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From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
	<daniel@iogearbox.net>
Cc: <andrii@kernel.org>, <kernel-team@fb.com>
Subject: [PATCH v2 bpf-next 07/17] libbpf: factor out symtab and relos sanity checks
Date: Fri, 16 Apr 2021 13:23:54 -0700	[thread overview]
Message-ID: <20210416202404.3443623-8-andrii@kernel.org> (raw)
In-Reply-To: <20210416202404.3443623-1-andrii@kernel.org>

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: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/linker.c | 233 ++++++++++++++++++++++-------------------
 1 file changed, 127 insertions(+), 106 deletions(-)

diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index 4e08bc07e635..0bb927226370 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -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_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_ext(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)
 
 static int linker_sanity_check_elf(struct src_obj *obj)
 {
-	struct src_sec *sec, *link_sec;
-	int i, j, n;
+	struct src_sec *sec;
+	int i, err;
 
 	if (!obj->symtab_sec_idx) {
 		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)
 			return -EINVAL;
 
 		switch (sec->shdr->sh_type) {
-		case SHT_SYMTAB: {
-			Elf64_Sym *sym;
-
-			if (sec->shdr->sh_entsize != sizeof(Elf64_Sym))
-				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;
-				}
-			}
+		case SHT_SYMTAB:
+			err = linker_sanity_check_elf_symtab(obj, sec);
+			if (err)
+				return err;
 			break;
-		}
 		case SHT_STRTAB:
 			break;
 		case SHT_PROGBITS:
@@ -739,87 +709,138 @@ static int linker_sanity_check_elf(struct src_obj *obj)
 			break;
 		case SHT_NOBITS:
 			break;
-		case SHT_REL: {
-			Elf64_Rel *relo;
-			struct src_sec *sym_sec;
+		case SHT_REL:
+			err = linker_sanity_check_elf_relos(obj, 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 -EINVAL;
-			if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
-				return -EINVAL;
+	return 0;
+}
 
-			/* SHT_REL's sh_link should point to SYMTAB */
-			if (sec->shdr->sh_link != obj->symtab_sec_idx) {
-				pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n",
-					sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
-				return -EINVAL;
-			}
+static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec)
+{
+	struct src_sec *link_sec;
+	Elf64_Sym *sym;
+	int i, n;
 
-			/* SHT_REL's sh_info points to relocated section */
-			if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) {
-				pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n",
-					sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
-				return -EINVAL;
-			}
-			link_sec = &obj->secs[sec->shdr->sh_info];
+	if (sec->shdr->sh_entsize != sizeof(Elf64_Sym))
+		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;
+	}
 
-			/* .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);
+	n = sec->shdr->sh_size / sec->shdr->sh_entsize;
+	sym = sec->data->d_buf;
+	for (i = 0; i < n; i++, 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",
+				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;
-			}
+			continue;
+		}
+	}
 
-			/* don't further validate relocations for ignored sections */
-			if (link_sec->skipped)
-				break;
+	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;
-			}
+static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec)
+{
+	struct src_sec *link_sec, *sym_sec;
+	Elf64_Rel *relo;
+	int i, n;
 
-			/* 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 (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 (sec->shdr->sh_entsize != sizeof(Elf64_Rel))
+		return -EINVAL;
+	if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
+		return -EINVAL;
 
-				if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) {
-					pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n",
-						j, sec->sec_idx, sym_idx, obj->filename);
-					return -EINVAL;
-				}
+	/* SHT_REL's sh_link should point to SYMTAB */
+	if (sec->shdr->sh_link != obj->symtab_sec_idx) {
+		pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n",
+			sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
+		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",
-							j, sec->sec_idx, sym_idx, obj->filename);
-						return -EINVAL;
-					}
-				}
-			}
-			break;
+	/* SHT_REL's sh_info points to relocated section */
+	if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) {
+		pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n",
+			sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
+		return -EINVAL;
+	}
+	link_sec = &obj->secs[sec->shdr->sh_info];
+
+	/* .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;
-		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);
+
+		if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) {
+			pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n",
+				i, sec->sec_idx, sym_idx, obj->filename);
 			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;
-- 
2.30.2


  parent reply	other threads:[~2021-04-16 20:24 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16 20:23 [PATCH v2 bpf-next 00/17] BPF static linker: support externs Andrii Nakryiko
2021-04-16 20:23 ` [PATCH v2 bpf-next 01/17] bpftool: support dumping BTF VAR's "extern" linkage Andrii Nakryiko
2021-04-22  3:02   ` Yonghong Song
2021-04-16 20:23 ` [PATCH v2 bpf-next 02/17] bpftool: dump more info about DATASEC members Andrii Nakryiko
2021-04-22  3:09   ` Yonghong Song
2021-04-16 20:23 ` [PATCH v2 bpf-next 03/17] libbpf: suppress compiler warning when using SEC() macro with externs Andrii Nakryiko
2021-04-22  3:47   ` Yonghong Song
2021-04-22  3:59     ` Andrii Nakryiko
2021-04-16 20:23 ` [PATCH v2 bpf-next 04/17] libbpf: mark BPF subprogs with hidden visibility as static for BPF verifier Andrii Nakryiko
2021-04-22  5:43   ` Yonghong Song
2021-04-22 18:09     ` Andrii Nakryiko
2021-04-22 23:00       ` Yonghong Song
2021-04-22 23:28         ` Andrii Nakryiko
2021-04-16 20:23 ` [PATCH v2 bpf-next 05/17] libbpf: allow gaps in BPF program sections to support overriden weak functions Andrii Nakryiko
2021-04-22  6:25   ` Yonghong Song
2021-04-22 18:10     ` Andrii Nakryiko
2021-04-16 20:23 ` [PATCH v2 bpf-next 06/17] libbpf: refactor BTF map definition parsing Andrii Nakryiko
2021-04-22 15:33   ` Yonghong Song
2021-04-22 18:40     ` Andrii Nakryiko
2021-04-16 20:23 ` Andrii Nakryiko [this message]
2021-04-22 16:06   ` [PATCH v2 bpf-next 07/17] libbpf: factor out symtab and relos sanity checks Yonghong Song
2021-04-22 18:16     ` Andrii Nakryiko
2021-04-16 20:23 ` [PATCH v2 bpf-next 08/17] libbpf: make few internal helpers available outside of libbpf.c Andrii Nakryiko
2021-04-22 16:19   ` Yonghong Song
2021-04-22 18:18     ` Andrii Nakryiko
2021-04-16 20:23 ` [PATCH v2 bpf-next 09/17] libbpf: extend sanity checking ELF symbols with externs validation Andrii Nakryiko
2021-04-22 16:35   ` Yonghong Song
2021-04-22 18:20     ` Andrii Nakryiko
2021-04-22 23:13       ` Yonghong Song
2021-04-16 20:23 ` [PATCH v2 bpf-next 10/17] libbpf: tighten BTF type ID rewriting with error checking Andrii Nakryiko
2021-04-22 16:50   ` Yonghong Song
2021-04-22 18:24     ` Andrii Nakryiko
2021-04-23  2:54       ` Alexei Starovoitov
2021-04-23  4:25         ` Andrii Nakryiko
2021-04-23  5:11           ` Alexei Starovoitov
2021-04-23 16:09             ` Andrii Nakryiko
2021-04-23 16:18               ` Alexei Starovoitov
2021-04-23 16:30                 ` Andrii Nakryiko
2021-04-23 16:34                   ` Alexei Starovoitov
2021-04-23 17:02                     ` Andrii Nakryiko
2021-04-16 20:23 ` [PATCH v2 bpf-next 11/17] libbpf: add linker extern resolution support for functions and global variables Andrii Nakryiko
2021-04-22 21:27   ` Yonghong Song
2021-04-22 22:12     ` Andrii Nakryiko
2021-04-22 23:57       ` Yonghong Song
2021-04-23  2:36         ` Yonghong Song
2021-04-23  4:28           ` Andrii Nakryiko
2021-04-23  4:27         ` Andrii Nakryiko
2021-04-16 20:23 ` [PATCH v2 bpf-next 12/17] libbpf: support extern resolution for BTF-defined maps in .maps section Andrii Nakryiko
2021-04-22 22:56   ` Yonghong Song
2021-04-22 23:32     ` Andrii Nakryiko
2021-04-16 20:24 ` [PATCH v2 bpf-next 13/17] selftests/bpf: use -O0 instead of -Og in selftests builds Andrii Nakryiko
2021-04-23  0:05   ` Yonghong Song
2021-04-16 20:24 ` [PATCH v2 bpf-next 14/17] selftests/bpf: omit skeleton generation for multi-linked BPF object files Andrii Nakryiko
2021-04-23  0:13   ` Yonghong Song
2021-04-16 20:24 ` [PATCH v2 bpf-next 15/17] selftests/bpf: add function linking selftest Andrii Nakryiko
2021-04-23  0:50   ` Yonghong Song
2021-04-23  2:34     ` Alexei Starovoitov
2021-04-23  4:29       ` Andrii Nakryiko
2021-04-23 17:18     ` Andrii Nakryiko
2021-04-23 17:35       ` Yonghong Song
2021-04-23 17:55         ` Andrii Nakryiko
2021-04-23 17:58           ` Yonghong Song
2021-04-23 17:59             ` Andrii Nakryiko
2021-04-16 20:24 ` [PATCH v2 bpf-next 16/17] selftests/bpf: add global variables " Andrii Nakryiko
2021-04-23  1:01   ` Yonghong Song
2021-04-16 20:24 ` [PATCH v2 bpf-next 17/17] sleftests/bpf: add map " Andrii Nakryiko
2021-04-23  1:20   ` Yonghong Song

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