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Date: Thu, 22 Apr 2021 17:26:40 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: davem@...emloft.net
Cc: daniel@...earbox.net, andrii@...nel.org, netdev@...r.kernel.org,
bpf@...r.kernel.org, kernel-team@...com
Subject: [PATCH v2 bpf-next 10/16] bpf: Add bpf_btf_find_by_name_kind() helper.
From: Alexei Starovoitov <ast@...nel.org>
Add new helper:
long bpf_btf_find_by_name_kind(u32 btf_fd, char *name, u32 kind, int flags)
Description
Find given name with given type in BTF pointed to by btf_fd.
If btf_fd is zero look for the name in vmlinux BTF and in module's BTFs.
Return
Returns btf_id and btf_obj_fd in lower and upper 32 bits.
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 8 ++++
kernel/bpf/btf.c | 68 ++++++++++++++++++++++++++++++++++
kernel/bpf/syscall.c | 2 +
tools/include/uapi/linux/bpf.h | 8 ++++
5 files changed, 87 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0f841bd0cb85..4cf361eb6a80 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1972,6 +1972,7 @@ extern const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto;
extern const struct bpf_func_proto bpf_task_storage_get_proto;
extern const struct bpf_func_proto bpf_task_storage_delete_proto;
extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
+extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
const struct bpf_func_proto *bpf_tracing_func_proto(
enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index de58a714ed36..253f5f031f08 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4748,6 +4748,13 @@ union bpf_attr {
* Execute bpf syscall with given arguments.
* Return
* A syscall result.
+ *
+ * long bpf_btf_find_by_name_kind(u32 btf_fd, char *name, u32 kind, int flags)
+ * Description
+ * Find given name with given type in BTF pointed to by btf_fd.
+ * If btf_fd is zero look for the name in vmlinux BTF and in module's BTFs.
+ * Return
+ * Returns btf_id and btf_obj_fd in lower and upper 32 bits.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -4917,6 +4924,7 @@ union bpf_attr {
FN(for_each_map_elem), \
FN(snprintf), \
FN(sys_bpf), \
+ FN(btf_find_by_name_kind), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index fbf6c06a9d62..446c64171464 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6085,3 +6085,71 @@ struct module *btf_try_get_module(const struct btf *btf)
return res;
}
+
+BPF_CALL_4(bpf_btf_find_by_name_kind, int, btf_fd, char *, name, u32, kind, int, flags)
+{
+ char kname[KSYM_NAME_LEN];
+ struct btf *btf;
+ long ret;
+
+ if (flags)
+ return -EINVAL;
+
+ ret = strncpy_from_kernel_nofault(kname, name, sizeof(kname));
+ if (ret < 0)
+ return ret;
+ if (btf_fd)
+ btf = btf_get_by_fd(btf_fd);
+ else
+ btf = bpf_get_btf_vmlinux();
+ if (IS_ERR(btf))
+ return PTR_ERR(btf);
+
+ ret = btf_find_by_name_kind(btf, kname, kind);
+ /* ret is never zero, since btf_find_by_name_kind returns
+ * positive btf_id or negative error.
+ */
+ if (btf_fd)
+ btf_put(btf);
+ else if (ret < 0) {
+ struct btf *mod_btf;
+ int id;
+
+ /* If name is not found in vmlinux's BTF then search in module's BTFs */
+ spin_lock_bh(&btf_idr_lock);
+ idr_for_each_entry(&btf_idr, mod_btf, id) {
+ if (!btf_is_module(mod_btf))
+ continue;
+ /* linear search could be slow hence unlock/lock
+ * the IDR to avoiding holding it for too long
+ */
+ btf_get(mod_btf);
+ spin_unlock_bh(&btf_idr_lock);
+ ret = btf_find_by_name_kind(mod_btf, kname, kind);
+ if (ret > 0) {
+ int btf_obj_fd;
+
+ btf_obj_fd = __btf_new_fd(mod_btf);
+ if (btf_obj_fd < 0) {
+ btf_put(mod_btf);
+ return btf_obj_fd;
+ }
+ return ret | (((u64)btf_obj_fd) << 32);
+ }
+ spin_lock_bh(&btf_idr_lock);
+ btf_put(mod_btf);
+ }
+ spin_unlock_bh(&btf_idr_lock);
+ }
+ return ret;
+}
+
+const struct bpf_func_proto bpf_btf_find_by_name_kind_proto = {
+ .func = bpf_btf_find_by_name_kind,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_ANYTHING,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_ANYTHING,
+};
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a81496c5d09f..638c7acad925 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4574,6 +4574,8 @@ syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
switch (func_id) {
case BPF_FUNC_sys_bpf:
return &bpf_sys_bpf_proto;
+ case BPF_FUNC_btf_find_by_name_kind:
+ return &bpf_btf_find_by_name_kind_proto;
default:
return tracing_prog_func_proto(func_id, prog);
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 6c8e178d8ffa..5841adb44de6 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4748,6 +4748,13 @@ union bpf_attr {
* Execute bpf syscall with given arguments.
* Return
* A syscall result.
+ *
+ * long bpf_btf_find_by_name_kind(u32 btf_fd, char *name, u32 kind, int flags)
+ * Description
+ * Find given name with given type in BTF pointed to by btf_fd.
+ * If btf_fd is zero look for the name in vmlinux BTF and in module's BTFs.
+ * Return
+ * Returns btf_id and btf_obj_fd in lower and upper 32 bits.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -4917,6 +4924,7 @@ union bpf_attr {
FN(for_each_map_elem), \
FN(snprintf), \
FN(sys_bpf), \
+ FN(btf_find_by_name_kind), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.30.2
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