raw_data; diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index 6017902c687e..92b7eae10c6d 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -19,6 +19,7 @@ #pragma GCC poison reallocarray
#include "libbpf.h" +#include "btf.h"
#ifndef EM_BPF #define EM_BPF 247 @@ -132,6 +133,11 @@ struct btf_type;
struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id);
+static inline __u32 btf_type_info(int kind, int vlen, int kflag) +{ + return (kflag << 31) | (kind << 24) | vlen; +} + void *libbpf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t cur_cnt, size_t max_cnt, size_t add_cnt); int libbpf_ensure_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t need_cnt);