Commit b8604247 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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libbpf: Remove assumption of single contiguous memory for BTF data 



Refactor internals of struct btf to remove assumptions that BTF header, type
data, and string data are layed out contiguously in a memory in a single
memory allocation. Now we have three separate pointers pointing to the start
of each respective are: header, types, strings. In the next patches, these
pointers will be re-assigned to point to independently allocated memory areas,
if BTF needs to be modified.

Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200926011357.2366158-3-andriin@fb.com
parent 740e69c3

tools/lib/bpf/bpf.c

+1 −1
Original line number Diff line number Diff line
@@ -846,7 +846,7 @@ int bpf_raw_tracepoint_open(const char *name, int prog_fd) 
	return sys_bpf(BPF_RAW_TRACEPOINT_OPEN, &attr, sizeof(attr));

}



int bpf_load_btf(void *btf, __u32 btf_size, char *log_buf, __u32 log_buf_size,

int bpf_load_btf(const void *btf, __u32 btf_size, char *log_buf, __u32 log_buf_size,

		 bool do_log)

{

	union bpf_attr attr = {};

tools/lib/bpf/bpf.h

+1 −1
Original line number Diff line number Diff line
@@ -234,7 +234,7 @@ LIBBPF_API int bpf_prog_query(int target_fd, enum bpf_attach_type type, 
			      __u32 query_flags, __u32 *attach_flags,

			      __u32 *prog_ids, __u32 *prog_cnt);

LIBBPF_API int bpf_raw_tracepoint_open(const char *name, int prog_fd);

LIBBPF_API int bpf_load_btf(void *btf, __u32 btf_size, char *log_buf,

LIBBPF_API int bpf_load_btf(const void *btf, __u32 btf_size, char *log_buf,

			    __u32 log_buf_size, bool do_log);

LIBBPF_API int bpf_task_fd_query(int pid, int fd, __u32 flags, char *buf,

				 __u32 *buf_len, __u32 *prog_id, __u32 *fd_type,

tools/lib/bpf/btf.c

+58 −41
Original line number Diff line number Diff line
@@ -27,18 +27,37 @@ 
static struct btf_type btf_void;



struct btf {

	union {

	void *raw_data;

	__u32 raw_size;



	/*

	 * When BTF is loaded from ELF or raw memory it is stored

	 * in contiguous memory block, pointed to by raw_data pointer, and

	 * hdr, types_data, and strs_data point inside that memory region to

	 * respective parts of BTF representation:

	 *

	 * +--------------------------------+

	 * |  Header  |  Types  |  Strings  |

	 * +--------------------------------+

	 * ^          ^         ^

	 * |          |         |

	 * hdr        |         |

	 * types_data-+         |

	 * strs_data------------+

	 */

	struct btf_header *hdr;

		void *data;

	};

	void *types_data;

	void *strs_data;



	/* type ID to `struct btf_type *` lookup index */

	__u32 *type_offs;

	__u32 type_offs_cap;

	const char *strings;

	void *nohdr_data;

	void *types_data;

	__u32 nr_types;

	__u32 data_size;



	/* BTF object FD, if loaded into kernel */

	int fd;



	/* Pointer size (in bytes) for a target architecture of this BTF */

	int ptr_sz;

};
@@ -80,7 +99,7 @@ static int btf_parse_hdr(struct btf *btf) 
	const struct btf_header *hdr = btf->hdr;

	__u32 meta_left;



	if (btf->data_size < sizeof(struct btf_header)) {

	if (btf->raw_size < sizeof(struct btf_header)) {

		pr_debug("BTF header not found\n");

		return -EINVAL;

	}
@@ -100,7 +119,7 @@ static int btf_parse_hdr(struct btf *btf) 
		return -ENOTSUP;

	}



	meta_left = btf->data_size - sizeof(*hdr);

	meta_left = btf->raw_size - sizeof(*hdr);

	if (!meta_left) {

		pr_debug("BTF has no data\n");

		return -EINVAL;
@@ -126,15 +145,13 @@ static int btf_parse_hdr(struct btf *btf) 
		return -EINVAL;

	}



	btf->nohdr_data = btf->hdr + 1;



	return 0;

}



static int btf_parse_str_sec(struct btf *btf)

{

	const struct btf_header *hdr = btf->hdr;

	const char *start = btf->nohdr_data + hdr->str_off;

	const char *start = btf->strs_data;

	const char *end = start + btf->hdr->str_len;



	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_STR_OFFSET ||
@@ -143,8 +160,6 @@ static int btf_parse_str_sec(struct btf *btf) 
		return -EINVAL;

	}



	btf->strings = start;



	return 0;

}
@@ -186,11 +201,9 @@ static int btf_type_size(const struct btf_type *t) 
static int btf_parse_type_sec(struct btf *btf)

{

	struct btf_header *hdr = btf->hdr;

	void *next_type = btf->nohdr_data + hdr->type_off;

	void *next_type = btf->types_data;

	void *end_type = next_type + hdr->type_len;



	btf->types_data = next_type;



	while (next_type < end_type) {

		int type_size;

		int err;
@@ -466,7 +479,7 @@ void btf__free(struct btf *btf) 
	if (btf->fd >= 0)

		close(btf->fd);



	free(btf->data);

	free(btf->raw_data);

	free(btf->type_offs);

	free(btf);

}
@@ -482,24 +495,24 @@ struct btf *btf__new(const void *data, __u32 size) 


	btf->fd = -1;



	btf->data = malloc(size);

	if (!btf->data) {

	btf->raw_data = malloc(size);

	if (!btf->raw_data) {

		err = -ENOMEM;

		goto done;

	}

	memcpy(btf->raw_data, data, size);

	btf->raw_size = size;



	memcpy(btf->data, data, size);

	btf->data_size = size;



	btf->hdr = btf->raw_data;

	err = btf_parse_hdr(btf);

	if (err)

		goto done;



	err = btf_parse_str_sec(btf);

	if (err)

		goto done;

	btf->strs_data = btf->raw_data + btf->hdr->hdr_len + btf->hdr->str_off;

	btf->types_data = btf->raw_data + btf->hdr->hdr_len + btf->hdr->type_off;



	err = btf_parse_type_sec(btf);

	err = btf_parse_str_sec(btf);

	err = err ?: btf_parse_type_sec(btf);



done:

	if (err) {
@@ -820,8 +833,9 @@ int btf__finalize_data(struct bpf_object *obj, struct btf *btf) 


int btf__load(struct btf *btf)

{

	__u32 log_buf_size = 0;

	__u32 log_buf_size = 0, raw_size;

	char *log_buf = NULL;

	const void *raw_data;

	int err = 0;



	if (btf->fd >= 0)
@@ -836,8 +850,13 @@ int btf__load(struct btf *btf) 
		*log_buf = 0;

	}



	btf->fd = bpf_load_btf(btf->data, btf->data_size,

			       log_buf, log_buf_size, false);

	raw_data = btf__get_raw_data(btf, &raw_size);

	if (!raw_data) {

		err = -ENOMEM;

		goto done;

	}



	btf->fd = bpf_load_btf(raw_data, raw_size, log_buf, log_buf_size, false);

	if (btf->fd < 0) {

		if (!log_buf || errno == ENOSPC) {

			log_buf_size = max((__u32)BPF_LOG_BUF_SIZE,
@@ -870,14 +889,14 @@ void btf__set_fd(struct btf *btf, int fd) 


const void *btf__get_raw_data(const struct btf *btf, __u32 *size)

{

	*size = btf->data_size;

	return btf->data;

	*size = btf->raw_size;

	return btf->raw_data;

}



const char *btf__name_by_offset(const struct btf *btf, __u32 offset)

{

	if (offset < btf->hdr->str_len)

		return &btf->strings[offset];

		return btf->strs_data + offset;

	else

		return NULL;

}
@@ -1860,8 +1879,7 @@ static int btf_str_remap_offset(__u32 *str_off_ptr, void *ctx) 
 */

static int btf_dedup_strings(struct btf_dedup *d)

{

	const struct btf_header *hdr = d->btf->hdr;

	char *start = (char *)d->btf->nohdr_data + hdr->str_off;

	char *start = d->btf->strs_data;

	char *end = start + d->btf->hdr->str_len;

	char *p = start, *tmp_strs = NULL;

	struct btf_str_ptrs strs = {
@@ -2970,12 +2988,11 @@ static int btf_dedup_compact_types(struct btf_dedup *d) 
	d->btf->type_offs = new_offs;



	/* make sure string section follows type information without gaps */

	d->btf->hdr->str_off = p - d->btf->nohdr_data;

	memmove(p, d->btf->strings, d->btf->hdr->str_len);

	d->btf->strings = p;

	p += d->btf->hdr->str_len;

	d->btf->hdr->str_off = p - d->btf->types_data;

	memmove(p, d->btf->strs_data, d->btf->hdr->str_len);

	d->btf->strs_data = p;



	d->btf->data_size = p - d->btf->data;

	d->btf->raw_size = d->btf->hdr->hdr_len + d->btf->hdr->type_len + d->btf->hdr->str_len;

	return 0;

}