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From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
	<daniel@iogearbox.net>
Cc: <andrii@kernel.org>, <kernel-team@fb.com>
Subject: [PATCH v6 bpf-next 10/14] bpf: allow to specify kernel module BTFs when attaching BPF programs
Date: Thu, 3 Dec 2020 12:46:30 -0800	[thread overview]
Message-ID: <20201203204634.1325171-11-andrii@kernel.org> (raw)
In-Reply-To: <20201203204634.1325171-1-andrii@kernel.org>

Add ability for user-space programs to specify non-vmlinux BTF when attaching
BTF-powered BPF programs: raw_tp, fentry/fexit/fmod_ret, LSM, etc. For this,
attach_prog_fd (now with the alias name attach_btf_obj_fd) should specify FD
of a module or vmlinux BTF object. For backwards compatibility reasons,
0 denotes vmlinux BTF. Only kernel BTF (vmlinux or module) can be specified.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 include/linux/btf.h            |  1 +
 include/uapi/linux/bpf.h       |  7 ++-
 kernel/bpf/btf.c               |  5 +++
 kernel/bpf/syscall.c           | 82 +++++++++++++++++++++-------------
 tools/include/uapi/linux/bpf.h |  7 ++-
 5 files changed, 69 insertions(+), 33 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index fb608e4de076..4c200f5d242b 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -90,6 +90,7 @@ int btf_type_snprintf_show(const struct btf *btf, u32 type_id, void *obj,
 
 int btf_get_fd_by_id(u32 id);
 u32 btf_obj_id(const struct btf *btf);
+bool btf_is_kernel(const struct btf *btf);
 bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
 			   const struct btf_member *m,
 			   u32 expected_offset, u32 expected_size);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c3458ec1f30a..1233f14f659f 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -557,7 +557,12 @@ union bpf_attr {
 		__aligned_u64	line_info;	/* line info */
 		__u32		line_info_cnt;	/* number of bpf_line_info records */
 		__u32		attach_btf_id;	/* in-kernel BTF type id to attach to */
-		__u32		attach_prog_fd; /* 0 to attach to vmlinux */
+		union {
+			/* valid prog_fd to attach to bpf prog */
+			__u32		attach_prog_fd;
+			/* or valid module BTF object fd or 0 to attach to vmlinux */
+			__u32		attach_btf_obj_fd;
+		};
 	};
 
 	struct { /* anonymous struct used by BPF_OBJ_* commands */
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 7a19bf5bfe97..8d6bdb4f4d61 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5738,6 +5738,11 @@ u32 btf_obj_id(const struct btf *btf)
 	return btf->id;
 }
 
+bool btf_is_kernel(const struct btf *btf)
+{
+	return btf->kernel_btf;
+}
+
 static int btf_id_cmp_func(const void *a, const void *b)
 {
 	const int *pa = a, *pb = b;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 184204169949..0cd3cc2af9c1 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1926,12 +1926,16 @@ static void bpf_prog_load_fixup_attach_type(union bpf_attr *attr)
 static int
 bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
 			   enum bpf_attach_type expected_attach_type,
-			   u32 btf_id, u32 prog_fd)
+			   struct btf *attach_btf, u32 btf_id,
+			   struct bpf_prog *dst_prog)
 {
 	if (btf_id) {
 		if (btf_id > BTF_MAX_TYPE)
 			return -EINVAL;
 
+		if (!attach_btf && !dst_prog)
+			return -EINVAL;
+
 		switch (prog_type) {
 		case BPF_PROG_TYPE_TRACING:
 		case BPF_PROG_TYPE_LSM:
@@ -1943,7 +1947,10 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
 		}
 	}
 
-	if (prog_fd && prog_type != BPF_PROG_TYPE_TRACING &&
+	if (attach_btf && (!btf_id || dst_prog))
+		return -EINVAL;
+
+	if (dst_prog && prog_type != BPF_PROG_TYPE_TRACING &&
 	    prog_type != BPF_PROG_TYPE_EXT)
 		return -EINVAL;
 
@@ -2060,7 +2067,8 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
 static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
 {
 	enum bpf_prog_type type = attr->prog_type;
-	struct bpf_prog *prog;
+	struct bpf_prog *prog, *dst_prog = NULL;
+	struct btf *attach_btf = NULL;
 	int err;
 	char license[128];
 	bool is_gpl;
@@ -2102,44 +2110,56 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
 	if (is_perfmon_prog_type(type) && !perfmon_capable())
 		return -EPERM;
 
+	/* attach_prog_fd/attach_btf_obj_fd can specify fd of either bpf_prog
+	 * or btf, we need to check which one it is
+	 */
+	if (attr->attach_prog_fd) {
+		dst_prog = bpf_prog_get(attr->attach_prog_fd);
+		if (IS_ERR(dst_prog)) {
+			dst_prog = NULL;
+			attach_btf = btf_get_by_fd(attr->attach_btf_obj_fd);
+			if (IS_ERR(attach_btf))
+				return -EINVAL;
+			if (!btf_is_kernel(attach_btf)) {
+				btf_put(attach_btf);
+				return -EINVAL;
+			}
+		}
+	} else if (attr->attach_btf_id) {
+		/* fall back to vmlinux BTF, if BTF type ID is specified */
+		attach_btf = bpf_get_btf_vmlinux();
+		if (IS_ERR(attach_btf))
+			return PTR_ERR(attach_btf);
+		if (!attach_btf)
+			return -EINVAL;
+		btf_get(attach_btf);
+	}
+
 	bpf_prog_load_fixup_attach_type(attr);
 	if (bpf_prog_load_check_attach(type, attr->expected_attach_type,
-				       attr->attach_btf_id,
-				       attr->attach_prog_fd))
+				       attach_btf, attr->attach_btf_id,
+				       dst_prog)) {
+		if (dst_prog)
+			bpf_prog_put(dst_prog);
+		if (attach_btf)
+			btf_put(attach_btf);
 		return -EINVAL;
+	}
 
 	/* plain bpf_prog allocation */
 	prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);
-	if (!prog)
+	if (!prog) {
+		if (dst_prog)
+			bpf_prog_put(dst_prog);
+		if (attach_btf)
+			btf_put(attach_btf);
 		return -ENOMEM;
+	}
 
 	prog->expected_attach_type = attr->expected_attach_type;
+	prog->aux->attach_btf = attach_btf;
 	prog->aux->attach_btf_id = attr->attach_btf_id;
-
-	if (attr->attach_btf_id && !attr->attach_prog_fd) {
-		struct btf *btf;
-
-		btf = bpf_get_btf_vmlinux();
-		if (IS_ERR(btf))
-			return PTR_ERR(btf);
-		if (!btf)
-			return -EINVAL;
-
-		btf_get(btf);
-		prog->aux->attach_btf = btf;
-	}
-
-	if (attr->attach_prog_fd) {
-		struct bpf_prog *dst_prog;
-
-		dst_prog = bpf_prog_get(attr->attach_prog_fd);
-		if (IS_ERR(dst_prog)) {
-			err = PTR_ERR(dst_prog);
-			goto free_prog;
-		}
-		prog->aux->dst_prog = dst_prog;
-	}
-
+	prog->aux->dst_prog = dst_prog;
 	prog->aux->offload_requested = !!attr->prog_ifindex;
 	prog->aux->sleepable = attr->prog_flags & BPF_F_SLEEPABLE;
 
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c3458ec1f30a..1233f14f659f 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -557,7 +557,12 @@ union bpf_attr {
 		__aligned_u64	line_info;	/* line info */
 		__u32		line_info_cnt;	/* number of bpf_line_info records */
 		__u32		attach_btf_id;	/* in-kernel BTF type id to attach to */
-		__u32		attach_prog_fd; /* 0 to attach to vmlinux */
+		union {
+			/* valid prog_fd to attach to bpf prog */
+			__u32		attach_prog_fd;
+			/* or valid module BTF object fd or 0 to attach to vmlinux */
+			__u32		attach_btf_obj_fd;
+		};
 	};
 
 	struct { /* anonymous struct used by BPF_OBJ_* commands */
-- 
2.24.1


  parent reply	other threads:[~2020-12-03 20:49 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-03 20:46 [PATCH v6 bpf-next 00/14] Support BTF-powered BPF tracing programs for kernel modules Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 01/14] bpf: fix bpf_put_raw_tracepoint()'s use of __module_address() Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 02/14] bpf: keep module's btf_data_size intact after load Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 03/14] libbpf: add internal helper to load BTF data by FD Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 04/14] libbpf: refactor CO-RE relocs to not assume a single BTF object Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 05/14] libbpf: add kernel module BTF support for CO-RE relocations Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 06/14] selftests/bpf: add bpf_testmod kernel module for testing Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 07/14] selftests/bpf: add support for marking sub-tests as skipped Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 08/14] selftests/bpf: add CO-RE relocs selftest relying on kernel module BTF Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 09/14] bpf: remove hard-coded btf_vmlinux assumption from BPF verifier Andrii Nakryiko
2020-12-03 20:46 ` Andrii Nakryiko [this message]
2020-12-04  1:53   ` [PATCH v6 bpf-next 10/14] bpf: allow to specify kernel module BTFs when attaching BPF programs Alexei Starovoitov
2020-12-04 19:31     ` Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 11/14] libbpf: factor out low-level BPF program loading helper Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 12/14] libbpf: support attachment of BPF tracing programs to kernel modules Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 13/14] selftests/bpf: add tp_btf CO-RE reloc test for modules Andrii Nakryiko
2020-12-03 20:46 ` [PATCH v6 bpf-next 14/14] selftests/bpf: add fentry/fexit/fmod_ret selftest for kernel module Andrii Nakryiko

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