[PATCH v3 bpf-next 00/10] BPF token support in libbpf's BPF object

[PATCH v3 bpf-next 00/10] BPF token support in libbpf's BPF object

[Andrii Nakryiko]

Add fuller support for BPF token in high-level BPF object APIs. This is the
most frequently used way to work with BPF using libbpf, so supporting BPF
token there is critical.

Patch #1 is improving kernel-side BPF_TOKEN_CREATE behavior by rejecting to
create "empty" BPF token with no delegation. This seems like saner behavior
which also makes libbpf's caching better overall. If we ever want to create
BPF token with no delegate_xxx options set on BPF FS, we can use a new flag to
enable that.

Patches #2-#5 refactor libbpf internals, mostly feature detection code, to
prepare it from BPF token FD.

Patch #6 adds options to pass BPF token into BPF object open options. It also
adds implicit BPF token creation logic to BPF object load step, even without
any explicit involvement of the user. If the environment is setup properly,
BPF token will be created transparently and used implicitly. This allows for
all existing application to gain BPF token support by just linking with
latest version of libbpf library. No source code modifications are required.
All that under assumption that privileged container management agent properly
set up default BPF FS instance at /sys/bpf/fs to allow BPF token creation.

Patches #7-#8 adds more selftests, validating BPF object APIs work as expected
under unprivileged user namespaced conditions in the presence of BPF token.

Patch #9 extends libbpf with LIBBPF_BPF_TOKEN_PATH envvar knowledge, which can
be used to override custom BPF FS location used for implicit BPF token
creation logic without needing to adjust application code. This allows admins
or container managers to mount BPF token-enabled BPF FS at non-standard
location without the need to coordinate with applications.
LIBBPF_BPF_TOKEN_PATH can also be used to disable BPF token implicit creation
by setting it to an empty value. Patch #10 tests this new envvar functionality.

v2->v3:
  - move some stray feature cache refactorings into patch #4 (Alexei);
  - add LIBBPF_BPF_TOKEN_PATH envvar support (Alexei);
v1->v2:
  - remove minor code redundancies (Eduard, John);
  - add acks and rebase.

Andrii Nakryiko (10):
  bpf: fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS
  libbpf: split feature detectors definitions from cached results
  libbpf: further decouple feature checking logic from bpf_object
  libbpf: move feature detection code into its own file
  libbpf: wire up token_fd into feature probing logic
  libbpf: wire up BPF token support at BPF object level
  selftests/bpf: add BPF object loading tests with explicit token
    passing
  selftests/bpf: add tests for BPF object load with implicit token
  libbpf: support BPF token path setting through LIBBPF_BPF_TOKEN_PATH
    envvar
  selftests/bpf: add tests for LIBBPF_BPF_TOKEN_PATH envvar

 kernel/bpf/token.c                            |  10 +-
 tools/lib/bpf/Build                           |   2 +-
 tools/lib/bpf/bpf.c                           |   9 +-
 tools/lib/bpf/btf.c                           |   7 +-
 tools/lib/bpf/elf.c                           |   2 -
 tools/lib/bpf/features.c                      | 478 +++++++++++++++
 tools/lib/bpf/libbpf.c                        | 573 ++++--------------
 tools/lib/bpf/libbpf.h                        |  37 +-
 tools/lib/bpf/libbpf_internal.h               |  36 +-
 tools/lib/bpf/libbpf_probes.c                 |   8 +-
 tools/lib/bpf/str_error.h                     |   3 +
 .../testing/selftests/bpf/prog_tests/token.c  | 347 +++++++++++
 tools/testing/selftests/bpf/progs/priv_map.c  |  13 +
 tools/testing/selftests/bpf/progs/priv_prog.c |  13 +
 14 files changed, 1065 insertions(+), 473 deletions(-)
 create mode 100644 tools/lib/bpf/features.c
 create mode 100644 tools/testing/selftests/bpf/progs/priv_map.c
 create mode 100644 tools/testing/selftests/bpf/progs/priv_prog.c

-- 
2.34.1

[PATCH v3 bpf-next 01/10] bpf: fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS

[Andrii Nakryiko]

It's quite confusing in practice when it's possible to successfully
create a BPF token from BPF FS that didn't have any of delegate_xxx
mount options set up. While it's not wrong, it's actually more
meaningful to reject BPF_TOKEN_CREATE with specific error code (-ENOENT)
to let user-space know that no token delegation is setup up.

So, instead of creating empty BPF token that will be always ignored
because it doesn't have any of the allow_xxx bits set, reject it with
-ENOENT. If we ever need empty BPF token to be possible, we can support
that with extra flag passed into BPF_TOKEN_CREATE.

Acked-by: Christian Brauner <brauner@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 kernel/bpf/token.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/token.c b/kernel/bpf/token.c
index 17212efcde60..a86fccd57e2d 100644
--- a/kernel/bpf/token.c
+++ b/kernel/bpf/token.c
@@ -152,6 +152,15 @@ int bpf_token_create(union bpf_attr *attr)
 		goto out_path;
 	}
 
+	mnt_opts = path.dentry->d_sb->s_fs_info;
+	if (mnt_opts->delegate_cmds == 0 &&
+	    mnt_opts->delegate_maps == 0 &&
+	    mnt_opts->delegate_progs == 0 &&
+	    mnt_opts->delegate_attachs == 0) {
+		err = -ENOENT; /* no BPF token delegation is set up */
+		goto out_path;
+	}
+
 	mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
 	inode = bpf_get_inode(path.mnt->mnt_sb, NULL, mode);
 	if (IS_ERR(inode)) {
@@ -181,7 +190,6 @@ int bpf_token_create(union bpf_attr *attr)
 	/* remember bpffs owning userns for future ns_capable() checks */
 	token->userns = get_user_ns(userns);
 
-	mnt_opts = path.dentry->d_sb->s_fs_info;
 	token->allowed_cmds = mnt_opts->delegate_cmds;
 	token->allowed_maps = mnt_opts->delegate_maps;
 	token->allowed_progs = mnt_opts->delegate_progs;
-- 
2.34.1

[PATCH v3 bpf-next 02/10] libbpf: split feature detectors definitions from cached results

[Andrii Nakryiko]

Split a list of supported feature detectors with their corresponding
callbacks from actual cached supported/missing values. This will allow
to have more flexible per-token or per-object feature detectors in
subsequent refactorings.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/libbpf.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ac54ebc0629f..d2828a26b011 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4999,12 +4999,17 @@ enum kern_feature_result {
 	FEAT_MISSING = 2,
 };
 
+struct kern_feature_cache {
+	enum kern_feature_result res[__FEAT_CNT];
+};
+
 typedef int (*feature_probe_fn)(void);
 
+static struct kern_feature_cache feature_cache;
+
 static struct kern_feature_desc {
 	const char *desc;
 	feature_probe_fn probe;
-	enum kern_feature_result res;
 } feature_probes[__FEAT_CNT] = {
 	[FEAT_PROG_NAME] = {
 		"BPF program name", probe_kern_prog_name,
@@ -5072,6 +5077,7 @@ static struct kern_feature_desc {
 bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
 {
 	struct kern_feature_desc *feat = &feature_probes[feat_id];
+	struct kern_feature_cache *cache = &feature_cache;
 	int ret;
 
 	if (obj && obj->gen_loader)
@@ -5080,19 +5086,19 @@ bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
 		 */
 		return true;
 
-	if (READ_ONCE(feat->res) == FEAT_UNKNOWN) {
+	if (READ_ONCE(cache->res[feat_id]) == FEAT_UNKNOWN) {
 		ret = feat->probe();
 		if (ret > 0) {
-			WRITE_ONCE(feat->res, FEAT_SUPPORTED);
+			WRITE_ONCE(cache->res[feat_id], FEAT_SUPPORTED);
 		} else if (ret == 0) {
-			WRITE_ONCE(feat->res, FEAT_MISSING);
+			WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
 		} else {
 			pr_warn("Detection of kernel %s support failed: %d\n", feat->desc, ret);
-			WRITE_ONCE(feat->res, FEAT_MISSING);
+			WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
 		}
 	}
 
-	return READ_ONCE(feat->res) == FEAT_SUPPORTED;
+	return READ_ONCE(cache->res[feat_id]) == FEAT_SUPPORTED;
 }
 
 static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
-- 
2.34.1

[PATCH v3 bpf-next 03/10] libbpf: further decouple feature checking logic from bpf_object

[Andrii Nakryiko]

Add feat_supported() helper that accepts feature cache instead of
bpf_object. This allows low-level code in bpf.c to not know or care
about higher-level concept of bpf_object, yet it will be able to utilize
custom feature checking in cases where BPF token might influence the
outcome.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/bpf.c             |  6 +++---
 tools/lib/bpf/libbpf.c          | 22 +++++++++++++++-------
 tools/lib/bpf/libbpf_internal.h |  5 ++++-
 3 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index f4e1da3c6d5f..120855ac6859 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -146,7 +146,7 @@ int bump_rlimit_memlock(void)
 	struct rlimit rlim;
 
 	/* if kernel supports memcg-based accounting, skip bumping RLIMIT_MEMLOCK */
-	if (memlock_bumped || kernel_supports(NULL, FEAT_MEMCG_ACCOUNT))
+	if (memlock_bumped || feat_supported(NULL, FEAT_MEMCG_ACCOUNT))
 		return 0;
 
 	memlock_bumped = true;
@@ -181,7 +181,7 @@ int bpf_map_create(enum bpf_map_type map_type,
 		return libbpf_err(-EINVAL);
 
 	attr.map_type = map_type;
-	if (map_name && kernel_supports(NULL, FEAT_PROG_NAME))
+	if (map_name && feat_supported(NULL, FEAT_PROG_NAME))
 		libbpf_strlcpy(attr.map_name, map_name, sizeof(attr.map_name));
 	attr.key_size = key_size;
 	attr.value_size = value_size;
@@ -265,7 +265,7 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
 	attr.kern_version = OPTS_GET(opts, kern_version, 0);
 	attr.prog_token_fd = OPTS_GET(opts, token_fd, 0);
 
-	if (prog_name && kernel_supports(NULL, FEAT_PROG_NAME))
+	if (prog_name && feat_supported(NULL, FEAT_PROG_NAME))
 		libbpf_strlcpy(attr.prog_name, prog_name, sizeof(attr.prog_name));
 	attr.license = ptr_to_u64(license);
 
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index d2828a26b011..2b7962120730 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5074,17 +5074,14 @@ static struct kern_feature_desc {
 	},
 };
 
-bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
+bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id)
 {
 	struct kern_feature_desc *feat = &feature_probes[feat_id];
-	struct kern_feature_cache *cache = &feature_cache;
 	int ret;
 
-	if (obj && obj->gen_loader)
-		/* To generate loader program assume the latest kernel
-		 * to avoid doing extra prog_load, map_create syscalls.
-		 */
-		return true;
+	/* assume global feature cache, unless custom one is provided */
+	if (!cache)
+		cache = &feature_cache;
 
 	if (READ_ONCE(cache->res[feat_id]) == FEAT_UNKNOWN) {
 		ret = feat->probe();
@@ -5101,6 +5098,17 @@ bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
 	return READ_ONCE(cache->res[feat_id]) == FEAT_SUPPORTED;
 }
 
+bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
+{
+	if (obj && obj->gen_loader)
+		/* To generate loader program assume the latest kernel
+		 * to avoid doing extra prog_load, map_create syscalls.
+		 */
+		return true;
+
+	return feat_supported(NULL, feat_id);
+}
+
 static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
 {
 	struct bpf_map_info map_info;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index b5d334754e5d..754a432335e4 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -360,8 +360,11 @@ enum kern_feature_id {
 	__FEAT_CNT,
 };
 
-int probe_memcg_account(void);
+struct kern_feature_cache;
+bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id);
 bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id);
+
+int probe_memcg_account(void);
 int bump_rlimit_memlock(void);
 
 int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz);
-- 
2.34.1

[PATCH v3 bpf-next 04/10] libbpf: move feature detection code into its own file

[Andrii Nakryiko]

It's quite a lot of well isolated code, so it seems like a good
candidate to move it out of libbpf.c to reduce its size.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/Build             |   2 +-
 tools/lib/bpf/elf.c             |   2 -
 tools/lib/bpf/features.c        | 463 ++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.c          | 463 +-------------------------------
 tools/lib/bpf/libbpf_internal.h |  12 +-
 tools/lib/bpf/str_error.h       |   3 +
 6 files changed, 479 insertions(+), 466 deletions(-)
 create mode 100644 tools/lib/bpf/features.c

diff --git a/tools/lib/bpf/Build b/tools/lib/bpf/Build
index 2d0c282c8588..b6619199a706 100644
--- a/tools/lib/bpf/Build
+++ b/tools/lib/bpf/Build
@@ -1,4 +1,4 @@
 libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o \
 	    netlink.o bpf_prog_linfo.o libbpf_probes.o hashmap.o \
 	    btf_dump.o ringbuf.o strset.o linker.o gen_loader.o relo_core.o \
-	    usdt.o zip.o elf.o
+	    usdt.o zip.o elf.o features.o
diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
index b02faec748a5..c92e02394159 100644
--- a/tools/lib/bpf/elf.c
+++ b/tools/lib/bpf/elf.c
@@ -11,8 +11,6 @@
 #include "libbpf_internal.h"
 #include "str_error.h"
 
-#define STRERR_BUFSIZE  128
-
 /* A SHT_GNU_versym section holds 16-bit words. This bit is set if
  * the symbol is hidden and can only be seen when referenced using an
  * explicit version number. This is a GNU extension.
diff --git a/tools/lib/bpf/features.c b/tools/lib/bpf/features.c
new file mode 100644
index 000000000000..338fd0dcd3bd
--- /dev/null
+++ b/tools/lib/bpf/features.c
@@ -0,0 +1,463 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+#include <linux/kernel.h>
+#include <linux/filter.h>
+#include "bpf.h"
+#include "libbpf.h"
+#include "libbpf_common.h"
+#include "libbpf_internal.h"
+#include "str_error.h"
+
+static inline __u64 ptr_to_u64(const void *ptr)
+{
+	return (__u64)(unsigned long)ptr;
+}
+
+static int probe_fd(int fd)
+{
+	if (fd >= 0)
+		close(fd);
+	return fd >= 0;
+}
+
+static int probe_kern_prog_name(void)
+{
+	const size_t attr_sz = offsetofend(union bpf_attr, prog_name);
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	union bpf_attr attr;
+	int ret;
+
+	memset(&attr, 0, attr_sz);
+	attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+	attr.license = ptr_to_u64("GPL");
+	attr.insns = ptr_to_u64(insns);
+	attr.insn_cnt = (__u32)ARRAY_SIZE(insns);
+	libbpf_strlcpy(attr.prog_name, "libbpf_nametest", sizeof(attr.prog_name));
+
+	/* make sure loading with name works */
+	ret = sys_bpf_prog_load(&attr, attr_sz, PROG_LOAD_ATTEMPTS);
+	return probe_fd(ret);
+}
+
+static int probe_kern_global_data(void)
+{
+	char *cp, errmsg[STRERR_BUFSIZE];
+	struct bpf_insn insns[] = {
+		BPF_LD_MAP_VALUE(BPF_REG_1, 0, 16),
+		BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 42),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	int ret, map, insn_cnt = ARRAY_SIZE(insns);
+
+	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_global", sizeof(int), 32, 1, NULL);
+	if (map < 0) {
+		ret = -errno;
+		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
+		pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
+			__func__, cp, -ret);
+		return ret;
+	}
+
+	insns[0].imm = map;
+
+	ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
+	close(map);
+	return probe_fd(ret);
+}
+
+static int probe_kern_btf(void)
+{
+	static const char strs[] = "\0int";
+	__u32 types[] = {
+		/* int */
+		BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
+static int probe_kern_btf_func(void)
+{
+	static const char strs[] = "\0int\0x\0a";
+	/* void x(int a) {} */
+	__u32 types[] = {
+		/* int */
+		BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
+		/* FUNC_PROTO */                                /* [2] */
+		BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 0),
+		BTF_PARAM_ENC(7, 1),
+		/* FUNC x */                                    /* [3] */
+		BTF_TYPE_ENC(5, BTF_INFO_ENC(BTF_KIND_FUNC, 0, 0), 2),
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
+static int probe_kern_btf_func_global(void)
+{
+	static const char strs[] = "\0int\0x\0a";
+	/* static void x(int a) {} */
+	__u32 types[] = {
+		/* int */
+		BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
+		/* FUNC_PROTO */                                /* [2] */
+		BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 0),
+		BTF_PARAM_ENC(7, 1),
+		/* FUNC x BTF_FUNC_GLOBAL */                    /* [3] */
+		BTF_TYPE_ENC(5, BTF_INFO_ENC(BTF_KIND_FUNC, 0, BTF_FUNC_GLOBAL), 2),
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
+static int probe_kern_btf_datasec(void)
+{
+	static const char strs[] = "\0x\0.data";
+	/* static int a; */
+	__u32 types[] = {
+		/* int */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
+		/* VAR x */                                     /* [2] */
+		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
+		BTF_VAR_STATIC,
+		/* DATASEC val */                               /* [3] */
+		BTF_TYPE_ENC(3, BTF_INFO_ENC(BTF_KIND_DATASEC, 0, 1), 4),
+		BTF_VAR_SECINFO_ENC(2, 0, 4),
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
+static int probe_kern_btf_float(void)
+{
+	static const char strs[] = "\0float";
+	__u32 types[] = {
+		/* float */
+		BTF_TYPE_FLOAT_ENC(1, 4),
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
+static int probe_kern_btf_decl_tag(void)
+{
+	static const char strs[] = "\0tag";
+	__u32 types[] = {
+		/* int */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
+		/* VAR x */                                     /* [2] */
+		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
+		BTF_VAR_STATIC,
+		/* attr */
+		BTF_TYPE_DECL_TAG_ENC(1, 2, -1),
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
+static int probe_kern_btf_type_tag(void)
+{
+	static const char strs[] = "\0tag";
+	__u32 types[] = {
+		/* int */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),		/* [1] */
+		/* attr */
+		BTF_TYPE_TYPE_TAG_ENC(1, 1),				/* [2] */
+		/* ptr */
+		BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_PTR, 0, 0), 2),	/* [3] */
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
+static int probe_kern_array_mmap(void)
+{
+	LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE);
+	int fd;
+
+	fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_mmap", sizeof(int), sizeof(int), 1, &opts);
+	return probe_fd(fd);
+}
+
+static int probe_kern_exp_attach_type(void)
+{
+	LIBBPF_OPTS(bpf_prog_load_opts, opts, .expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE);
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	int fd, insn_cnt = ARRAY_SIZE(insns);
+
+	/* use any valid combination of program type and (optional)
+	 * non-zero expected attach type (i.e., not a BPF_CGROUP_INET_INGRESS)
+	 * to see if kernel supports expected_attach_type field for
+	 * BPF_PROG_LOAD command
+	 */
+	fd = bpf_prog_load(BPF_PROG_TYPE_CGROUP_SOCK, NULL, "GPL", insns, insn_cnt, &opts);
+	return probe_fd(fd);
+}
+
+static int probe_kern_probe_read_kernel(void)
+{
+	struct bpf_insn insns[] = {
+		BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),	/* r1 = r10 (fp) */
+		BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),	/* r1 += -8 */
+		BPF_MOV64_IMM(BPF_REG_2, 8),		/* r2 = 8 */
+		BPF_MOV64_IMM(BPF_REG_3, 0),		/* r3 = 0 */
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_probe_read_kernel),
+		BPF_EXIT_INSN(),
+	};
+	int fd, insn_cnt = ARRAY_SIZE(insns);
+
+	fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, NULL);
+	return probe_fd(fd);
+}
+
+static int probe_prog_bind_map(void)
+{
+	char *cp, errmsg[STRERR_BUFSIZE];
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	int ret, map, prog, insn_cnt = ARRAY_SIZE(insns);
+
+	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_det_bind", sizeof(int), 32, 1, NULL);
+	if (map < 0) {
+		ret = -errno;
+		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
+		pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
+			__func__, cp, -ret);
+		return ret;
+	}
+
+	prog = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
+	if (prog < 0) {
+		close(map);
+		return 0;
+	}
+
+	ret = bpf_prog_bind_map(prog, map, NULL);
+
+	close(map);
+	close(prog);
+
+	return ret >= 0;
+}
+
+static int probe_module_btf(void)
+{
+	static const char strs[] = "\0int";
+	__u32 types[] = {
+		/* int */
+		BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
+	};
+	struct bpf_btf_info info;
+	__u32 len = sizeof(info);
+	char name[16];
+	int fd, err;
+
+	fd = libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs));
+	if (fd < 0)
+		return 0; /* BTF not supported at all */
+
+	memset(&info, 0, sizeof(info));
+	info.name = ptr_to_u64(name);
+	info.name_len = sizeof(name);
+
+	/* check that BPF_OBJ_GET_INFO_BY_FD supports specifying name pointer;
+	 * kernel's module BTF support coincides with support for
+	 * name/name_len fields in struct bpf_btf_info.
+	 */
+	err = bpf_btf_get_info_by_fd(fd, &info, &len);
+	close(fd);
+	return !err;
+}
+
+static int probe_perf_link(void)
+{
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	int prog_fd, link_fd, err;
+
+	prog_fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL",
+				insns, ARRAY_SIZE(insns), NULL);
+	if (prog_fd < 0)
+		return -errno;
+
+	/* use invalid perf_event FD to get EBADF, if link is supported;
+	 * otherwise EINVAL should be returned
+	 */
+	link_fd = bpf_link_create(prog_fd, -1, BPF_PERF_EVENT, NULL);
+	err = -errno; /* close() can clobber errno */
+
+	if (link_fd >= 0)
+		close(link_fd);
+	close(prog_fd);
+
+	return link_fd < 0 && err == -EBADF;
+}
+
+static int probe_uprobe_multi_link(void)
+{
+	LIBBPF_OPTS(bpf_prog_load_opts, load_opts,
+		.expected_attach_type = BPF_TRACE_UPROBE_MULTI,
+	);
+	LIBBPF_OPTS(bpf_link_create_opts, link_opts);
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	int prog_fd, link_fd, err;
+	unsigned long offset = 0;
+
+	prog_fd = bpf_prog_load(BPF_PROG_TYPE_KPROBE, NULL, "GPL",
+				insns, ARRAY_SIZE(insns), &load_opts);
+	if (prog_fd < 0)
+		return -errno;
+
+	/* Creating uprobe in '/' binary should fail with -EBADF. */
+	link_opts.uprobe_multi.path = "/";
+	link_opts.uprobe_multi.offsets = &offset;
+	link_opts.uprobe_multi.cnt = 1;
+
+	link_fd = bpf_link_create(prog_fd, -1, BPF_TRACE_UPROBE_MULTI, &link_opts);
+	err = -errno; /* close() can clobber errno */
+
+	if (link_fd >= 0)
+		close(link_fd);
+	close(prog_fd);
+
+	return link_fd < 0 && err == -EBADF;
+}
+
+static int probe_kern_bpf_cookie(void)
+{
+	struct bpf_insn insns[] = {
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_attach_cookie),
+		BPF_EXIT_INSN(),
+	};
+	int ret, insn_cnt = ARRAY_SIZE(insns);
+
+	ret = bpf_prog_load(BPF_PROG_TYPE_KPROBE, NULL, "GPL", insns, insn_cnt, NULL);
+	return probe_fd(ret);
+}
+
+static int probe_kern_btf_enum64(void)
+{
+	static const char strs[] = "\0enum64";
+	__u32 types[] = {
+		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_ENUM64, 0, 0), 8),
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
+typedef int (*feature_probe_fn)(void);
+
+static struct kern_feature_cache feature_cache;
+
+static struct kern_feature_desc {
+	const char *desc;
+	feature_probe_fn probe;
+} feature_probes[__FEAT_CNT] = {
+	[FEAT_PROG_NAME] = {
+		"BPF program name", probe_kern_prog_name,
+	},
+	[FEAT_GLOBAL_DATA] = {
+		"global variables", probe_kern_global_data,
+	},
+	[FEAT_BTF] = {
+		"minimal BTF", probe_kern_btf,
+	},
+	[FEAT_BTF_FUNC] = {
+		"BTF functions", probe_kern_btf_func,
+	},
+	[FEAT_BTF_GLOBAL_FUNC] = {
+		"BTF global function", probe_kern_btf_func_global,
+	},
+	[FEAT_BTF_DATASEC] = {
+		"BTF data section and variable", probe_kern_btf_datasec,
+	},
+	[FEAT_ARRAY_MMAP] = {
+		"ARRAY map mmap()", probe_kern_array_mmap,
+	},
+	[FEAT_EXP_ATTACH_TYPE] = {
+		"BPF_PROG_LOAD expected_attach_type attribute",
+		probe_kern_exp_attach_type,
+	},
+	[FEAT_PROBE_READ_KERN] = {
+		"bpf_probe_read_kernel() helper", probe_kern_probe_read_kernel,
+	},
+	[FEAT_PROG_BIND_MAP] = {
+		"BPF_PROG_BIND_MAP support", probe_prog_bind_map,
+	},
+	[FEAT_MODULE_BTF] = {
+		"module BTF support", probe_module_btf,
+	},
+	[FEAT_BTF_FLOAT] = {
+		"BTF_KIND_FLOAT support", probe_kern_btf_float,
+	},
+	[FEAT_PERF_LINK] = {
+		"BPF perf link support", probe_perf_link,
+	},
+	[FEAT_BTF_DECL_TAG] = {
+		"BTF_KIND_DECL_TAG support", probe_kern_btf_decl_tag,
+	},
+	[FEAT_BTF_TYPE_TAG] = {
+		"BTF_KIND_TYPE_TAG support", probe_kern_btf_type_tag,
+	},
+	[FEAT_MEMCG_ACCOUNT] = {
+		"memcg-based memory accounting", probe_memcg_account,
+	},
+	[FEAT_BPF_COOKIE] = {
+		"BPF cookie support", probe_kern_bpf_cookie,
+	},
+	[FEAT_BTF_ENUM64] = {
+		"BTF_KIND_ENUM64 support", probe_kern_btf_enum64,
+	},
+	[FEAT_SYSCALL_WRAPPER] = {
+		"Kernel using syscall wrapper", probe_kern_syscall_wrapper,
+	},
+	[FEAT_UPROBE_MULTI_LINK] = {
+		"BPF multi-uprobe link support", probe_uprobe_multi_link,
+	},
+};
+
+bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id)
+{
+	struct kern_feature_desc *feat = &feature_probes[feat_id];
+	int ret;
+
+	/* assume global feature cache, unless custom one is provided */
+	if (!cache)
+		cache = &feature_cache;
+
+	if (READ_ONCE(cache->res[feat_id]) == FEAT_UNKNOWN) {
+		ret = feat->probe();
+		if (ret > 0) {
+			WRITE_ONCE(cache->res[feat_id], FEAT_SUPPORTED);
+		} else if (ret == 0) {
+			WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
+		} else {
+			pr_warn("Detection of kernel %s support failed: %d\n", feat->desc, ret);
+			WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
+		}
+	}
+
+	return READ_ONCE(cache->res[feat_id]) == FEAT_SUPPORTED;
+}
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2b7962120730..4e6f8d225caa 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4637,467 +4637,6 @@ bpf_object__probe_loading(struct bpf_object *obj)
 	return 0;
 }
 
-static int probe_fd(int fd)
-{
-	if (fd >= 0)
-		close(fd);
-	return fd >= 0;
-}
-
-static int probe_kern_prog_name(void)
-{
-	const size_t attr_sz = offsetofend(union bpf_attr, prog_name);
-	struct bpf_insn insns[] = {
-		BPF_MOV64_IMM(BPF_REG_0, 0),
-		BPF_EXIT_INSN(),
-	};
-	union bpf_attr attr;
-	int ret;
-
-	memset(&attr, 0, attr_sz);
-	attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
-	attr.license = ptr_to_u64("GPL");
-	attr.insns = ptr_to_u64(insns);
-	attr.insn_cnt = (__u32)ARRAY_SIZE(insns);
-	libbpf_strlcpy(attr.prog_name, "libbpf_nametest", sizeof(attr.prog_name));
-
-	/* make sure loading with name works */
-	ret = sys_bpf_prog_load(&attr, attr_sz, PROG_LOAD_ATTEMPTS);
-	return probe_fd(ret);
-}
-
-static int probe_kern_global_data(void)
-{
-	char *cp, errmsg[STRERR_BUFSIZE];
-	struct bpf_insn insns[] = {
-		BPF_LD_MAP_VALUE(BPF_REG_1, 0, 16),
-		BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 42),
-		BPF_MOV64_IMM(BPF_REG_0, 0),
-		BPF_EXIT_INSN(),
-	};
-	int ret, map, insn_cnt = ARRAY_SIZE(insns);
-
-	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_global", sizeof(int), 32, 1, NULL);
-	if (map < 0) {
-		ret = -errno;
-		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
-		pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
-			__func__, cp, -ret);
-		return ret;
-	}
-
-	insns[0].imm = map;
-
-	ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
-	close(map);
-	return probe_fd(ret);
-}
-
-static int probe_kern_btf(void)
-{
-	static const char strs[] = "\0int";
-	__u32 types[] = {
-		/* int */
-		BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
-	};
-
-	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
-}
-
-static int probe_kern_btf_func(void)
-{
-	static const char strs[] = "\0int\0x\0a";
-	/* void x(int a) {} */
-	__u32 types[] = {
-		/* int */
-		BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
-		/* FUNC_PROTO */                                /* [2] */
-		BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 0),
-		BTF_PARAM_ENC(7, 1),
-		/* FUNC x */                                    /* [3] */
-		BTF_TYPE_ENC(5, BTF_INFO_ENC(BTF_KIND_FUNC, 0, 0), 2),
-	};
-
-	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
-}
-
-static int probe_kern_btf_func_global(void)
-{
-	static const char strs[] = "\0int\0x\0a";
-	/* static void x(int a) {} */
-	__u32 types[] = {
-		/* int */
-		BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
-		/* FUNC_PROTO */                                /* [2] */
-		BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_FUNC_PROTO, 0, 1), 0),
-		BTF_PARAM_ENC(7, 1),
-		/* FUNC x BTF_FUNC_GLOBAL */                    /* [3] */
-		BTF_TYPE_ENC(5, BTF_INFO_ENC(BTF_KIND_FUNC, 0, BTF_FUNC_GLOBAL), 2),
-	};
-
-	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
-}
-
-static int probe_kern_btf_datasec(void)
-{
-	static const char strs[] = "\0x\0.data";
-	/* static int a; */
-	__u32 types[] = {
-		/* int */
-		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
-		/* VAR x */                                     /* [2] */
-		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
-		BTF_VAR_STATIC,
-		/* DATASEC val */                               /* [3] */
-		BTF_TYPE_ENC(3, BTF_INFO_ENC(BTF_KIND_DATASEC, 0, 1), 4),
-		BTF_VAR_SECINFO_ENC(2, 0, 4),
-	};
-
-	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
-}
-
-static int probe_kern_btf_float(void)
-{
-	static const char strs[] = "\0float";
-	__u32 types[] = {
-		/* float */
-		BTF_TYPE_FLOAT_ENC(1, 4),
-	};
-
-	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
-}
-
-static int probe_kern_btf_decl_tag(void)
-{
-	static const char strs[] = "\0tag";
-	__u32 types[] = {
-		/* int */
-		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
-		/* VAR x */                                     /* [2] */
-		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),
-		BTF_VAR_STATIC,
-		/* attr */
-		BTF_TYPE_DECL_TAG_ENC(1, 2, -1),
-	};
-
-	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
-}
-
-static int probe_kern_btf_type_tag(void)
-{
-	static const char strs[] = "\0tag";
-	__u32 types[] = {
-		/* int */
-		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),		/* [1] */
-		/* attr */
-		BTF_TYPE_TYPE_TAG_ENC(1, 1),				/* [2] */
-		/* ptr */
-		BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_PTR, 0, 0), 2),	/* [3] */
-	};
-
-	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
-}
-
-static int probe_kern_array_mmap(void)
-{
-	LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE);
-	int fd;
-
-	fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_mmap", sizeof(int), sizeof(int), 1, &opts);
-	return probe_fd(fd);
-}
-
-static int probe_kern_exp_attach_type(void)
-{
-	LIBBPF_OPTS(bpf_prog_load_opts, opts, .expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE);
-	struct bpf_insn insns[] = {
-		BPF_MOV64_IMM(BPF_REG_0, 0),
-		BPF_EXIT_INSN(),
-	};
-	int fd, insn_cnt = ARRAY_SIZE(insns);
-
-	/* use any valid combination of program type and (optional)
-	 * non-zero expected attach type (i.e., not a BPF_CGROUP_INET_INGRESS)
-	 * to see if kernel supports expected_attach_type field for
-	 * BPF_PROG_LOAD command
-	 */
-	fd = bpf_prog_load(BPF_PROG_TYPE_CGROUP_SOCK, NULL, "GPL", insns, insn_cnt, &opts);
-	return probe_fd(fd);
-}
-
-static int probe_kern_probe_read_kernel(void)
-{
-	struct bpf_insn insns[] = {
-		BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),	/* r1 = r10 (fp) */
-		BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),	/* r1 += -8 */
-		BPF_MOV64_IMM(BPF_REG_2, 8),		/* r2 = 8 */
-		BPF_MOV64_IMM(BPF_REG_3, 0),		/* r3 = 0 */
-		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_probe_read_kernel),
-		BPF_EXIT_INSN(),
-	};
-	int fd, insn_cnt = ARRAY_SIZE(insns);
-
-	fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, NULL);
-	return probe_fd(fd);
-}
-
-static int probe_prog_bind_map(void)
-{
-	char *cp, errmsg[STRERR_BUFSIZE];
-	struct bpf_insn insns[] = {
-		BPF_MOV64_IMM(BPF_REG_0, 0),
-		BPF_EXIT_INSN(),
-	};
-	int ret, map, prog, insn_cnt = ARRAY_SIZE(insns);
-
-	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_det_bind", sizeof(int), 32, 1, NULL);
-	if (map < 0) {
-		ret = -errno;
-		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
-		pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
-			__func__, cp, -ret);
-		return ret;
-	}
-
-	prog = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
-	if (prog < 0) {
-		close(map);
-		return 0;
-	}
-
-	ret = bpf_prog_bind_map(prog, map, NULL);
-
-	close(map);
-	close(prog);
-
-	return ret >= 0;
-}
-
-static int probe_module_btf(void)
-{
-	static const char strs[] = "\0int";
-	__u32 types[] = {
-		/* int */
-		BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
-	};
-	struct bpf_btf_info info;
-	__u32 len = sizeof(info);
-	char name[16];
-	int fd, err;
-
-	fd = libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs));
-	if (fd < 0)
-		return 0; /* BTF not supported at all */
-
-	memset(&info, 0, sizeof(info));
-	info.name = ptr_to_u64(name);
-	info.name_len = sizeof(name);
-
-	/* check that BPF_OBJ_GET_INFO_BY_FD supports specifying name pointer;
-	 * kernel's module BTF support coincides with support for
-	 * name/name_len fields in struct bpf_btf_info.
-	 */
-	err = bpf_btf_get_info_by_fd(fd, &info, &len);
-	close(fd);
-	return !err;
-}
-
-static int probe_perf_link(void)
-{
-	struct bpf_insn insns[] = {
-		BPF_MOV64_IMM(BPF_REG_0, 0),
-		BPF_EXIT_INSN(),
-	};
-	int prog_fd, link_fd, err;
-
-	prog_fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL",
-				insns, ARRAY_SIZE(insns), NULL);
-	if (prog_fd < 0)
-		return -errno;
-
-	/* use invalid perf_event FD to get EBADF, if link is supported;
-	 * otherwise EINVAL should be returned
-	 */
-	link_fd = bpf_link_create(prog_fd, -1, BPF_PERF_EVENT, NULL);
-	err = -errno; /* close() can clobber errno */
-
-	if (link_fd >= 0)
-		close(link_fd);
-	close(prog_fd);
-
-	return link_fd < 0 && err == -EBADF;
-}
-
-static int probe_uprobe_multi_link(void)
-{
-	LIBBPF_OPTS(bpf_prog_load_opts, load_opts,
-		.expected_attach_type = BPF_TRACE_UPROBE_MULTI,
-	);
-	LIBBPF_OPTS(bpf_link_create_opts, link_opts);
-	struct bpf_insn insns[] = {
-		BPF_MOV64_IMM(BPF_REG_0, 0),
-		BPF_EXIT_INSN(),
-	};
-	int prog_fd, link_fd, err;
-	unsigned long offset = 0;
-
-	prog_fd = bpf_prog_load(BPF_PROG_TYPE_KPROBE, NULL, "GPL",
-				insns, ARRAY_SIZE(insns), &load_opts);
-	if (prog_fd < 0)
-		return -errno;
-
-	/* Creating uprobe in '/' binary should fail with -EBADF. */
-	link_opts.uprobe_multi.path = "/";
-	link_opts.uprobe_multi.offsets = &offset;
-	link_opts.uprobe_multi.cnt = 1;
-
-	link_fd = bpf_link_create(prog_fd, -1, BPF_TRACE_UPROBE_MULTI, &link_opts);
-	err = -errno; /* close() can clobber errno */
-
-	if (link_fd >= 0)
-		close(link_fd);
-	close(prog_fd);
-
-	return link_fd < 0 && err == -EBADF;
-}
-
-static int probe_kern_bpf_cookie(void)
-{
-	struct bpf_insn insns[] = {
-		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_attach_cookie),
-		BPF_EXIT_INSN(),
-	};
-	int ret, insn_cnt = ARRAY_SIZE(insns);
-
-	ret = bpf_prog_load(BPF_PROG_TYPE_KPROBE, NULL, "GPL", insns, insn_cnt, NULL);
-	return probe_fd(ret);
-}
-
-static int probe_kern_btf_enum64(void)
-{
-	static const char strs[] = "\0enum64";
-	__u32 types[] = {
-		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_ENUM64, 0, 0), 8),
-	};
-
-	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
-}
-
-static int probe_kern_syscall_wrapper(void);
-
-enum kern_feature_result {
-	FEAT_UNKNOWN = 0,
-	FEAT_SUPPORTED = 1,
-	FEAT_MISSING = 2,
-};
-
-struct kern_feature_cache {
-	enum kern_feature_result res[__FEAT_CNT];
-};
-
-typedef int (*feature_probe_fn)(void);
-
-static struct kern_feature_cache feature_cache;
-
-static struct kern_feature_desc {
-	const char *desc;
-	feature_probe_fn probe;
-} feature_probes[__FEAT_CNT] = {
-	[FEAT_PROG_NAME] = {
-		"BPF program name", probe_kern_prog_name,
-	},
-	[FEAT_GLOBAL_DATA] = {
-		"global variables", probe_kern_global_data,
-	},
-	[FEAT_BTF] = {
-		"minimal BTF", probe_kern_btf,
-	},
-	[FEAT_BTF_FUNC] = {
-		"BTF functions", probe_kern_btf_func,
-	},
-	[FEAT_BTF_GLOBAL_FUNC] = {
-		"BTF global function", probe_kern_btf_func_global,
-	},
-	[FEAT_BTF_DATASEC] = {
-		"BTF data section and variable", probe_kern_btf_datasec,
-	},
-	[FEAT_ARRAY_MMAP] = {
-		"ARRAY map mmap()", probe_kern_array_mmap,
-	},
-	[FEAT_EXP_ATTACH_TYPE] = {
-		"BPF_PROG_LOAD expected_attach_type attribute",
-		probe_kern_exp_attach_type,
-	},
-	[FEAT_PROBE_READ_KERN] = {
-		"bpf_probe_read_kernel() helper", probe_kern_probe_read_kernel,
-	},
-	[FEAT_PROG_BIND_MAP] = {
-		"BPF_PROG_BIND_MAP support", probe_prog_bind_map,
-	},
-	[FEAT_MODULE_BTF] = {
-		"module BTF support", probe_module_btf,
-	},
-	[FEAT_BTF_FLOAT] = {
-		"BTF_KIND_FLOAT support", probe_kern_btf_float,
-	},
-	[FEAT_PERF_LINK] = {
-		"BPF perf link support", probe_perf_link,
-	},
-	[FEAT_BTF_DECL_TAG] = {
-		"BTF_KIND_DECL_TAG support", probe_kern_btf_decl_tag,
-	},
-	[FEAT_BTF_TYPE_TAG] = {
-		"BTF_KIND_TYPE_TAG support", probe_kern_btf_type_tag,
-	},
-	[FEAT_MEMCG_ACCOUNT] = {
-		"memcg-based memory accounting", probe_memcg_account,
-	},
-	[FEAT_BPF_COOKIE] = {
-		"BPF cookie support", probe_kern_bpf_cookie,
-	},
-	[FEAT_BTF_ENUM64] = {
-		"BTF_KIND_ENUM64 support", probe_kern_btf_enum64,
-	},
-	[FEAT_SYSCALL_WRAPPER] = {
-		"Kernel using syscall wrapper", probe_kern_syscall_wrapper,
-	},
-	[FEAT_UPROBE_MULTI_LINK] = {
-		"BPF multi-uprobe link support", probe_uprobe_multi_link,
-	},
-};
-
-bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id)
-{
-	struct kern_feature_desc *feat = &feature_probes[feat_id];
-	int ret;
-
-	/* assume global feature cache, unless custom one is provided */
-	if (!cache)
-		cache = &feature_cache;
-
-	if (READ_ONCE(cache->res[feat_id]) == FEAT_UNKNOWN) {
-		ret = feat->probe();
-		if (ret > 0) {
-			WRITE_ONCE(cache->res[feat_id], FEAT_SUPPORTED);
-		} else if (ret == 0) {
-			WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
-		} else {
-			pr_warn("Detection of kernel %s support failed: %d\n", feat->desc, ret);
-			WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
-		}
-	}
-
-	return READ_ONCE(cache->res[feat_id]) == FEAT_SUPPORTED;
-}
-
 bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
 {
 	if (obj && obj->gen_loader)
@@ -10626,7 +10165,7 @@ static const char *arch_specific_syscall_pfx(void)
 #endif
 }
 
-static int probe_kern_syscall_wrapper(void)
+int probe_kern_syscall_wrapper(void)
 {
 	char syscall_name[64];
 	const char *ksys_pfx;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 754a432335e4..db4a499c0ec5 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -360,10 +360,20 @@ enum kern_feature_id {
 	__FEAT_CNT,
 };
 
-struct kern_feature_cache;
+enum kern_feature_result {
+	FEAT_UNKNOWN = 0,
+	FEAT_SUPPORTED = 1,
+	FEAT_MISSING = 2,
+};
+
+struct kern_feature_cache {
+	enum kern_feature_result res[__FEAT_CNT];
+};
+
 bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id);
 bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id);
 
+int probe_kern_syscall_wrapper(void);
 int probe_memcg_account(void);
 int bump_rlimit_memlock(void);
 
diff --git a/tools/lib/bpf/str_error.h b/tools/lib/bpf/str_error.h
index a139334d57b6..626d7ffb03d6 100644
--- a/tools/lib/bpf/str_error.h
+++ b/tools/lib/bpf/str_error.h
@@ -2,5 +2,8 @@
 #ifndef __LIBBPF_STR_ERROR_H
 #define __LIBBPF_STR_ERROR_H
 
+#define STRERR_BUFSIZE  128
+
 char *libbpf_strerror_r(int err, char *dst, int len);
+
 #endif /* __LIBBPF_STR_ERROR_H */
-- 
2.34.1

[PATCH v3 bpf-next 05/10] libbpf: wire up token_fd into feature probing logic

[Andrii Nakryiko]

Adjust feature probing callbacks to take into account optional token_fd.
In unprivileged contexts, some feature detectors would fail to detect
kernel support just because BPF program, BPF map, or BTF object can't be
loaded due to privileged nature of those operations. So when BPF object
is loaded with BPF token, this token should be used for feature probing.

This patch is setting support for this scenario, but we don't yet pass
non-zero token FD. This will be added in the next patch.

We also switched BPF cookie detector from using kprobe program to
tracepoint one, as tracepoint is somewhat less dangerous BPF program
type and has higher likelihood of being allowed through BPF token in the
future. This change has no effect on detection behavior.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/bpf.c             |  3 +-
 tools/lib/bpf/features.c        | 91 +++++++++++++++++++--------------
 tools/lib/bpf/libbpf.c          |  2 +-
 tools/lib/bpf/libbpf_internal.h |  8 +--
 tools/lib/bpf/libbpf_probes.c   |  8 +--
 5 files changed, 66 insertions(+), 46 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 120855ac6859..0ad8e532b3cf 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -103,7 +103,7 @@ int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts)
  *   [0] https://lore.kernel.org/bpf/20201201215900.3569844-1-guro@fb.com/
  *   [1] d05512618056 ("bpf: Add bpf_ktime_get_coarse_ns helper")
  */
-int probe_memcg_account(void)
+int probe_memcg_account(int token_fd)
 {
 	const size_t attr_sz = offsetofend(union bpf_attr, attach_btf_obj_fd);
 	struct bpf_insn insns[] = {
@@ -120,6 +120,7 @@ int probe_memcg_account(void)
 	attr.insns = ptr_to_u64(insns);
 	attr.insn_cnt = insn_cnt;
 	attr.license = ptr_to_u64("GPL");
+	attr.prog_token_fd = token_fd;
 
 	prog_fd = sys_bpf_fd(BPF_PROG_LOAD, &attr, attr_sz);
 	if (prog_fd >= 0) {
diff --git a/tools/lib/bpf/features.c b/tools/lib/bpf/features.c
index 338fd0dcd3bd..ce98a334be21 100644
--- a/tools/lib/bpf/features.c
+++ b/tools/lib/bpf/features.c
@@ -20,7 +20,7 @@ static int probe_fd(int fd)
 	return fd >= 0;
 }
 
-static int probe_kern_prog_name(void)
+static int probe_kern_prog_name(int token_fd)
 {
 	const size_t attr_sz = offsetofend(union bpf_attr, prog_name);
 	struct bpf_insn insns[] = {
@@ -35,6 +35,7 @@ static int probe_kern_prog_name(void)
 	attr.license = ptr_to_u64("GPL");
 	attr.insns = ptr_to_u64(insns);
 	attr.insn_cnt = (__u32)ARRAY_SIZE(insns);
+	attr.prog_token_fd = token_fd;
 	libbpf_strlcpy(attr.prog_name, "libbpf_nametest", sizeof(attr.prog_name));
 
 	/* make sure loading with name works */
@@ -42,7 +43,7 @@ static int probe_kern_prog_name(void)
 	return probe_fd(ret);
 }
 
-static int probe_kern_global_data(void)
+static int probe_kern_global_data(int token_fd)
 {
 	char *cp, errmsg[STRERR_BUFSIZE];
 	struct bpf_insn insns[] = {
@@ -51,9 +52,11 @@ static int probe_kern_global_data(void)
 		BPF_MOV64_IMM(BPF_REG_0, 0),
 		BPF_EXIT_INSN(),
 	};
+	LIBBPF_OPTS(bpf_map_create_opts, map_opts, .token_fd = token_fd);
+	LIBBPF_OPTS(bpf_prog_load_opts, prog_opts, .token_fd = token_fd);
 	int ret, map, insn_cnt = ARRAY_SIZE(insns);
 
-	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_global", sizeof(int), 32, 1, NULL);
+	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_global", sizeof(int), 32, 1, &map_opts);
 	if (map < 0) {
 		ret = -errno;
 		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
@@ -64,12 +67,12 @@ static int probe_kern_global_data(void)
 
 	insns[0].imm = map;
 
-	ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
+	ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, &prog_opts);
 	close(map);
 	return probe_fd(ret);
 }
 
-static int probe_kern_btf(void)
+static int probe_kern_btf(int token_fd)
 {
 	static const char strs[] = "\0int";
 	__u32 types[] = {
@@ -78,10 +81,10 @@ static int probe_kern_btf(void)
 	};
 
 	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
+					     strs, sizeof(strs), token_fd));
 }
 
-static int probe_kern_btf_func(void)
+static int probe_kern_btf_func(int token_fd)
 {
 	static const char strs[] = "\0int\0x\0a";
 	/* void x(int a) {} */
@@ -96,10 +99,10 @@ static int probe_kern_btf_func(void)
 	};
 
 	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
+					     strs, sizeof(strs), token_fd));
 }
 
-static int probe_kern_btf_func_global(void)
+static int probe_kern_btf_func_global(int token_fd)
 {
 	static const char strs[] = "\0int\0x\0a";
 	/* static void x(int a) {} */
@@ -114,10 +117,10 @@ static int probe_kern_btf_func_global(void)
 	};
 
 	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
+					     strs, sizeof(strs), token_fd));
 }
 
-static int probe_kern_btf_datasec(void)
+static int probe_kern_btf_datasec(int token_fd)
 {
 	static const char strs[] = "\0x\0.data";
 	/* static int a; */
@@ -133,10 +136,10 @@ static int probe_kern_btf_datasec(void)
 	};
 
 	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
+					     strs, sizeof(strs), token_fd));
 }
 
-static int probe_kern_btf_float(void)
+static int probe_kern_btf_float(int token_fd)
 {
 	static const char strs[] = "\0float";
 	__u32 types[] = {
@@ -145,10 +148,10 @@ static int probe_kern_btf_float(void)
 	};
 
 	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
+					     strs, sizeof(strs), token_fd));
 }
 
-static int probe_kern_btf_decl_tag(void)
+static int probe_kern_btf_decl_tag(int token_fd)
 {
 	static const char strs[] = "\0tag";
 	__u32 types[] = {
@@ -162,10 +165,10 @@ static int probe_kern_btf_decl_tag(void)
 	};
 
 	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
+					     strs, sizeof(strs), token_fd));
 }
 
-static int probe_kern_btf_type_tag(void)
+static int probe_kern_btf_type_tag(int token_fd)
 {
 	static const char strs[] = "\0tag";
 	__u32 types[] = {
@@ -178,21 +181,27 @@ static int probe_kern_btf_type_tag(void)
 	};
 
 	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
+					     strs, sizeof(strs), token_fd));
 }
 
-static int probe_kern_array_mmap(void)
+static int probe_kern_array_mmap(int token_fd)
 {
-	LIBBPF_OPTS(bpf_map_create_opts, opts, .map_flags = BPF_F_MMAPABLE);
+	LIBBPF_OPTS(bpf_map_create_opts, opts,
+		.map_flags = BPF_F_MMAPABLE,
+		.token_fd = token_fd,
+	);
 	int fd;
 
 	fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_mmap", sizeof(int), sizeof(int), 1, &opts);
 	return probe_fd(fd);
 }
 
-static int probe_kern_exp_attach_type(void)
+static int probe_kern_exp_attach_type(int token_fd)
 {
-	LIBBPF_OPTS(bpf_prog_load_opts, opts, .expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE);
+	LIBBPF_OPTS(bpf_prog_load_opts, opts,
+		.expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE,
+		.token_fd = token_fd,
+	);
 	struct bpf_insn insns[] = {
 		BPF_MOV64_IMM(BPF_REG_0, 0),
 		BPF_EXIT_INSN(),
@@ -208,8 +217,9 @@ static int probe_kern_exp_attach_type(void)
 	return probe_fd(fd);
 }
 
-static int probe_kern_probe_read_kernel(void)
+static int probe_kern_probe_read_kernel(int token_fd)
 {
+	LIBBPF_OPTS(bpf_prog_load_opts, opts, .token_fd = token_fd);
 	struct bpf_insn insns[] = {
 		BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),	/* r1 = r10 (fp) */
 		BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),	/* r1 += -8 */
@@ -220,20 +230,22 @@ static int probe_kern_probe_read_kernel(void)
 	};
 	int fd, insn_cnt = ARRAY_SIZE(insns);
 
-	fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, NULL);
+	fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, &opts);
 	return probe_fd(fd);
 }
 
-static int probe_prog_bind_map(void)
+static int probe_prog_bind_map(int token_fd)
 {
 	char *cp, errmsg[STRERR_BUFSIZE];
 	struct bpf_insn insns[] = {
 		BPF_MOV64_IMM(BPF_REG_0, 0),
 		BPF_EXIT_INSN(),
 	};
+	LIBBPF_OPTS(bpf_map_create_opts, map_opts, .token_fd = token_fd);
+	LIBBPF_OPTS(bpf_prog_load_opts, prog_opts, .token_fd = token_fd);
 	int ret, map, prog, insn_cnt = ARRAY_SIZE(insns);
 
-	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_det_bind", sizeof(int), 32, 1, NULL);
+	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_det_bind", sizeof(int), 32, 1, &map_opts);
 	if (map < 0) {
 		ret = -errno;
 		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
@@ -242,7 +254,7 @@ static int probe_prog_bind_map(void)
 		return ret;
 	}
 
-	prog = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
+	prog = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, &prog_opts);
 	if (prog < 0) {
 		close(map);
 		return 0;
@@ -256,7 +268,7 @@ static int probe_prog_bind_map(void)
 	return ret >= 0;
 }
 
-static int probe_module_btf(void)
+static int probe_module_btf(int token_fd)
 {
 	static const char strs[] = "\0int";
 	__u32 types[] = {
@@ -268,7 +280,7 @@ static int probe_module_btf(void)
 	char name[16];
 	int fd, err;
 
-	fd = libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs));
+	fd = libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs), token_fd);
 	if (fd < 0)
 		return 0; /* BTF not supported at all */
 
@@ -285,16 +297,17 @@ static int probe_module_btf(void)
 	return !err;
 }
 
-static int probe_perf_link(void)
+static int probe_perf_link(int token_fd)
 {
 	struct bpf_insn insns[] = {
 		BPF_MOV64_IMM(BPF_REG_0, 0),
 		BPF_EXIT_INSN(),
 	};
+	LIBBPF_OPTS(bpf_prog_load_opts, opts, .token_fd = token_fd);
 	int prog_fd, link_fd, err;
 
 	prog_fd = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL",
-				insns, ARRAY_SIZE(insns), NULL);
+				insns, ARRAY_SIZE(insns), &opts);
 	if (prog_fd < 0)
 		return -errno;
 
@@ -311,10 +324,11 @@ static int probe_perf_link(void)
 	return link_fd < 0 && err == -EBADF;
 }
 
-static int probe_uprobe_multi_link(void)
+static int probe_uprobe_multi_link(int token_fd)
 {
 	LIBBPF_OPTS(bpf_prog_load_opts, load_opts,
 		.expected_attach_type = BPF_TRACE_UPROBE_MULTI,
+		.token_fd = token_fd,
 	);
 	LIBBPF_OPTS(bpf_link_create_opts, link_opts);
 	struct bpf_insn insns[] = {
@@ -344,19 +358,20 @@ static int probe_uprobe_multi_link(void)
 	return link_fd < 0 && err == -EBADF;
 }
 
-static int probe_kern_bpf_cookie(void)
+static int probe_kern_bpf_cookie(int token_fd)
 {
 	struct bpf_insn insns[] = {
 		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_attach_cookie),
 		BPF_EXIT_INSN(),
 	};
+	LIBBPF_OPTS(bpf_prog_load_opts, opts, .token_fd = token_fd);
 	int ret, insn_cnt = ARRAY_SIZE(insns);
 
-	ret = bpf_prog_load(BPF_PROG_TYPE_KPROBE, NULL, "GPL", insns, insn_cnt, NULL);
+	ret = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, &opts);
 	return probe_fd(ret);
 }
 
-static int probe_kern_btf_enum64(void)
+static int probe_kern_btf_enum64(int token_fd)
 {
 	static const char strs[] = "\0enum64";
 	__u32 types[] = {
@@ -364,10 +379,10 @@ static int probe_kern_btf_enum64(void)
 	};
 
 	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
-					     strs, sizeof(strs)));
+					     strs, sizeof(strs), token_fd));
 }
 
-typedef int (*feature_probe_fn)(void);
+typedef int (*feature_probe_fn)(int /* token_fd */);
 
 static struct kern_feature_cache feature_cache;
 
@@ -448,7 +463,7 @@ bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_
 		cache = &feature_cache;
 
 	if (READ_ONCE(cache->res[feat_id]) == FEAT_UNKNOWN) {
-		ret = feat->probe();
+		ret = feat->probe(cache->token_fd);
 		if (ret > 0) {
 			WRITE_ONCE(cache->res[feat_id], FEAT_SUPPORTED);
 		} else if (ret == 0) {
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4e6f8d225caa..1acd1c224c5e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10165,7 +10165,7 @@ static const char *arch_specific_syscall_pfx(void)
 #endif
 }
 
-int probe_kern_syscall_wrapper(void)
+int probe_kern_syscall_wrapper(int token_fd)
 {
 	char syscall_name[64];
 	const char *ksys_pfx;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index db4a499c0ec5..b45566e428d7 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -368,19 +368,21 @@ enum kern_feature_result {
 
 struct kern_feature_cache {
 	enum kern_feature_result res[__FEAT_CNT];
+	int token_fd;
 };
 
 bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_id);
 bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id);
 
-int probe_kern_syscall_wrapper(void);
-int probe_memcg_account(void);
+int probe_kern_syscall_wrapper(int token_fd);
+int probe_memcg_account(int token_fd);
 int bump_rlimit_memlock(void);
 
 int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz);
 int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz);
 int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
-			 const char *str_sec, size_t str_len);
+			 const char *str_sec, size_t str_len,
+			 int token_fd);
 int btf_load_into_kernel(struct btf *btf, char *log_buf, size_t log_sz, __u32 log_level);
 
 struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf);
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 9c4db90b92b6..8e7437006639 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -219,7 +219,8 @@ int libbpf_probe_bpf_prog_type(enum bpf_prog_type prog_type, const void *opts)
 }
 
 int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
-			 const char *str_sec, size_t str_len)
+			 const char *str_sec, size_t str_len,
+			 int token_fd)
 {
 	struct btf_header hdr = {
 		.magic = BTF_MAGIC,
@@ -229,6 +230,7 @@ int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
 		.str_off = types_len,
 		.str_len = str_len,
 	};
+	LIBBPF_OPTS(bpf_btf_load_opts, opts, .token_fd = token_fd);
 	int btf_fd, btf_len;
 	__u8 *raw_btf;
 
@@ -241,7 +243,7 @@ int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
 	memcpy(raw_btf + hdr.hdr_len, raw_types, hdr.type_len);
 	memcpy(raw_btf + hdr.hdr_len + hdr.type_len, str_sec, hdr.str_len);
 
-	btf_fd = bpf_btf_load(raw_btf, btf_len, NULL);
+	btf_fd = bpf_btf_load(raw_btf, btf_len, &opts);
 
 	free(raw_btf);
 	return btf_fd;
@@ -271,7 +273,7 @@ static int load_local_storage_btf(void)
 	};
 
 	return libbpf__load_raw_btf((char *)types, sizeof(types),
-				     strs, sizeof(strs));
+				     strs, sizeof(strs), 0);
 }
 
 static int probe_map_create(enum bpf_map_type map_type)
-- 
2.34.1

[PATCH v3 bpf-next 06/10] libbpf: wire up BPF token support at BPF object level

[Andrii Nakryiko]

Add BPF token support to BPF object-level functionality.

BPF token is supported by BPF object logic either as an explicitly
provided BPF token from outside (through BPF FS path or explicit BPF
token FD), or implicitly (unless prevented through
bpf_object_open_opts).

Implicit mode is assumed to be the most common one for user namespaced
unprivileged workloads. The assumption is that privileged container
manager sets up default BPF FS mount point at /sys/fs/bpf with BPF token
delegation options (delegate_{cmds,maps,progs,attachs} mount options).
BPF object during loading will attempt to create BPF token from
/sys/fs/bpf location, and pass it for all relevant operations
(currently, map creation, BTF load, and program load).

In this implicit mode, if BPF token creation fails due to whatever
reason (BPF FS is not mounted, or kernel doesn't support BPF token,
etc), this is not considered an error. BPF object loading sequence will
proceed with no BPF token.

In explicit BPF token mode, user provides explicitly either custom BPF
FS mount point path or creates BPF token on their own and just passes
token FD directly. In such case, BPF object will either dup() token FD
(to not require caller to hold onto it for entire duration of BPF object
lifetime) or will attempt to create BPF token from provided BPF FS
location. If BPF token creation fails, that is considered a critical
error and BPF object load fails with an error.

Libbpf provides a way to disable implicit BPF token creation, if it
causes any troubles (BPF token is designed to be completely optional and
shouldn't cause any problems even if provided, but in the world of BPF
LSM, custom security logic can be installed that might change outcome
dependin on the presence of BPF token). To disable libbpf's default BPF
token creation behavior user should provide either invalid BPF token FD
(negative), or empty bpf_token_path option.

BPF token presence can influence libbpf's feature probing, so if BPF
object has associated BPF token, feature probing is instructed to use
BPF object-specific feature detection cache and token FD.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/btf.c             |   7 +-
 tools/lib/bpf/libbpf.c          | 118 ++++++++++++++++++++++++++++++--
 tools/lib/bpf/libbpf.h          |  28 +++++++-
 tools/lib/bpf/libbpf_internal.h |  17 ++++-
 4 files changed, 158 insertions(+), 12 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index ee95fd379d4d..63033c334320 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1317,7 +1317,9 @@ struct btf *btf__parse_split(const char *path, struct btf *base_btf)
 
 static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endian);
 
-int btf_load_into_kernel(struct btf *btf, char *log_buf, size_t log_sz, __u32 log_level)
+int btf_load_into_kernel(struct btf *btf,
+			 char *log_buf, size_t log_sz, __u32 log_level,
+			 int token_fd)
 {
 	LIBBPF_OPTS(bpf_btf_load_opts, opts);
 	__u32 buf_sz = 0, raw_size;
@@ -1367,6 +1369,7 @@ int btf_load_into_kernel(struct btf *btf, char *log_buf, size_t log_sz, __u32 lo
 		opts.log_level = log_level;
 	}
 
+	opts.token_fd = token_fd;
 	btf->fd = bpf_btf_load(raw_data, raw_size, &opts);
 	if (btf->fd < 0) {
 		/* time to turn on verbose mode and try again */
@@ -1394,7 +1397,7 @@ int btf_load_into_kernel(struct btf *btf, char *log_buf, size_t log_sz, __u32 lo
 
 int btf__load_into_kernel(struct btf *btf)
 {
-	return btf_load_into_kernel(btf, NULL, 0, 0);
+	return btf_load_into_kernel(btf, NULL, 0, 0, 0);
 }
 
 int btf__fd(const struct btf *btf)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1acd1c224c5e..db94bbe163e3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -59,6 +59,8 @@
 #define BPF_FS_MAGIC		0xcafe4a11
 #endif
 
+#define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"
+
 #define BPF_INSN_SZ (sizeof(struct bpf_insn))
 
 /* vsprintf() in __base_pr() uses nonliteral format string. It may break
@@ -693,6 +695,10 @@ struct bpf_object {
 
 	struct usdt_manager *usdt_man;
 
+	struct kern_feature_cache *feat_cache;
+	char *token_path;
+	int token_fd;
+
 	char path[];
 };
 
@@ -2192,7 +2198,7 @@ static int build_map_pin_path(struct bpf_map *map, const char *path)
 	int err;
 
 	if (!path)
-		path = "/sys/fs/bpf";
+		path = BPF_FS_DEFAULT_PATH;
 
 	err = pathname_concat(buf, sizeof(buf), path, bpf_map__name(map));
 	if (err)
@@ -3279,7 +3285,7 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 	} else {
 		/* currently BPF_BTF_LOAD only supports log_level 1 */
 		err = btf_load_into_kernel(kern_btf, obj->log_buf, obj->log_size,
-					   obj->log_level ? 1 : 0);
+					   obj->log_level ? 1 : 0, obj->token_fd);
 	}
 	if (sanitize) {
 		if (!err) {
@@ -4602,6 +4608,63 @@ int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries)
 	return 0;
 }
 
+static int bpf_object_prepare_token(struct bpf_object *obj)
+{
+	const char *bpffs_path;
+	int bpffs_fd = -1, token_fd, err;
+	bool mandatory;
+	enum libbpf_print_level level;
+
+	/* token is already set up */
+	if (obj->token_fd > 0)
+		return 0;
+	/* token is explicitly prevented */
+	if (obj->token_fd < 0) {
+		pr_debug("object '%s': token is prevented, skipping...\n", obj->name);
+		/* reset to zero to avoid extra checks during map_create and prog_load steps */
+		obj->token_fd = 0;
+		return 0;
+	}
+
+	mandatory = obj->token_path != NULL;
+	level = mandatory ? LIBBPF_WARN : LIBBPF_DEBUG;
+
+	bpffs_path = obj->token_path ?: BPF_FS_DEFAULT_PATH;
+	bpffs_fd = open(bpffs_path, O_DIRECTORY, O_RDWR);
+	if (bpffs_fd < 0) {
+		err = -errno;
+		__pr(level, "object '%s': failed (%d) to open BPF FS mount at '%s'%s\n",
+		     obj->name, err, bpffs_path,
+		     mandatory ? "" : ", skipping optional step...");
+		return mandatory ? err : 0;
+	}
+
+	token_fd = bpf_token_create(bpffs_fd, 0);
+	close(bpffs_fd);
+	if (token_fd < 0) {
+		if (!mandatory && token_fd == -ENOENT) {
+			pr_debug("object '%s': BPF FS at '%s' doesn't have BPF token delegation set up, skipping...\n",
+				 obj->name, bpffs_path);
+			return 0;
+		}
+		__pr(level, "object '%s': failed (%d) to create BPF token from '%s'%s\n",
+		     obj->name, token_fd, bpffs_path,
+		     mandatory ? "" : ", skipping optional step...");
+		return mandatory ? token_fd : 0;
+	}
+
+	obj->feat_cache = calloc(1, sizeof(*obj->feat_cache));
+	if (!obj->feat_cache) {
+		close(token_fd);
+		return -ENOMEM;
+	}
+
+	obj->token_fd = token_fd;
+	obj->feat_cache->token_fd = token_fd;
+
+	return 0;
+}
+
 static int
 bpf_object__probe_loading(struct bpf_object *obj)
 {
@@ -4611,6 +4674,7 @@ bpf_object__probe_loading(struct bpf_object *obj)
 		BPF_EXIT_INSN(),
 	};
 	int ret, insn_cnt = ARRAY_SIZE(insns);
+	LIBBPF_OPTS(bpf_prog_load_opts, opts, .token_fd = obj->token_fd);
 
 	if (obj->gen_loader)
 		return 0;
@@ -4620,9 +4684,9 @@ bpf_object__probe_loading(struct bpf_object *obj)
 		pr_warn("Failed to bump RLIMIT_MEMLOCK (err = %d), you might need to do it explicitly!\n", ret);
 
 	/* make sure basic loading works */
-	ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, NULL);
+	ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, &opts);
 	if (ret < 0)
-		ret = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, NULL);
+		ret = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, &opts);
 	if (ret < 0) {
 		ret = errno;
 		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
@@ -4645,6 +4709,9 @@ bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
 		 */
 		return true;
 
+	if (obj->token_fd)
+		return feat_supported(obj->feat_cache, feat_id);
+
 	return feat_supported(NULL, feat_id);
 }
 
@@ -4764,6 +4831,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 	create_attr.map_flags = def->map_flags;
 	create_attr.numa_node = map->numa_node;
 	create_attr.map_extra = map->map_extra;
+	create_attr.token_fd = obj->token_fd;
 
 	if (bpf_map__is_struct_ops(map))
 		create_attr.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;
@@ -6599,6 +6667,7 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
 	load_attr.attach_btf_id = prog->attach_btf_id;
 	load_attr.kern_version = kern_version;
 	load_attr.prog_ifindex = prog->prog_ifindex;
+	load_attr.token_fd = obj->token_fd;
 
 	/* specify func_info/line_info only if kernel supports them */
 	btf_fd = bpf_object__btf_fd(obj);
@@ -7060,10 +7129,10 @@ static int bpf_object_init_progs(struct bpf_object *obj, const struct bpf_object
 static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf, size_t obj_buf_sz,
 					  const struct bpf_object_open_opts *opts)
 {
-	const char *obj_name, *kconfig, *btf_tmp_path;
+	const char *obj_name, *kconfig, *btf_tmp_path, *token_path;
 	struct bpf_object *obj;
 	char tmp_name[64];
-	int err;
+	int err, token_fd;
 	char *log_buf;
 	size_t log_size;
 	__u32 log_level;
@@ -7097,6 +7166,22 @@ static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf,
 	if (log_size && !log_buf)
 		return ERR_PTR(-EINVAL);
 
+	token_path = OPTS_GET(opts, bpf_token_path, NULL);
+	token_fd = OPTS_GET(opts, bpf_token_fd, -1);
+	/* non-empty token path can't be combined with invalid token FD */
+	if (token_path && token_path[0] != '\0' && token_fd < 0)
+		return ERR_PTR(-EINVAL);
+	if (token_path && token_path[0] == '\0') {
+		/* empty token path can't be combined with valid token FD */
+		if (token_fd > 0)
+			return ERR_PTR(-EINVAL);
+		/* empty token_path is equivalent to invalid token_fd */
+		token_path = NULL;
+		token_fd = -1;
+	}
+	if (token_path && strlen(token_path) >= PATH_MAX)
+		return ERR_PTR(-ENAMETOOLONG);
+
 	obj = bpf_object__new(path, obj_buf, obj_buf_sz, obj_name);
 	if (IS_ERR(obj))
 		return obj;
@@ -7105,6 +7190,19 @@ static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf,
 	obj->log_size = log_size;
 	obj->log_level = log_level;
 
+	obj->token_fd = token_fd <= 0 ? token_fd : dup_good_fd(token_fd);
+	if (token_fd > 0 && obj->token_fd < 0) {
+		err = -errno;
+		goto out;
+	}
+	if (token_path) {
+		obj->token_path = strdup(token_path);
+		if (!obj->token_path) {
+			err = -ENOMEM;
+			goto out;
+		}
+	}
+
 	btf_tmp_path = OPTS_GET(opts, btf_custom_path, NULL);
 	if (btf_tmp_path) {
 		if (strlen(btf_tmp_path) >= PATH_MAX) {
@@ -7615,7 +7713,8 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch
 	if (obj->gen_loader)
 		bpf_gen__init(obj->gen_loader, extra_log_level, obj->nr_programs, obj->nr_maps);
 
-	err = bpf_object__probe_loading(obj);
+	err = bpf_object_prepare_token(obj);
+	err = err ? : bpf_object__probe_loading(obj);
 	err = err ? : bpf_object__load_vmlinux_btf(obj, false);
 	err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
 	err = err ? : bpf_object__sanitize_and_load_btf(obj);
@@ -8152,6 +8251,11 @@ void bpf_object__close(struct bpf_object *obj)
 	}
 	zfree(&obj->programs);
 
+	zfree(&obj->feat_cache);
+	zfree(&obj->token_path);
+	if (obj->token_fd > 0)
+		close(obj->token_fd);
+
 	free(obj);
 }
 
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 6cd9c501624f..d3de39b537f3 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -177,10 +177,36 @@ struct bpf_object_open_opts {
 	 * logs through its print callback.
 	 */
 	__u32 kernel_log_level;
+	/* FD of a BPF token instantiated by user through bpf_token_create()
+	 * API. BPF object will keep dup()'ed FD internally, so passed token
+	 * FD can be closed after BPF object/skeleton open step.
+	 *
+	 * Setting bpf_token_fd to negative value disables libbpf's automatic
+	 * attempt to create BPF token from default BPF FS mount point
+	 * (/sys/fs/bpf), in case this default behavior is undesirable.
+	 *
+	 * bpf_token_path and bpf_token_fd are mutually exclusive and only one
+	 * of those options should be set.
+	 */
+	int bpf_token_fd;
+	/* Path to BPF FS mount point to derive BPF token from.
+	 *
+	 * Created BPF token will be used for all bpf() syscall operations
+	 * that accept BPF token (e.g., map creation, BTF and program loads,
+	 * etc) automatically within instantiated BPF object.
+	 *
+	 * Setting bpf_token_path option to empty string disables libbpf's
+	 * automatic attempt to create BPF token from default BPF FS mount
+	 * point (/sys/fs/bpf), in case this default behavior is undesirable.
+	 *
+	 * bpf_token_path and bpf_token_fd are mutually exclusive and only one
+	 * of those options should be set.
+	 */
+	const char *bpf_token_path;
 
 	size_t :0;
 };
-#define bpf_object_open_opts__last_field kernel_log_level
+#define bpf_object_open_opts__last_field bpf_token_path
 
 /**
  * @brief **bpf_object__open()** creates a bpf_object by opening
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index b45566e428d7..4cda32298c49 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -383,7 +383,9 @@ int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz);
 int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
 			 const char *str_sec, size_t str_len,
 			 int token_fd);
-int btf_load_into_kernel(struct btf *btf, char *log_buf, size_t log_sz, __u32 log_level);
+int btf_load_into_kernel(struct btf *btf,
+			 char *log_buf, size_t log_sz, __u32 log_level,
+			 int token_fd);
 
 struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf);
 void btf_get_kernel_prefix_kind(enum bpf_attach_type attach_type,
@@ -547,6 +549,17 @@ static inline bool is_ldimm64_insn(struct bpf_insn *insn)
 	return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
 }
 
+/* Unconditionally dup FD, ensuring it doesn't use [0, 2] range.
+ * Original FD is not closed or altered in any other way.
+ * Preserves original FD value, if it's invalid (negative).
+ */
+static inline int dup_good_fd(int fd)
+{
+	if (fd < 0)
+		return fd;
+	return fcntl(fd, F_DUPFD_CLOEXEC, 3);
+}
+
 /* if fd is stdin, stdout, or stderr, dup to a fd greater than 2
  * Takes ownership of the fd passed in, and closes it if calling
  * fcntl(fd, F_DUPFD_CLOEXEC, 3).
@@ -558,7 +571,7 @@ static inline int ensure_good_fd(int fd)
 	if (fd < 0)
 		return fd;
 	if (fd < 3) {
-		fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
+		fd = dup_good_fd(fd);
 		saved_errno = errno;
 		close(old_fd);
 		errno = saved_errno;
-- 
2.34.1

[PATCH v3 bpf-next 07/10] selftests/bpf: add BPF object loading tests with explicit token passing

[Andrii Nakryiko]

Add a few tests that attempt to load BPF object containing privileged
map, program, and the one requiring mandatory BTF uploading into the
kernel (to validate token FD propagation to BPF_BTF_LOAD command).

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 .../testing/selftests/bpf/prog_tests/token.c  | 159 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/priv_map.c  |  13 ++
 tools/testing/selftests/bpf/progs/priv_prog.c |  13 ++
 3 files changed, 185 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/priv_map.c
 create mode 100644 tools/testing/selftests/bpf/progs/priv_prog.c

diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c
index dc03790c6272..9812292336c9 100644
--- a/tools/testing/selftests/bpf/prog_tests/token.c
+++ b/tools/testing/selftests/bpf/prog_tests/token.c
@@ -14,6 +14,9 @@
 #include <sys/socket.h>
 #include <sys/syscall.h>
 #include <sys/un.h>
+#include "priv_map.skel.h"
+#include "priv_prog.skel.h"
+#include "dummy_st_ops_success.skel.h"
 
 static inline int sys_mount(const char *dev_name, const char *dir_name,
 			    const char *type, unsigned long flags,
@@ -643,6 +646,123 @@ static int userns_prog_load(int mnt_fd)
 	return err;
 }
 
+static int userns_obj_priv_map(int mnt_fd)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	char buf[256];
+	struct priv_map *skel;
+	int err, token_fd;
+
+	skel = priv_map__open_and_load();
+	if (!ASSERT_ERR_PTR(skel, "obj_tokenless_load")) {
+		priv_map__destroy(skel);
+		return -EINVAL;
+	}
+
+	/* use bpf_token_path to provide BPF FS path */
+	snprintf(buf, sizeof(buf), "/proc/self/fd/%d", mnt_fd);
+	opts.bpf_token_path = buf;
+	skel = priv_map__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "obj_token_path_open"))
+		return -EINVAL;
+
+	err = priv_map__load(skel);
+	priv_map__destroy(skel);
+	if (!ASSERT_OK(err, "obj_token_path_load"))
+		return -EINVAL;
+
+	/* create token and pass it through bpf_token_fd */
+	token_fd = bpf_token_create(mnt_fd, NULL);
+	if (!ASSERT_GT(token_fd, 0, "create_token"))
+		return -EINVAL;
+
+	opts.bpf_token_path = NULL;
+	opts.bpf_token_fd = token_fd;
+	skel = priv_map__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "obj_token_fd_open"))
+		return -EINVAL;
+
+	/* we can close our token FD, bpf_object owns dup()'ed FD now */
+	close(token_fd);
+
+	err = priv_map__load(skel);
+	priv_map__destroy(skel);
+	if (!ASSERT_OK(err, "obj_token_fd_load"))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int userns_obj_priv_prog(int mnt_fd)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	char buf[256];
+	struct priv_prog *skel;
+	int err;
+
+	skel = priv_prog__open_and_load();
+	if (!ASSERT_ERR_PTR(skel, "obj_tokenless_load")) {
+		priv_prog__destroy(skel);
+		return -EINVAL;
+	}
+
+	/* use bpf_token_path to provide BPF FS path */
+	snprintf(buf, sizeof(buf), "/proc/self/fd/%d", mnt_fd);
+	opts.bpf_token_path = buf;
+	skel = priv_prog__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "obj_token_path_open"))
+		return -EINVAL;
+
+	err = priv_prog__load(skel);
+	priv_prog__destroy(skel);
+	if (!ASSERT_OK(err, "obj_token_path_load"))
+		return -EINVAL;
+
+	return 0;
+}
+
+/* this test is called with BPF FS that doesn't delegate BPF_BTF_LOAD command,
+ * which should cause struct_ops application to fail, as BTF won't be uploaded
+ * into the kernel, even if STRUCT_OPS programs themselves are allowed
+ */
+static int validate_struct_ops_load(int mnt_fd, bool expect_success)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	char buf[256];
+	struct dummy_st_ops_success *skel;
+	int err;
+
+	snprintf(buf, sizeof(buf), "/proc/self/fd/%d", mnt_fd);
+	opts.bpf_token_path = buf;
+	skel = dummy_st_ops_success__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "obj_token_path_open"))
+		return -EINVAL;
+
+	err = dummy_st_ops_success__load(skel);
+	dummy_st_ops_success__destroy(skel);
+	if (expect_success) {
+		if (!ASSERT_OK(err, "obj_token_path_load"))
+			return -EINVAL;
+	} else /* expect failure */ {
+		if (!ASSERT_ERR(err, "obj_token_path_load"))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int userns_obj_priv_btf_fail(int mnt_fd)
+{
+	return validate_struct_ops_load(mnt_fd, false /* should fail */);
+}
+
+static int userns_obj_priv_btf_success(int mnt_fd)
+{
+	return validate_struct_ops_load(mnt_fd, true /* should succeed */);
+}
+
+#define bit(n) (1ULL << (n))
+
 void test_token(void)
 {
 	if (test__start_subtest("map_token")) {
@@ -669,4 +789,43 @@ void test_token(void)
 
 		subtest_userns(&opts, userns_prog_load);
 	}
+	if (test__start_subtest("obj_priv_map")) {
+		struct bpffs_opts opts = {
+			.cmds = bit(BPF_MAP_CREATE),
+			.maps = bit(BPF_MAP_TYPE_QUEUE),
+		};
+
+		subtest_userns(&opts, userns_obj_priv_map);
+	}
+	if (test__start_subtest("obj_priv_prog")) {
+		struct bpffs_opts opts = {
+			.cmds = bit(BPF_PROG_LOAD),
+			.progs = bit(BPF_PROG_TYPE_KPROBE),
+			.attachs = ~0ULL,
+		};
+
+		subtest_userns(&opts, userns_obj_priv_prog);
+	}
+	if (test__start_subtest("obj_priv_btf_fail")) {
+		struct bpffs_opts opts = {
+			/* disallow BTF loading */
+			.cmds = bit(BPF_MAP_CREATE) | bit(BPF_PROG_LOAD),
+			.maps = bit(BPF_MAP_TYPE_STRUCT_OPS),
+			.progs = bit(BPF_PROG_TYPE_STRUCT_OPS),
+			.attachs = ~0ULL,
+		};
+
+		subtest_userns(&opts, userns_obj_priv_btf_fail);
+	}
+	if (test__start_subtest("obj_priv_btf_success")) {
+		struct bpffs_opts opts = {
+			/* allow BTF loading */
+			.cmds = bit(BPF_BTF_LOAD) | bit(BPF_MAP_CREATE) | bit(BPF_PROG_LOAD),
+			.maps = bit(BPF_MAP_TYPE_STRUCT_OPS),
+			.progs = bit(BPF_PROG_TYPE_STRUCT_OPS),
+			.attachs = ~0ULL,
+		};
+
+		subtest_userns(&opts, userns_obj_priv_btf_success);
+	}
 }
diff --git a/tools/testing/selftests/bpf/progs/priv_map.c b/tools/testing/selftests/bpf/progs/priv_map.c
new file mode 100644
index 000000000000..9085be50f03b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/priv_map.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_QUEUE);
+	__uint(max_entries, 1);
+	__type(value, __u32);
+} priv_map SEC(".maps");
diff --git a/tools/testing/selftests/bpf/progs/priv_prog.c b/tools/testing/selftests/bpf/progs/priv_prog.c
new file mode 100644
index 000000000000..3c7b2b618c8a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/priv_prog.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("kprobe")
+int kprobe_prog(void *ctx)
+{
+	return 1;
+}
-- 
2.34.1

[PATCH v3 bpf-next 08/10] selftests/bpf: add tests for BPF object load with implicit token

[Andrii Nakryiko]

Add a test to validate libbpf's implicit BPF token creation from default
BPF FS location (/sys/fs/bpf). Also validate that disabling this
implicit BPF token creation works.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 .../testing/selftests/bpf/prog_tests/token.c  | 76 +++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c
index 9812292336c9..1a3c3aacf537 100644
--- a/tools/testing/selftests/bpf/prog_tests/token.c
+++ b/tools/testing/selftests/bpf/prog_tests/token.c
@@ -12,6 +12,7 @@
 #include <linux/unistd.h>
 #include <linux/mount.h>
 #include <sys/socket.h>
+#include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/un.h>
 #include "priv_map.skel.h"
@@ -45,6 +46,13 @@ static inline int sys_fsmount(int fs_fd, unsigned flags, unsigned ms_flags)
 	return syscall(__NR_fsmount, fs_fd, flags, ms_flags);
 }
 
+static inline int sys_move_mount(int from_dfd, const char *from_path,
+				 int to_dfd, const char *to_path,
+				 unsigned flags)
+{
+	return syscall(__NR_move_mount, from_dfd, from_path, to_dfd, to_path, flags);
+}
+
 static int drop_priv_caps(__u64 *old_caps)
 {
 	return cap_disable_effective((1ULL << CAP_BPF) |
@@ -761,6 +769,63 @@ static int userns_obj_priv_btf_success(int mnt_fd)
 	return validate_struct_ops_load(mnt_fd, true /* should succeed */);
 }
 
+static int userns_obj_priv_implicit_token(int mnt_fd)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	struct dummy_st_ops_success *skel;
+	int err;
+
+	/* before we mount BPF FS with token delegation, struct_ops skeleton
+	 * should fail to load
+	 */
+	skel = dummy_st_ops_success__open_and_load();
+	if (!ASSERT_ERR_PTR(skel, "obj_tokenless_load")) {
+		dummy_st_ops_success__destroy(skel);
+		return -EINVAL;
+	}
+
+	/* mount custom BPF FS over /sys/fs/bpf so that libbpf can create BPF
+	 * token automatically and implicitly
+	 */
+	err = sys_move_mount(mnt_fd, "", AT_FDCWD, "/sys/fs/bpf", MOVE_MOUNT_F_EMPTY_PATH);
+	if (!ASSERT_OK(err, "move_mount_bpffs"))
+		return -EINVAL;
+
+	/* now the same struct_ops skeleton should succeed thanks to libppf
+	 * creating BPF token from /sys/fs/bpf mount point
+	 */
+	skel = dummy_st_ops_success__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "obj_implicit_token_load"))
+		return -EINVAL;
+
+	dummy_st_ops_success__destroy(skel);
+
+	/* now disable implicit token through empty bpf_token_path, should fail */
+	opts.bpf_token_path = "";
+	skel = dummy_st_ops_success__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "obj_empty_token_path_open"))
+		return -EINVAL;
+
+	err = dummy_st_ops_success__load(skel);
+	dummy_st_ops_success__destroy(skel);
+	if (!ASSERT_ERR(err, "obj_empty_token_path_load"))
+		return -EINVAL;
+
+	/* now disable implicit token through negative bpf_token_fd, should fail */
+	opts.bpf_token_path = NULL;
+	opts.bpf_token_fd = -1;
+	skel = dummy_st_ops_success__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "obj_neg_token_fd_open"))
+		return -EINVAL;
+
+	err = dummy_st_ops_success__load(skel);
+	dummy_st_ops_success__destroy(skel);
+	if (!ASSERT_ERR(err, "obj_neg_token_fd_load"))
+		return -EINVAL;
+
+	return 0;
+}
+
 #define bit(n) (1ULL << (n))
 
 void test_token(void)
@@ -828,4 +893,15 @@ void test_token(void)
 
 		subtest_userns(&opts, userns_obj_priv_btf_success);
 	}
+	if (test__start_subtest("obj_priv_implicit_token")) {
+		struct bpffs_opts opts = {
+			/* allow BTF loading */
+			.cmds = bit(BPF_BTF_LOAD) | bit(BPF_MAP_CREATE) | bit(BPF_PROG_LOAD),
+			.maps = bit(BPF_MAP_TYPE_STRUCT_OPS),
+			.progs = bit(BPF_PROG_TYPE_STRUCT_OPS),
+			.attachs = ~0ULL,
+		};
+
+		subtest_userns(&opts, userns_obj_priv_implicit_token);
+	}
 }
-- 
2.34.1

[PATCH v3 bpf-next 09/10] libbpf: support BPF token path setting through LIBBPF_BPF_TOKEN_PATH envvar

[Andrii Nakryiko]

To allow external admin authority to override default BPF FS location
(/sys/fs/bpf) for implicit BPF token creation, teach libbpf to recognize
LIBBPF_BPF_TOKEN_PATH envvar. If it is specified and user application
didn't explicitly specify neither bpf_token_path nor bpf_token_fd
option, it will be treated exactly like bpf_token_path option,
overriding default /sys/fs/bpf location and making BPF token mandatory.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/libbpf.c | 14 ++++++++++----
 tools/lib/bpf/libbpf.h | 13 +++++++++++--
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index db94bbe163e3..4b5ff9508e18 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -7171,11 +7171,17 @@ static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf,
 	/* non-empty token path can't be combined with invalid token FD */
 	if (token_path && token_path[0] != '\0' && token_fd < 0)
 		return ERR_PTR(-EINVAL);
+	/* empty token path can't be combined with valid token FD */
+	if (token_path && token_path[0] == '\0' && token_fd > 0)
+		return ERR_PTR(-EINVAL);
+	/* if user didn't specify bpf_token_path/bpf_token_fd explicitly,
+	 * check if LIBBPF_BPF_TOKEN_PATH envvar was set and treat it as
+	 * bpf_token_path option
+	 */
+	if (token_fd == 0 && !token_path)
+		token_path = getenv("LIBBPF_BPF_TOKEN_PATH");
+	/* empty token_path is equivalent to invalid token_fd */
 	if (token_path && token_path[0] == '\0') {
-		/* empty token path can't be combined with valid token FD */
-		if (token_fd > 0)
-			return ERR_PTR(-EINVAL);
-		/* empty token_path is equivalent to invalid token_fd */
 		token_path = NULL;
 		token_fd = -1;
 	}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index d3de39b537f3..916904bd2a7a 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -185,8 +185,16 @@ struct bpf_object_open_opts {
 	 * attempt to create BPF token from default BPF FS mount point
 	 * (/sys/fs/bpf), in case this default behavior is undesirable.
 	 *
+	 * If bpf_token_path and bpf_token_fd are not specified, libbpf will
+	 * consult LIBBPF_BPF_TOKEN_PATH environment variable. If set, it will
+	 * be taken as a value of bpf_token_path option and will force libbpf
+	 * to either create BPF token from provided custom BPF FS path, or
+	 * will disable implicit BPF token creation, if envvar value is an
+	 * empty string.
+	 *
 	 * bpf_token_path and bpf_token_fd are mutually exclusive and only one
-	 * of those options should be set.
+	 * of those options should be set. Either of them overrides
+	 * LIBBPF_BPF_TOKEN_PATH envvar.
 	 */
 	int bpf_token_fd;
 	/* Path to BPF FS mount point to derive BPF token from.
@@ -200,7 +208,8 @@ struct bpf_object_open_opts {
 	 * point (/sys/fs/bpf), in case this default behavior is undesirable.
 	 *
 	 * bpf_token_path and bpf_token_fd are mutually exclusive and only one
-	 * of those options should be set.
+	 * of those options should be set. Either of them overrides
+	 * LIBBPF_BPF_TOKEN_PATH envvar.
 	 */
 	const char *bpf_token_path;
 
-- 
2.34.1

[PATCH v3 bpf-next 10/10] selftests/bpf: add tests for LIBBPF_BPF_TOKEN_PATH envvar

[Andrii Nakryiko]

Add new subtest validating LIBBPF_BPF_TOKEN_PATH envvar semantics.
Extend existing test to validate that LIBBPF_BPF_TOKEN_PATH allows to
disable implicit BPF token creation by setting envvar to empty string.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 .../testing/selftests/bpf/prog_tests/token.c  | 112 ++++++++++++++++++
 1 file changed, 112 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c
index 1a3c3aacf537..548aeb91ab0d 100644
--- a/tools/testing/selftests/bpf/prog_tests/token.c
+++ b/tools/testing/selftests/bpf/prog_tests/token.c
@@ -769,6 +769,9 @@ static int userns_obj_priv_btf_success(int mnt_fd)
 	return validate_struct_ops_load(mnt_fd, true /* should succeed */);
 }
 
+#define TOKEN_ENVVAR "LIBBPF_BPF_TOKEN_PATH"
+#define TOKEN_BPFFS_CUSTOM "/bpf-token-fs"
+
 static int userns_obj_priv_implicit_token(int mnt_fd)
 {
 	LIBBPF_OPTS(bpf_object_open_opts, opts);
@@ -791,6 +794,20 @@ static int userns_obj_priv_implicit_token(int mnt_fd)
 	if (!ASSERT_OK(err, "move_mount_bpffs"))
 		return -EINVAL;
 
+	/* disable implicit BPF token creation by setting
+	 * LIBBPF_BPF_TOKEN_PATH envvar to empty value, load should fail
+	 */
+	err = setenv(TOKEN_ENVVAR, "", 1 /*overwrite*/);
+	if (!ASSERT_OK(err, "setenv_token_path"))
+		return -EINVAL;
+	skel = dummy_st_ops_success__open_and_load();
+	if (!ASSERT_ERR_PTR(skel, "obj_token_envvar_disabled_load")) {
+		unsetenv(TOKEN_ENVVAR);
+		dummy_st_ops_success__destroy(skel);
+		return -EINVAL;
+	}
+	unsetenv(TOKEN_ENVVAR);
+
 	/* now the same struct_ops skeleton should succeed thanks to libppf
 	 * creating BPF token from /sys/fs/bpf mount point
 	 */
@@ -826,6 +843,90 @@ static int userns_obj_priv_implicit_token(int mnt_fd)
 	return 0;
 }
 
+static int userns_obj_priv_implicit_token_envvar(int mnt_fd)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	struct dummy_st_ops_success *skel;
+	int err;
+
+	/* before we mount BPF FS with token delegation, struct_ops skeleton
+	 * should fail to load
+	 */
+	skel = dummy_st_ops_success__open_and_load();
+	if (!ASSERT_ERR_PTR(skel, "obj_tokenless_load")) {
+		dummy_st_ops_success__destroy(skel);
+		return -EINVAL;
+	}
+
+	/* mount custom BPF FS over custom location, so libbpf can't create
+	 * BPF token implicitly, unless pointed to it through
+	 * LIBBPF_BPF_TOKEN_PATH envvar
+	 */
+	rmdir(TOKEN_BPFFS_CUSTOM);
+	if (!ASSERT_OK(mkdir(TOKEN_BPFFS_CUSTOM, 0777), "mkdir_bpffs_custom"))
+		goto err_out;
+	err = sys_move_mount(mnt_fd, "", AT_FDCWD, TOKEN_BPFFS_CUSTOM, MOVE_MOUNT_F_EMPTY_PATH);
+	if (!ASSERT_OK(err, "move_mount_bpffs"))
+		goto err_out;
+
+	/* even though we have BPF FS with delegation, it's not at default
+	 * /sys/fs/bpf location, so we still fail to load until envvar is set up
+	 */
+	skel = dummy_st_ops_success__open_and_load();
+	if (!ASSERT_ERR_PTR(skel, "obj_tokenless_load2")) {
+		dummy_st_ops_success__destroy(skel);
+		goto err_out;
+	}
+
+	err = setenv(TOKEN_ENVVAR, TOKEN_BPFFS_CUSTOM, 1 /*overwrite*/);
+	if (!ASSERT_OK(err, "setenv_token_path"))
+		goto err_out;
+
+	/* now the same struct_ops skeleton should succeed thanks to libppf
+	 * creating BPF token from custom mount point
+	 */
+	skel = dummy_st_ops_success__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "obj_implicit_token_load"))
+		goto err_out;
+
+	dummy_st_ops_success__destroy(skel);
+
+	/* now disable implicit token through empty bpf_token_path, envvar
+	 * will be ignored, should fail
+	 */
+	opts.bpf_token_path = "";
+	skel = dummy_st_ops_success__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "obj_empty_token_path_open"))
+		goto err_out;
+
+	err = dummy_st_ops_success__load(skel);
+	dummy_st_ops_success__destroy(skel);
+	if (!ASSERT_ERR(err, "obj_empty_token_path_load"))
+		goto err_out;
+
+	/* now disable implicit token through negative bpf_token_fd, envvar
+	 * will be ignored, should fail
+	 */
+	opts.bpf_token_path = NULL;
+	opts.bpf_token_fd = -1;
+	skel = dummy_st_ops_success__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "obj_neg_token_fd_open"))
+		goto err_out;
+
+	err = dummy_st_ops_success__load(skel);
+	dummy_st_ops_success__destroy(skel);
+	if (!ASSERT_ERR(err, "obj_neg_token_fd_load"))
+		goto err_out;
+
+	rmdir(TOKEN_BPFFS_CUSTOM);
+	unsetenv(TOKEN_ENVVAR);
+	return 0;
+err_out:
+	rmdir(TOKEN_BPFFS_CUSTOM);
+	unsetenv(TOKEN_ENVVAR);
+	return -EINVAL;
+}
+
 #define bit(n) (1ULL << (n))
 
 void test_token(void)
@@ -904,4 +1005,15 @@ void test_token(void)
 
 		subtest_userns(&opts, userns_obj_priv_implicit_token);
 	}
+	if (test__start_subtest("obj_priv_implicit_token_envvar")) {
+		struct bpffs_opts opts = {
+			/* allow BTF loading */
+			.cmds = bit(BPF_BTF_LOAD) | bit(BPF_MAP_CREATE) | bit(BPF_PROG_LOAD),
+			.maps = bit(BPF_MAP_TYPE_STRUCT_OPS),
+			.progs = bit(BPF_PROG_TYPE_STRUCT_OPS),
+			.attachs = ~0ULL,
+		};
+
+		subtest_userns(&opts, userns_obj_priv_implicit_token_envvar);
+	}
 }
-- 
2.34.1

Re: [PATCH v3 bpf-next 00/10] BPF token support in libbpf's BPF object

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Wed, 13 Dec 2023 11:08:32 -0800 you wrote:
> Add fuller support for BPF token in high-level BPF object APIs. This is the
> most frequently used way to work with BPF using libbpf, so supporting BPF
> token there is critical.
> 
> Patch #1 is improving kernel-side BPF_TOKEN_CREATE behavior by rejecting to
> create "empty" BPF token with no delegation. This seems like saner behavior
> which also makes libbpf's caching better overall. If we ever want to create
> BPF token with no delegate_xxx options set on BPF FS, we can use a new flag to
> enable that.
> 
> [...]

Here is the summary with links:
  - [v3,bpf-next,01/10] bpf: fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS
    https://git.kernel.org/bpf/bpf-next/c/f5fdb51fb980
  - [v3,bpf-next,02/10] libbpf: split feature detectors definitions from cached results
    https://git.kernel.org/bpf/bpf-next/c/c6c5be3eee97
  - [v3,bpf-next,03/10] libbpf: further decouple feature checking logic from bpf_object
    https://git.kernel.org/bpf/bpf-next/c/29c302a2e265
  - [v3,bpf-next,04/10] libbpf: move feature detection code into its own file
    https://git.kernel.org/bpf/bpf-next/c/ab8fc393b27c
  - [v3,bpf-next,05/10] libbpf: wire up token_fd into feature probing logic
    https://git.kernel.org/bpf/bpf-next/c/a75bb6a16518
  - [v3,bpf-next,06/10] libbpf: wire up BPF token support at BPF object level
    https://git.kernel.org/bpf/bpf-next/c/1d0dd6ea2e38
  - [v3,bpf-next,07/10] selftests/bpf: add BPF object loading tests with explicit token passing
    https://git.kernel.org/bpf/bpf-next/c/98e0eaa36adf
  - [v3,bpf-next,08/10] selftests/bpf: add tests for BPF object load with implicit token
    https://git.kernel.org/bpf/bpf-next/c/18678cf0ee13
  - [v3,bpf-next,09/10] libbpf: support BPF token path setting through LIBBPF_BPF_TOKEN_PATH envvar
    https://git.kernel.org/bpf/bpf-next/c/ed54124b8805
  - [v3,bpf-next,10/10] selftests/bpf: add tests for LIBBPF_BPF_TOKEN_PATH envvar
    https://git.kernel.org/bpf/bpf-next/c/322122bf8c75

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

RE: [PATCH v3 bpf-next 00/10] BPF token support in libbpf's BPF object

[John Fastabend]

Andrii Nakryiko wrote:
> Add fuller support for BPF token in high-level BPF object APIs. This is the
> most frequently used way to work with BPF using libbpf, so supporting BPF
> token there is critical.
> 
> Patch #1 is improving kernel-side BPF_TOKEN_CREATE behavior by rejecting to
> create "empty" BPF token with no delegation. This seems like saner behavior
> which also makes libbpf's caching better overall. If we ever want to create
> BPF token with no delegate_xxx options set on BPF FS, we can use a new flag to
> enable that.
> 
> Patches #2-#5 refactor libbpf internals, mostly feature detection code, to
> prepare it from BPF token FD.
> 
> Patch #6 adds options to pass BPF token into BPF object open options. It also
> adds implicit BPF token creation logic to BPF object load step, even without
> any explicit involvement of the user. If the environment is setup properly,
> BPF token will be created transparently and used implicitly. This allows for
> all existing application to gain BPF token support by just linking with
> latest version of libbpf library. No source code modifications are required.
> All that under assumption that privileged container management agent properly
> set up default BPF FS instance at /sys/bpf/fs to allow BPF token creation.
> 
> Patches #7-#8 adds more selftests, validating BPF object APIs work as expected
> under unprivileged user namespaced conditions in the presence of BPF token.
> 
> Patch #9 extends libbpf with LIBBPF_BPF_TOKEN_PATH envvar knowledge, which can
> be used to override custom BPF FS location used for implicit BPF token
> creation logic without needing to adjust application code. This allows admins
> or container managers to mount BPF token-enabled BPF FS at non-standard
> location without the need to coordinate with applications.
> LIBBPF_BPF_TOKEN_PATH can also be used to disable BPF token implicit creation
> by setting it to an empty value. Patch #10 tests this new envvar functionality.
> 
> v2->v3:
>   - move some stray feature cache refactorings into patch #4 (Alexei);
>   - add LIBBPF_BPF_TOKEN_PATH envvar support (Alexei);

We can do same thing from golang ebpf lib when we get around to adding it.
Looks good to me.

I see its merged but, Ack for me.

> v1->v2:
>   - remove minor code redundancies (Eduard, John);
>   - add acks and rebase.
> 
> Andrii Nakryiko (10):
>   bpf: fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS
>   libbpf: split feature detectors definitions from cached results
>   libbpf: further decouple feature checking logic from bpf_object
>   libbpf: move feature detection code into its own file
>   libbpf: wire up token_fd into feature probing logic
>   libbpf: wire up BPF token support at BPF object level
>   selftests/bpf: add BPF object loading tests with explicit token
>     passing
>   selftests/bpf: add tests for BPF object load with implicit token
>   libbpf: support BPF token path setting through LIBBPF_BPF_TOKEN_PATH
>     envvar
>   selftests/bpf: add tests for LIBBPF_BPF_TOKEN_PATH envvar
> 
>  kernel/bpf/token.c                            |  10 +-
>  tools/lib/bpf/Build                           |   2 +-
>  tools/lib/bpf/bpf.c                           |   9 +-
>  tools/lib/bpf/btf.c                           |   7 +-
>  tools/lib/bpf/elf.c                           |   2 -
>  tools/lib/bpf/features.c                      | 478 +++++++++++++++
>  tools/lib/bpf/libbpf.c                        | 573 ++++--------------
>  tools/lib/bpf/libbpf.h                        |  37 +-
>  tools/lib/bpf/libbpf_internal.h               |  36 +-
>  tools/lib/bpf/libbpf_probes.c                 |   8 +-
>  tools/lib/bpf/str_error.h                     |   3 +
>  .../testing/selftests/bpf/prog_tests/token.c  | 347 +++++++++++
>  tools/testing/selftests/bpf/progs/priv_map.c  |  13 +
>  tools/testing/selftests/bpf/progs/priv_prog.c |  13 +
>  14 files changed, 1065 insertions(+), 473 deletions(-)
>  create mode 100644 tools/lib/bpf/features.c
>  create mode 100644 tools/testing/selftests/bpf/progs/priv_map.c
>  create mode 100644 tools/testing/selftests/bpf/progs/priv_prog.c
> 
> -- 
> 2.34.1
> 
>