[gentoo-commits] proj/pax-utils:master commit in: /

["Mike Frysinger" <vapier@gentoo.org>]

commit:     2eb852129394f97dae89c0ff1f9f48637edcb0e9
Author:     Mike Frysinger <vapier <AT> gentoo <DOT> org>
AuthorDate: Fri Nov 25 06:30:32 2016 +0000
Commit:     Mike Frysinger <vapier <AT> gentoo <DOT> org>
CommitDate: Fri Nov 25 06:30:32 2016 +0000
URL:        https://gitweb.gentoo.org/proj/pax-utils.git/commit/?id=2eb85212

scanelf: rewrite textrels decoder to use program segments

Previously, we only looked at the section name ".text".  This fails when
other names are used, or when the section headers are incomplete.  Since
the runtime only looks at program headers, change the code to match.

 scanelf.c | 116 +++++++++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 88 insertions(+), 28 deletions(-)

diff --git a/scanelf.c b/scanelf.c
index 2a7c0ce..9c52ced 100644
--- a/scanelf.c
+++ b/scanelf.c
@@ -572,8 +572,8 @@ static const char *scanelf_file_textrel(elfobj *elf, char *found_textrel)
  */
 static char *scanelf_file_textrels(elfobj *elf, char *found_textrels, char *found_textrel)
 {
-	unsigned long s, r, rmax;
-	void *symtab_void, *strtab_void, *text_void;
+	unsigned long r, rmax;
+	void *symtab_void, *strtab_void;
 
 	if (!show_textrels) return NULL;
 
@@ -582,32 +582,87 @@ static char *scanelf_file_textrels(elfobj *elf, char *found_textrels, char *foun
 	if (!*found_textrel) return NULL;
 
 	scanelf_file_get_symtabs(elf, &symtab_void, &strtab_void);
-	text_void = elf_findsecbyname(elf, ".text");
 
 #define SHOW_TEXTRELS(B) \
+	size_t i; \
 	Elf ## B ## _Ehdr *ehdr = EHDR ## B (elf->ehdr); \
-	Elf ## B ## _Shdr *shdr = SHDR ## B (elf->shdr); \
+	Elf ## B ## _Phdr *phdr; \
+	Elf ## B ## _Off offset; \
 	Elf ## B ## _Shdr *symtab = SHDR ## B (symtab_void); \
 	Elf ## B ## _Shdr *strtab = SHDR ## B (strtab_void); \
-	Elf ## B ## _Shdr *text = SHDR ## B (text_void); \
-	Elf ## B ## _Addr vaddr = EGET(text->sh_addr); \
-	uint ## B ## _t memsz = EGET(text->sh_size); \
 	Elf ## B ## _Rel *rel; \
 	Elf ## B ## _Rela *rela; \
-	/* search the section headers for relocations */ \
-	for (s = 0; s < EGET(ehdr->e_shnum); ++s) { \
-		uint32_t sh_type = EGET(shdr[s].sh_type); \
-		if (sh_type == SHT_REL) { \
-			rel = REL ## B (elf->vdata + EGET(shdr[s].sh_offset)); \
-			rela = NULL; \
-			rmax = EGET(shdr[s].sh_size) / sizeof(*rel); \
-		} else if (sh_type == SHT_RELA) { \
-			rel = NULL; \
-			rela = RELA ## B (elf->vdata + EGET(shdr[s].sh_offset)); \
-			rmax = EGET(shdr[s].sh_size) / sizeof(*rela); \
-		} else \
+	Elf ## B ## _Dyn *dyn, *drel, *drelsz, *drelent, *dpltrel; \
+	uint32_t pltrel; \
+	\
+	/* Find the dynamic headers */ \
+	phdr = scanelf_file_get_pt_dynamic(elf); \
+	if (phdr == NULL) \
+		break; \
+	offset = EGET(phdr->p_offset); \
+	\
+	/* Walk all the dynamic tags to find relocation info */ \
+	dyn = DYN ## B (elf->vdata + offset); \
+	drel = drelsz = drelent = dpltrel = NULL; \
+	while (EGET(dyn->d_tag) != DT_NULL) { \
+		switch (EGET(dyn->d_tag)) { \
+		case DT_REL: \
+		case DT_RELA: \
+			drel = dyn; \
+			break; \
+		case DT_RELSZ: \
+		case DT_RELASZ: \
+			drelsz = dyn; \
+			break; \
+		case DT_RELENT: \
+		case DT_RELAENT: \
+			drelent = dyn; \
+			break; \
+		case DT_PLTREL: \
+			dpltrel = dyn; \
+			break; \
+		} \
+		++dyn; \
+	} \
+	if (!drel || !drelsz || !drelent || !dpltrel) { \
+		warnf("ELF is missing relocation information"); \
+		break; \
+	} \
+	switch (EGET(dpltrel->d_un.d_val)) { \
+	case DT_REL: \
+		rel = REL##B(elf->vdata + EGET(drel->d_un.d_val)); \
+		rela = NULL; \
+		pltrel = DT_REL; \
+		break; \
+	case DT_RELA: \
+		rel = NULL; \
+		rela = RELA##B(elf->vdata + EGET(drel->d_un.d_val)); \
+		pltrel = DT_RELA; \
+		break; \
+	default: \
+		warn("Unknown relocation type"); \
+		rel = NULL; \
+		rela = NULL; \
+		break; \
+	} \
+	if (!rel && !rela) \
+		break; \
+	rmax = EGET(drelsz->d_un.d_val) / EGET(drelent->d_un.d_val); \
+	\
+	/* search the program segments for relocations */ \
+	phdr = PHDR ## B(elf->phdr); \
+	for (i = 0; i < EGET(ehdr->e_phnum); ++i) { \
+		Elf ## B ## _Addr vaddr = EGET(phdr[i].p_vaddr); \
+		uint ## B ## _t memsz = EGET(phdr[i].p_memsz); \
+		\
+		/* Only care about loadable segments. */ \
+		if (EGET(phdr[i].p_type) != PT_LOAD) \
 			continue; \
-		/* now see if any of the relocs are in the .text */ \
+		/* Only care about executable segments. */ \
+		if ((EGET(phdr[i].p_flags) & PF_X) != PF_X) \
+			continue; \
+		\
+		/* now see if any of the relocs touch this segment */ \
 		for (r = 0; r < rmax; ++r) { \
 			unsigned long sym_max; \
 			Elf ## B ## _Addr offset_tmp; \
@@ -615,7 +670,7 @@ static char *scanelf_file_textrels(elfobj *elf, char *found_textrels, char *foun
 			Elf ## B ## _Sym *sym; \
 			Elf ## B ## _Addr r_offset; \
 			uint ## B ## _t r_info; \
-			if (sh_type == SHT_REL) { \
+			if (pltrel == DT_REL) { \
 				r_offset = EGET(rel[r].r_offset); \
 				r_info = EGET(rel[r].r_info); \
 			} else { \
@@ -641,7 +696,9 @@ static char *scanelf_file_textrels(elfobj *elf, char *found_textrels, char *foun
 			sym_max = EGET(symtab->sh_size) / EGET(symtab->sh_entsize); \
 			/* show the raw details about this reloc */ \
 			printf("  %s: ", elf->base_filename); \
-			if (sym && sym->st_name) \
+			if (!strtab) \
+				printf("(missing symbols)"); \
+			else if (sym && sym->st_name) \
 				printf("%s", elf->data + EGET(strtab->sh_offset) + EGET(sym->st_name)); \
 			else \
 				printf("(memory/data?)"); \
@@ -659,11 +716,14 @@ static char *scanelf_file_textrels(elfobj *elf, char *found_textrels, char *foun
 			} \
 			printf(" in "); \
 			if (func && func->st_name) { \
-				const char *func_name = elf->data + EGET(strtab->sh_offset) + EGET(func->st_name); \
-				if (r_offset > EGET(func->st_size)) \
-					printf("(optimized out: previous %s)", func_name); \
-				else \
-					printf("%s", func_name); \
+				if (strtab) { \
+					const char *func_name = elf->data + EGET(strtab->sh_offset) + EGET(func->st_name); \
+					if (r_offset > EGET(func->st_size)) \
+						printf("(optimized out: previous %s)", func_name); \
+					else \
+						printf("%s", func_name); \
+				} else \
+					printf("(missing symbols)"); \
 			} else \
 				printf("(optimized out)"); \
 			printf(" [0x%lX]\n", (unsigned long)offset_tmp); \
@@ -690,7 +750,7 @@ static char *scanelf_file_textrels(elfobj *elf, char *found_textrels, char *foun
 			} \
 		} \
 	}
-	if (symtab_void && strtab_void && text_void && elf->shdr)
+	if (symtab_void && elf->phdr)
 		SCANELF_ELF_SIZED(SHOW_TEXTRELS);
 	if (!*found_textrels)
 		warnf("ELF %s has TEXTREL markings but doesnt appear to have any real TEXTREL's !?", elf->filename);