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Commit beaa3711 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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libbpf: Factor out symtab and relos sanity checks 

Factor out logic for sanity checking SHT_SYMTAB and SHT_REL sections into
separate sections. They are already quite extensive and are suffering from too
deep indentation. Subsequent changes will extend SYMTAB sanity checking
further, so it's better to factor each into a separate function.

No functional changes are intended.
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210423181348.1801389-8-andrii@kernel.org
parent c7ef5ec9
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Inline Side-by-side
Showing with 127 additions and 106 deletions
tools/lib/bpf/linker.c
View file @ beaa3711
...@@ -131,6 +131,8 @@ static int init_output_elf(struct bpf_linker *linker, const char *file); ...@@ -131,6 +131,8 @@ static int init_output_elf(struct bpf_linker *linker, const char *file);
static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, struct src_obj *obj); static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, struct src_obj *obj);
static int linker_sanity_check_elf(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);
static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec);
static int linker_sanity_check_btf(struct src_obj *obj); static int linker_sanity_check_btf(struct src_obj *obj);
static int linker_sanity_check_btf_ext(struct src_obj *obj); static int linker_sanity_check_btf_ext(struct src_obj *obj);
static int linker_fixup_btf(struct src_obj *obj); static int linker_fixup_btf(struct src_obj *obj);
...@@ -663,8 +665,8 @@ static bool is_pow_of_2(size_t x) ...@@ -663,8 +665,8 @@ static bool is_pow_of_2(size_t x)
static int linker_sanity_check_elf(struct src_obj *obj) static int linker_sanity_check_elf(struct src_obj *obj)
{ {
struct src_sec *sec, *link_sec; struct src_sec *sec;
int i, j, n; int i, err;
if (!obj->symtab_sec_idx) { if (!obj->symtab_sec_idx) {
pr_warn("ELF is missing SYMTAB section in %s\n", obj->filename); pr_warn("ELF is missing SYMTAB section in %s\n", obj->filename);
...@@ -692,43 +694,11 @@ static int linker_sanity_check_elf(struct src_obj *obj) ...@@ -692,43 +694,11 @@ static int linker_sanity_check_elf(struct src_obj *obj)
return -EINVAL; return -EINVAL;
switch (sec->shdr->sh_type) { switch (sec->shdr->sh_type) {
case SHT_SYMTAB: { case SHT_SYMTAB:
Elf64_Sym *sym; err = linker_sanity_check_elf_symtab(obj, sec);
if (err)
if (sec->shdr->sh_entsize != sizeof(Elf64_Sym)) return err;
return -EINVAL;
if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
return -EINVAL;
if (!sec->shdr->sh_link || sec->shdr->sh_link >= obj->sec_cnt) {
pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n",
sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
return -EINVAL;
}
link_sec = &obj->secs[sec->shdr->sh_link];
if (link_sec->shdr->sh_type != SHT_STRTAB) {
pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n",
sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
return -EINVAL;
}
n = sec->shdr->sh_size / sec->shdr->sh_entsize;
sym = sec->data->d_buf;
for (j = 0; j < n; j++, sym++) {
if (sym->st_shndx
&& sym->st_shndx < SHN_LORESERVE
&& sym->st_shndx >= obj->sec_cnt) {
pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n",
j, sec->sec_idx, (size_t)sym->st_shndx, obj->filename);
return -EINVAL;
}
if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION) {
if (sym->st_value != 0)
return -EINVAL;
}
}
break; break;
}
case SHT_STRTAB: case SHT_STRTAB:
break; break;
case SHT_PROGBITS: case SHT_PROGBITS:
...@@ -739,87 +709,138 @@ static int linker_sanity_check_elf(struct src_obj *obj) ...@@ -739,87 +709,138 @@ static int linker_sanity_check_elf(struct src_obj *obj)
break; break;
case SHT_NOBITS: case SHT_NOBITS:
break; break;
case SHT_REL: { case SHT_REL:
Elf64_Rel *relo; err = linker_sanity_check_elf_relos(obj, sec);
struct src_sec *sym_sec; if (err)
return err;
break;
case SHT_LLVM_ADDRSIG:
break;
default:
pr_warn("ELF section #%zu (%s) has unrecognized type %zu in %s\n",
sec->sec_idx, sec->sec_name, (size_t)sec->shdr->sh_type, obj->filename);
return -EINVAL;
}
}
if (sec->shdr->sh_entsize != sizeof(Elf64_Rel)) return 0;
return -EINVAL; }
if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
return -EINVAL;
/* SHT_REL's sh_link should point to SYMTAB */ static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec)
if (sec->shdr->sh_link != obj->symtab_sec_idx) { {
pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n", struct src_sec *link_sec;
sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename); Elf64_Sym *sym;
return -EINVAL; int i, n;
}
/* SHT_REL's sh_info points to relocated section */ if (sec->shdr->sh_entsize != sizeof(Elf64_Sym))
if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) { return -EINVAL;
pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n", if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename); return -EINVAL;
return -EINVAL;
} if (!sec->shdr->sh_link || sec->shdr->sh_link >= obj->sec_cnt) {
link_sec = &obj->secs[sec->shdr->sh_info]; pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n",
sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
return -EINVAL;
}
link_sec = &obj->secs[sec->shdr->sh_link];
if (link_sec->shdr->sh_type != SHT_STRTAB) {
pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n",
sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
return -EINVAL;
}
/* .rel<secname> -> <secname> pattern is followed */ n = sec->shdr->sh_size / sec->shdr->sh_entsize;
if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0 sym = sec->data->d_buf;
|| strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) { for (i = 0; i < n; i++, sym++) {
pr_warn("ELF relo section #%zu name has invalid name in %s\n", if (sym->st_shndx
sec->sec_idx, obj->filename); && sym->st_shndx < SHN_LORESERVE
&& sym->st_shndx >= obj->sec_cnt) {
pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n",
i, sec->sec_idx, (size_t)sym->st_shndx, obj->filename);
return -EINVAL;
}
if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION) {
if (sym->st_value != 0)
return -EINVAL; return -EINVAL;
} continue;
}
}
/* don't further validate relocations for ignored sections */ return 0;
if (link_sec->skipped) }
break;
/* relocatable section is data or instructions */ static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec)
if (link_sec->shdr->sh_type != SHT_PROGBITS {
&& link_sec->shdr->sh_type != SHT_NOBITS) { struct src_sec *link_sec, *sym_sec;
pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n", Elf64_Rel *relo;
sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename); int i, n;
return -EINVAL;
}
/* check sanity of each relocation */ if (sec->shdr->sh_entsize != sizeof(Elf64_Rel))
n = sec->shdr->sh_size / sec->shdr->sh_entsize; return -EINVAL;
relo = sec->data->d_buf; if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
sym_sec = &obj->secs[obj->symtab_sec_idx]; return -EINVAL;
for (j = 0; j < n; j++, relo++) {
size_t sym_idx = ELF64_R_SYM(relo->r_info);
size_t sym_type = ELF64_R_TYPE(relo->r_info);
if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32) {
pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n",
j, sec->sec_idx, sym_type, obj->filename);
return -EINVAL;
}
if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) { /* SHT_REL's sh_link should point to SYMTAB */
pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n", if (sec->shdr->sh_link != obj->symtab_sec_idx) {
j, sec->sec_idx, sym_idx, obj->filename); pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n",
return -EINVAL; sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
} return -EINVAL;
}
if (link_sec->shdr->sh_flags & SHF_EXECINSTR) { /* SHT_REL's sh_info points to relocated section */
if (relo->r_offset % sizeof(struct bpf_insn) != 0) { if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) {
pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n", pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n",
j, sec->sec_idx, sym_idx, obj->filename); sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
return -EINVAL; return -EINVAL;
} }
} link_sec = &obj->secs[sec->shdr->sh_info];
}
break; /* .rel<secname> -> <secname> pattern is followed */
if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0
|| strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) {
pr_warn("ELF relo section #%zu name has invalid name in %s\n",
sec->sec_idx, obj->filename);
return -EINVAL;
}
/* don't further validate relocations for ignored sections */
if (link_sec->skipped)
return 0;
/* relocatable section is data or instructions */
if (link_sec->shdr->sh_type != SHT_PROGBITS && link_sec->shdr->sh_type != SHT_NOBITS) {
pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n",
sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
return -EINVAL;
}
/* check sanity of each relocation */
n = sec->shdr->sh_size / sec->shdr->sh_entsize;
relo = sec->data->d_buf;
sym_sec = &obj->secs[obj->symtab_sec_idx];
for (i = 0; i < n; i++, relo++) {
size_t sym_idx = ELF64_R_SYM(relo->r_info);
size_t sym_type = ELF64_R_TYPE(relo->r_info);
if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32) {
pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n",
i, sec->sec_idx, sym_type, obj->filename);
return -EINVAL;
} }
case SHT_LLVM_ADDRSIG:
break; if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) {
default: pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n",
pr_warn("ELF section #%zu (%s) has unrecognized type %zu in %s\n", i, sec->sec_idx, sym_idx, obj->filename);
sec->sec_idx, sec->sec_name, (size_t)sec->shdr->sh_type, obj->filename);
return -EINVAL; return -EINVAL;
} }
if (link_sec->shdr->sh_flags & SHF_EXECINSTR) {
if (relo->r_offset % sizeof(struct bpf_insn) != 0) {
pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n",
i, sec->sec_idx, sym_idx, obj->filename);
return -EINVAL;
}
}
} }
return 0; return 0;
......
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