[PATCH 1/9] bpf: Add d_path helper

Jiri Olsa
2020-05-06T13:30:09Z

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@kernel.org>
---
include/uapi/linux/bpf.h | 14 +++++++++++++-
kernel/trace/bpf_trace.c | 31 +++++++++++++++++++++++++++++++
scripts/bpf_helpers_doc.py | 2 ++
tools/include/uapi/linux/bpf.h | 14 +++++++++++++-
4 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index b3643e27e264..bc13cad27872 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3068,6 +3068,17 @@ union bpf_attr {
* See: clock_gettime(CLOCK_BOOTTIME)
* Return
* Current *ktime*.
+ *
+ * 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), \
@@ -3195,7 +3206,8 @@ union bpf_attr {
FN(get_netns_cookie), \
FN(get_current_ancestor_cgroup_id), \
FN(sk_assign), \
- FN(ktime_get_boot_ns),
+ FN(ktime_get_boot_ns), \
+ 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/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index e875c95d3ced..3097ab04bdc4 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -779,6 +779,35 @@ 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 u32 bpf_d_path_btf_ids[3];
+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,
+};
+
const struct bpf_func_proto *
bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
@@ -1226,6 +1255,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_xdp_output:
return &bpf_xdp_output_proto;
#endif
+ 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 f43d193aff3a..8f62cbc4c3ff 100755
--- a/scripts/bpf_helpers_doc.py
+++ b/scripts/bpf_helpers_doc.py
@@ -418,6 +418,7 @@ class PrinterHelpers(Printer):
'struct __sk_buff',
'struct sk_msg_md',
'struct xdp_md',
+ 'struct path',
]
known_types = {
'...',
@@ -450,6 +451,7 @@ class PrinterHelpers(Printer):
'struct sk_reuseport_md',
'struct sockaddr',
'struct tcphdr',
+ 'struct path',
}
mapped_types = {
'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index b3643e27e264..bc13cad27872 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3068,6 +3068,17 @@ union bpf_attr {
* See: clock_gettime(CLOCK_BOOTTIME)
* Return
* Current *ktime*.
+ *
+ * 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), \
@@ -3195,7 +3206,8 @@ union bpf_attr {
FN(get_netns_cookie), \
FN(get_current_ancestor_cgroup_id), \
FN(sk_assign), \
- FN(ktime_get_boot_ns),
+ FN(ktime_get_boot_ns), \
+ FN(d_path),

/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
--
2.25.4