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: Alastair Robertson <ajor@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241211164030.573042-2-ajor@meta.com

diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index e56ba6e67451d6c2c506356cd320587ed65b6373..c49e94506d9c66491df04dceecf883231974b190 100644 (file)
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -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;
                }