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linux/tools/bpf/bpftool/gen.c
Andrii Nakryiko 06e71ad534 bpftool: improve skeleton backwards compat with old buggy libbpfs 
Old versions of libbpf don't handle varying sizes of bpf_map_skeleton
struct correctly. As such, BPF skeleton generated by newest bpftool
might not be compatible with older libbpf (though only when libbpf is
used as a shared library), even though it, by design, should.

Going forward libbpf will be fixed, plus we'll release bug fixed
versions of relevant old libbpfs, but meanwhile try to mitigate from
bpftool side by conservatively assuming older and smaller definition of
bpf_map_skeleton, if possible. Meaning, if there are no struct_ops maps.

If there are struct_ops, then presumably user would like to have
auto-attaching logic and struct_ops map link placeholders, so use the
full bpf_map_skeleton definition in that case.

Acked-by: Quentin Monnet <qmo@kernel.org>
Co-developed-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240708204540.4188946-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2024-07-09 19:03:05 -07:00

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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 <libgen.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 const struct btf_type *
resolve_func_ptr(const struct btf *btf, __u32 id, __u32 *res_id)
{
const struct btf_type *t;
t = skip_mods_and_typedefs(btf, id, NULL);
if (!btf_is_ptr(t))
return NULL;
t = skip_mods_and_typedefs(btf, t->type, res_id);
return btf_is_func_proto(t) ? t : NULL;
}
static void get_obj_name(char *name, const char *file)
{
char file_copy[PATH_MAX];
/* Using basename() POSIX version to be more portable. */
strncpy(file_copy, file, PATH_MAX - 1)[PATH_MAX - 1] = '\0';
strncpy(name, basename(file_copy), MAX_OBJ_NAME_LEN - 1)[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, const char *suffix)
{
int i;
sprintf(guard, "__%s_%s__", obj_name, suffix);
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;
/* recognize hard coded LLVM section name */
if (strcmp(sec_name, ".addr_space.1") == 0) {
/* this is the name to use in skeleton */
snprintf(buf, buf_sz, "arena");
return true;
}
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 bool is_mmapable_map(const struct bpf_map *map, char *buf, size_t sz)
{
size_t tmp_sz;
if (bpf_map__type(map) == BPF_MAP_TYPE_ARENA && bpf_map__initial_value(map, &tmp_sz)) {
snprintf(buf, sz, "arena");
return true;
}
if (!bpf_map__is_internal(map) || !(bpf_map__map_flags(map) & BPF_F_MMAPABLE))
return false;
if (!get_map_ident(map, buf, sz))
return false;
return true;
}
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);
if (!d)
return -errno;
bpf_object__for_each_map(map, obj) {
/* only generate definitions for memory-mapped internal maps */
if (!is_mmapable_map(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 bool btf_is_ptr_to_func_proto(const struct btf *btf,
const struct btf_type *v)
{
return btf_is_ptr(v) && btf_is_func_proto(btf__type_by_id(btf, v->type));
}
static int codegen_subskel_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, *var;
const struct btf_var_secinfo *sec_var;
int i, err = 0, vlen;
char map_ident[256], sec_ident[256];
bool strip_mods = false, needs_typeof = false;
const char *sec_name, *var_name;
__u32 var_type_id;
d = btf_dump__new(btf, codegen_btf_dump_printf, NULL, NULL);
if (!d)
return -errno;
bpf_object__for_each_map(map, obj) {
/* only generate definitions for memory-mapped internal maps */
if (!is_mmapable_map(map, map_ident, sizeof(map_ident)))
continue;
sec = find_type_for_map(btf, map_ident);
if (!sec)
continue;
sec_name = btf__name_by_offset(btf, sec->name_off);
if (!get_datasec_ident(sec_name, sec_ident, sizeof(sec_ident)))
continue;
strip_mods = strcmp(sec_name, ".kconfig") != 0;
printf(" struct %s__%s {\n", obj_name, sec_ident);
sec_var = btf_var_secinfos(sec);
vlen = btf_vlen(sec);
for (i = 0; i < vlen; i++, sec_var++) {
DECLARE_LIBBPF_OPTS(btf_dump_emit_type_decl_opts, opts,
.indent_level = 2,
.strip_mods = strip_mods,
/* we'll print the name separately */
.field_name = "",
);
var = btf__type_by_id(btf, sec_var->type);
var_name = btf__name_by_offset(btf, var->name_off);
var_type_id = var->type;
/* static variables are not exposed through BPF skeleton */
if (btf_var(var)->linkage == BTF_VAR_STATIC)
continue;
/* The datasec member has KIND_VAR but we want the
* underlying type of the variable (e.g. KIND_INT).
*/
var = skip_mods_and_typedefs(btf, var->type, NULL);
printf("\t\t");
/* Func and array members require special handling.
* Instead of producing `typename *var`, they produce
* `typeof(typename) *var`. This allows us to keep a
* similar syntax where the identifier is just prefixed
* by *, allowing us to ignore C declaration minutiae.
*/
needs_typeof = btf_is_array(var) || btf_is_ptr_to_func_proto(btf, var);
if (needs_typeof)
printf("__typeof__(");
err = btf_dump__emit_type_decl(d, var_type_id, &opts);
if (err)
goto out;
if (needs_typeof)
printf(")");
printf(" *%s;\n", var_name);
}
printf(" } %s;\n", sec_ident);
}
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];
if (!btf)
return;
codegen("\
\n\
__attribute__((unused)) static void \n\
%1$s__assert(struct %1$s *s __attribute__((unused))) \n\
{ \n\
#ifdef __cplusplus \n\
#define _Static_assert static_assert \n\
#endif \n\
", obj_name);
bpf_object__for_each_map(map, obj) {
if (!is_mmapable_map(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:
case BPF_PROG_TYPE_LSM:
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$s *skel; \n\
\n\
skel = skel_alloc(sizeof(*skel)); \n\
if (!skel) \n\
goto cleanup; \n\
skel->ctx.sz = (void *)&skel->links - (void *)skel; \n\
",
obj_name, opts.data_sz);
bpf_object__for_each_map(map, obj) {
const void *mmap_data = NULL;
size_t mmap_size = 0;
if (!is_mmapable_map(map, ident, sizeof(ident)))
continue;
codegen("\
\n\
{ \n\
static const char data[] __attribute__((__aligned__(8))) = \"\\\n\
");
mmap_data = bpf_map__initial_value(map, &mmap_size);
print_hex(mmap_data, mmap_size);
codegen("\
\n\
\"; \n\
\n\
skel->%1$s = skel_prep_map_data((void *)data, %2$zd,\n\
sizeof(data) - 1);\n\
if (!skel->%1$s) \n\
goto cleanup; \n\
skel->maps.%1$s.initial_value = (__u64) (long) skel->%1$s;\n\
} \n\
", ident, bpf_map_mmap_sz(map));
}
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$s *skel) \n\
{ \n\
struct bpf_load_and_run_opts opts = {}; \n\
int err; \n\
static const char opts_data[] __attribute__((__aligned__(8))) = \"\\\n\
",
obj_name);
print_hex(opts.data, opts.data_sz);
codegen("\
\n\
\"; \n\
static const char opts_insn[] __attribute__((__aligned__(8))) = \"\\\n\
");
print_hex(opts.insns, opts.insns_sz);
codegen("\
\n\
\"; \n\
\n\
opts.ctx = (struct bpf_loader_ctx *)skel; \n\
opts.data_sz = sizeof(opts_data) - 1; \n\
opts.data = (void *)opts_data; \n\
opts.insns_sz = sizeof(opts_insn) - 1; \n\
opts.insns = (void *)opts_insn; \n\
\n\
err = bpf_load_and_run(&opts); \n\
if (err < 0) \n\
return err; \n\
");
bpf_object__for_each_map(map, obj) {
const char *mmap_flags;
if (!is_mmapable_map(map, ident, sizeof(ident)))
continue;
if (bpf_map__map_flags(map) & BPF_F_RDONLY_PROG)
mmap_flags = "PROT_READ";
else
mmap_flags = "PROT_READ | PROT_WRITE";
codegen("\
\n\
skel->%1$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 void
codegen_maps_skeleton(struct bpf_object *obj, size_t map_cnt, bool mmaped, bool populate_links)
{
struct bpf_map *map;
char ident[256];
size_t i, map_sz;
if (!map_cnt)
return;
/* for backward compatibility with old libbpf versions that don't
* handle new BPF skeleton with new struct bpf_map_skeleton definition
* that includes link field, avoid specifying new increased size,
* unless we absolutely have to (i.e., if there are struct_ops maps
* present)
*/
map_sz = offsetof(struct bpf_map_skeleton, link);
if (populate_links) {
bpf_object__for_each_map(map, obj) {
if (bpf_map__type(map) == BPF_MAP_TYPE_STRUCT_OPS) {
map_sz = sizeof(struct bpf_map_skeleton);
break;
}
}
}
codegen("\
\n\
\n\
/* maps */ \n\
s->map_cnt = %zu; \n\
s->map_skel_sz = %zu; \n\
s->maps = (struct bpf_map_skeleton *)calloc(s->map_cnt,\n\
sizeof(*s->maps) > %zu ? sizeof(*s->maps) : %zu);\n\
if (!s->maps) { \n\
err = -ENOMEM; \n\
goto err; \n\
} \n\
",
map_cnt, map_sz, map_sz, map_sz
);
i = 0;
bpf_object__for_each_map(map, obj) {
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
codegen("\
\n\
\n\
map = (struct bpf_map_skeleton *)((char *)s->maps + %zu * s->map_skel_sz);\n\
map->name = \"%s\"; \n\
map->map = &obj->maps.%s; \n\
",
i, bpf_map__name(map), ident);
/* memory-mapped internal maps */
if (mmaped && is_mmapable_map(map, ident, sizeof(ident))) {
printf("\tmap->mmaped = (void **)&obj->%s;\n", ident);
}
if (populate_links && bpf_map__type(map) == BPF_MAP_TYPE_STRUCT_OPS) {
codegen("\
\n\
map->link = &obj->links.%s; \n\
", ident);
}
i++;
}
}
static void
codegen_progs_skeleton(struct bpf_object *obj, size_t prog_cnt, bool populate_links)
{
struct bpf_program *prog;
int i;
if (!prog_cnt)
return;
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\
err = -ENOMEM; \n\
goto err; \n\
} \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$s;\n\
",
i, bpf_program__name(prog));
if (populate_links) {
codegen("\
\n\
s->progs[%1$zu].link = &obj->links.%2$s;\n\
",
i, bpf_program__name(prog));
}
i++;
}
}
static int walk_st_ops_shadow_vars(struct btf *btf, const char *ident,
const struct btf_type *map_type, __u32 map_type_id)
{
LIBBPF_OPTS(btf_dump_emit_type_decl_opts, opts, .indent_level = 3);
const struct btf_type *member_type;
__u32 offset, next_offset = 0;
const struct btf_member *m;
struct btf_dump *d = NULL;
const char *member_name;
__u32 member_type_id;
int i, err = 0, n;
int size;
d = btf_dump__new(btf, codegen_btf_dump_printf, NULL, NULL);
if (!d)
return -errno;
n = btf_vlen(map_type);
for (i = 0, m = btf_members(map_type); i < n; i++, m++) {
member_type = skip_mods_and_typedefs(btf, m->type, &member_type_id);
member_name = btf__name_by_offset(btf, m->name_off);
offset = m->offset / 8;
if (next_offset < offset)
printf("\t\t\tchar __padding_%d[%d];\n", i, offset - next_offset);
switch (btf_kind(member_type)) {
case BTF_KIND_INT:
case BTF_KIND_FLOAT:
case BTF_KIND_ENUM:
case BTF_KIND_ENUM64:
/* scalar type */
printf("\t\t\t");
opts.field_name = member_name;
err = btf_dump__emit_type_decl(d, member_type_id, &opts);
if (err) {
p_err("Failed to emit type declaration for %s: %d", member_name, err);
goto out;
}
printf(";\n");
size = btf__resolve_size(btf, member_type_id);
if (size < 0) {
p_err("Failed to resolve size of %s: %d\n", member_name, size);
err = size;
goto out;
}
next_offset = offset + size;
break;
case BTF_KIND_PTR:
if (resolve_func_ptr(btf, m->type, NULL)) {
/* Function pointer */
printf("\t\t\tstruct bpf_program *%s;\n", member_name);
next_offset = offset + sizeof(void *);
break;
}
/* All pointer types are unsupported except for
* function pointers.
*/
fallthrough;
default:
/* Unsupported types
*
* Types other than scalar types and function
* pointers are currently not supported in order to
* prevent conflicts in the generated code caused
* by multiple definitions. For instance, if the
* struct type FOO is used in a struct_ops map,
* bpftool has to generate definitions for FOO,
* which may result in conflicts if FOO is defined
* in different skeleton files.
*/
size = btf__resolve_size(btf, member_type_id);
if (size < 0) {
p_err("Failed to resolve size of %s: %d\n", member_name, size);
err = size;
goto out;
}
printf("\t\t\tchar __unsupported_%d[%d];\n", i, size);
next_offset = offset + size;
break;
}
}
/* Cannot fail since it must be a struct type */
size = btf__resolve_size(btf, map_type_id);
if (next_offset < (__u32)size)
printf("\t\t\tchar __padding_end[%d];\n", size - next_offset);
out:
btf_dump__free(d);
return err;
}
/* Generate the pointer of the shadow type for a struct_ops map.
*
* This function adds a pointer of the shadow type for a struct_ops map.
* The members of a struct_ops map can be exported through a pointer to a
* shadow type. The user can access these members through the pointer.
*
* A shadow type includes not all members, only members of some types.
* They are scalar types and function pointers. The function pointers are
* translated to the pointer of the struct bpf_program. The scalar types
* are translated to the original type without any modifiers.
*
* Unsupported types will be translated to a char array to occupy the same
* space as the original field, being renamed as __unsupported_*. The user
* should treat these fields as opaque data.
*/
static int gen_st_ops_shadow_type(const char *obj_name, struct btf *btf, const char *ident,
const struct bpf_map *map)
{
const struct btf_type *map_type;
const char *type_name;
__u32 map_type_id;
int err;
map_type_id = bpf_map__btf_value_type_id(map);
if (map_type_id == 0)
return -EINVAL;
map_type = btf__type_by_id(btf, map_type_id);
if (!map_type)
return -EINVAL;
type_name = btf__name_by_offset(btf, map_type->name_off);
printf("\t\tstruct %s__%s__%s {\n", obj_name, ident, type_name);
err = walk_st_ops_shadow_vars(btf, ident, map_type, map_type_id);
if (err)
return err;
printf("\t\t} *%s;\n", ident);
return 0;
}
static int gen_st_ops_shadow(const char *obj_name, struct btf *btf, struct bpf_object *obj)
{
int err, st_ops_cnt = 0;
struct bpf_map *map;
char ident[256];
if (!btf)
return 0;
/* Generate the pointers to shadow types of
* struct_ops maps.
*/
bpf_object__for_each_map(map, obj) {
if (bpf_map__type(map) != BPF_MAP_TYPE_STRUCT_OPS)
continue;
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
if (st_ops_cnt == 0) /* first struct_ops map */
printf("\tstruct {\n");
st_ops_cnt++;
err = gen_st_ops_shadow_type(obj_name, btf, ident, map);
if (err)
return err;
}
if (st_ops_cnt)
printf("\t} struct_ops;\n");
return 0;
}
/* Generate the code to initialize the pointers of shadow types. */
static void gen_st_ops_shadow_init(struct btf *btf, struct bpf_object *obj)
{
struct bpf_map *map;
char ident[256];
if (!btf)
return;
/* Initialize the pointers to_ops shadow types of
* struct_ops maps.
*/
bpf_object__for_each_map(map, obj) {
if (bpf_map__type(map) != BPF_MAP_TYPE_STRUCT_OPS)
continue;
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
codegen("\
\n\
obj->struct_ops.%1$s = (__typeof__(obj->struct_ops.%1$s))\n\
bpf_map__initial_value(obj->maps.%1$s, NULL);\n\
\n\
", ident);
}
}
static int do_skeleton(int argc, char **argv)
{
char header_guard[MAX_OBJ_NAME_LEN + sizeof("__SKEL_H__")];
size_t map_cnt = 0, prog_cnt = 0, attach_map_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);
if (!obj) {
char err_buf[256];
err = -errno;
libbpf_strerror(err, err_buf, sizeof(err_buf));
p_err("failed to open BPF object file: %s", err_buf);
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;
}
if (bpf_map__type(map) == BPF_MAP_TYPE_STRUCT_OPS)
attach_map_cnt++;
map_cnt++;
}
bpf_object__for_each_program(prog, obj) {
prog_cnt++;
}
get_header_guard(header_guard, obj_name, "SKEL_H");
if (use_loader) {
codegen("\
\n\
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ \n\
/* THIS FILE IS AUTOGENERATED BY BPFTOOL! */ \n\
#ifndef %2$s \n\
#define %2$s \n\
\n\
#include <bpf/skel_internal.h> \n\
\n\
struct %1$s { \n\
struct bpf_loader_ctx ctx; \n\
",
obj_name, header_guard
);
} else {
codegen("\
\n\
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ \n\
\n\
/* THIS FILE IS AUTOGENERATED BY BPFTOOL! */ \n\
#ifndef %2$s \n\
#define %2$s \n\
\n\
#include <errno.h> \n\
#include <stdlib.h> \n\
#include <bpf/libbpf.h> \n\
\n\
#define BPF_SKEL_SUPPORTS_MAP_AUTO_ATTACH 1 \n\
\n\
struct %1$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");
}
btf = bpf_object__btf(obj);
err = gen_st_ops_shadow(obj_name, btf, obj);
if (err)
goto out;
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");
}
if (prog_cnt + attach_map_cnt) {
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));
}
bpf_object__for_each_map(map, obj) {
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
if (bpf_map__type(map) != BPF_MAP_TYPE_STRUCT_OPS)
continue;
if (use_loader)
printf("t\tint %s_fd;\n", ident);
else
printf("\t\tstruct bpf_link *%s;\n", ident);
}
printf("\t} links;\n");
}
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$s__create_skeleton(obj); \n\
if (err) \n\
goto err_out; \n\
\n\
err = bpf_object__open_skeleton(obj->skeleton, opts);\n\
if (err) \n\
goto err_out; \n\
\n\
", obj_name);
gen_st_ops_shadow_init(btf, obj);
codegen("\
\n\
return obj; \n\
err_out: \n\
%1$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$s *obj) \n\
{ \n\
bpf_object__detach_skeleton(obj->skeleton); \n\
} \n\
",
obj_name
);
codegen("\
\n\
\n\
static inline const void *%1$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\
struct bpf_map_skeleton *map __attribute__((unused));\n\
int err; \n\
\n\
s = (struct bpf_object_skeleton *)calloc(1, sizeof(*s));\n\
if (!s) { \n\
err = -ENOMEM; \n\
goto err; \n\
} \n\
\n\
s->sz = sizeof(*s); \n\
s->name = \"%1$s\"; \n\
s->obj = &obj->obj; \n\
",
obj_name
);
codegen_maps_skeleton(obj, map_cnt, true /*mmaped*/, true /*links*/);
codegen_progs_skeleton(obj, prog_cnt, true /*populate_links*/);
codegen("\
\n\
\n\
s->data = %1$s__elf_bytes(&s->data_sz); \n\
\n\
obj->skeleton = s; \n\
return 0; \n\
err: \n\
bpf_object__destroy_skeleton(s); \n\
return err; \n\
} \n\
\n\
static inline const void *%1$s__elf_bytes(size_t *sz) \n\
{ \n\
static const char data[] __attribute__((__aligned__(8))) = \"\\\n\
",
obj_name
);
/* embed contents of BPF object file */
print_hex(obj_data, file_sz);
codegen("\
\n\
\"; \n\
\n\
*sz = sizeof(data) - 1; \n\
return (const void *)data; \n\
} \n\
\n\
#ifdef __cplusplus \n\
struct %1$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;
}
/* Subskeletons are like skeletons, except they don't own the bpf_object,
* associated maps, links, etc. Instead, they know about the existence of
* variables, maps, programs and are able to find their locations
* _at runtime_ from an already loaded bpf_object.
*
* This allows for library-like BPF objects to have userspace counterparts
* with access to their own items without having to know anything about the
* final BPF object that the library was linked into.
*/
static int do_subskeleton(int argc, char **argv)
{
char header_guard[MAX_OBJ_NAME_LEN + sizeof("__SUBSKEL_H__")];
size_t i, len, file_sz, map_cnt = 0, prog_cnt = 0, mmap_sz, var_cnt = 0, var_idx = 0;
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, *var_name;
char ident[256];
int fd, err = -1, map_type_id;
const struct bpf_map *map;
struct bpf_program *prog;
struct btf *btf;
const struct btf_type *map_type, *var_type;
const struct btf_var_secinfo *var;
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 (use_loader) {
p_err("cannot use loader for subskeletons");
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);
/* The empty object name allows us to use bpf_map__name and produce
* ELF section names out of it. (".data" instead of "obj.data")
*/
opts.object_name = "";
obj = bpf_object__open_mem(obj_data, file_sz, &opts);
if (!obj) {
char err_buf[256];
libbpf_strerror(errno, err_buf, sizeof(err_buf));
p_err("failed to open BPF object file: %s", err_buf);
obj = NULL;
goto out;
}
btf = bpf_object__btf(obj);
if (!btf) {
err = -1;
p_err("need btf type information for %s", obj_name);
goto out;
}
bpf_object__for_each_program(prog, obj) {
prog_cnt++;
}
/* First, count how many variables we have to find.
* We need this in advance so the subskel can allocate the right
* amount of storage.
*/
bpf_object__for_each_map(map, obj) {
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
/* Also count all maps that have a name */
map_cnt++;
if (!is_mmapable_map(map, ident, sizeof(ident)))
continue;
map_type_id = bpf_map__btf_value_type_id(map);
if (map_type_id <= 0) {
err = map_type_id;
goto out;
}
map_type = btf__type_by_id(btf, map_type_id);
var = btf_var_secinfos(map_type);
len = btf_vlen(map_type);
for (i = 0; i < len; i++, var++) {
var_type = btf__type_by_id(btf, var->type);
if (btf_var(var_type)->linkage == BTF_VAR_STATIC)
continue;
var_cnt++;
}
}
get_header_guard(header_guard, obj_name, "SUBSKEL_H");
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$s { \n\
struct bpf_object *obj; \n\
struct bpf_object_subskeleton *subskel; \n\
", obj_name, header_guard);
if (map_cnt) {
printf("\tstruct {\n");
bpf_object__for_each_map(map, obj) {
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
printf("\t\tstruct bpf_map *%s;\n", ident);
}
printf("\t} maps;\n");
}
err = gen_st_ops_shadow(obj_name, btf, obj);
if (err)
goto out;
if (prog_cnt) {
printf("\tstruct {\n");
bpf_object__for_each_program(prog, obj) {
printf("\t\tstruct bpf_program *%s;\n",
bpf_program__name(prog));
}
printf("\t} progs;\n");
}
err = codegen_subskel_datasecs(obj, obj_name);
if (err)
goto out;
/* emit code that will allocate enough storage for all symbols */
codegen("\
\n\
\n\
#ifdef __cplusplus \n\
static inline struct %1$s *open(const struct bpf_object *src);\n\
static inline void destroy(struct %1$s *skel); \n\
#endif /* __cplusplus */ \n\
}; \n\
\n\
static inline void \n\
%1$s__destroy(struct %1$s *skel) \n\
{ \n\
if (!skel) \n\
return; \n\
if (skel->subskel) \n\
bpf_object__destroy_subskeleton(skel->subskel);\n\
free(skel); \n\
} \n\
\n\
static inline struct %1$s * \n\
%1$s__open(const struct bpf_object *src) \n\
{ \n\
struct %1$s *obj; \n\
struct bpf_object_subskeleton *s; \n\
struct bpf_map_skeleton *map __attribute__((unused));\n\
int err; \n\
\n\
obj = (struct %1$s *)calloc(1, sizeof(*obj)); \n\
if (!obj) { \n\
err = -ENOMEM; \n\
goto err; \n\
} \n\
s = (struct bpf_object_subskeleton *)calloc(1, sizeof(*s));\n\
if (!s) { \n\
err = -ENOMEM; \n\
goto err; \n\
} \n\
s->sz = sizeof(*s); \n\
s->obj = src; \n\
s->var_skel_sz = sizeof(*s->vars); \n\
obj->subskel = s; \n\
\n\
/* vars */ \n\
s->var_cnt = %2$d; \n\
s->vars = (struct bpf_var_skeleton *)calloc(%2$d, sizeof(*s->vars));\n\
if (!s->vars) { \n\
err = -ENOMEM; \n\
goto err; \n\
} \n\
",
obj_name, var_cnt
);
/* walk through each symbol and emit the runtime representation */
bpf_object__for_each_map(map, obj) {
if (!is_mmapable_map(map, ident, sizeof(ident)))
continue;
map_type_id = bpf_map__btf_value_type_id(map);
if (map_type_id <= 0)
/* skip over internal maps with no type*/
continue;
map_type = btf__type_by_id(btf, map_type_id);
var = btf_var_secinfos(map_type);
len = btf_vlen(map_type);
for (i = 0; i < len; i++, var++) {
var_type = btf__type_by_id(btf, var->type);
var_name = btf__name_by_offset(btf, var_type->name_off);
if (btf_var(var_type)->linkage == BTF_VAR_STATIC)
continue;
/* Note that we use the dot prefix in .data as the
* field access operator i.e. maps%s becomes maps.data
*/
codegen("\
\n\
\n\
s->vars[%3$d].name = \"%1$s\"; \n\
s->vars[%3$d].map = &obj->maps.%2$s; \n\
s->vars[%3$d].addr = (void **) &obj->%2$s.%1$s;\n\
", var_name, ident, var_idx);
var_idx++;
}
}
codegen_maps_skeleton(obj, map_cnt, false /*mmaped*/, false /*links*/);
codegen_progs_skeleton(obj, prog_cnt, false /*links*/);
codegen("\
\n\
\n\
err = bpf_object__open_subskeleton(s); \n\
if (err) \n\
goto err; \n\
\n\
");
gen_st_ops_shadow_init(btf, obj);
codegen("\
\n\
return obj; \n\
err: \n\
%1$s__destroy(obj); \n\
errno = -err; \n\
return NULL; \n\
} \n\
\n\
#ifdef __cplusplus \n\
struct %1$s *%1$s::open(const struct bpf_object *src) { return %1$s__open(src); }\n\
void %1$s::destroy(struct %1$s *skel) { %1$s__destroy(skel); }\n\
#endif /* __cplusplus */ \n\
\n\
#endif /* %2$s */ \n\
",
obj_name, 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(errno), errno);
goto out;
}
}
err = bpf_linker__finalize(linker);
if (err) {
p_err("failed to finalize ELF file: %s (%d)", strerror(errno), errno);
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 subskeleton 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(long key, void *ctx)
{
return key;
}
static bool btfgen_equal_fn(long k1, long k2, void *ctx)
{
return k1 == k2;
}
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_ENUM64:
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_RESTRICT:
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;
}
/* Mark types, members, and member types. Compared to btfgen_record_field_relo,
* this function does not rely on the target spec for inferring members, but
* uses the associated BTF.
*
* The `behind_ptr` argument is used to stop marking of composite types reached
* through a pointer. This way, we can keep BTF size in check while providing
* reasonable match semantics.
*/
static int btfgen_mark_type_match(struct btfgen_info *info, __u32 type_id, bool behind_ptr)
{
const struct btf_type *btf_type;
struct btf *btf = info->src_btf;
struct btf_type *cloned_type;
int i, err;
if (type_id == 0)
return 0;
btf_type = btf__type_by_id(btf, type_id);
/* 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;
switch (btf_kind(btf_type)) {
case BTF_KIND_UNKN:
case BTF_KIND_INT:
case BTF_KIND_FLOAT:
case BTF_KIND_ENUM:
case BTF_KIND_ENUM64:
break;
case BTF_KIND_STRUCT:
case BTF_KIND_UNION: {
struct btf_member *m = btf_members(btf_type);
__u16 vlen = btf_vlen(btf_type);
if (behind_ptr)
break;
for (i = 0; i < vlen; i++, m++) {
/* mark member */
btfgen_mark_member(info, type_id, i);
/* mark member's type */
err = btfgen_mark_type_match(info, m->type, false);
if (err)
return err;
}
break;
}
case BTF_KIND_CONST:
case BTF_KIND_FWD:
case BTF_KIND_RESTRICT:
case BTF_KIND_TYPEDEF:
case BTF_KIND_VOLATILE:
return btfgen_mark_type_match(info, btf_type->type, behind_ptr);
case BTF_KIND_PTR:
return btfgen_mark_type_match(info, btf_type->type, true);
case BTF_KIND_ARRAY: {
struct btf_array *array;
array = btf_array(btf_type);
/* mark array type */
err = btfgen_mark_type_match(info, array->type, false);
/* mark array's index type */
err = err ? : btfgen_mark_type_match(info, array->index_type, false);
if (err)
return err;
break;
}
case BTF_KIND_FUNC_PROTO: {
__u16 vlen = btf_vlen(btf_type);
struct btf_param *param;
/* mark ret type */
err = btfgen_mark_type_match(info, btf_type->type, false);
if (err)
return err;
/* mark parameters types */
param = btf_params(btf_type);
for (i = 0; i < vlen; i++) {
err = btfgen_mark_type_match(info, param->type, false);
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;
}
/* Mark types, members, and member types. Compared to btfgen_record_field_relo,
* this function does not rely on the target spec for inferring members, but
* uses the associated BTF.
*/
static int btfgen_record_type_match_relo(struct btfgen_info *info, struct bpf_core_spec *targ_spec)
{
return btfgen_mark_type_match(info, targ_spec->root_type_id, false);
}
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_TYPE_MATCHES:
return btfgen_record_type_match_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 char *sec_name = btf__name_by_offset(btf, sec->sec_name_off);
if (relo->kind != BPF_CORE_TYPE_ID_LOCAL &&
!hashmap__find(cand_cache, relo->type_id, &cands)) {
cands = btfgen_find_cands(btf, info->src_btf, relo->type_id);
if (!cands) {
err = -errno;
goto out;
}
err = hashmap__set(cand_cache, relo->type_id, 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->pvalue);
}
hashmap__free(cand_cache);
}
return err;
}
/* 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);
struct btf_field_iter it;
__u32 *type_id;
err = btf_field_iter_init(&it, btf_type, BTF_FIELD_ITER_IDS);
if (err)
goto err_out;
while ((type_id = btf_field_iter_next(&it)))
*type_id = ids[*type_id];
}
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 },
{ "subskeleton", do_subskeleton },
{ "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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