Adding d_path helper function that returns full path
for give 'struct path' object, which needs to be the
kernel BTF 'path' object.
The helper calls directly d_path function.
Updating also bpf.h tools uapi header and adding
'path' to bpf_helpers_doc.py script.
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
include/linux/bpf.h | 4 ++++
include/uapi/linux/bpf.h | 14 ++++++++++++-
kernel/bpf/btf_ids.c | 11 ++++++++++
kernel/trace/bpf_trace.c | 38 ++++++++++++++++++++++++++++++++++
scripts/bpf_helpers_doc.py | 2 ++
tools/include/uapi/linux/bpf.h | 14 ++++++++++++-
6 files changed, 81 insertions(+), 2 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a94e85c2ec50..d35265b6c574 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1752,5 +1752,9 @@ extern int bpf_skb_output_btf_ids[];
extern int bpf_seq_printf_btf_ids[];
extern int bpf_seq_write_btf_ids[];
extern int bpf_xdp_output_btf_ids[];
+extern int bpf_d_path_btf_ids[];
+
+extern int btf_whitelist_d_path[];
+extern int btf_whitelist_d_path_cnt;
#endif /* _LINUX_BPF_H */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c65b374a5090..e308746b9344 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3252,6 +3252,17 @@ union bpf_attr {
* case of **BPF_CSUM_LEVEL_QUERY**, the current skb->csum_level
* is returned or the error code -EACCES in case the skb is not
* subject to CHECKSUM_UNNECESSARY.
+ *
+ * int bpf_d_path(struct path *path, char *buf, u32 sz)
+ * Description
+ * Return full path for given 'struct path' object, which
+ * needs to be the kernel BTF 'path' object. The path is
+ * returned in buffer provided 'buf' of size 'sz'.
+ *
+ * Return
+ * length of returned string on success, or a negative
+ * error in case of failure
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3389,7 +3400,8 @@ union bpf_attr {
FN(ringbuf_submit), \
FN(ringbuf_discard), \
FN(ringbuf_query), \
- FN(csum_level),
+ FN(csum_level), \
+ FN(d_path),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
diff --git a/kernel/bpf/btf_ids.c b/kernel/bpf/btf_ids.c
index d8d0df162f04..853c8fd59b06 100644
--- a/kernel/bpf/btf_ids.c
+++ b/kernel/bpf/btf_ids.c
@@ -13,3 +13,14 @@ BTF_ID(struct, seq_file)
BTF_ID_LIST(bpf_xdp_output_btf_ids)
BTF_ID(struct, xdp_buff)
+
+BTF_ID_LIST(bpf_d_path_btf_ids)
+BTF_ID(struct, path)
+
+BTF_WHITELIST_ENTRY(btf_whitelist_d_path)
+BTF_ID(func, vfs_truncate)
+BTF_ID(func, vfs_fallocate)
+BTF_ID(func, dentry_open)
+BTF_ID(func, vfs_getattr)
+BTF_ID(func, filp_close)
+BTF_WHITELIST_END(btf_whitelist_d_path)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index c1866d76041f..0ff5d8434d40 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1016,6 +1016,42 @@ static const struct bpf_func_proto bpf_send_signal_thread_proto = {
.arg1_type = ARG_ANYTHING,
};
+BPF_CALL_3(bpf_d_path, struct path *, path, char *, buf, u32, sz)
+{
+ char *p = d_path(path, buf, sz - 1);
+ int len;
+
+ if (IS_ERR(p)) {
+ len = PTR_ERR(p);
+ } else {
+ len = strlen(p);
+ if (len && p != buf) {
+ memmove(buf, p, len);
+ buf[len] = 0;
+ }
+ }
+
+ return len;
+}
+
+static bool bpf_d_path_allowed(const struct bpf_prog *prog)
+{
+ return btf_whitelist_search(prog->aux->attach_btf_id,
+ btf_whitelist_d_path,
+ btf_whitelist_d_path_cnt);
+}
+
+static const struct bpf_func_proto bpf_d_path_proto = {
+ .func = bpf_d_path,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg2_type = ARG_PTR_TO_MEM,
+ .arg3_type = ARG_CONST_SIZE,
+ .btf_id = bpf_d_path_btf_ids,
+ .allowed = bpf_d_path_allowed,
+};
+
const struct bpf_func_proto *
bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
@@ -1483,6 +1519,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return prog->expected_attach_type == BPF_TRACE_ITER ?
&bpf_seq_write_proto :
NULL;
+ case BPF_FUNC_d_path:
+ return &bpf_d_path_proto;
default:
return raw_tp_prog_func_proto(func_id, prog);
}
diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
index 91fa668fa860..3161bf4ccee4 100755
--- a/scripts/bpf_helpers_doc.py
+++ b/scripts/bpf_helpers_doc.py
@@ -425,6 +425,7 @@ class PrinterHelpers(Printer):
'struct __sk_buff',
'struct sk_msg_md',
'struct xdp_md',
+ 'struct path',
]
known_types = {
'...',
@@ -458,6 +459,7 @@ class PrinterHelpers(Printer):
'struct sockaddr',
'struct tcphdr',
'struct seq_file',
+ 'struct path',
}
mapped_types = {
'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c65b374a5090..e308746b9344 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3252,6 +3252,17 @@ union bpf_attr {
* case of **BPF_CSUM_LEVEL_QUERY**, the current skb->csum_level
* is returned or the error code -EACCES in case the skb is not
* subject to CHECKSUM_UNNECESSARY.
+ *
+ * int bpf_d_path(struct path *path, char *buf, u32 sz)
+ * Description
+ * Return full path for given 'struct path' object, which
+ * needs to be the kernel BTF 'path' object. The path is
+ * returned in buffer provided 'buf' of size 'sz'.
+ *
+ * Return
+ * length of returned string on success, or a negative
+ * error in case of failure
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3389,7 +3400,8 @@ union bpf_attr {
FN(ringbuf_submit), \
FN(ringbuf_discard), \
FN(ringbuf_query), \
- FN(csum_level),
+ FN(csum_level), \
+ FN(d_path),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
--
2.25.4
