From 01b29d1dc9a06e2cdc6a0172d35605eb0300ecb2 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Mon, 17 Jun 2019 12:26:52 -0700 Subject: [PATCH] libbpf: streamline ELF parsing error-handling Simplify ELF parsing logic by exiting early, as there is no common clean up path to execute. That makes it unnecessary to track when err was set and when it was cleared. It also reduces nesting in some places. Signed-off-by: Andrii Nakryiko Acked-by: Song Liu Signed-off-by: Daniel Borkmann --- tools/lib/bpf/libbpf.c | 44 ++++++++++++++++++++------------------------ 1 file changed, 20 insertions(+), 24 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 49d3a80..7ee44d8 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1154,24 +1154,21 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags) if (gelf_getshdr(scn, &sh) != &sh) { pr_warning("failed to get section(%d) header from %s\n", idx, obj->path); - err = -LIBBPF_ERRNO__FORMAT; - goto out; + return -LIBBPF_ERRNO__FORMAT; } name = elf_strptr(elf, ep->e_shstrndx, sh.sh_name); if (!name) { pr_warning("failed to get section(%d) name from %s\n", idx, obj->path); - err = -LIBBPF_ERRNO__FORMAT; - goto out; + return -LIBBPF_ERRNO__FORMAT; } data = elf_getdata(scn, 0); if (!data) { pr_warning("failed to get section(%d) data from %s(%s)\n", idx, name, obj->path); - err = -LIBBPF_ERRNO__FORMAT; - goto out; + return -LIBBPF_ERRNO__FORMAT; } pr_debug("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n", idx, name, (unsigned long)data->d_size, @@ -1182,10 +1179,14 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags) err = bpf_object__init_license(obj, data->d_buf, data->d_size); + if (err) + return err; } else if (strcmp(name, "version") == 0) { err = bpf_object__init_kversion(obj, data->d_buf, data->d_size); + if (err) + return err; } else if (strcmp(name, "maps") == 0) { obj->efile.maps_shndx = idx; } else if (strcmp(name, BTF_ELF_SEC) == 0) { @@ -1196,11 +1197,10 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags) if (obj->efile.symbols) { pr_warning("bpf: multiple SYMTAB in %s\n", obj->path); - err = -LIBBPF_ERRNO__FORMAT; - } else { - obj->efile.symbols = data; - obj->efile.strtabidx = sh.sh_link; + return -LIBBPF_ERRNO__FORMAT; } + obj->efile.symbols = data; + obj->efile.strtabidx = sh.sh_link; } else if (sh.sh_type == SHT_PROGBITS && data->d_size > 0) { if (sh.sh_flags & SHF_EXECINSTR) { if (strcmp(name, ".text") == 0) @@ -1214,6 +1214,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags) pr_warning("failed to alloc program %s (%s): %s", name, obj->path, cp); + return err; } } else if (strcmp(name, ".data") == 0) { obj->efile.data = data; @@ -1225,8 +1226,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags) pr_debug("skip section(%d) %s\n", idx, name); } } else if (sh.sh_type == SHT_REL) { + int nr_reloc = obj->efile.nr_reloc; void *reloc = obj->efile.reloc; - int nr_reloc = obj->efile.nr_reloc + 1; int sec = sh.sh_info; /* points to other section */ /* Only do relo for section with exec instructions */ @@ -1236,28 +1237,24 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags) continue; } - reloc = reallocarray(reloc, nr_reloc, + reloc = reallocarray(reloc, nr_reloc + 1, sizeof(*obj->efile.reloc)); if (!reloc) { pr_warning("realloc failed\n"); - err = -ENOMEM; - } else { - int n = nr_reloc - 1; + return -ENOMEM; + } - obj->efile.reloc = reloc; - obj->efile.nr_reloc = nr_reloc; + obj->efile.reloc = reloc; + obj->efile.nr_reloc++; - obj->efile.reloc[n].shdr = sh; - obj->efile.reloc[n].data = data; - } + obj->efile.reloc[nr_reloc].shdr = sh; + obj->efile.reloc[nr_reloc].data = data; } else if (sh.sh_type == SHT_NOBITS && strcmp(name, ".bss") == 0) { obj->efile.bss = data; obj->efile.bss_shndx = idx; } else { pr_debug("skip section(%d) %s\n", idx, name); } - if (err) - goto out; } if (!obj->efile.strtabidx || obj->efile.strtabidx >= idx) { @@ -1270,10 +1267,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags) if (bpf_object__has_maps(obj)) { err = bpf_object__init_maps(obj, flags); if (err) - goto out; + return err; } err = bpf_object__init_prog_names(obj); -out: return err; } -- 2.7.4