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bpf: libbpf: Refactor and bug fix on the bpf_func_info loading logic
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This patch refactor and fix a bug in the libbpf's bpf_func_info loading
logic.  The bug fix and refactoring are targeting the same
commit 2993e05 ("tools/bpf: add support to read .BTF.ext sections")
which is in the bpf-next branch.

1) In bpf_load_program_xattr(), it should retry when errno == E2BIG
   regardless of log_buf and log_buf_sz.  This patch fixes it.

2) btf_ext__reloc_init() and btf_ext__reloc() are essentially
   the same except btf_ext__reloc_init() always has insns_cnt == 0.
   Hence, btf_ext__reloc_init() is removed.

   btf_ext__reloc() is also renamed to btf_ext__reloc_func_info()
   to get ready for the line_info support in the next patch.

3) Consolidate func_info section logic from "btf_ext_parse_hdr()",
   "btf_ext_validate_func_info()" and "btf_ext__new()" to
   a new function "btf_ext_copy_func_info()" such that similar
   logic can be reused by the later libbpf's line_info patch.

4) The next line_info patch will store line_info_cnt instead of
   line_info_len in the bpf_program because the kernel is taking
   line_info_cnt also.  It will save a few "len" to "cnt" conversions
   and will also save some function args.

   Hence, this patch also makes bpf_program to store func_info_cnt
   instead of func_info_len.

5) btf_ext depends on btf.  e.g. the func_info's type_id
   in ".BTF.ext" is not useful when ".BTF" is absent.
   This patch only init the obj->btf_ext pointer after
   it has successfully init the obj->btf pointer.

   This can avoid always checking "obj->btf && obj->btf_ext"
   together for accessing ".BTF.ext".  Checking "obj->btf_ext"
   alone will do.

6) Move "struct btf_sec_func_info" from btf.h to btf.c.
   There is no external usage outside btf.c.

Fixes: 2993e05 ("tools/bpf: add support to read .BTF.ext sections")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Martin KaFai Lau authored and Alexei Starovoitov committed Dec 9, 2018
1 parent 4d6304c commit f0187f0
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Showing 4 changed files with 177 additions and 177 deletions.
7 changes: 5 additions & 2 deletions tools/lib/bpf/bpf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -205,7 +205,7 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
min(name_len, BPF_OBJ_NAME_LEN - 1));

fd = sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
if (fd >= 0 || !log_buf || !log_buf_sz)
if (fd >= 0)
return fd;

/* After bpf_prog_load, the kernel may modify certain attributes
Expand Down Expand Up @@ -244,10 +244,13 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,

fd = sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));

if (fd >= 0 || !log_buf || !log_buf_sz)
if (fd >= 0)
goto done;
}

if (!log_buf || !log_buf_sz)
goto done;

/* Try again with log */
attr.log_buf = ptr_to_u64(log_buf);
attr.log_size = log_buf_sz;
Expand Down
191 changes: 73 additions & 118 deletions tools/lib/bpf/btf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,13 @@ struct btf_ext {
__u32 func_info_len;
};

struct btf_sec_func_info {
__u32 sec_name_off;
__u32 num_func_info;
/* Followed by num_func_info number of bpf func_info records */
__u8 data[0];
};

/* The minimum bpf_func_info checked by the loader */
struct bpf_func_info_min {
__u32 insn_off;
Expand Down Expand Up @@ -479,41 +486,66 @@ int btf__get_from_id(__u32 id, struct btf **btf)
return err;
}

static int btf_ext_validate_func_info(const void *finfo, __u32 size,
btf_print_fn_t err_log)
static int btf_ext_copy_func_info(struct btf_ext *btf_ext,
__u8 *data, __u32 data_size,
btf_print_fn_t err_log)
{
int sec_hdrlen = sizeof(struct btf_sec_func_info);
__u32 size_left, num_records, record_size;
const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
const struct btf_sec_func_info *sinfo;
__u64 total_record_size;
__u32 info_left, record_size;
/* The start of the info sec (including the __u32 record_size). */
const void *info;

/* data and data_size do not include btf_ext_header from now on */
data = data + hdr->hdr_len;
data_size -= hdr->hdr_len;

if (hdr->func_info_off & 0x03) {
elog("BTF.ext func_info section is not aligned to 4 bytes\n");
return -EINVAL;
}

if (data_size < hdr->func_info_off ||
hdr->func_info_len > data_size - hdr->func_info_off) {
elog("func_info section (off:%u len:%u) is beyond the end of the ELF section .BTF.ext\n",
hdr->func_info_off, hdr->func_info_len);
return -EINVAL;
}

info = data + hdr->func_info_off;
info_left = hdr->func_info_len;

/* At least a func_info record size */
if (size < sizeof(__u32)) {
if (info_left < sizeof(__u32)) {
elog("BTF.ext func_info record size not found");
return -EINVAL;
}

/* The record size needs to meet below minimum standard */
record_size = *(__u32 *)finfo;
/* The record size needs to meet the minimum standard */
record_size = *(__u32 *)info;
if (record_size < sizeof(struct bpf_func_info_min) ||
record_size % sizeof(__u32)) {
record_size & 0x03) {
elog("BTF.ext func_info invalid record size");
return -EINVAL;
}

sinfo = finfo + sizeof(__u32);
size_left = size - sizeof(__u32);
sinfo = info + sizeof(__u32);
info_left -= sizeof(__u32);

/* If no func_info records, return failure now so .BTF.ext
* won't be used.
*/
if (!size_left) {
if (!info_left) {
elog("BTF.ext no func info records");
return -EINVAL;
}

while (size_left) {
if (size_left < sec_hdrlen) {
while (info_left) {
unsigned int sec_hdrlen = sizeof(struct btf_sec_func_info);
__u64 total_record_size;
__u32 num_records;

if (info_left < sec_hdrlen) {
elog("BTF.ext func_info header not found");
return -EINVAL;
}
Expand All @@ -526,24 +558,30 @@ static int btf_ext_validate_func_info(const void *finfo, __u32 size,

total_record_size = sec_hdrlen +
(__u64)num_records * record_size;
if (size_left < total_record_size) {
if (info_left < total_record_size) {
elog("incorrect BTF.ext num_func_info");
return -EINVAL;
}

size_left -= total_record_size;
info_left -= total_record_size;
sinfo = (void *)sinfo + total_record_size;
}

btf_ext->func_info_len = hdr->func_info_len - sizeof(__u32);
btf_ext->func_info_rec_size = record_size;
btf_ext->func_info = malloc(btf_ext->func_info_len);
if (!btf_ext->func_info)
return -ENOMEM;
memcpy(btf_ext->func_info, info + sizeof(__u32),
btf_ext->func_info_len);

return 0;
}

static int btf_ext_parse_hdr(__u8 *data, __u32 data_size,
btf_print_fn_t err_log)
{
const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
__u32 meta_left, last_func_info_pos;
void *finfo;

if (data_size < offsetof(struct btf_ext_header, func_info_off) ||
data_size < hdr->hdr_len) {
Expand All @@ -566,34 +604,12 @@ static int btf_ext_parse_hdr(__u8 *data, __u32 data_size,
return -ENOTSUP;
}

meta_left = data_size - hdr->hdr_len;
if (!meta_left) {
if (data_size == hdr->hdr_len) {
elog("BTF.ext has no data\n");
return -EINVAL;
}

if (meta_left < hdr->func_info_off) {
elog("Invalid BTF.ext func_info section offset:%u\n",
hdr->func_info_off);
return -EINVAL;
}

if (hdr->func_info_off & 0x03) {
elog("BTF.ext func_info section is not aligned to 4 bytes\n");
return -EINVAL;
}

last_func_info_pos = hdr->hdr_len + hdr->func_info_off +
hdr->func_info_len;
if (last_func_info_pos > data_size) {
elog("Invalid BTF.ext func_info section size:%u\n",
hdr->func_info_len);
return -EINVAL;
}

finfo = data + hdr->hdr_len + hdr->func_info_off;
return btf_ext_validate_func_info(finfo, hdr->func_info_len,
err_log);
return 0;
}

void btf_ext__free(struct btf_ext *btf_ext)
Expand All @@ -607,10 +623,7 @@ void btf_ext__free(struct btf_ext *btf_ext)

struct btf_ext *btf_ext__new(__u8 *data, __u32 size, btf_print_fn_t err_log)
{
const struct btf_ext_header *hdr;
struct btf_ext *btf_ext;
void *org_fdata, *fdata;
__u32 hdrlen, size_u32;
int err;

err = btf_ext_parse_hdr(data, size, err_log);
Expand All @@ -621,81 +634,18 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size, btf_print_fn_t err_log)
if (!btf_ext)
return ERR_PTR(-ENOMEM);

hdr = (const struct btf_ext_header *)data;
hdrlen = hdr->hdr_len;
size_u32 = sizeof(__u32);
fdata = malloc(hdr->func_info_len - size_u32);
if (!fdata) {
free(btf_ext);
return ERR_PTR(-ENOMEM);
err = btf_ext_copy_func_info(btf_ext, data, size, err_log);
if (err) {
btf_ext__free(btf_ext);
return ERR_PTR(err);
}

/* remember record size and copy rest of func_info data */
org_fdata = data + hdrlen + hdr->func_info_off;
btf_ext->func_info_rec_size = *(__u32 *)org_fdata;
memcpy(fdata, org_fdata + size_u32, hdr->func_info_len - size_u32);
btf_ext->func_info = fdata;
btf_ext->func_info_len = hdr->func_info_len - size_u32;

return btf_ext;
}

int btf_ext__reloc_init(struct btf *btf, struct btf_ext *btf_ext,
const char *sec_name, void **func_info,
__u32 *func_info_rec_size, __u32 *func_info_len)
{
__u32 sec_hdrlen = sizeof(struct btf_sec_func_info);
__u32 i, record_size, records_len;
struct btf_sec_func_info *sinfo;
const char *info_sec_name;
__s64 remain_len;
void *data;

record_size = btf_ext->func_info_rec_size;
sinfo = btf_ext->func_info;
remain_len = btf_ext->func_info_len;

while (remain_len > 0) {
records_len = sinfo->num_func_info * record_size;
info_sec_name = btf__name_by_offset(btf, sinfo->sec_name_off);
if (strcmp(info_sec_name, sec_name)) {
remain_len -= sec_hdrlen + records_len;
sinfo = (void *)sinfo + sec_hdrlen + records_len;
continue;
}

data = malloc(records_len);
if (!data)
return -ENOMEM;

memcpy(data, sinfo->data, records_len);

/* adjust the insn_off, the data in .BTF.ext is
* the actual byte offset, and the kernel expects
* the offset in term of bpf_insn.
*
* adjust the insn offset only, the rest data will
* be passed to kernel.
*/
for (i = 0; i < sinfo->num_func_info; i++) {
struct bpf_func_info_min *record;

record = data + i * record_size;
record->insn_off /= sizeof(struct bpf_insn);
}

*func_info = data;
*func_info_len = records_len;
*func_info_rec_size = record_size;
return 0;
}

return -EINVAL;
}

int btf_ext__reloc(struct btf *btf, struct btf_ext *btf_ext,
const char *sec_name, __u32 insns_cnt,
void **func_info, __u32 *func_info_len)
int btf_ext__reloc_func_info(struct btf *btf, struct btf_ext *btf_ext,
const char *sec_name, __u32 insns_cnt,
void **func_info, __u32 *cnt)
{
__u32 sec_hdrlen = sizeof(struct btf_sec_func_info);
__u32 i, record_size, existing_flen, records_len;
Expand All @@ -716,7 +666,7 @@ int btf_ext__reloc(struct btf *btf, struct btf_ext *btf_ext,
continue;
}

existing_flen = *func_info_len;
existing_flen = (*cnt) * record_size;
data = realloc(*func_info, existing_flen + records_len);
if (!data)
return -ENOMEM;
Expand All @@ -734,9 +684,14 @@ int btf_ext__reloc(struct btf *btf, struct btf_ext *btf_ext,
insns_cnt;
}
*func_info = data;
*func_info_len = existing_flen + records_len;
*cnt += sinfo->num_func_info;
return 0;
}

return -EINVAL;
return -ENOENT;
}

__u32 btf_ext__func_info_rec_size(const struct btf_ext *btf_ext)
{
return btf_ext->func_info_rec_size;
}
17 changes: 4 additions & 13 deletions tools/lib/bpf/btf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,13 +53,6 @@ struct btf_ext_header {
__u32 func_info_len;
};

struct btf_sec_func_info {
__u32 sec_name_off;
__u32 num_func_info;
/* Followed by num_func_info number of bpf func_info records */
__u8 data[0];
};

typedef int (*btf_print_fn_t)(const char *, ...)
__attribute__((format(printf, 1, 2)));

Expand All @@ -77,12 +70,10 @@ LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);

struct btf_ext *btf_ext__new(__u8 *data, __u32 size, btf_print_fn_t err_log);
void btf_ext__free(struct btf_ext *btf_ext);
int btf_ext__reloc_init(struct btf *btf, struct btf_ext *btf_ext,
const char *sec_name, void **func_info,
__u32 *func_info_rec_size, __u32 *func_info_len);
int btf_ext__reloc(struct btf *btf, struct btf_ext *btf_ext,
const char *sec_name, __u32 insns_cnt, void **func_info,
__u32 *func_info_len);
int btf_ext__reloc_func_info(struct btf *btf, struct btf_ext *btf_ext,
const char *sec_name, __u32 insns_cnt,
void **func_info, __u32 *func_info_len);
__u32 btf_ext__func_info_rec_size(const struct btf_ext *btf_ext);

#ifdef __cplusplus
} /* extern "C" */
Expand Down
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