The new_fd, add_fd and finalize_fd functions correspond to the original
new, add_file and finalize functions, but accept an FD instead of a file
name. This gives API consumers the option of using anonymous
files/memfds to avoid writing ELFs to disk.
This new API will be useful for performing linking as part of
bpftrace's JIT compilation.
The add_buf function is a convenience wrapper that does the work of
creating a memfd for the caller.
Signed-off-by: Alastair Robertson <ajor@xxxxxxxx>
---
tools/lib/bpf/libbpf.h | 9 ++
tools/lib/bpf/libbpf.map | 4 +
tools/lib/bpf/linker.c | 229 +++++++++++++++++++++++++++++----------
3 files changed, 185 insertions(+), 57 deletions(-)
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index b2ce3a72b11d..aae8f954c4fc 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1796,10 +1796,19 @@ struct bpf_linker_file_opts {
struct bpf_linker;
LIBBPF_API struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts *opts);
+LIBBPF_API struct bpf_linker *bpf_linker__new_fd(const char *name, int fd,
+ struct bpf_linker_opts *opts);
LIBBPF_API int bpf_linker__add_file(struct bpf_linker *linker,
const char *filename,
const struct bpf_linker_file_opts *opts);
+LIBBPF_API int bpf_linker__add_fd(struct bpf_linker *linker,
+ const char *name, int fd,
+ const struct bpf_linker_file_opts *opts);
+LIBBPF_API int bpf_linker__add_buf(struct bpf_linker *linker, const char *name,
+ void *buffer, int buffer_sz,
+ const struct bpf_linker_file_opts *opts);
LIBBPF_API int bpf_linker__finalize(struct bpf_linker *linker);
+LIBBPF_API int bpf_linker__finalize_fd(struct bpf_linker *linker);
LIBBPF_API void bpf_linker__free(struct bpf_linker *linker);
/*
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 54b6f312cfa8..e767f34c1d08 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -432,4 +432,8 @@ LIBBPF_1.5.0 {
} LIBBPF_1.4.0;
LIBBPF_1.6.0 {
+ bpf_linker__new_fd;
+ bpf_linker__add_fd;
+ bpf_linker__add_buf;
+ bpf_linker__finalize_fd;
} LIBBPF_1.5.0;
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index cf71d149fe26..6571ed8b858f 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -4,6 +4,8 @@
*
* Copyright (c) 2021 Facebook
*/
+#define _GNU_SOURCE
+
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
@@ -16,6 +18,7 @@
#include <elf.h>
#include <libelf.h>
#include <fcntl.h>
+#include <sys/mman.h>
#include "libbpf.h"
#include "btf.h"
#include "libbpf_internal.h"
@@ -157,9 +160,9 @@ struct bpf_linker {
#define pr_warn_elf(fmt, ...) \
libbpf_print(LIBBPF_WARN, "libbpf: " fmt ": %s\n", ##__VA_ARGS__, elf_errmsg(-1))
-static int init_output_elf(struct bpf_linker *linker, const char *file);
+static int init_output_elf(struct bpf_linker *linker);
-static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
+static int linker_load_obj_file(struct bpf_linker *linker,
const struct bpf_linker_file_opts *opts,
struct src_obj *obj);
static int linker_sanity_check_elf(struct src_obj *obj);
@@ -233,9 +236,56 @@ struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts
if (!linker)
return errno = ENOMEM, NULL;
- linker->fd = -1;
+ linker->filename = strdup(filename);
+ if (!linker->filename)
+ return errno = ENOMEM, NULL;
+
+ linker->fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644);
+ if (linker->fd < 0) {
+ err = -errno;
+ pr_warn("failed to create '%s': %d\n", filename, err);
+ goto err_out;
+ }
+
+ err = init_output_elf(linker);
+ if (err)
+ goto err_out;
+
+ return linker;
+
+err_out:
+ bpf_linker__free(linker);
+ return errno = -err, NULL;
+}
+
+struct bpf_linker *bpf_linker__new_fd(const char *name, int fd,
+ struct bpf_linker_opts *opts)
+{
+ struct bpf_linker *linker;
+ int err;
+
+ if (fd < 0)
+ return errno = EINVAL, NULL;
+
+ if (!OPTS_VALID(opts, bpf_linker_opts))
+ return errno = EINVAL, NULL;
+
+ if (elf_version(EV_CURRENT) == EV_NONE) {
+ pr_warn_elf("libelf initialization failed");
+ return errno = EINVAL, NULL;
+ }
+
+ linker = calloc(1, sizeof(*linker));
+ if (!linker)
+ return errno = ENOMEM, NULL;
+
+ linker->filename = strdup(name);
+ if (!linker->filename)
+ return errno = ENOMEM, NULL;
+
+ linker->fd = fd;
- err = init_output_elf(linker, filename);
+ err = init_output_elf(linker);
if (err)
goto err_out;
@@ -294,23 +344,12 @@ static Elf64_Sym *add_new_sym(struct bpf_linker *linker, size_t *sym_idx)
return sym;
}
-static int init_output_elf(struct bpf_linker *linker, const char *file)
+static int init_output_elf(struct bpf_linker *linker)
{
int err, str_off;
Elf64_Sym *init_sym;
struct dst_sec *sec;
- linker->filename = strdup(file);
- if (!linker->filename)
- return -ENOMEM;
-
- linker->fd = open(file, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644);
- if (linker->fd < 0) {
- err = -errno;
- pr_warn("failed to create '%s': %s\n", file, errstr(err));
- return err;
- }
-
linker->elf = elf_begin(linker->fd, ELF_C_WRITE, NULL);
if (!linker->elf) {
pr_warn_elf("failed to create ELF object");
@@ -436,10 +475,9 @@ static int init_output_elf(struct bpf_linker *linker, const char *file)
return 0;
}
-int bpf_linker__add_file(struct bpf_linker *linker, const char *filename,
- const struct bpf_linker_file_opts *opts)
+static int linker_add_common(struct bpf_linker *linker, struct src_obj *obj,
+ const struct bpf_linker_file_opts *opts)
{
- struct src_obj obj = {};
int err = 0;
if (!OPTS_VALID(opts, bpf_linker_file_opts))
@@ -448,25 +486,91 @@ int bpf_linker__add_file(struct bpf_linker *linker, const char *filename,
if (!linker->elf)
return libbpf_err(-EINVAL);
- err = err ?: linker_load_obj_file(linker, filename, opts, &obj);
- err = err ?: linker_append_sec_data(linker, &obj);
- err = err ?: linker_append_elf_syms(linker, &obj);
- err = err ?: linker_append_elf_relos(linker, &obj);
- err = err ?: linker_append_btf(linker, &obj);
- err = err ?: linker_append_btf_ext(linker, &obj);
+ err = err ?: linker_load_obj_file(linker, opts, obj);
+ err = err ?: linker_append_sec_data(linker, obj);
+ err = err ?: linker_append_elf_syms(linker, obj);
+ err = err ?: linker_append_elf_relos(linker, obj);
+ err = err ?: linker_append_btf(linker, obj);
+ err = err ?: linker_append_btf_ext(linker, obj);
/* free up src_obj resources */
- free(obj.btf_type_map);
- btf__free(obj.btf);
- btf_ext__free(obj.btf_ext);
- free(obj.secs);
- free(obj.sym_map);
- if (obj.elf)
- elf_end(obj.elf);
+ free(obj->btf_type_map);
+ btf__free(obj->btf);
+ btf_ext__free(obj->btf_ext);
+ free(obj->secs);
+ free(obj->sym_map);
+ if (obj->elf)
+ elf_end(obj->elf);
+ /* leave obj->fd for the caller to clean up if appropriate */
+
+ return libbpf_err(err);
+}
+
+int bpf_linker__add_file(struct bpf_linker *linker, const char *filename,
+ const struct bpf_linker_file_opts *opts)
+{
+ struct src_obj obj = {};
+ int ret;
+
+ obj.filename = filename;
+ obj.fd = open(filename, O_RDONLY | O_CLOEXEC);
+ if (obj.fd < 0) {
+ pr_warn("failed to open file '%s': %s\n", filename, errstr(errno));
+ return -errno;
+ }
+
+ ret = linker_add_common(linker, &obj, opts);
+
if (obj.fd >= 0)
close(obj.fd);
- return libbpf_err(err);
+ return ret;
+}
+
+int bpf_linker__add_fd(struct bpf_linker *linker, const char *name, int fd,
+ const struct bpf_linker_file_opts *opts)
+{
+ struct src_obj obj = {};
+
+ if (fd < 0)
+ return libbpf_err(-EINVAL);
+
+ obj.filename = name;
+ obj.fd = fd;
+
+ return linker_add_common(linker, &obj, opts);
+}
+
+int bpf_linker__add_buf(struct bpf_linker *linker, const char *name,
+ void *buffer, int buffer_sz,
+ const struct bpf_linker_file_opts *opts)
+{
+ struct src_obj obj = {};
+ int written, ret;
+
+ obj.filename = name;
+ obj.fd = memfd_create(name, 0);
+ if (obj.fd < 0) {
+ pr_warn("failed to create memfd '%s': %s\n", name, errstr(errno));
+ return -errno;
+ }
+
+ written = 0;
+ while (written < buffer_sz) {
+ ret = write(obj.fd, buffer, buffer_sz);
+ if (ret < 0) {
+ pr_warn("failed to write '%s': %s\n", name, errstr(errno));
+ return -errno;
+ }
+ written += ret;
+ }
+
+ ret = linker_add_common(linker, &obj, opts);
+
+ if (obj.fd >= 0)
+ close(obj.fd);
+
+ return ret;
}
static bool is_dwarf_sec_name(const char *name)
@@ -534,7 +638,7 @@ static struct src_sec *add_src_sec(struct src_obj *obj, const char *sec_name)
return sec;
}
-static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
+static int linker_load_obj_file(struct bpf_linker *linker,
const struct bpf_linker_file_opts *opts,
struct src_obj *obj)
{
@@ -554,20 +658,12 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
#error "Unknown __BYTE_ORDER__"
#endif
- pr_debug("linker: adding object file '%s'...\n", filename);
-
- obj->filename = filename;
+ pr_debug("linker: adding object file '%s'...\n", obj->filename);
- obj->fd = open(filename, O_RDONLY | O_CLOEXEC);
- if (obj->fd < 0) {
- err = -errno;
- pr_warn("failed to open file '%s': %s\n", filename, errstr(err));
- return err;
- }
obj->elf = elf_begin(obj->fd, ELF_C_READ_MMAP, NULL);
if (!obj->elf) {
err = -errno;
- pr_warn_elf("failed to parse ELF file '%s'", filename);
+ pr_warn_elf("failed to parse ELF file '%s'", obj->filename);
return err;
}
@@ -575,7 +671,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
ehdr = elf64_getehdr(obj->elf);
if (!ehdr) {
err = -errno;
- pr_warn_elf("failed to get ELF header for %s", filename);
+ pr_warn_elf("failed to get ELF header for %s", obj->filename);
return err;
}
@@ -583,7 +679,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
obj_byteorder = ehdr->e_ident[EI_DATA];
if (obj_byteorder != ELFDATA2LSB && obj_byteorder != ELFDATA2MSB) {
err = -EOPNOTSUPP;
- pr_warn("unknown byte order of ELF file %s\n", filename);
+ pr_warn("unknown byte order of ELF file %s\n", obj->filename);
return err;
}
if (link_byteorder == ELFDATANONE) {
@@ -593,7 +689,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
obj_byteorder == ELFDATA2MSB ? "big" : "little");
} else if (link_byteorder != obj_byteorder) {
err = -EOPNOTSUPP;
- pr_warn("byte order mismatch with ELF file %s\n", filename);
+ pr_warn("byte order mismatch with ELF file %s\n", obj->filename);
return err;
}
@@ -601,13 +697,13 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
|| ehdr->e_machine != EM_BPF
|| ehdr->e_ident[EI_CLASS] != ELFCLASS64) {
err = -EOPNOTSUPP;
- pr_warn_elf("unsupported kind of ELF file %s", filename);
+ pr_warn_elf("unsupported kind of ELF file %s", obj->filename);
return err;
}
if (elf_getshdrstrndx(obj->elf, &obj->shstrs_sec_idx)) {
err = -errno;
- pr_warn_elf("failed to get SHSTRTAB section index for %s", filename);
+ pr_warn_elf("failed to get SHSTRTAB section index for %s", obj->filename);
return err;
}
@@ -620,7 +716,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
if (!shdr) {
err = -errno;
pr_warn_elf("failed to get section #%zu header for %s",
- sec_idx, filename);
+ sec_idx, obj->filename);
return err;
}
@@ -628,7 +724,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
if (!sec_name) {
err = -errno;
pr_warn_elf("failed to get section #%zu name for %s",
- sec_idx, filename);
+ sec_idx, obj->filename);
return err;
}
@@ -636,7 +732,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
if (!data) {
err = -errno;
pr_warn_elf("failed to get section #%zu (%s) data from %s",
- sec_idx, sec_name, filename);
+ sec_idx, sec_name, obj->filename);
return err;
}
@@ -672,7 +768,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
err = libbpf_get_error(obj->btf);
if (err) {
pr_warn("failed to parse .BTF from %s: %s\n",
- filename, errstr(err));
+ obj->filename, errstr(err));
return err;
}
sec->skipped = true;
@@ -683,7 +779,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
err = libbpf_get_error(obj->btf_ext);
if (err) {
pr_warn("failed to parse .BTF.ext from '%s': %s\n",
- filename, errstr(err));
+ obj->filename, errstr(err));
return err;
}
sec->skipped = true;
@@ -700,7 +796,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
break;
default:
pr_warn("unrecognized section #%zu (%s) in %s\n",
- sec_idx, sec_name, filename);
+ sec_idx, sec_name, obj->filename);
err = -EINVAL;
return err;
}
@@ -2634,7 +2730,7 @@ static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj)
return 0;
}
-int bpf_linker__finalize(struct bpf_linker *linker)
+int linker_finalize_common(struct bpf_linker *linker)
{
struct dst_sec *sec;
size_t strs_sz;
@@ -2693,9 +2789,28 @@ int bpf_linker__finalize(struct bpf_linker *linker)
}
elf_end(linker->elf);
+ linker->elf = NULL;
+
+ /* leave linker->fd for the caller to close if appropriate */
+
+ return 0;
+}
+
+int bpf_linker__finalize(struct bpf_linker *linker)
+{
+ linker_finalize_common(linker);
+
close(linker->fd);
+ linker->fd = -1;
- linker->elf = NULL;
+ return 0;
+}
+
+int bpf_linker__finalize_fd(struct bpf_linker *linker)
+{
+ linker_finalize_common(linker);
+
+ /* linker->fd was opened by the caller, so do not close it here */
linker->fd = -1;
return 0;
--
2.43.5
