From: YiFei Zhu <zhuyifei@xxxxxxxxxx>
The patch adds a simple wrapper bpf_prog_bind_map around the syscall.
And when using libbpf to load a program, it will probe the kernel for
the support of this syscall, and scan for the .metadata ELF section
and load it as an internal map like a .data section.
In the case that kernel supports the BPF_PROG_BIND_MAP syscall and
a .metadata section exists, the map will be explicitly bound to
the program via the syscall immediately after program is loaded.
-EEXIST is ignored for this syscall.
Cc: YiFei Zhu <zhuyifei1999@xxxxxxxxx>
Signed-off-by: YiFei Zhu <zhuyifei@xxxxxxxxxx>
Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
---
tools/lib/bpf/bpf.c | 13 ++++
tools/lib/bpf/bpf.h | 8 +++
tools/lib/bpf/libbpf.c | 130 ++++++++++++++++++++++++++++++++-------
tools/lib/bpf/libbpf.map | 1 +
4 files changed, 131 insertions(+), 21 deletions(-)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 82b983ff6569..5f6c5676cc45 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -872,3 +872,16 @@ int bpf_enable_stats(enum bpf_stats_type type)
return sys_bpf(BPF_ENABLE_STATS, &attr, sizeof(attr));
}
+
+int bpf_prog_bind_map(int prog_fd, int map_fd,
+ const struct bpf_prog_bind_opts *opts)
+{
+ union bpf_attr attr;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_bind_map.prog_fd = prog_fd;
+ attr.prog_bind_map.map_fd = map_fd;
+ attr.prog_bind_map.flags = OPTS_GET(opts, flags, 0);
+
+ return sys_bpf(BPF_PROG_BIND_MAP, &attr, sizeof(attr));
+}
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 015d13f25fcc..8c1ac4b42f90 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -243,6 +243,14 @@ LIBBPF_API int bpf_task_fd_query(int pid, int fd, __u32 flags, char *buf,
enum bpf_stats_type; /* defined in up-to-date linux/bpf.h */
LIBBPF_API int bpf_enable_stats(enum bpf_stats_type type);
+struct bpf_prog_bind_opts {
+ size_t sz; /* size of this struct for forward/backward compatibility */
+ __u32 flags;
+};
+#define bpf_prog_bind_opts__last_field flags
+
+LIBBPF_API int bpf_prog_bind_map(int prog_fd, int map_fd,
+ const struct bpf_prog_bind_opts *opts);
#ifdef __cplusplus
} /* extern "C" */
#endif
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8cdb2528482e..2b21021b66bb 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -176,6 +176,8 @@ enum kern_feature_id {
FEAT_EXP_ATTACH_TYPE,
/* bpf_probe_read_{kernel,user}[_str] helpers */
FEAT_PROBE_READ_KERN,
+ /* BPF_PROG_BIND_MAP is supported */
+ FEAT_PROG_BIND_MAP,
__FEAT_CNT,
};
@@ -285,6 +287,7 @@ struct bpf_struct_ops {
#define KCONFIG_SEC ".kconfig"
#define KSYMS_SEC ".ksyms"
#define STRUCT_OPS_SEC ".struct_ops"
+#define METADATA_SEC ".metadata"
enum libbpf_map_type {
LIBBPF_MAP_UNSPEC,
@@ -292,6 +295,7 @@ enum libbpf_map_type {
LIBBPF_MAP_BSS,
LIBBPF_MAP_RODATA,
LIBBPF_MAP_KCONFIG,
+ LIBBPF_MAP_METADATA,
};
static const char * const libbpf_type_to_btf_name[] = {
@@ -299,6 +303,7 @@ static const char * const libbpf_type_to_btf_name[] = {
[LIBBPF_MAP_BSS] = BSS_SEC,
[LIBBPF_MAP_RODATA] = RODATA_SEC,
[LIBBPF_MAP_KCONFIG] = KCONFIG_SEC,
+ [LIBBPF_MAP_METADATA] = METADATA_SEC,
};
struct bpf_map {
@@ -381,6 +386,7 @@ struct bpf_object {
struct extern_desc *externs;
int nr_extern;
int kconfig_map_idx;
+ int metadata_map_idx;
bool loaded;
bool has_pseudo_calls;
@@ -400,6 +406,7 @@ struct bpf_object {
Elf_Data *rodata;
Elf_Data *bss;
Elf_Data *st_ops_data;
+ Elf_Data *metadata;
size_t shstrndx; /* section index for section name strings */
size_t strtabidx;
struct {
@@ -416,6 +423,7 @@ struct bpf_object {
int rodata_shndx;
int bss_shndx;
int st_ops_shndx;
+ int metadata_shndx;
} efile;
/*
* All loaded bpf_object is linked in a list, which is
@@ -1027,11 +1035,13 @@ static struct bpf_object *bpf_object__new(const char *path,
obj->efile.obj_buf_sz = obj_buf_sz;
obj->efile.maps_shndx = -1;
obj->efile.btf_maps_shndx = -1;
+ obj->efile.metadata_shndx = -1;
obj->efile.data_shndx = -1;
obj->efile.rodata_shndx = -1;
obj->efile.bss_shndx = -1;
obj->efile.st_ops_shndx = -1;
obj->kconfig_map_idx = -1;
+ obj->metadata_map_idx = -1;
obj->kern_version = get_kernel_version();
obj->loaded = false;
@@ -1343,7 +1353,8 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
def->key_size = sizeof(int);
def->value_size = data_sz;
def->max_entries = 1;
- def->map_flags = type == LIBBPF_MAP_RODATA || type == LIBBPF_MAP_KCONFIG
+ def->map_flags = type == LIBBPF_MAP_RODATA || type == LIBBPF_MAP_KCONFIG ||
+ type == LIBBPF_MAP_METADATA
? BPF_F_RDONLY_PROG : 0;
def->map_flags |= BPF_F_MMAPABLE;
@@ -1399,6 +1410,16 @@ static int bpf_object__init_global_data_maps(struct bpf_object *obj)
if (err)
return err;
}
+ if (obj->efile.metadata_shndx >= 0) {
+ err = bpf_object__init_internal_map(obj, LIBBPF_MAP_METADATA,
+ obj->efile.metadata_shndx,
+ obj->efile.metadata->d_buf,
+ obj->efile.metadata->d_size);
+ if (err)
+ return err;
+
+ obj->metadata_map_idx = obj->nr_maps - 1;
+ }
return 0;
}
@@ -2790,6 +2811,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
} else if (strcmp(name, STRUCT_OPS_SEC) == 0) {
obj->efile.st_ops_data = data;
obj->efile.st_ops_shndx = idx;
+ } else if (strcmp(name, METADATA_SEC) == 0) {
+ obj->efile.metadata = data;
+ obj->efile.metadata_shndx = idx;
} else {
pr_info("elf: skipping unrecognized data section(%d) %s\n",
idx, name);
@@ -3201,7 +3225,8 @@ static bool bpf_object__shndx_is_data(const struct bpf_object *obj,
{
return shndx == obj->efile.data_shndx ||
shndx == obj->efile.bss_shndx ||
- shndx == obj->efile.rodata_shndx;
+ shndx == obj->efile.rodata_shndx ||
+ shndx == obj->efile.metadata_shndx;
}
static bool bpf_object__shndx_is_maps(const struct bpf_object *obj,
@@ -3222,6 +3247,8 @@ bpf_object__section_to_libbpf_map_type(const struct bpf_object *obj, int shndx)
return LIBBPF_MAP_RODATA;
else if (shndx == obj->efile.symbols_shndx)
return LIBBPF_MAP_KCONFIG;
+ else if (shndx == obj->efile.metadata_shndx)
+ return LIBBPF_MAP_METADATA;
else
return LIBBPF_MAP_UNSPEC;
}
@@ -3592,18 +3619,13 @@ static int probe_kern_prog_name(void)
return probe_fd(ret);
}
-static int probe_kern_global_data(void)
+static void __probe_create_global_data(int *prog, int *map,
+ struct bpf_insn *insns, size_t insns_cnt)
{
struct bpf_load_program_attr prg_attr;
struct bpf_create_map_attr map_attr;
char *cp, errmsg[STRERR_BUFSIZE];
- struct bpf_insn insns[] = {
- BPF_LD_MAP_VALUE(BPF_REG_1, 0, 16),
- BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 42),
- BPF_MOV64_IMM(BPF_REG_0, 0),
- BPF_EXIT_INSN(),
- };
- int ret, map;
+ int err;
memset(&map_attr, 0, sizeof(map_attr));
map_attr.map_type = BPF_MAP_TYPE_ARRAY;
@@ -3611,26 +3633,40 @@ static int probe_kern_global_data(void)
map_attr.value_size = 32;
map_attr.max_entries = 1;
- map = bpf_create_map_xattr(&map_attr);
- if (map < 0) {
- ret = -errno;
- cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
+ *map = bpf_create_map_xattr(&map_attr);
+ if (*map < 0) {
+ err = errno;
+ cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
- __func__, cp, -ret);
- return ret;
+ __func__, cp, -err);
+ return;
}
- insns[0].imm = map;
+ insns[0].imm = *map;
memset(&prg_attr, 0, sizeof(prg_attr));
prg_attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
prg_attr.insns = insns;
- prg_attr.insns_cnt = ARRAY_SIZE(insns);
+ prg_attr.insns_cnt = insns_cnt;
prg_attr.license = "GPL";
- ret = bpf_load_program_xattr(&prg_attr, NULL, 0);
+ *prog = bpf_load_program_xattr(&prg_attr, NULL, 0);
+}
+
+static int probe_kern_global_data(void)
+{
+ struct bpf_insn insns[] = {
+ BPF_LD_MAP_VALUE(BPF_REG_1, 0, 16),
+ BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 42),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ int prog = -1, map = -1;
+
+ __probe_create_global_data(&prog, &map, insns, ARRAY_SIZE(insns));
+
close(map);
- return probe_fd(ret);
+ return probe_fd(prog);
}
static int probe_kern_btf(void)
@@ -3757,6 +3793,32 @@ static int probe_kern_probe_read_kernel(void)
return probe_fd(bpf_load_program_xattr(&attr, NULL, 0));
}
+static int probe_prog_bind_map(void)
+{
+ struct bpf_insn insns[] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ int prog = -1, map = -1, ret = 0;
+
+ if (!kernel_supports(FEAT_GLOBAL_DATA))
+ return 0;
+
+ __probe_create_global_data(&prog, &map, insns, ARRAY_SIZE(insns));
+
+ if (map >= 0 && prog < 0) {
+ close(map);
+ return 0;
+ }
+
+ if (!bpf_prog_bind_map(prog, map, NULL))
+ ret = 1;
+
+ close(map);
+ close(prog);
+ return ret;
+}
+
enum kern_feature_result {
FEAT_UNKNOWN = 0,
FEAT_SUPPORTED = 1,
@@ -3797,6 +3859,9 @@ static struct kern_feature_desc {
},
[FEAT_PROBE_READ_KERN] = {
"bpf_probe_read_kernel() helper", probe_kern_probe_read_kernel,
+ },
+ [FEAT_PROG_BIND_MAP] = {
+ "BPF_PROG_BIND_MAP support", probe_prog_bind_map,
}
};
@@ -3897,7 +3962,8 @@ bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map)
}
/* Freeze .rodata and .kconfig map as read-only from syscall side. */
- if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG) {
+ if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG ||
+ map_type == LIBBPF_MAP_METADATA) {
err = bpf_map_freeze(map->fd);
if (err) {
err = -errno;
@@ -6057,6 +6123,28 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
if (ret >= 0) {
if (log_buf && load_attr.log_level)
pr_debug("verifier log:\n%s", log_buf);
+
+ if (prog->obj->metadata_map_idx >= 0 &&
+ kernel_supports(FEAT_PROG_BIND_MAP)) {
+ struct bpf_map *metadata_map =
+ &prog->obj->maps[prog->obj->metadata_map_idx];
+
+ /* EEXIST to bpf_prog_bind_map means the map is already
+ * bound to the program. This can happen if the program
+ * refers to the map in its code. Since all we are doing
+ * is to make sure when we iterate the program's maps
+ * metadata map is always inside, EXIST is okay; we
+ * ignore this errno
+ */
+ if (bpf_prog_bind_map(ret, bpf_map__fd(metadata_map), NULL) &&
+ errno != EEXIST) {
+ cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
+ pr_warn("prog '%s': failed to bind .metadata map: %s\n",
+ prog->name, cp);
+ /* Don't fail hard if can't load metadata. */
+ }
+ }
+
*pfd = ret;
ret = 0;
goto out;
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 66a6286d0716..529b99c0c2c3 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -302,6 +302,7 @@ LIBBPF_0.1.0 {
LIBBPF_0.2.0 {
global:
+ bpf_prog_bind_map;
perf_buffer__buffer_cnt;
perf_buffer__buffer_fd;
perf_buffer__epoll_fd;
--
2.28.0.402.g5ffc5be6b7-goog
