Commit fb2426ad authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

libbpf: Expose bpf_find_kernel_btf as a LIBBPF_API 



This patch exposes bpf_find_kernel_btf() as a LIBBPF_API.
It will be used in 'bpftool map dump' in a following patch
to dump a map with btf_vmlinux_value_type_id set.

bpf_find_kernel_btf() is renamed to libbpf_find_kernel_btf()
and moved to btf.c.  As <linux/kernel.h> is included,
some of the max/min type casting needs to be fixed.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200115230031.1102305-1-kafai@fb.com
parent 188a4866

tools/lib/bpf/btf.c

+96 −6
Original line number Diff line number Diff line
@@ -8,6 +8,10 @@ 
#include <fcntl.h>

#include <unistd.h>

#include <errno.h>

#include <sys/utsname.h>

#include <sys/param.h>

#include <sys/stat.h>

#include <linux/kernel.h>

#include <linux/err.h>

#include <linux/btf.h>

#include <gelf.h>
@@ -20,8 +24,8 @@ 
/* make sure libbpf doesn't use kernel-only integer typedefs */

#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64



#define BTF_MAX_NR_TYPES 0x7fffffff

#define BTF_MAX_STR_OFFSET 0x7fffffff

#define BTF_MAX_NR_TYPES 0x7fffffffU

#define BTF_MAX_STR_OFFSET 0x7fffffffU



static struct btf_type btf_void;
@@ -53,7 +57,7 @@ static int btf_add_type(struct btf *btf, struct btf_type *t) 
		if (btf->types_size == BTF_MAX_NR_TYPES)

			return -E2BIG;



		expand_by = max(btf->types_size >> 2, 16);

		expand_by = max(btf->types_size >> 2, 16U);

		new_size = min(BTF_MAX_NR_TYPES, btf->types_size + expand_by);



		new_types = realloc(btf->types, sizeof(*new_types) * new_size);
@@ -289,7 +293,7 @@ int btf__align_of(const struct btf *btf, __u32 id) 
	switch (kind) {

	case BTF_KIND_INT:

	case BTF_KIND_ENUM:

		return min(sizeof(void *), t->size);

		return min(sizeof(void *), (size_t)t->size);

	case BTF_KIND_PTR:

		return sizeof(void *);

	case BTF_KIND_TYPEDEF:
@@ -1401,7 +1405,7 @@ static int btf_dedup_hypot_map_add(struct btf_dedup *d, 
	if (d->hypot_cnt == d->hypot_cap) {

		__u32 *new_list;



		d->hypot_cap += max(16, d->hypot_cap / 2);

		d->hypot_cap += max((size_t)16, d->hypot_cap / 2);

		new_list = realloc(d->hypot_list, sizeof(__u32) * d->hypot_cap);

		if (!new_list)

			return -ENOMEM;
@@ -1697,7 +1701,7 @@ static int btf_dedup_strings(struct btf_dedup *d) 
		if (strs.cnt + 1 > strs.cap) {

			struct btf_str_ptr *new_ptrs;



			strs.cap += max(strs.cnt / 2, 16);

			strs.cap += max(strs.cnt / 2, 16U);

			new_ptrs = realloc(strs.ptrs,

					   sizeof(strs.ptrs[0]) * strs.cap);

			if (!new_ptrs) {
@@ -2931,3 +2935,89 @@ static int btf_dedup_remap_types(struct btf_dedup *d) 
	}

	return 0;

}



static struct btf *btf_load_raw(const char *path)

{

	struct btf *btf;

	size_t read_cnt;

	struct stat st;

	void *data;

	FILE *f;



	if (stat(path, &st))

		return ERR_PTR(-errno);



	data = malloc(st.st_size);

	if (!data)

		return ERR_PTR(-ENOMEM);



	f = fopen(path, "rb");

	if (!f) {

		btf = ERR_PTR(-errno);

		goto cleanup;

	}



	read_cnt = fread(data, 1, st.st_size, f);

	fclose(f);

	if (read_cnt < st.st_size) {

		btf = ERR_PTR(-EBADF);

		goto cleanup;

	}



	btf = btf__new(data, read_cnt);



cleanup:

	free(data);

	return btf;

}



/*

 * Probe few well-known locations for vmlinux kernel image and try to load BTF

 * data out of it to use for target BTF.

 */

struct btf *libbpf_find_kernel_btf(void)

{

	struct {

		const char *path_fmt;

		bool raw_btf;

	} locations[] = {

		/* try canonical vmlinux BTF through sysfs first */

		{ "/sys/kernel/btf/vmlinux", true /* raw BTF */ },

		/* fall back to trying to find vmlinux ELF on disk otherwise */

		{ "/boot/vmlinux-%1$s" },

		{ "/lib/modules/%1$s/vmlinux-%1$s" },

		{ "/lib/modules/%1$s/build/vmlinux" },

		{ "/usr/lib/modules/%1$s/kernel/vmlinux" },

		{ "/usr/lib/debug/boot/vmlinux-%1$s" },

		{ "/usr/lib/debug/boot/vmlinux-%1$s.debug" },

		{ "/usr/lib/debug/lib/modules/%1$s/vmlinux" },

	};

	char path[PATH_MAX + 1];

	struct utsname buf;

	struct btf *btf;

	int i;



	uname(&buf);



	for (i = 0; i < ARRAY_SIZE(locations); i++) {

		snprintf(path, PATH_MAX, locations[i].path_fmt, buf.release);



		if (access(path, R_OK))

			continue;



		if (locations[i].raw_btf)

			btf = btf_load_raw(path);

		else

			btf = btf__parse_elf(path, NULL);



		pr_debug("loading kernel BTF '%s': %ld\n",

			 path, IS_ERR(btf) ? PTR_ERR(btf) : 0);

		if (IS_ERR(btf))

			continue;



		return btf;

	}



	pr_warn("failed to find valid kernel BTF\n");

	return ERR_PTR(-ESRCH);

}

tools/lib/bpf/btf.h

+2 −0
Original line number Diff line number Diff line
@@ -102,6 +102,8 @@ LIBBPF_API int btf_ext__reloc_line_info(const struct btf *btf, 
LIBBPF_API __u32 btf_ext__func_info_rec_size(const struct btf_ext *btf_ext);

LIBBPF_API __u32 btf_ext__line_info_rec_size(const struct btf_ext *btf_ext);



LIBBPF_API struct btf *libbpf_find_kernel_btf(void);



struct btf_dedup_opts {

	unsigned int dedup_table_size;

	bool dont_resolve_fwds;

tools/lib/bpf/libbpf.c

+3 −90
Original line number Diff line number Diff line
@@ -73,7 +73,6 @@ 


#define __printf(a, b)	__attribute__((format(printf, a, b)))



static struct btf *bpf_find_kernel_btf(void);

static struct bpf_map *bpf_object__add_map(struct bpf_object *obj);

static struct bpf_program *bpf_object__find_prog_by_idx(struct bpf_object *obj,

							int idx);
@@ -848,7 +847,7 @@ static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj) 
			continue;



		if (!kern_btf) {

			kern_btf = bpf_find_kernel_btf();

			kern_btf = libbpf_find_kernel_btf();

			if (IS_ERR(kern_btf))

				return PTR_ERR(kern_btf);

		}
@@ -4300,92 +4299,6 @@ static int bpf_core_reloc_insn(struct bpf_program *prog, 
	return 0;

}



static struct btf *btf_load_raw(const char *path)

{

	struct btf *btf;

	size_t read_cnt;

	struct stat st;

	void *data;

	FILE *f;



	if (stat(path, &st))

		return ERR_PTR(-errno);



	data = malloc(st.st_size);

	if (!data)

		return ERR_PTR(-ENOMEM);



	f = fopen(path, "rb");

	if (!f) {

		btf = ERR_PTR(-errno);

		goto cleanup;

	}



	read_cnt = fread(data, 1, st.st_size, f);

	fclose(f);

	if (read_cnt < st.st_size) {

		btf = ERR_PTR(-EBADF);

		goto cleanup;

	}



	btf = btf__new(data, read_cnt);



cleanup:

	free(data);

	return btf;

}



/*

 * Probe few well-known locations for vmlinux kernel image and try to load BTF

 * data out of it to use for target BTF.

 */

static struct btf *bpf_find_kernel_btf(void)

{

	struct {

		const char *path_fmt;

		bool raw_btf;

	} locations[] = {

		/* try canonical vmlinux BTF through sysfs first */

		{ "/sys/kernel/btf/vmlinux", true /* raw BTF */ },

		/* fall back to trying to find vmlinux ELF on disk otherwise */

		{ "/boot/vmlinux-%1$s" },

		{ "/lib/modules/%1$s/vmlinux-%1$s" },

		{ "/lib/modules/%1$s/build/vmlinux" },

		{ "/usr/lib/modules/%1$s/kernel/vmlinux" },

		{ "/usr/lib/debug/boot/vmlinux-%1$s" },

		{ "/usr/lib/debug/boot/vmlinux-%1$s.debug" },

		{ "/usr/lib/debug/lib/modules/%1$s/vmlinux" },

	};

	char path[PATH_MAX + 1];

	struct utsname buf;

	struct btf *btf;

	int i;



	uname(&buf);



	for (i = 0; i < ARRAY_SIZE(locations); i++) {

		snprintf(path, PATH_MAX, locations[i].path_fmt, buf.release);



		if (access(path, R_OK))

			continue;



		if (locations[i].raw_btf)

			btf = btf_load_raw(path);

		else

			btf = btf__parse_elf(path, NULL);



		pr_debug("loading kernel BTF '%s': %ld\n",

			 path, IS_ERR(btf) ? PTR_ERR(btf) : 0);

		if (IS_ERR(btf))

			continue;



		return btf;

	}



	pr_warn("failed to find valid kernel BTF\n");

	return ERR_PTR(-ESRCH);

}



/* Output spec definition in the format:

 * [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>,

 * where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b
@@ -4620,7 +4533,7 @@ bpf_core_reloc_fields(struct bpf_object *obj, const char *targ_btf_path) 
	if (targ_btf_path)

		targ_btf = btf__parse_elf(targ_btf_path, NULL);

	else

		targ_btf = bpf_find_kernel_btf();

		targ_btf = libbpf_find_kernel_btf();

	if (IS_ERR(targ_btf)) {

		pr_warn("failed to get target BTF: %ld\n", PTR_ERR(targ_btf));

		return PTR_ERR(targ_btf);
@@ -6595,7 +6508,7 @@ invalid_prog: 
int libbpf_find_vmlinux_btf_id(const char *name,

			       enum bpf_attach_type attach_type)

{

	struct btf *btf = bpf_find_kernel_btf();

	struct btf *btf = libbpf_find_kernel_btf();

	char raw_tp_btf[128] = BTF_PREFIX;

	char *dst = raw_tp_btf + sizeof(BTF_PREFIX) - 1;

	const char *btf_name;

tools/lib/bpf/libbpf.map

+1 −0
Original line number Diff line number Diff line
@@ -231,4 +231,5 @@ LIBBPF_0.0.7 { 
		bpf_program__is_struct_ops;

		bpf_program__set_struct_ops;

		btf__align_of;

		libbpf_find_kernel_btf;

} LIBBPF_0.0.6;

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