Commit b6417129 authored by Alastair Robertson's avatar Alastair Robertson Committed by Andrii Nakryiko
Browse files

libbpf: Pull file-opening logic up to top-level functions 



Move the filename arguments and file-descriptor handling from
init_output_elf() and linker_load_obj_file() and instead handle them
at the top-level in bpf_linker__new() and bpf_linker__add_file().

This will allow the inner functions to be shared with a new,
non-filename-based, API in the next commit.

Signed-off-by: default avatarAlastair Robertson <ajor@meta.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241211164030.573042-2-ajor@meta.com
parent b9fee10a

tools/lib/bpf/linker.c

+42 −42
Original line number Diff line number Diff line
@@ -157,10 +157,9 @@ 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,

				const struct bpf_linker_file_opts *opts,

static int linker_load_obj_file(struct bpf_linker *linker,

				struct src_obj *obj);

static int linker_sanity_check_elf(struct src_obj *obj);

static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec);
@@ -233,9 +232,20 @@ 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) {

		err = -ENOMEM;

		goto err_out;

	}



	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, filename);

	err = init_output_elf(linker);

	if (err)

		goto err_out;
@@ -294,23 +304,12 @@ 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");
@@ -440,7 +439,7 @@ int bpf_linker__add_file(struct bpf_linker *linker, const char *filename, 
			 const struct bpf_linker_file_opts *opts)

{

	struct src_obj obj = {};

	int err = 0;

	int err = 0, fd;



	if (!OPTS_VALID(opts, bpf_linker_file_opts))

		return libbpf_err(-EINVAL);
@@ -448,7 +447,17 @@ 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);

	fd = open(filename, O_RDONLY | O_CLOEXEC);

	if (fd < 0) {

		err = -errno;

		pr_warn("failed to open file '%s': %s\n", filename, errstr(err));

		return libbpf_err(err);

	}



	obj.filename = filename;

	obj.fd = fd;



	err = err ?: linker_load_obj_file(linker, &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);
@@ -534,8 +543,7 @@ 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,

				const struct bpf_linker_file_opts *opts,

static int linker_load_obj_file(struct bpf_linker *linker,

				struct src_obj *obj)

{

	int err = 0;
@@ -554,26 +562,18 @@ 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) {

		pr_warn_elf("failed to parse ELF file '%s'", filename);

		pr_warn_elf("failed to parse ELF file '%s'", obj->filename);

		return -EINVAL;

	}



	/* Sanity check ELF file high-level properties */

	ehdr = elf64_getehdr(obj->elf);

	if (!ehdr) {

		pr_warn_elf("failed to get ELF header for %s", filename);

		pr_warn_elf("failed to get ELF header for %s", obj->filename);

		return -EINVAL;

	}
@@ -581,7 +581,7 @@ 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) {
@@ -591,7 +591,7 @@ 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;

	}
@@ -599,12 +599,12 @@ 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)) {

		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 -EINVAL;

	}
@@ -616,21 +616,21 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, 
		shdr = elf64_getshdr(scn);

		if (!shdr) {

			pr_warn_elf("failed to get section #%zu header for %s",

				    sec_idx, filename);

				    sec_idx, obj->filename);

			return -EINVAL;

		}



		sec_name = elf_strptr(obj->elf, obj->shstrs_sec_idx, shdr->sh_name);

		if (!sec_name) {

			pr_warn_elf("failed to get section #%zu name for %s",

				    sec_idx, filename);

				    sec_idx, obj->filename);

			return -EINVAL;

		}



		data = elf_getdata(scn, 0);

		if (!data) {

			pr_warn_elf("failed to get section #%zu (%s) data from %s",

				    sec_idx, sec_name, filename);

				    sec_idx, sec_name, obj->filename);

			return -EINVAL;

		}
@@ -666,7 +666,7 @@ 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;
@@ -677,7 +677,7 @@ 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;
@@ -694,7 +694,7 @@ 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;

		}