From: YiFei Zhu <zhuyifei@xxxxxxxxxx>
The patch adds a simple wrapper bpf_prog_bind_map around the syscall.
When the libbpf tries to load a program, it will probe the kernel for
the support of this syscall and unconditionally bind .rodata section
to the program.
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 | 94 ++++++++++++++++++++++++++++++++--------
tools/lib/bpf/libbpf.map | 1 +
4 files changed, 98 insertions(+), 18 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 550950eb1860..f500ae7e9126 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -174,6 +174,8 @@ 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,
};
@@ -409,6 +411,7 @@ struct bpf_object {
struct extern_desc *externs;
int nr_extern;
int kconfig_map_idx;
+ int rodata_map_idx;
bool loaded;
bool has_subcalls;
@@ -1070,6 +1073,7 @@ static struct bpf_object *bpf_object__new(const char *path,
obj->efile.bss_shndx = -1;
obj->efile.st_ops_shndx = -1;
obj->kconfig_map_idx = -1;
+ obj->rodata_map_idx = -1;
obj->kern_version = get_kernel_version();
obj->loaded = false;
@@ -1428,6 +1432,8 @@ static int bpf_object__init_global_data_maps(struct bpf_object *obj)
obj->efile.rodata->d_size);
if (err)
return err;
+
+ obj->rodata_map_idx = obj->nr_maps - 1;
}
if (obj->efile.bss_shndx >= 0) {
err = bpf_object__init_internal_map(obj, LIBBPF_MAP_BSS,
@@ -3729,18 +3735,13 @@ 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;
@@ -3748,26 +3749,40 @@ 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)
@@ -3894,6 +3909,32 @@ 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,
@@ -3934,6 +3975,9 @@ 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,
}
};
@@ -6468,6 +6512,20 @@ 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->rodata_map_idx >= 0 &&
+ kernel_supports(FEAT_PROG_BIND_MAP)) {
+ struct bpf_map *rodata_map =
+ &prog->obj->maps[prog->obj->rodata_map_idx];
+
+ if (bpf_prog_bind_map(ret, bpf_map__fd(rodata_map), NULL)) {
+ cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
+ pr_warn("prog '%s': failed to bind .rodata map: %s\n",
+ prog->name, cp);
+ /* Don't fail hard if can't bind rodata. */
+ }
+ }
+
*pfd = ret;
ret = 0;
goto out;
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 92ceb48a5ca2..0b7830f4ff8b 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -308,4 +308,5 @@ LIBBPF_0.2.0 {
perf_buffer__epoll_fd;
perf_buffer__consume_buffer;
xsk_socket__create_shared;
+ bpf_prog_bind_map;
} LIBBPF_0.1.0;
--
2.28.0.526.ge36021eeef-goog
