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Vendor deprecated btf_ext APIs and structs
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Some btf_ext-related APIs in libbpf are being deprecated because they
make incorrect assumptions. They're being used only by bcc currently, so
vendor them before they get deleted.

After / as part of iovisor#3660, may need to revisit the incorrect assumptions
being made here.

The functions and structs were ripped directly from libbpf with minimal
changes:
  * Change void* arithmetic to uint8_t
  * __u32 -> uint32_t and similar
  * Add a wrapping namespace
  * `rec_size` functions were not needed - just grab the rec_size
directly since type is no longer opaque to bcc
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@davemarchevsky
davemarchevsky committed Jan 4, 2022
1 parent b82de2d commit 3a17a38
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Showing 2 changed files with 409 additions and 26 deletions.
334 changes: 327 additions & 7 deletions src/cc/bcc_btf.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -21,10 +21,330 @@
#include "libbpf.h"
#include "bcc_libbpf_inc.h"
#include <vector>
#include <byteswap.h>

#define BCC_MAX_ERRNO 4095
#define BCC_IS_ERR_VALUE(x) ((x) >= (unsigned long)-BCC_MAX_ERRNO)
#define BCC_IS_ERR(ptr) BCC_IS_ERR_VALUE((unsigned long)ptr)
#ifndef offsetofend
# define offsetofend(TYPE, FIELD) \
(offsetof(TYPE, FIELD) + sizeof(((TYPE *)0)->FIELD))
#endif

namespace btf_ext_vendored {

/* The minimum bpf_func_info checked by the loader */
struct bpf_func_info_min {
uint32_t insn_off;
uint32_t type_id;
};

/* The minimum bpf_line_info checked by the loader */
struct bpf_line_info_min {
uint32_t insn_off;
uint32_t file_name_off;
uint32_t line_off;
uint32_t line_col;
};

struct btf_ext_sec_setup_param {
uint32_t off;
uint32_t len;
uint32_t min_rec_size;
struct btf_ext_info *ext_info;
const char *desc;
};

static int btf_ext_setup_info(struct btf_ext *btf_ext,
struct btf_ext_sec_setup_param *ext_sec)
{
const struct btf_ext_info_sec *sinfo;
struct btf_ext_info *ext_info;
uint32_t info_left, record_size;
/* The start of the info sec (including the __u32 record_size). */
void *info;

if (ext_sec->len == 0)
return 0;

if (ext_sec->off & 0x03) {
/*pr_debug(".BTF.ext %s section is not aligned to 4 bytes\n",
ext_sec->desc);*/
return -EINVAL;
}

info = (uint8_t*)btf_ext->data + btf_ext->hdr->hdr_len + ext_sec->off;
info_left = ext_sec->len;

if ((uint8_t*)btf_ext->data + btf_ext->data_size < (uint8_t*)info + ext_sec->len) {
/*pr_debug("%s section (off:%u len:%u) is beyond the end of the ELF section .BTF.ext\n",
ext_sec->desc, ext_sec->off, ext_sec->len);*/
return -EINVAL;
}

/* At least a record size */
if (info_left < sizeof(uint32_t)) {
/*pr_debug(".BTF.ext %s record size not found\n", ext_sec->desc);*/
return -EINVAL;
}

/* The record size needs to meet the minimum standard */
record_size = *(uint32_t *)info;
if (record_size < ext_sec->min_rec_size ||
record_size & 0x03) {
/*pr_debug("%s section in .BTF.ext has invalid record size %u\n",
ext_sec->desc, record_size);*/
return -EINVAL;
}

sinfo = (struct btf_ext_info_sec*)((uint8_t*)info + sizeof(uint32_t));
info_left -= sizeof(uint32_t);

/* If no records, return failure now so .BTF.ext won't be used. */
if (!info_left) {
/*pr_debug("%s section in .BTF.ext has no records", ext_sec->desc);*/
return -EINVAL;
}

while (info_left) {
unsigned int sec_hdrlen = sizeof(struct btf_ext_info_sec);
uint64_t total_record_size;
uint32_t num_records;

if (info_left < sec_hdrlen) {
/*pr_debug("%s section header is not found in .BTF.ext\n",
ext_sec->desc);*/
return -EINVAL;
}

num_records = sinfo->num_info;
if (num_records == 0) {
/*pr_debug("%s section has incorrect num_records in .BTF.ext\n",
ext_sec->desc);*/
return -EINVAL;
}

total_record_size = sec_hdrlen +
(uint64_t)num_records * record_size;
if (info_left < total_record_size) {
/*pr_debug("%s section has incorrect num_records in .BTF.ext\n",
ext_sec->desc);*/
return -EINVAL;
}

info_left -= total_record_size;
sinfo = (struct btf_ext_info_sec *)((uint8_t*)sinfo + total_record_size);
}

ext_info = ext_sec->ext_info;
ext_info->len = ext_sec->len - sizeof(uint32_t);
ext_info->rec_size = record_size;
ext_info->info = (uint8_t*)info + sizeof(uint32_t);

return 0;
}

static int btf_ext_setup_func_info(struct btf_ext *btf_ext)
{
struct btf_ext_sec_setup_param param = {
.off = btf_ext->hdr->func_info_off,
.len = btf_ext->hdr->func_info_len,
.min_rec_size = sizeof(struct bpf_func_info_min),
.ext_info = &btf_ext->func_info,
.desc = "func_info"
};

return btf_ext_setup_info(btf_ext, &param);
}

static int btf_ext_setup_line_info(struct btf_ext *btf_ext)
{
struct btf_ext_sec_setup_param param = {
.off = btf_ext->hdr->line_info_off,
.len = btf_ext->hdr->line_info_len,
.min_rec_size = sizeof(struct bpf_line_info_min),
.ext_info = &btf_ext->line_info,
.desc = "line_info",
};

return btf_ext_setup_info(btf_ext, &param);
}

static int btf_ext_setup_core_relos(struct btf_ext *btf_ext)
{
struct btf_ext_sec_setup_param param = {
.off = btf_ext->hdr->core_relo_off,
.len = btf_ext->hdr->core_relo_len,
.min_rec_size = sizeof(struct bpf_core_relo),
.ext_info = &btf_ext->core_relo_info,
.desc = "core_relo",
};

return btf_ext_setup_info(btf_ext, &param);
}

static int btf_ext_parse_hdr(uint8_t *data, uint32_t data_size)
{
const struct btf_ext_header *hdr = (struct btf_ext_header *)data;

if (data_size < offsetofend(struct btf_ext_header, hdr_len) ||
data_size < hdr->hdr_len) {
//pr_debug("BTF.ext header not found");
return -EINVAL;
}

if (hdr->magic == bswap_16(BTF_MAGIC)) {
//pr_warn("BTF.ext in non-native endianness is not supported\n");
return -ENOTSUP;
} else if (hdr->magic != BTF_MAGIC) {
//pr_debug("Invalid BTF.ext magic:%x\n", hdr->magic);
return -EINVAL;
}

if (hdr->version != BTF_VERSION) {
//pr_debug("Unsupported BTF.ext version:%u\n", hdr->version);
return -ENOTSUP;
}

if (hdr->flags) {
//pr_debug("Unsupported BTF.ext flags:%x\n", hdr->flags);
return -ENOTSUP;
}

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

return 0;
}

void btf_ext__free(struct btf_ext *btf_ext)
{
if((!btf_ext) || BCC_IS_ERR_VALUE((unsigned long)btf_ext))
return;
free(btf_ext->data);
free(btf_ext);
}

struct btf_ext *btf_ext__new(const uint8_t *data, uint32_t size)
{
struct btf_ext *btf_ext;
int err;

btf_ext = (struct btf_ext*)calloc(1, sizeof(struct btf_ext));
if (!btf_ext)
return (struct btf_ext*)-ENOMEM;

btf_ext->data_size = size;
btf_ext->data = malloc(size);
if (!btf_ext->data) {
err = -ENOMEM;
goto done;
}
memcpy(btf_ext->data, data, size);

err = btf_ext_parse_hdr((uint8_t*)btf_ext->data, size);
if (err)
goto done;

if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, line_info_len)) {
err = -EINVAL;
goto done;
}

err = btf_ext_setup_func_info(btf_ext);
if (err)
goto done;

err = btf_ext_setup_line_info(btf_ext);
if (err)
goto done;

if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len)) {
err = -EINVAL;
goto done;
}

err = btf_ext_setup_core_relos(btf_ext);
if (err)
goto done;

done:
if (err) {
btf_ext__free(btf_ext);
return (struct btf_ext*)err;
}

return btf_ext;
}

static int btf_ext_reloc_info(const struct btf *btf,
const struct btf_ext_info *ext_info,
const char *sec_name, uint32_t insns_cnt,
void **info, uint32_t *cnt)
{
uint32_t sec_hdrlen = sizeof(struct btf_ext_info_sec);
uint32_t i, record_size, existing_len, records_len;
struct btf_ext_info_sec *sinfo;
const char *info_sec_name;
uint64_t remain_len;
void *data;

record_size = ext_info->rec_size;
sinfo = (struct btf_ext_info_sec*)ext_info->info;
remain_len = ext_info->len;
while (remain_len > 0) {
records_len = sinfo->num_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 = (struct btf_ext_info_sec*)((uint8_t *)sinfo + sec_hdrlen + records_len);
continue;
}

existing_len = (*cnt) * record_size;
data = realloc(*info, existing_len + records_len);
if (!data)
return -ENOMEM;

memcpy((uint8_t*)data + existing_len, sinfo->data, records_len);
/* adjust insn_off only, the rest data will be passed
* to the kernel.
*/
for (i = 0; i < sinfo->num_info; i++) {
uint32_t *insn_off;

insn_off = (uint32_t *)((uint8_t*)data + existing_len + (i * record_size));
*insn_off = *insn_off / sizeof(struct bpf_insn) + insns_cnt;
}
*info = data;
*cnt += sinfo->num_info;
return 0;
}

return -ENOENT;
}

int btf_ext__reloc_func_info(const struct btf *btf,
const struct btf_ext *btf_ext,
const char *sec_name, uint32_t insns_cnt,
void **func_info, uint32_t *cnt)
{
return btf_ext_vendored::btf_ext_reloc_info(btf, &btf_ext->func_info, sec_name,
insns_cnt, func_info, cnt);
}

int btf_ext__reloc_line_info(const struct btf *btf,
const struct btf_ext *btf_ext,
const char *sec_name, uint32_t insns_cnt,
void **line_info, uint32_t *cnt)
{
return btf_ext_vendored::btf_ext_reloc_info(btf, &btf_ext->line_info, sec_name,
insns_cnt, line_info, cnt);
}

} // namespace btf_ext_vendored

namespace ebpf {

Expand Down Expand Up @@ -185,7 +505,7 @@ void BTF::adjust(uint8_t *btf_sec, uintptr_t btf_sec_size,
}

struct btf_header *hdr = (struct btf_header *)btf_sec;
struct bcc_btf_ext_header *ehdr = (struct bcc_btf_ext_header *)btf_ext_sec;
struct btf_ext_vendored::btf_ext_header *ehdr = (struct btf_ext_vendored::btf_ext_header *)btf_ext_sec;

// Fixup btf for old kernels or kernel requirements.
fixup_btf(btf_sec + hdr->hdr_len + hdr->type_off, hdr->type_len,
Expand Down Expand Up @@ -259,7 +579,7 @@ int BTF::load(uint8_t *btf_sec, uintptr_t btf_sec_size,
uint8_t *btf_ext_sec, uintptr_t btf_ext_sec_size,
std::map<std::string, std::string> &remapped_sources) {
struct btf *btf;
struct btf_ext *btf_ext;
struct btf_ext_vendored::btf_ext *btf_ext;
uint8_t *new_btf_sec = NULL;
uintptr_t new_btf_sec_size = 0;

Expand All @@ -283,7 +603,7 @@ int BTF::load(uint8_t *btf_sec, uintptr_t btf_sec_size,
return -1;
}

btf_ext = btf_ext__new(btf_ext_sec, btf_ext_sec_size);
btf_ext = btf_ext_vendored::btf_ext__new(btf_ext_sec, btf_ext_sec_size);
if (BCC_IS_ERR(btf_ext)) {
btf__free(btf);
warning("Processing .BTF.ext section failed\n");
Expand All @@ -309,17 +629,17 @@ int BTF::get_btf_info(const char *fname,
*func_info = *line_info = NULL;
*func_info_cnt = *line_info_cnt = 0;

*finfo_rec_size = btf_ext__func_info_rec_size(btf_ext_);
*linfo_rec_size = btf_ext__line_info_rec_size(btf_ext_);
*finfo_rec_size = btf_ext_->func_info.rec_size;
*linfo_rec_size = btf_ext_->line_info.rec_size;

ret = btf_ext__reloc_func_info(btf_, btf_ext_, fname, 0,
ret = btf_ext_vendored::btf_ext__reloc_func_info(btf_, btf_ext_, fname, 0,
func_info, func_info_cnt);
if (ret) {
warning(".BTF.ext reloc func_info failed\n");
return ret;
}

ret = btf_ext__reloc_line_info(btf_, btf_ext_, fname, 0,
ret = btf_ext_vendored::btf_ext__reloc_line_info(btf_, btf_ext_, fname, 0,
line_info, line_info_cnt);
if (ret) {
warning(".BTF.ext reloc line_info failed\n");
Expand Down
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