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linux-stable/tools/bpf/bpftool/gen.c
Delyan Kratunov 08d4dba6ae bpftool: Bpf skeletons assert type sizes 
When emitting type declarations in skeletons, bpftool will now also emit
static assertions on the size of the data/bss/rodata/etc fields. This
ensures that in situations where userspace and kernel types have the same
name but differ in size we do not silently produce incorrect results but
instead break the build.

This was reported in [1] and as expected the repro in [2] fails to build
on the new size assert after this change.

  [1]: Closes: https://github.com/libbpf/libbpf/issues/433
  [2]: https://github.com/fuweid/iovisor-bcc-pr-3777

Signed-off-by: Delyan Kratunov <delyank@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Hengqi Chen <hengqi.chen@gmail.com>
Acked-by: Hengqi Chen <hengqi.chen@gmail.com>
Link: https://lore.kernel.org/bpf/f562455d7b3cf338e59a7976f4690ec5a0057f7f.camel@fb.com
2022-02-23 17:33:16 -08:00

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// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/* Copyright (C) 2019 Facebook */
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/err.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include <bpf/libbpf_internal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <bpf/btf.h>
#include "json_writer.h"
#include "main.h"
#define MAX_OBJ_NAME_LEN 64
static void sanitize_identifier(char *name)
{
int i;
for (i = 0; name[i]; i++)
if (!isalnum(name[i]) && name[i] != '_')
name[i] = '_';
}
static bool str_has_prefix(const char *str, const char *prefix)
{
return strncmp(str, prefix, strlen(prefix)) == 0;
}
static bool str_has_suffix(const char *str, const char *suffix)
{
size_t i, n1 = strlen(str), n2 = strlen(suffix);
if (n1 < n2)
return false;
for (i = 0; i < n2; i++) {
if (str[n1 - i - 1] != suffix[n2 - i - 1])
return false;
}
return true;
}
static void get_obj_name(char *name, const char *file)
{
/* Using basename() GNU version which doesn't modify arg. */
strncpy(name, basename(file), MAX_OBJ_NAME_LEN - 1);
name[MAX_OBJ_NAME_LEN - 1] = '\0';
if (str_has_suffix(name, ".o"))
name[strlen(name) - 2] = '\0';
sanitize_identifier(name);
}
static void get_header_guard(char *guard, const char *obj_name)
{
int i;
sprintf(guard, "__%s_SKEL_H__", obj_name);
for (i = 0; guard[i]; i++)
guard[i] = toupper(guard[i]);
}
static bool get_map_ident(const struct bpf_map *map, char *buf, size_t buf_sz)
{
static const char *sfxs[] = { ".data", ".rodata", ".bss", ".kconfig" };
const char *name = bpf_map__name(map);
int i, n;
if (!bpf_map__is_internal(map)) {
snprintf(buf, buf_sz, "%s", name);
return true;
}
for (i = 0, n = ARRAY_SIZE(sfxs); i < n; i++) {
const char *sfx = sfxs[i], *p;
p = strstr(name, sfx);
if (p) {
snprintf(buf, buf_sz, "%s", p + 1);
sanitize_identifier(buf);
return true;
}
}
return false;
}
static bool get_datasec_ident(const char *sec_name, char *buf, size_t buf_sz)
{
static const char *pfxs[] = { ".data", ".rodata", ".bss", ".kconfig" };
int i, n;
for (i = 0, n = ARRAY_SIZE(pfxs); i < n; i++) {
const char *pfx = pfxs[i];
if (str_has_prefix(sec_name, pfx)) {
snprintf(buf, buf_sz, "%s", sec_name + 1);
sanitize_identifier(buf);
return true;
}
}
return false;
}
static void codegen_btf_dump_printf(void *ctx, const char *fmt, va_list args)
{
vprintf(fmt, args);
}
static int codegen_datasec_def(struct bpf_object *obj,
struct btf *btf,
struct btf_dump *d,
const struct btf_type *sec,
const char *obj_name)
{
const char *sec_name = btf__name_by_offset(btf, sec->name_off);
const struct btf_var_secinfo *sec_var = btf_var_secinfos(sec);
int i, err, off = 0, pad_cnt = 0, vlen = btf_vlen(sec);
char var_ident[256], sec_ident[256];
bool strip_mods = false;
if (!get_datasec_ident(sec_name, sec_ident, sizeof(sec_ident)))
return 0;
if (strcmp(sec_name, ".kconfig") != 0)
strip_mods = true;
printf(" struct %s__%s {\n", obj_name, sec_ident);
for (i = 0; i < vlen; i++, sec_var++) {
const struct btf_type *var = btf__type_by_id(btf, sec_var->type);
const char *var_name = btf__name_by_offset(btf, var->name_off);
DECLARE_LIBBPF_OPTS(btf_dump_emit_type_decl_opts, opts,
.field_name = var_ident,
.indent_level = 2,
.strip_mods = strip_mods,
);
int need_off = sec_var->offset, align_off, align;
__u32 var_type_id = var->type;
/* static variables are not exposed through BPF skeleton */
if (btf_var(var)->linkage == BTF_VAR_STATIC)
continue;
if (off > need_off) {
p_err("Something is wrong for %s's variable #%d: need offset %d, already at %d.\n",
sec_name, i, need_off, off);
return -EINVAL;
}
align = btf__align_of(btf, var->type);
if (align <= 0) {
p_err("Failed to determine alignment of variable '%s': %d",
var_name, align);
return -EINVAL;
}
/* Assume 32-bit architectures when generating data section
* struct memory layout. Given bpftool can't know which target
* host architecture it's emitting skeleton for, we need to be
* conservative and assume 32-bit one to ensure enough padding
* bytes are generated for pointer and long types. This will
* still work correctly for 64-bit architectures, because in
* the worst case we'll generate unnecessary padding field,
* which on 64-bit architectures is not strictly necessary and
* would be handled by natural 8-byte alignment. But it still
* will be a correct memory layout, based on recorded offsets
* in BTF.
*/
if (align > 4)
align = 4;
align_off = (off + align - 1) / align * align;
if (align_off != need_off) {
printf("\t\tchar __pad%d[%d];\n",
pad_cnt, need_off - off);
pad_cnt++;
}
/* sanitize variable name, e.g., for static vars inside
* a function, it's name is '<function name>.<variable name>',
* which we'll turn into a '<function name>_<variable name>'
*/
var_ident[0] = '\0';
strncat(var_ident, var_name, sizeof(var_ident) - 1);
sanitize_identifier(var_ident);
printf("\t\t");
err = btf_dump__emit_type_decl(d, var_type_id, &opts);
if (err)
return err;
printf(";\n");
off = sec_var->offset + sec_var->size;
}
printf(" } *%s;\n", sec_ident);
return 0;
}
static const struct btf_type *find_type_for_map(struct btf *btf, const char *map_ident)
{
int n = btf__type_cnt(btf), i;
char sec_ident[256];
for (i = 1; i < n; i++) {
const struct btf_type *t = btf__type_by_id(btf, i);
const char *name;
if (!btf_is_datasec(t))
continue;
name = btf__str_by_offset(btf, t->name_off);
if (!get_datasec_ident(name, sec_ident, sizeof(sec_ident)))
continue;
if (strcmp(sec_ident, map_ident) == 0)
return t;
}
return NULL;
}
static int codegen_datasecs(struct bpf_object *obj, const char *obj_name)
{
struct btf *btf = bpf_object__btf(obj);
struct btf_dump *d;
struct bpf_map *map;
const struct btf_type *sec;
char map_ident[256];
int err = 0;
d = btf_dump__new(btf, codegen_btf_dump_printf, NULL, NULL);
err = libbpf_get_error(d);
if (err)
return err;
bpf_object__for_each_map(map, obj) {
/* only generate definitions for memory-mapped internal maps */
if (!bpf_map__is_internal(map))
continue;
if (!(bpf_map__map_flags(map) & BPF_F_MMAPABLE))
continue;
if (!get_map_ident(map, map_ident, sizeof(map_ident)))
continue;
sec = find_type_for_map(btf, map_ident);
/* In some cases (e.g., sections like .rodata.cst16 containing
* compiler allocated string constants only) there will be
* special internal maps with no corresponding DATASEC BTF
* type. In such case, generate empty structs for each such
* map. It will still be memory-mapped and its contents
* accessible from user-space through BPF skeleton.
*/
if (!sec) {
printf(" struct %s__%s {\n", obj_name, map_ident);
printf(" } *%s;\n", map_ident);
} else {
err = codegen_datasec_def(obj, btf, d, sec, obj_name);
if (err)
goto out;
}
}
out:
btf_dump__free(d);
return err;
}
static void codegen(const char *template, ...)
{
const char *src, *end;
int skip_tabs = 0, n;
char *s, *dst;
va_list args;
char c;
n = strlen(template);
s = malloc(n + 1);
if (!s)
exit(-1);
src = template;
dst = s;
/* find out "baseline" indentation to skip */
while ((c = *src++)) {
if (c == '\t') {
skip_tabs++;
} else if (c == '\n') {
break;
} else {
p_err("unrecognized character at pos %td in template '%s': '%c'",
src - template - 1, template, c);
free(s);
exit(-1);
}
}
while (*src) {
/* skip baseline indentation tabs */
for (n = skip_tabs; n > 0; n--, src++) {
if (*src != '\t') {
p_err("not enough tabs at pos %td in template '%s'",
src - template - 1, template);
free(s);
exit(-1);
}
}
/* trim trailing whitespace */
end = strchrnul(src, '\n');
for (n = end - src; n > 0 && isspace(src[n - 1]); n--)
;
memcpy(dst, src, n);
dst += n;
if (*end)
*dst++ = '\n';
src = *end ? end + 1 : end;
}
*dst++ = '\0';
/* print out using adjusted template */
va_start(args, template);
n = vprintf(s, args);
va_end(args);
free(s);
}
static void print_hex(const char *data, int data_sz)
{
int i, len;
for (i = 0, len = 0; i < data_sz; i++) {
int w = data[i] ? 4 : 2;
len += w;
if (len > 78) {
printf("\\\n");
len = w;
}
if (!data[i])
printf("\\0");
else
printf("\\x%02x", (unsigned char)data[i]);
}
}
static size_t bpf_map_mmap_sz(const struct bpf_map *map)
{
long page_sz = sysconf(_SC_PAGE_SIZE);
size_t map_sz;
map_sz = (size_t)roundup(bpf_map__value_size(map), 8) * bpf_map__max_entries(map);
map_sz = roundup(map_sz, page_sz);
return map_sz;
}
/* Emit type size asserts for all top-level fields in memory-mapped internal maps. */
static void codegen_asserts(struct bpf_object *obj, const char *obj_name)
{
struct btf *btf = bpf_object__btf(obj);
struct bpf_map *map;
struct btf_var_secinfo *sec_var;
int i, vlen;
const struct btf_type *sec;
char map_ident[256], var_ident[256];
codegen("\
\n\
__attribute__((unused)) static void \n\
%1$s__assert(struct %1$s *s) \n\
{ \n\
#ifdef __cplusplus \n\
#define _Static_assert static_assert \n\
#endif \n\
", obj_name);
bpf_object__for_each_map(map, obj) {
if (!bpf_map__is_internal(map))
continue;
if (!(bpf_map__map_flags(map) & BPF_F_MMAPABLE))
continue;
if (!get_map_ident(map, map_ident, sizeof(map_ident)))
continue;
sec = find_type_for_map(btf, map_ident);
if (!sec) {
/* best effort, couldn't find the type for this map */
continue;
}
sec_var = btf_var_secinfos(sec);
vlen = btf_vlen(sec);
for (i = 0; i < vlen; i++, sec_var++) {
const struct btf_type *var = btf__type_by_id(btf, sec_var->type);
const char *var_name = btf__name_by_offset(btf, var->name_off);
long var_size;
/* static variables are not exposed through BPF skeleton */
if (btf_var(var)->linkage == BTF_VAR_STATIC)
continue;
var_size = btf__resolve_size(btf, var->type);
if (var_size < 0)
continue;
var_ident[0] = '\0';
strncat(var_ident, var_name, sizeof(var_ident) - 1);
sanitize_identifier(var_ident);
printf("\t_Static_assert(sizeof(s->%s->%s) == %ld, \"unexpected size of '%s'\");\n",
map_ident, var_ident, var_size, var_ident);
}
}
codegen("\
\n\
#ifdef __cplusplus \n\
#undef _Static_assert \n\
#endif \n\
} \n\
");
}
static void codegen_attach_detach(struct bpf_object *obj, const char *obj_name)
{
struct bpf_program *prog;
bpf_object__for_each_program(prog, obj) {
const char *tp_name;
codegen("\
\n\
\n\
static inline int \n\
%1$s__%2$s__attach(struct %1$s *skel) \n\
{ \n\
int prog_fd = skel->progs.%2$s.prog_fd; \n\
", obj_name, bpf_program__name(prog));
switch (bpf_program__type(prog)) {
case BPF_PROG_TYPE_RAW_TRACEPOINT:
tp_name = strchr(bpf_program__section_name(prog), '/') + 1;
printf("\tint fd = skel_raw_tracepoint_open(\"%s\", prog_fd);\n", tp_name);
break;
case BPF_PROG_TYPE_TRACING:
if (bpf_program__expected_attach_type(prog) == BPF_TRACE_ITER)
printf("\tint fd = skel_link_create(prog_fd, 0, BPF_TRACE_ITER);\n");
else
printf("\tint fd = skel_raw_tracepoint_open(NULL, prog_fd);\n");
break;
default:
printf("\tint fd = ((void)prog_fd, 0); /* auto-attach not supported */\n");
break;
}
codegen("\
\n\
\n\
if (fd > 0) \n\
skel->links.%1$s_fd = fd; \n\
return fd; \n\
} \n\
", bpf_program__name(prog));
}
codegen("\
\n\
\n\
static inline int \n\
%1$s__attach(struct %1$s *skel) \n\
{ \n\
int ret = 0; \n\
\n\
", obj_name);
bpf_object__for_each_program(prog, obj) {
codegen("\
\n\
ret = ret < 0 ? ret : %1$s__%2$s__attach(skel); \n\
", obj_name, bpf_program__name(prog));
}
codegen("\
\n\
return ret < 0 ? ret : 0; \n\
} \n\
\n\
static inline void \n\
%1$s__detach(struct %1$s *skel) \n\
{ \n\
", obj_name);
bpf_object__for_each_program(prog, obj) {
codegen("\
\n\
skel_closenz(skel->links.%1$s_fd); \n\
", bpf_program__name(prog));
}
codegen("\
\n\
} \n\
");
}
static void codegen_destroy(struct bpf_object *obj, const char *obj_name)
{
struct bpf_program *prog;
struct bpf_map *map;
char ident[256];
codegen("\
\n\
static void \n\
%1$s__destroy(struct %1$s *skel) \n\
{ \n\
if (!skel) \n\
return; \n\
%1$s__detach(skel); \n\
",
obj_name);
bpf_object__for_each_program(prog, obj) {
codegen("\
\n\
skel_closenz(skel->progs.%1$s.prog_fd); \n\
", bpf_program__name(prog));
}
bpf_object__for_each_map(map, obj) {
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
if (bpf_map__is_internal(map) &&
(bpf_map__map_flags(map) & BPF_F_MMAPABLE))
printf("\tskel_free_map_data(skel->%1$s, skel->maps.%1$s.initial_value, %2$zd);\n",
ident, bpf_map_mmap_sz(map));
codegen("\
\n\
skel_closenz(skel->maps.%1$s.map_fd); \n\
", ident);
}
codegen("\
\n\
skel_free(skel); \n\
} \n\
",
obj_name);
}
static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *header_guard)
{
DECLARE_LIBBPF_OPTS(gen_loader_opts, opts);
struct bpf_map *map;
char ident[256];
int err = 0;
err = bpf_object__gen_loader(obj, &opts);
if (err)
return err;
err = bpf_object__load(obj);
if (err) {
p_err("failed to load object file");
goto out;
}
/* If there was no error during load then gen_loader_opts
* are populated with the loader program.
*/
/* finish generating 'struct skel' */
codegen("\
\n\
}; \n\
", obj_name);
codegen_attach_detach(obj, obj_name);
codegen_destroy(obj, obj_name);
codegen("\
\n\
static inline struct %1$s * \n\
%1$s__open(void) \n\
{ \n\
struct %1$s *skel; \n\
\n\
skel = skel_alloc(sizeof(*skel)); \n\
if (!skel) \n\
goto cleanup; \n\
skel->ctx.sz = (void *)&skel->links - (void *)skel; \n\
",
obj_name, opts.data_sz);
bpf_object__for_each_map(map, obj) {
const void *mmap_data = NULL;
size_t mmap_size = 0;
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
if (!bpf_map__is_internal(map) ||
!(bpf_map__map_flags(map) & BPF_F_MMAPABLE))
continue;
codegen("\
\n\
skel->%1$s = skel_prep_map_data((void *)\"\\ \n\
", ident);
mmap_data = bpf_map__initial_value(map, &mmap_size);
print_hex(mmap_data, mmap_size);
codegen("\
\n\
\", %1$zd, %2$zd); \n\
if (!skel->%3$s) \n\
goto cleanup; \n\
skel->maps.%3$s.initial_value = (__u64) (long) skel->%3$s;\n\
", bpf_map_mmap_sz(map), mmap_size, ident);
}
codegen("\
\n\
return skel; \n\
cleanup: \n\
%1$s__destroy(skel); \n\
return NULL; \n\
} \n\
\n\
static inline int \n\
%1$s__load(struct %1$s *skel) \n\
{ \n\
struct bpf_load_and_run_opts opts = {}; \n\
int err; \n\
\n\
opts.ctx = (struct bpf_loader_ctx *)skel; \n\
opts.data_sz = %2$d; \n\
opts.data = (void *)\"\\ \n\
",
obj_name, opts.data_sz);
print_hex(opts.data, opts.data_sz);
codegen("\
\n\
\"; \n\
");
codegen("\
\n\
opts.insns_sz = %d; \n\
opts.insns = (void *)\"\\ \n\
",
opts.insns_sz);
print_hex(opts.insns, opts.insns_sz);
codegen("\
\n\
\"; \n\
err = bpf_load_and_run(&opts); \n\
if (err < 0) \n\
return err; \n\
", obj_name);
bpf_object__for_each_map(map, obj) {
const char *mmap_flags;
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
if (!bpf_map__is_internal(map) ||
!(bpf_map__map_flags(map) & BPF_F_MMAPABLE))
continue;
if (bpf_map__map_flags(map) & BPF_F_RDONLY_PROG)
mmap_flags = "PROT_READ";
else
mmap_flags = "PROT_READ | PROT_WRITE";
codegen("\
\n\
skel->%1$s = skel_finalize_map_data(&skel->maps.%1$s.initial_value, \n\
%2$zd, %3$s, skel->maps.%1$s.map_fd);\n\
if (!skel->%1$s) \n\
return -ENOMEM; \n\
",
ident, bpf_map_mmap_sz(map), mmap_flags);
}
codegen("\
\n\
return 0; \n\
} \n\
\n\
static inline struct %1$s * \n\
%1$s__open_and_load(void) \n\
{ \n\
struct %1$s *skel; \n\
\n\
skel = %1$s__open(); \n\
if (!skel) \n\
return NULL; \n\
if (%1$s__load(skel)) { \n\
%1$s__destroy(skel); \n\
return NULL; \n\
} \n\
return skel; \n\
} \n\
\n\
", obj_name);
codegen_asserts(obj, obj_name);
codegen("\
\n\
\n\
#endif /* %s */ \n\
",
header_guard);
err = 0;
out:
return err;
}
static int do_skeleton(int argc, char **argv)
{
char header_guard[MAX_OBJ_NAME_LEN + sizeof("__SKEL_H__")];
size_t i, map_cnt = 0, prog_cnt = 0, file_sz, mmap_sz;
DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts);
char obj_name[MAX_OBJ_NAME_LEN] = "", *obj_data;
struct bpf_object *obj = NULL;
const char *file;
char ident[256];
struct bpf_program *prog;
int fd, err = -1;
struct bpf_map *map;
struct btf *btf;
struct stat st;
if (!REQ_ARGS(1)) {
usage();
return -1;
}
file = GET_ARG();
while (argc) {
if (!REQ_ARGS(2))
return -1;
if (is_prefix(*argv, "name")) {
NEXT_ARG();
if (obj_name[0] != '\0') {
p_err("object name already specified");
return -1;
}
strncpy(obj_name, *argv, MAX_OBJ_NAME_LEN - 1);
obj_name[MAX_OBJ_NAME_LEN - 1] = '\0';
} else {
p_err("unknown arg %s", *argv);
return -1;
}
NEXT_ARG();
}
if (argc) {
p_err("extra unknown arguments");
return -1;
}
if (stat(file, &st)) {
p_err("failed to stat() %s: %s", file, strerror(errno));
return -1;
}
file_sz = st.st_size;
mmap_sz = roundup(file_sz, sysconf(_SC_PAGE_SIZE));
fd = open(file, O_RDONLY);
if (fd < 0) {
p_err("failed to open() %s: %s", file, strerror(errno));
return -1;
}
obj_data = mmap(NULL, mmap_sz, PROT_READ, MAP_PRIVATE, fd, 0);
if (obj_data == MAP_FAILED) {
obj_data = NULL;
p_err("failed to mmap() %s: %s", file, strerror(errno));
goto out;
}
if (obj_name[0] == '\0')
get_obj_name(obj_name, file);
opts.object_name = obj_name;
if (verifier_logs)
/* log_level1 + log_level2 + stats, but not stable UAPI */
opts.kernel_log_level = 1 + 2 + 4;
obj = bpf_object__open_mem(obj_data, file_sz, &opts);
err = libbpf_get_error(obj);
if (err) {
char err_buf[256];
libbpf_strerror(err, err_buf, sizeof(err_buf));
p_err("failed to open BPF object file: %s", err_buf);
obj = NULL;
goto out;
}
bpf_object__for_each_map(map, obj) {
if (!get_map_ident(map, ident, sizeof(ident))) {
p_err("ignoring unrecognized internal map '%s'...",
bpf_map__name(map));
continue;
}
map_cnt++;
}
bpf_object__for_each_program(prog, obj) {
prog_cnt++;
}
get_header_guard(header_guard, obj_name);
if (use_loader) {
codegen("\
\n\
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ \n\
/* THIS FILE IS AUTOGENERATED! */ \n\
#ifndef %2$s \n\
#define %2$s \n\
\n\
#include <bpf/skel_internal.h> \n\
\n\
struct %1$s { \n\
struct bpf_loader_ctx ctx; \n\
",
obj_name, header_guard
);
} else {
codegen("\
\n\
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ \n\
\n\
/* THIS FILE IS AUTOGENERATED! */ \n\
#ifndef %2$s \n\
#define %2$s \n\
\n\
#include <errno.h> \n\
#include <stdlib.h> \n\
#include <bpf/libbpf.h> \n\
\n\
struct %1$s { \n\
struct bpf_object_skeleton *skeleton; \n\
struct bpf_object *obj; \n\
",
obj_name, header_guard
);
}
if (map_cnt) {
printf("\tstruct {\n");
bpf_object__for_each_map(map, obj) {
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
if (use_loader)
printf("\t\tstruct bpf_map_desc %s;\n", ident);
else
printf("\t\tstruct bpf_map *%s;\n", ident);
}
printf("\t} maps;\n");
}
if (prog_cnt) {
printf("\tstruct {\n");
bpf_object__for_each_program(prog, obj) {
if (use_loader)
printf("\t\tstruct bpf_prog_desc %s;\n",
bpf_program__name(prog));
else
printf("\t\tstruct bpf_program *%s;\n",
bpf_program__name(prog));
}
printf("\t} progs;\n");
printf("\tstruct {\n");
bpf_object__for_each_program(prog, obj) {
if (use_loader)
printf("\t\tint %s_fd;\n",
bpf_program__name(prog));
else
printf("\t\tstruct bpf_link *%s;\n",
bpf_program__name(prog));
}
printf("\t} links;\n");
}
btf = bpf_object__btf(obj);
if (btf) {
err = codegen_datasecs(obj, obj_name);
if (err)
goto out;
}
if (use_loader) {
err = gen_trace(obj, obj_name, header_guard);
goto out;
}
codegen("\
\n\
\n\
#ifdef __cplusplus \n\
static inline struct %1$s *open(const struct bpf_object_open_opts *opts = nullptr);\n\
static inline struct %1$s *open_and_load(); \n\
static inline int load(struct %1$s *skel); \n\
static inline int attach(struct %1$s *skel); \n\
static inline void detach(struct %1$s *skel); \n\
static inline void destroy(struct %1$s *skel); \n\
static inline const void *elf_bytes(size_t *sz); \n\
#endif /* __cplusplus */ \n\
}; \n\
\n\
static void \n\
%1$s__destroy(struct %1$s *obj) \n\
{ \n\
if (!obj) \n\
return; \n\
if (obj->skeleton) \n\
bpf_object__destroy_skeleton(obj->skeleton);\n\
free(obj); \n\
} \n\
\n\
static inline int \n\
%1$s__create_skeleton(struct %1$s *obj); \n\
\n\
static inline struct %1$s * \n\
%1$s__open_opts(const struct bpf_object_open_opts *opts) \n\
{ \n\
struct %1$s *obj; \n\
int err; \n\
\n\
obj = (struct %1$s *)calloc(1, sizeof(*obj)); \n\
if (!obj) { \n\
errno = ENOMEM; \n\
return NULL; \n\
} \n\
\n\
err = %1$s__create_skeleton(obj); \n\
if (err) \n\
goto err_out; \n\
\n\
err = bpf_object__open_skeleton(obj->skeleton, opts);\n\
if (err) \n\
goto err_out; \n\
\n\
return obj; \n\
err_out: \n\
%1$s__destroy(obj); \n\
errno = -err; \n\
return NULL; \n\
} \n\
\n\
static inline struct %1$s * \n\
%1$s__open(void) \n\
{ \n\
return %1$s__open_opts(NULL); \n\
} \n\
\n\
static inline int \n\
%1$s__load(struct %1$s *obj) \n\
{ \n\
return bpf_object__load_skeleton(obj->skeleton); \n\
} \n\
\n\
static inline struct %1$s * \n\
%1$s__open_and_load(void) \n\
{ \n\
struct %1$s *obj; \n\
int err; \n\
\n\
obj = %1$s__open(); \n\
if (!obj) \n\
return NULL; \n\
err = %1$s__load(obj); \n\
if (err) { \n\
%1$s__destroy(obj); \n\
errno = -err; \n\
return NULL; \n\
} \n\
return obj; \n\
} \n\
\n\
static inline int \n\
%1$s__attach(struct %1$s *obj) \n\
{ \n\
return bpf_object__attach_skeleton(obj->skeleton); \n\
} \n\
\n\
static inline void \n\
%1$s__detach(struct %1$s *obj) \n\
{ \n\
return bpf_object__detach_skeleton(obj->skeleton); \n\
} \n\
",
obj_name
);
codegen("\
\n\
\n\
static inline const void *%1$s__elf_bytes(size_t *sz); \n\
\n\
static inline int \n\
%1$s__create_skeleton(struct %1$s *obj) \n\
{ \n\
struct bpf_object_skeleton *s; \n\
\n\
s = (struct bpf_object_skeleton *)calloc(1, sizeof(*s));\n\
if (!s) \n\
goto err; \n\
\n\
s->sz = sizeof(*s); \n\
s->name = \"%1$s\"; \n\
s->obj = &obj->obj; \n\
",
obj_name
);
if (map_cnt) {
codegen("\
\n\
\n\
/* maps */ \n\
s->map_cnt = %zu; \n\
s->map_skel_sz = sizeof(*s->maps); \n\
s->maps = (struct bpf_map_skeleton *)calloc(s->map_cnt, s->map_skel_sz);\n\
if (!s->maps) \n\
goto err; \n\
",
map_cnt
);
i = 0;
bpf_object__for_each_map(map, obj) {
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
codegen("\
\n\
\n\
s->maps[%zu].name = \"%s\"; \n\
s->maps[%zu].map = &obj->maps.%s; \n\
",
i, bpf_map__name(map), i, ident);
/* memory-mapped internal maps */
if (bpf_map__is_internal(map) &&
(bpf_map__map_flags(map) & BPF_F_MMAPABLE)) {
printf("\ts->maps[%zu].mmaped = (void **)&obj->%s;\n",
i, ident);
}
i++;
}
}
if (prog_cnt) {
codegen("\
\n\
\n\
/* programs */ \n\
s->prog_cnt = %zu; \n\
s->prog_skel_sz = sizeof(*s->progs); \n\
s->progs = (struct bpf_prog_skeleton *)calloc(s->prog_cnt, s->prog_skel_sz);\n\
if (!s->progs) \n\
goto err; \n\
",
prog_cnt
);
i = 0;
bpf_object__for_each_program(prog, obj) {
codegen("\
\n\
\n\
s->progs[%1$zu].name = \"%2$s\"; \n\
s->progs[%1$zu].prog = &obj->progs.%2$s;\n\
s->progs[%1$zu].link = &obj->links.%2$s;\n\
",
i, bpf_program__name(prog));
i++;
}
}
codegen("\
\n\
\n\
s->data = (void *)%2$s__elf_bytes(&s->data_sz); \n\
\n\
obj->skeleton = s; \n\
return 0; \n\
err: \n\
bpf_object__destroy_skeleton(s); \n\
return -ENOMEM; \n\
} \n\
\n\
static inline const void *%2$s__elf_bytes(size_t *sz) \n\
{ \n\
*sz = %1$d; \n\
return (const void *)\"\\ \n\
"
, file_sz, obj_name);
/* embed contents of BPF object file */
print_hex(obj_data, file_sz);
codegen("\
\n\
\"; \n\
} \n\
\n\
#ifdef __cplusplus \n\
struct %1$s *%1$s::open(const struct bpf_object_open_opts *opts) { return %1$s__open_opts(opts); }\n\
struct %1$s *%1$s::open_and_load() { return %1$s__open_and_load(); } \n\
int %1$s::load(struct %1$s *skel) { return %1$s__load(skel); } \n\
int %1$s::attach(struct %1$s *skel) { return %1$s__attach(skel); } \n\
void %1$s::detach(struct %1$s *skel) { %1$s__detach(skel); } \n\
void %1$s::destroy(struct %1$s *skel) { %1$s__destroy(skel); } \n\
const void *%1$s::elf_bytes(size_t *sz) { return %1$s__elf_bytes(sz); } \n\
#endif /* __cplusplus */ \n\
\n\
",
obj_name);
codegen_asserts(obj, obj_name);
codegen("\
\n\
\n\
#endif /* %1$s */ \n\
",
header_guard);
err = 0;
out:
bpf_object__close(obj);
if (obj_data)
munmap(obj_data, mmap_sz);
close(fd);
return err;
}
static int do_object(int argc, char **argv)
{
struct bpf_linker *linker;
const char *output_file, *file;
int err = 0;
if (!REQ_ARGS(2)) {
usage();
return -1;
}
output_file = GET_ARG();
linker = bpf_linker__new(output_file, NULL);
if (!linker) {
p_err("failed to create BPF linker instance");
return -1;
}
while (argc) {
file = GET_ARG();
err = bpf_linker__add_file(linker, file, NULL);
if (err) {
p_err("failed to link '%s': %s (%d)", file, strerror(err), err);
goto out;
}
}
err = bpf_linker__finalize(linker);
if (err) {
p_err("failed to finalize ELF file: %s (%d)", strerror(err), err);
goto out;
}
err = 0;
out:
bpf_linker__free(linker);
return err;
}
static int do_help(int argc, char **argv)
{
if (json_output) {
jsonw_null(json_wtr);
return 0;
}
fprintf(stderr,
"Usage: %1$s %2$s object OUTPUT_FILE INPUT_FILE [INPUT_FILE...]\n"
" %1$s %2$s skeleton FILE [name OBJECT_NAME]\n"
" %1$s %2$s min_core_btf INPUT OUTPUT OBJECT [OBJECT...]\n"
" %1$s %2$s help\n"
"\n"
" " HELP_SPEC_OPTIONS " |\n"
" {-L|--use-loader} }\n"
"",
bin_name, "gen");
return 0;
}
static int btf_save_raw(const struct btf *btf, const char *path)
{
const void *data;
FILE *f = NULL;
__u32 data_sz;
int err = 0;
data = btf__raw_data(btf, &data_sz);
if (!data)
return -ENOMEM;
f = fopen(path, "wb");
if (!f)
return -errno;
if (fwrite(data, 1, data_sz, f) != data_sz)
err = -errno;
fclose(f);
return err;
}
struct btfgen_info {
struct btf *src_btf;
struct btf *marked_btf; /* btf structure used to mark used types */
};
static size_t btfgen_hash_fn(const void *key, void *ctx)
{
return (size_t)key;
}
static bool btfgen_equal_fn(const void *k1, const void *k2, void *ctx)
{
return k1 == k2;
}
static void *u32_as_hash_key(__u32 x)
{
return (void *)(uintptr_t)x;
}
static void btfgen_free_info(struct btfgen_info *info)
{
if (!info)
return;
btf__free(info->src_btf);
btf__free(info->marked_btf);
free(info);
}
static struct btfgen_info *
btfgen_new_info(const char *targ_btf_path)
{
struct btfgen_info *info;
int err;
info = calloc(1, sizeof(*info));
if (!info)
return NULL;
info->src_btf = btf__parse(targ_btf_path, NULL);
if (!info->src_btf) {
err = -errno;
p_err("failed parsing '%s' BTF file: %s", targ_btf_path, strerror(errno));
goto err_out;
}
info->marked_btf = btf__parse(targ_btf_path, NULL);
if (!info->marked_btf) {
err = -errno;
p_err("failed parsing '%s' BTF file: %s", targ_btf_path, strerror(errno));
goto err_out;
}
return info;
err_out:
btfgen_free_info(info);
errno = -err;
return NULL;
}
#define MARKED UINT32_MAX
static void btfgen_mark_member(struct btfgen_info *info, int type_id, int idx)
{
const struct btf_type *t = btf__type_by_id(info->marked_btf, type_id);
struct btf_member *m = btf_members(t) + idx;
m->name_off = MARKED;
}
static int
btfgen_mark_type(struct btfgen_info *info, unsigned int type_id, bool follow_pointers)
{
const struct btf_type *btf_type = btf__type_by_id(info->src_btf, type_id);
struct btf_type *cloned_type;
struct btf_param *param;
struct btf_array *array;
int err, i;
if (type_id == 0)
return 0;
/* mark type on cloned BTF as used */
cloned_type = (struct btf_type *) btf__type_by_id(info->marked_btf, type_id);
cloned_type->name_off = MARKED;
/* recursively mark other types needed by it */
switch (btf_kind(btf_type)) {
case BTF_KIND_UNKN:
case BTF_KIND_INT:
case BTF_KIND_FLOAT:
case BTF_KIND_ENUM:
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
break;
case BTF_KIND_PTR:
if (follow_pointers) {
err = btfgen_mark_type(info, btf_type->type, follow_pointers);
if (err)
return err;
}
break;
case BTF_KIND_CONST:
case BTF_KIND_VOLATILE:
case BTF_KIND_TYPEDEF:
err = btfgen_mark_type(info, btf_type->type, follow_pointers);
if (err)
return err;
break;
case BTF_KIND_ARRAY:
array = btf_array(btf_type);
/* mark array type */
err = btfgen_mark_type(info, array->type, follow_pointers);
/* mark array's index type */
err = err ? : btfgen_mark_type(info, array->index_type, follow_pointers);
if (err)
return err;
break;
case BTF_KIND_FUNC_PROTO:
/* mark ret type */
err = btfgen_mark_type(info, btf_type->type, follow_pointers);
if (err)
return err;
/* mark parameters types */
param = btf_params(btf_type);
for (i = 0; i < btf_vlen(btf_type); i++) {
err = btfgen_mark_type(info, param->type, follow_pointers);
if (err)
return err;
param++;
}
break;
/* tells if some other type needs to be handled */
default:
p_err("unsupported kind: %s (%d)", btf_kind_str(btf_type), type_id);
return -EINVAL;
}
return 0;
}
static int btfgen_record_field_relo(struct btfgen_info *info, struct bpf_core_spec *targ_spec)
{
struct btf *btf = info->src_btf;
const struct btf_type *btf_type;
struct btf_member *btf_member;
struct btf_array *array;
unsigned int type_id = targ_spec->root_type_id;
int idx, err;
/* mark root type */
btf_type = btf__type_by_id(btf, type_id);
err = btfgen_mark_type(info, type_id, false);
if (err)
return err;
/* mark types for complex types (arrays, unions, structures) */
for (int i = 1; i < targ_spec->raw_len; i++) {
/* skip typedefs and mods */
while (btf_is_mod(btf_type) || btf_is_typedef(btf_type)) {
type_id = btf_type->type;
btf_type = btf__type_by_id(btf, type_id);
}
switch (btf_kind(btf_type)) {
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
idx = targ_spec->raw_spec[i];
btf_member = btf_members(btf_type) + idx;
/* mark member */
btfgen_mark_member(info, type_id, idx);
/* mark member's type */
type_id = btf_member->type;
btf_type = btf__type_by_id(btf, type_id);
err = btfgen_mark_type(info, type_id, false);
if (err)
return err;
break;
case BTF_KIND_ARRAY:
array = btf_array(btf_type);
type_id = array->type;
btf_type = btf__type_by_id(btf, type_id);
break;
default:
p_err("unsupported kind: %s (%d)",
btf_kind_str(btf_type), btf_type->type);
return -EINVAL;
}
}
return 0;
}
static int btfgen_record_type_relo(struct btfgen_info *info, struct bpf_core_spec *targ_spec)
{
return btfgen_mark_type(info, targ_spec->root_type_id, true);
}
static int btfgen_record_enumval_relo(struct btfgen_info *info, struct bpf_core_spec *targ_spec)
{
return btfgen_mark_type(info, targ_spec->root_type_id, false);
}
static int btfgen_record_reloc(struct btfgen_info *info, struct bpf_core_spec *res)
{
switch (res->relo_kind) {
case BPF_CORE_FIELD_BYTE_OFFSET:
case BPF_CORE_FIELD_BYTE_SIZE:
case BPF_CORE_FIELD_EXISTS:
case BPF_CORE_FIELD_SIGNED:
case BPF_CORE_FIELD_LSHIFT_U64:
case BPF_CORE_FIELD_RSHIFT_U64:
return btfgen_record_field_relo(info, res);
case BPF_CORE_TYPE_ID_LOCAL: /* BPF_CORE_TYPE_ID_LOCAL doesn't require kernel BTF */
return 0;
case BPF_CORE_TYPE_ID_TARGET:
case BPF_CORE_TYPE_EXISTS:
case BPF_CORE_TYPE_SIZE:
return btfgen_record_type_relo(info, res);
case BPF_CORE_ENUMVAL_EXISTS:
case BPF_CORE_ENUMVAL_VALUE:
return btfgen_record_enumval_relo(info, res);
default:
return -EINVAL;
}
}
static struct bpf_core_cand_list *
btfgen_find_cands(const struct btf *local_btf, const struct btf *targ_btf, __u32 local_id)
{
const struct btf_type *local_type;
struct bpf_core_cand_list *cands = NULL;
struct bpf_core_cand local_cand = {};
size_t local_essent_len;
const char *local_name;
int err;
local_cand.btf = local_btf;
local_cand.id = local_id;
local_type = btf__type_by_id(local_btf, local_id);
if (!local_type) {
err = -EINVAL;
goto err_out;
}
local_name = btf__name_by_offset(local_btf, local_type->name_off);
if (!local_name) {
err = -EINVAL;
goto err_out;
}
local_essent_len = bpf_core_essential_name_len(local_name);
cands = calloc(1, sizeof(*cands));
if (!cands)
return NULL;
err = bpf_core_add_cands(&local_cand, local_essent_len, targ_btf, "vmlinux", 1, cands);
if (err)
goto err_out;
return cands;
err_out:
bpf_core_free_cands(cands);
errno = -err;
return NULL;
}
/* Record relocation information for a single BPF object */
static int btfgen_record_obj(struct btfgen_info *info, const char *obj_path)
{
const struct btf_ext_info_sec *sec;
const struct bpf_core_relo *relo;
const struct btf_ext_info *seg;
struct hashmap_entry *entry;
struct hashmap *cand_cache = NULL;
struct btf_ext *btf_ext = NULL;
unsigned int relo_idx;
struct btf *btf = NULL;
size_t i;
int err;
btf = btf__parse(obj_path, &btf_ext);
if (!btf) {
err = -errno;
p_err("failed to parse BPF object '%s': %s", obj_path, strerror(errno));
return err;
}
if (!btf_ext) {
p_err("failed to parse BPF object '%s': section %s not found",
obj_path, BTF_EXT_ELF_SEC);
err = -EINVAL;
goto out;
}
if (btf_ext->core_relo_info.len == 0) {
err = 0;
goto out;
}
cand_cache = hashmap__new(btfgen_hash_fn, btfgen_equal_fn, NULL);
if (IS_ERR(cand_cache)) {
err = PTR_ERR(cand_cache);
goto out;
}
seg = &btf_ext->core_relo_info;
for_each_btf_ext_sec(seg, sec) {
for_each_btf_ext_rec(seg, sec, relo_idx, relo) {
struct bpf_core_spec specs_scratch[3] = {};
struct bpf_core_relo_res targ_res = {};
struct bpf_core_cand_list *cands = NULL;
const void *type_key = u32_as_hash_key(relo->type_id);
const char *sec_name = btf__name_by_offset(btf, sec->sec_name_off);
if (relo->kind != BPF_CORE_TYPE_ID_LOCAL &&
!hashmap__find(cand_cache, type_key, (void **)&cands)) {
cands = btfgen_find_cands(btf, info->src_btf, relo->type_id);
if (!cands) {
err = -errno;
goto out;
}
err = hashmap__set(cand_cache, type_key, cands, NULL, NULL);
if (err)
goto out;
}
err = bpf_core_calc_relo_insn(sec_name, relo, relo_idx, btf, cands,
specs_scratch, &targ_res);
if (err)
goto out;
/* specs_scratch[2] is the target spec */
err = btfgen_record_reloc(info, &specs_scratch[2]);
if (err)
goto out;
}
}
out:
btf__free(btf);
btf_ext__free(btf_ext);
if (!IS_ERR_OR_NULL(cand_cache)) {
hashmap__for_each_entry(cand_cache, entry, i) {
bpf_core_free_cands(entry->value);
}
hashmap__free(cand_cache);
}
return err;
}
static int btfgen_remap_id(__u32 *type_id, void *ctx)
{
unsigned int *ids = ctx;
*type_id = ids[*type_id];
return 0;
}
/* Generate BTF from relocation information previously recorded */
static struct btf *btfgen_get_btf(struct btfgen_info *info)
{
struct btf *btf_new = NULL;
unsigned int *ids = NULL;
unsigned int i, n = btf__type_cnt(info->marked_btf);
int err = 0;
btf_new = btf__new_empty();
if (!btf_new) {
err = -errno;
goto err_out;
}
ids = calloc(n, sizeof(*ids));
if (!ids) {
err = -errno;
goto err_out;
}
/* first pass: add all marked types to btf_new and add their new ids to the ids map */
for (i = 1; i < n; i++) {
const struct btf_type *cloned_type, *type;
const char *name;
int new_id;
cloned_type = btf__type_by_id(info->marked_btf, i);
if (cloned_type->name_off != MARKED)
continue;
type = btf__type_by_id(info->src_btf, i);
/* add members for struct and union */
if (btf_is_composite(type)) {
struct btf_member *cloned_m, *m;
unsigned short vlen;
int idx_src;
name = btf__str_by_offset(info->src_btf, type->name_off);
if (btf_is_struct(type))
err = btf__add_struct(btf_new, name, type->size);
else
err = btf__add_union(btf_new, name, type->size);
if (err < 0)
goto err_out;
new_id = err;
cloned_m = btf_members(cloned_type);
m = btf_members(type);
vlen = btf_vlen(cloned_type);
for (idx_src = 0; idx_src < vlen; idx_src++, cloned_m++, m++) {
/* add only members that are marked as used */
if (cloned_m->name_off != MARKED)
continue;
name = btf__str_by_offset(info->src_btf, m->name_off);
err = btf__add_field(btf_new, name, m->type,
btf_member_bit_offset(cloned_type, idx_src),
btf_member_bitfield_size(cloned_type, idx_src));
if (err < 0)
goto err_out;
}
} else {
err = btf__add_type(btf_new, info->src_btf, type);
if (err < 0)
goto err_out;
new_id = err;
}
/* add ID mapping */
ids[i] = new_id;
}
/* second pass: fix up type ids */
for (i = 1; i < btf__type_cnt(btf_new); i++) {
struct btf_type *btf_type = (struct btf_type *) btf__type_by_id(btf_new, i);
err = btf_type_visit_type_ids(btf_type, btfgen_remap_id, ids);
if (err)
goto err_out;
}
free(ids);
return btf_new;
err_out:
btf__free(btf_new);
free(ids);
errno = -err;
return NULL;
}
/* Create minimized BTF file for a set of BPF objects.
*
* The BTFGen algorithm is divided in two main parts: (1) collect the
* BTF types that are involved in relocations and (2) generate the BTF
* object using the collected types.
*
* In order to collect the types involved in the relocations, we parse
* the BTF and BTF.ext sections of the BPF objects and use
* bpf_core_calc_relo_insn() to get the target specification, this
* indicates how the types and fields are used in a relocation.
*
* Types are recorded in different ways according to the kind of the
* relocation. For field-based relocations only the members that are
* actually used are saved in order to reduce the size of the generated
* BTF file. For type-based relocations empty struct / unions are
* generated and for enum-based relocations the whole type is saved.
*
* The second part of the algorithm generates the BTF object. It creates
* an empty BTF object and fills it with the types recorded in the
* previous step. This function takes care of only adding the structure
* and union members that were marked as used and it also fixes up the
* type IDs on the generated BTF object.
*/
static int minimize_btf(const char *src_btf, const char *dst_btf, const char *objspaths[])
{
struct btfgen_info *info;
struct btf *btf_new = NULL;
int err, i;
info = btfgen_new_info(src_btf);
if (!info) {
err = -errno;
p_err("failed to allocate info structure: %s", strerror(errno));
goto out;
}
for (i = 0; objspaths[i] != NULL; i++) {
err = btfgen_record_obj(info, objspaths[i]);
if (err) {
p_err("error recording relocations for %s: %s", objspaths[i],
strerror(errno));
goto out;
}
}
btf_new = btfgen_get_btf(info);
if (!btf_new) {
err = -errno;
p_err("error generating BTF: %s", strerror(errno));
goto out;
}
err = btf_save_raw(btf_new, dst_btf);
if (err) {
p_err("error saving btf file: %s", strerror(errno));
goto out;
}
out:
btf__free(btf_new);
btfgen_free_info(info);
return err;
}
static int do_min_core_btf(int argc, char **argv)
{
const char *input, *output, **objs;
int i, err;
if (!REQ_ARGS(3)) {
usage();
return -1;
}
input = GET_ARG();
output = GET_ARG();
objs = (const char **) calloc(argc + 1, sizeof(*objs));
if (!objs) {
p_err("failed to allocate array for object names");
return -ENOMEM;
}
i = 0;
while (argc)
objs[i++] = GET_ARG();
err = minimize_btf(input, output, objs);
free(objs);
return err;
}
static const struct cmd cmds[] = {
{ "object", do_object },
{ "skeleton", do_skeleton },
{ "min_core_btf", do_min_core_btf},
{ "help", do_help },
{ 0 }
};
int do_gen(int argc, char **argv)
{
return cmd_select(cmds, argc, argv, do_help);
}
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