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Message-Id: <20200915234543.3220146-4-sdf@google.com>
Date: Tue, 15 Sep 2020 16:45:41 -0700
From: Stanislav Fomichev <sdf@...gle.com>
To: netdev@...r.kernel.org, bpf@...r.kernel.org
Cc: davem@...emloft.net, ast@...nel.org, daniel@...earbox.net,
YiFei Zhu <zhuyifei1999@...il.com>,
Stanislav Fomichev <sdf@...gle.com>
Subject: [PATCH bpf-next v6 3/5] libbpf: Add BPF_PROG_BIND_MAP syscall and use
it on .rodata section
From: YiFei Zhu <zhuyifei@...gle.com>
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@...il.com>
Signed-off-by: YiFei Zhu <zhuyifei@...gle.com>
Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
---
tools/lib/bpf/bpf.c | 16 ++++++++++
tools/lib/bpf/bpf.h | 8 +++++
tools/lib/bpf/libbpf.c | 69 ++++++++++++++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.map | 1 +
4 files changed, 94 insertions(+)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 82b983ff6569..2baa1308737c 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -872,3 +872,19 @@ 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;
+
+ if (!OPTS_VALID(opts, bpf_prog_bind_opts))
+ return -EINVAL;
+
+ 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..570235dbc922 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,
@@ -3894,6 +3900,52 @@ 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_load_program_attr prg_attr;
+ struct bpf_create_map_attr map_attr;
+ char *cp, errmsg[STRERR_BUFSIZE];
+ struct bpf_insn insns[] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ int ret, map, prog;
+
+ memset(&map_attr, 0, sizeof(map_attr));
+ map_attr.map_type = BPF_MAP_TYPE_ARRAY;
+ map_attr.key_size = sizeof(int);
+ 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));
+ pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
+ __func__, cp, -ret);
+ return ret;
+ }
+
+ 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.license = "GPL";
+
+ prog = bpf_load_program_xattr(&prg_attr, NULL, 0);
+ if (prog < 0) {
+ close(map);
+ return 0;
+ }
+
+ ret = bpf_prog_bind_map(prog, map, NULL);
+
+ close(map);
+ close(prog);
+
+ return ret >= 0;
+}
+
enum kern_feature_result {
FEAT_UNKNOWN = 0,
FEAT_SUPPORTED = 1,
@@ -3934,6 +3986,9 @@ 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 +6523,20 @@ 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..5f054dadf082 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;
bpf_program__section_name;
perf_buffer__buffer_cnt;
perf_buffer__buffer_fd;
--
2.28.0.618.gf4bc123cb7-goog
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