Commit 05f9cdd5 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

libbpf: Move feature detection code into its own file 



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.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-24-andrii@kernel.org
parent d6dd1d49

tools/lib/bpf/Build

+1 −1
Original line number Diff line number Diff line 
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

tools/lib/bpf/elf.c

+0 −2
Original line number Diff line number Diff line
@@ -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.

tools/lib/bpf/features.c

0 → 100644
+463 −0
Original line number Diff line number Diff line 
// 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;

}



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;

}

tools/lib/bpf/libbpf.c

+1 −462

File changed.

Preview size limit exceeded, changes collapsed.

tools/lib/bpf/libbpf_internal.h

+13 −1
Original line number Diff line number Diff line
@@ -361,10 +361,20 @@ 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);
@@ -626,4 +636,6 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt, 
int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,

				 unsigned long **poffsets, size_t *pcnt);



int probe_fd(int fd);



#endif /* __LIBBPF_LIBBPF_INTERNAL_H */