Netdev Archive on lore.kernel.org
 help / color / Atom feed
From: Jiri Olsa <jolsa@kernel.org>
To: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andriin@fb.com>
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
	Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
	Martin KaFai Lau <kafai@fb.com>, David Miller <davem@redhat.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Wenbo Zhang <ethercflow@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Brendan Gregg <bgregg@netflix.com>,
	Florent Revest <revest@chromium.org>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: [PATCH v9 bpf-next 07/14] bpf: Factor btf_struct_access function
Date: Sat,  1 Aug 2020 19:03:15 +0200
Message-ID: <20200801170322.75218-8-jolsa@kernel.org> (raw)
In-Reply-To: <20200801170322.75218-1-jolsa@kernel.org>

Adding btf_struct_walk function that walks through the
struct type + given offset and returns following values:

  enum bpf_struct_walk_result {
       /* < 0 error */
       WALK_SCALAR = 0,
       WALK_PTR,
       WALK_STRUCT,
  };

WALK_SCALAR - when SCALAR_VALUE is found
WALK_PTR    - when pointer value is found, its ID is stored
              in 'next_btf_id' output param
WALK_STRUCT - when nested struct object is found, its ID is stored
              in 'next_btf_id' output param

It will be used in following patches to get all nested
struct objects for given type and offset.

The btf_struct_access now calls btf_struct_walk function,
as long as it gets nested structs as return value.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/bpf/btf.c | 75 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 65 insertions(+), 10 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 0f995038b589..7bacc2f56061 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3886,16 +3886,22 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
 	return true;
 }
 
-int btf_struct_access(struct bpf_verifier_log *log,
-		      const struct btf_type *t, int off, int size,
-		      enum bpf_access_type atype,
-		      u32 *next_btf_id)
+enum bpf_struct_walk_result {
+	/* < 0 error */
+	WALK_SCALAR = 0,
+	WALK_PTR,
+	WALK_STRUCT,
+};
+
+static int btf_struct_walk(struct bpf_verifier_log *log,
+			   const struct btf_type *t, int off, int size,
+			   u32 *next_btf_id)
 {
 	u32 i, moff, mtrue_end, msize = 0, total_nelems = 0;
 	const struct btf_type *mtype, *elem_type = NULL;
 	const struct btf_member *member;
 	const char *tname, *mname;
-	u32 vlen;
+	u32 vlen, elem_id, mid;
 
 again:
 	tname = __btf_name_by_offset(btf_vmlinux, t->name_off);
@@ -3966,7 +3972,7 @@ int btf_struct_access(struct bpf_verifier_log *log,
 			 */
 			if (off <= moff &&
 			    BITS_ROUNDUP_BYTES(end_bit) <= off + size)
-				return SCALAR_VALUE;
+				return WALK_SCALAR;
 
 			/* off may be accessing a following member
 			 *
@@ -3988,11 +3994,13 @@ int btf_struct_access(struct bpf_verifier_log *log,
 			break;
 
 		/* type of the field */
+		mid = member->type;
 		mtype = btf_type_by_id(btf_vmlinux, member->type);
 		mname = __btf_name_by_offset(btf_vmlinux, member->name_off);
 
 		mtype = __btf_resolve_size(btf_vmlinux, mtype, &msize,
-					   &elem_type, NULL, &total_nelems, NULL);
+					   &elem_type, &elem_id, &total_nelems,
+					   &mid);
 		if (IS_ERR(mtype)) {
 			bpf_log(log, "field %s doesn't have size\n", mname);
 			return -EFAULT;
@@ -4054,6 +4062,7 @@ int btf_struct_access(struct bpf_verifier_log *log,
 			elem_idx = (off - moff) / msize;
 			moff += elem_idx * msize;
 			mtype = elem_type;
+			mid = elem_id;
 		}
 
 		/* the 'off' we're looking for is either equal to start
@@ -4063,6 +4072,12 @@ int btf_struct_access(struct bpf_verifier_log *log,
 			/* our field must be inside that union or struct */
 			t = mtype;
 
+			/* return if the offset matches the member offset */
+			if (off == moff) {
+				*next_btf_id = mid;
+				return WALK_STRUCT;
+			}
+
 			/* adjust offset we're looking for */
 			off -= moff;
 			goto again;
@@ -4078,11 +4093,10 @@ int btf_struct_access(struct bpf_verifier_log *log,
 					mname, moff, tname, off, size);
 				return -EACCES;
 			}
-
 			stype = btf_type_skip_modifiers(btf_vmlinux, mtype->type, &id);
 			if (btf_type_is_struct(stype)) {
 				*next_btf_id = id;
-				return PTR_TO_BTF_ID;
+				return WALK_PTR;
 			}
 		}
 
@@ -4099,12 +4113,53 @@ int btf_struct_access(struct bpf_verifier_log *log,
 			return -EACCES;
 		}
 
-		return SCALAR_VALUE;
+		return WALK_SCALAR;
 	}
 	bpf_log(log, "struct %s doesn't have field at offset %d\n", tname, off);
 	return -EINVAL;
 }
 
+int btf_struct_access(struct bpf_verifier_log *log,
+		      const struct btf_type *t, int off, int size,
+		      enum bpf_access_type atype __maybe_unused,
+		      u32 *next_btf_id)
+{
+	int err;
+	u32 id;
+
+	do {
+		err = btf_struct_walk(log, t, off, size, &id);
+
+		switch (err) {
+		case WALK_PTR:
+			/* If we found the pointer or scalar on t+off,
+			 * we're done.
+			 */
+			*next_btf_id = id;
+			return PTR_TO_BTF_ID;
+		case WALK_SCALAR:
+			return SCALAR_VALUE;
+		case WALK_STRUCT:
+			/* We found nested struct, so continue the search
+			 * by diving in it. At this point the offset is
+			 * aligned with the new type, so set it to 0.
+			 */
+			t = btf_type_by_id(btf_vmlinux, id);
+			off = 0;
+			break;
+		default:
+			/* It's either error or unknown return value..
+			 * scream and leave.
+			 */
+			if (WARN_ONCE(err > 0, "unknown btf_struct_walk return value"))
+				return -EINVAL;
+			return err;
+		}
+	} while (t);
+
+	return -EINVAL;
+}
+
 int btf_resolve_helper_id(struct bpf_verifier_log *log,
 			  const struct bpf_func_proto *fn, int arg)
 {
-- 
2.25.4


  parent reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-01 17:03 [PATCH v9 bpf-next 00/14] bpf: Add d_path helper Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 01/14] tools resolve_btfids: Add size check to get_id function Jiri Olsa
2020-08-05  6:00   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 02/14] tools resolve_btfids: Add support for set symbols Jiri Olsa
2020-08-05  6:04   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 03/14] bpf: Move btf_resolve_size into __btf_resolve_size Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 04/14] bpf: Add elem_id pointer as argument to __btf_resolve_size Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 05/14] bpf: Add type_id " Jiri Olsa
2020-08-05  6:05   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 06/14] bpf: Remove recursion call in btf_struct_access Jiri Olsa
2020-08-05  6:12   ` Andrii Nakryiko
2020-08-05 17:36     ` Jiri Olsa
2020-08-01 17:03 ` Jiri Olsa [this message]
2020-08-05  6:18   ` [PATCH v9 bpf-next 07/14] bpf: Factor btf_struct_access function Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 08/14] bpf: Add btf_struct_ids_match function Jiri Olsa
2020-08-05  6:27   ` Andrii Nakryiko
2020-08-05 17:56     ` Jiri Olsa
2020-08-05 21:31       ` Jiri Olsa
2020-08-05 21:57         ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 09/14] bpf: Add BTF_SET_START/END macros Jiri Olsa
2020-08-05  6:29   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 10/14] bpf: Add d_path helper Jiri Olsa
2020-08-02  3:13   ` Alexei Starovoitov
2020-08-02 18:26     ` Jiri Olsa
2020-08-05  6:35   ` Andrii Nakryiko
2020-08-05 17:58     ` Jiri Olsa
2020-08-05 21:01       ` Jiri Olsa
2020-08-05 21:09         ` Andrii Nakryiko
2020-08-07  0:31   ` KP Singh
2020-08-07  8:35     ` Jiri Olsa
2020-08-07  9:42       ` KP Singh
2020-08-01 17:03 ` [PATCH v9 bpf-next 11/14] bpf: Update .BTF_ids section in btf.rst with sets info Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 12/14] selftests/bpf: Add verifier test for d_path helper Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 13/14] selftests/bpf: Add " Jiri Olsa
2020-08-05  6:40   ` Andrii Nakryiko
2020-08-05 18:00     ` Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 14/14] selftests/bpf: Add set test to resolve_btfids Jiri Olsa
2020-08-05  6:41   ` Andrii Nakryiko

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200801170322.75218-8-jolsa@kernel.org \
    --to=jolsa@kernel.org \
    --cc=andriin@fb.com \
    --cc=ast@kernel.org \
    --cc=bgregg@netflix.com \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=davem@redhat.com \
    --cc=ethercflow@gmail.com \
    --cc=john.fastabend@gmail.com \
    --cc=kafai@fb.com \
    --cc=kpsingh@chromium.org \
    --cc=netdev@vger.kernel.org \
    --cc=revest@chromium.org \
    --cc=songliubraving@fb.com \
    --cc=viro@zeniv.linux.org.uk \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Netdev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/netdev/0 netdev/git/0.git
	git clone --mirror https://lore.kernel.org/netdev/1 netdev/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 netdev netdev/ https://lore.kernel.org/netdev \
		netdev@vger.kernel.org
	public-inbox-index netdev

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.netdev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git