iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

libbpf: Remove assumption of single contiguous memory for BTF data

Browse Source 
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: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200926011357.2366158-3-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-09-25 18:13:50 -07:00 committed by Alexei Starovoitov
parent 740e69c3c5
commit b86042478f
3 changed files with 60 additions and 43 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
tools/lib/bpf/bpf.c
View File

@ -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 = {};

2
tools/lib/bpf/bpf.h
View File

@ -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,

99
tools/lib/bpf/btf.c
View File

@ -27,18 +27,37 @@
static struct btf_type btf_void;
struct btf {
union {
struct btf_header *hdr;
void *data;
};
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 *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 @@ retry_load:
*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;
}