diff mbox series

[v12,bpf-next,10/14] bpf: Add d_path helper

Message ID 20200825192124.710397-11-jolsa@kernel.org
State Accepted
Delegated to: BPF Maintainers
Headers show
Series bpf: Add d_path helper | expand

Commit Message

Jiri Olsa Aug. 25, 2020, 7:21 p.m. UTC 
Adding d_path helper function that returns 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' and is zero terminated.

  bpf_d_path(&file->f_path, buf, size);

The helper calls directly d_path function, so there's only
limited set of function it can be called from. Adding just
very modest set for the start.

Updating also bpf.h tools uapi header and adding 'path' to
bpf_helpers_doc.py script.

Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: KP Singh <kpsingh@google.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/uapi/linux/bpf.h       | 16 +++++++++++-
 kernel/trace/bpf_trace.c       | 48 ++++++++++++++++++++++++++++++++++
 scripts/bpf_helpers_doc.py     |  2 ++
 tools/include/uapi/linux/bpf.h | 16 +++++++++++-
 4 files changed, 80 insertions(+), 2 deletions(-)

Comments

Alexei Starovoitov Aug. 25, 2020, 10:58 p.m. UTC | #1 
On Tue, Aug 25, 2020 at 12:23 PM Jiri Olsa <jolsa@kernel.org> wrote:
>  #define __BPF_FUNC_MAPPER(FN)          \
>         FN(unspec),                     \
> @@ -3655,7 +3668,8 @@ union bpf_attr {
>         FN(get_task_stack),             \
>         FN(load_hdr_opt),               \
>         FN(store_hdr_opt),              \
> -       FN(reserve_hdr_opt),
> +       FN(reserve_hdr_opt),            \
> +       FN(d_path),
>         /* */

This is not correct. Please keep "\" at the end.
I've missed it while applying Martin's patch.
I've manually rebased this set due to conflict with KP's changes,
fixed the above issue and applied.
Jiri Olsa Aug. 26, 2020, 9:25 a.m. UTC | #2 
On Tue, Aug 25, 2020 at 03:58:32PM -0700, Alexei Starovoitov wrote:
> On Tue, Aug 25, 2020 at 12:23 PM Jiri Olsa <jolsa@kernel.org> wrote:
> >  #define __BPF_FUNC_MAPPER(FN)          \
> >         FN(unspec),                     \
> > @@ -3655,7 +3668,8 @@ union bpf_attr {
> >         FN(get_task_stack),             \
> >         FN(load_hdr_opt),               \
> >         FN(store_hdr_opt),              \
> > -       FN(reserve_hdr_opt),
> > +       FN(reserve_hdr_opt),            \
> > +       FN(d_path),
> >         /* */
> 
> This is not correct. Please keep "\" at the end.
> I've missed it while applying Martin's patch.
> I've manually rebased this set due to conflict with KP's changes,
> fixed the above issue and applied.

thanks,
jirka
diff mbox series

Patch

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 544b89a64918..1dfcc390d147 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3509,6 +3509,19 @@  union bpf_attr {
  *
  *		**-EPERM** This helper cannot be used under the
  *			   current sock_ops->op.
+ *
+ * long 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 the provided buffer 'buf' of size 'sz' and
+ *		is zero terminated.
+ *
+ *	Return
+ *		On success, the strictly positive length of the string,
+ *		including the trailing NUL character. On error, a negative
+ *		value.
+ *
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -3655,7 +3668,8 @@  union bpf_attr {
 	FN(get_task_stack),		\
 	FN(load_hdr_opt),		\
 	FN(store_hdr_opt),		\
-	FN(reserve_hdr_opt),
+	FN(reserve_hdr_opt),		\
+	FN(d_path),
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index a8d4f253ed77..d973d891f2e2 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1098,6 +1098,52 @@  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)
+{
+	long len;
+	char *p;
+
+	if (!sz)
+		return 0;
+
+	p = d_path(path, buf, sz);
+	if (IS_ERR(p)) {
+		len = PTR_ERR(p);
+	} else {
+		len = buf + sz - p;
+		memmove(buf, p, len);
+	}
+
+	return len;
+}
+
+BTF_SET_START(btf_allowlist_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_SET_END(btf_allowlist_d_path)
+
+static bool bpf_d_path_allowed(const struct bpf_prog *prog)
+{
+	return btf_id_set_contains(&btf_allowlist_d_path, prog->aux->attach_btf_id);
+}
+
+BTF_ID_LIST(bpf_d_path_btf_ids)
+BTF_ID(struct, path)
+
+static const struct bpf_func_proto bpf_d_path_proto = {
+	.func		= bpf_d_path,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_BTF_ID,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
+	.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)
 {
@@ -1579,6 +1625,8 @@  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 5bfa448b4704..08388173973f 100755
--- a/scripts/bpf_helpers_doc.py
+++ b/scripts/bpf_helpers_doc.py
@@ -432,6 +432,7 @@  class PrinterHelpers(Printer):
             'struct __sk_buff',
             'struct sk_msg_md',
             'struct xdp_md',
+            'struct path',
     ]
     known_types = {
             '...',
@@ -472,6 +473,7 @@  class PrinterHelpers(Printer):
             'struct tcp_request_sock',
             'struct udp6_sock',
             'struct task_struct',
+            'struct path',
     }
     mapped_types = {
             'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 544b89a64918..1dfcc390d147 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3509,6 +3509,19 @@  union bpf_attr {
  *
  *		**-EPERM** This helper cannot be used under the
  *			   current sock_ops->op.
+ *
+ * long 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 the provided buffer 'buf' of size 'sz' and
+ *		is zero terminated.
+ *
+ *	Return
+ *		On success, the strictly positive length of the string,
+ *		including the trailing NUL character. On error, a negative
+ *		value.
+ *
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -3655,7 +3668,8 @@  union bpf_attr {
 	FN(get_task_stack),		\
 	FN(load_hdr_opt),		\
 	FN(store_hdr_opt),		\
-	FN(reserve_hdr_opt),
+	FN(reserve_hdr_opt),		\
+	FN(d_path),
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper