1 files changed, 141 insertions, 0 deletions

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index bf0cf8173beb..e95aa28ce0f7 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -875,6 +875,8 @@ static void check_section(const char *modname, struct elf_info *elf,
 #define DATA_SECTIONS ".data", ".data.rel"
 #define TEXT_SECTIONS ".text", ".text.unlikely", ".sched.text", \
 		".kprobes.text"
+#define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \
+		".fixup", ".entry.text"
 
 #define INIT_SECTIONS      ".init.*"
 #define MEM_INIT_SECTIONS  ".meminit.*"
@@ -882,6 +884,9 @@ static void check_section(const char *modname, struct elf_info *elf,
 #define EXIT_SECTIONS      ".exit.*"
 #define MEM_EXIT_SECTIONS  ".memexit.*"
 
+#define ALL_TEXT_SECTIONS  ALL_INIT_TEXT_SECTIONS, ALL_EXIT_TEXT_SECTIONS, \
+		TEXT_SECTIONS, OTHER_TEXT_SECTIONS
+
 /* init data sections */
 static const char *const init_data_sections[] =
 	{ ALL_INIT_DATA_SECTIONS, NULL };
@@ -922,6 +927,7 @@ enum mismatch {
 	ANY_INIT_TO_ANY_EXIT,
 	ANY_EXIT_TO_ANY_INIT,
 	EXPORT_TO_INIT_EXIT,
+	EXTABLE_TO_NON_TEXT,
 };
 
 struct sectioncheck {
@@ -936,6 +942,11 @@ struct sectioncheck {
 
 };
 
+static void extable_mismatch_handler(const char *modname, struct elf_info *elf,
+				     const struct sectioncheck* const mismatch,
+				     Elf_Rela *r, Elf_Sym *sym,
+				     const char *fromsec);
+
 static const struct sectioncheck sectioncheck[] = {
 /* Do not reference init/exit code/data from
  * normal code and data
@@ -1013,6 +1024,16 @@ static const struct sectioncheck sectioncheck[] = {
 	.bad_tosec = { INIT_SECTIONS, EXIT_SECTIONS, NULL },
 	.mismatch = EXPORT_TO_INIT_EXIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+},
+{
+	.fromsec = { "__ex_table", NULL },
+	/* If you're adding any new black-listed sections in here, consider
+	 * adding a special 'printer' for them in scripts/check_extable.
+	 */
+	.bad_tosec = { ".altinstr_replacement", NULL },
+	.good_tosec = {ALL_TEXT_SECTIONS , NULL},
+	.mismatch = EXTABLE_TO_NON_TEXT,
+	.handler = extable_mismatch_handler,
 }
 };
 
@@ -1418,6 +1439,10 @@ static void report_sec_mismatch(const char *modname,
 		tosym, prl_to, prl_to, tosym);
 		free(prl_to);
 		break;
+	case EXTABLE_TO_NON_TEXT:
+		fatal("There's a special handler for this mismatch type, "
+		      "we should never get here.");
+		break;
 	}
 	fprintf(stderr, "\n");
 }
@@ -1453,6 +1478,120 @@ static void default_mismatch_handler(const char *modname, struct elf_info *elf,
 	}
 }
 
+static int is_executable_section(struct elf_info* elf, unsigned int section_index)
+{
+	if (section_index > elf->num_sections)
+		fatal("section_index is outside elf->num_sections!\n");
+
+	return ((elf->sechdrs[section_index].sh_flags & SHF_EXECINSTR) == SHF_EXECINSTR);
+}
+
+/*
+ * We rely on a gross hack in section_rel[a]() calling find_extable_entry_size()
+ * to know the sizeof(struct exception_table_entry) for the target architecture.
+ */
+static unsigned int extable_entry_size = 0;
+static void find_extable_entry_size(const char* const sec, const Elf_Rela* r,
+				    const void* start, const void* cur)
+{
+	/*
+	 * If we're currently checking the second relocation within __ex_table,
+	 * that relocation offset tells us the offsetof(struct
+	 * exception_table_entry, fixup) which is equal to sizeof(struct
+	 * exception_table_entry) divided by two.  We use that to our advantage
+	 * since there's no portable way to get that size as every architecture
+	 * seems to go with different sized types.  Not pretty but better than
+	 * hard-coding the size for every architecture..
+	 */
+	if (!extable_entry_size && cur == start + 1 &&
+	    strcmp("__ex_table", sec) == 0)
+		extable_entry_size = r->r_offset * 2;
+}
+static inline bool is_extable_fault_address(Elf_Rela *r)
+{
+	if (!extable_entry_size == 0)
+		fatal("extable_entry size hasn't been discovered!\n");
+
+	return ((r->r_offset == 0) ||
+		(r->r_offset % extable_entry_size == 0));
+}
+
+static void report_extable_warnings(const char* modname, struct elf_info* elf,
+				    const struct sectioncheck* const mismatch,
+				    Elf_Rela* r, Elf_Sym* sym,
+				    const char* fromsec, const char* tosec)
+{
+	Elf_Sym* fromsym = find_elf_symbol2(elf, r->r_offset, fromsec);
+	const char* fromsym_name = sym_name(elf, fromsym);
+	Elf_Sym* tosym = find_elf_symbol(elf, r->r_addend, sym);
+	const char* tosym_name = sym_name(elf, tosym);
+	const char* from_pretty_name;
+	const char* from_pretty_name_p;
+	const char* to_pretty_name;
+	const char* to_pretty_name_p;
+
+	get_pretty_name(is_function(fromsym),
+			&from_pretty_name, &from_pretty_name_p);
+	get_pretty_name(is_function(tosym),
+			&to_pretty_name, &to_pretty_name_p);
+
+	warn("%s(%s+0x%lx): Section mismatch in reference"
+	     " from the %s %s%s to the %s %s:%s%s\n",
+	     modname, fromsec, (long)r->r_offset, from_pretty_name,
+	     fromsym_name, from_pretty_name_p,
+	     to_pretty_name, tosec, tosym_name, to_pretty_name_p);
+
+	if (!match(tosec, mismatch->bad_tosec) &&
+	    is_executable_section(elf, get_secindex(elf, sym)))
+		fprintf(stderr,
+			"The relocation at %s+0x%lx references\n"
+			"section \"%s\" which is not in the list of\n"
+			"authorized sections.  If you're adding a new section\n"
+			"and/or if this reference is valid, add \"%s\" to the\n"
+			"list of authorized sections to jump to on fault.\n"
+			"This can be achieved by adding \"%s\" to \n"
+			"OTHER_TEXT_SECTIONS in scripts/mod/modpost.c.\n",
+			fromsec, (long)r->r_offset, tosec, tosec, tosec);
+}
+
+static void extable_mismatch_handler(const char* modname, struct elf_info *elf,
+				     const struct sectioncheck* const mismatch,
+				     Elf_Rela* r, Elf_Sym* sym,
+				     const char *fromsec)
+{
+	const char* tosec = sec_name(elf, get_secindex(elf, sym));
+
+	sec_mismatch_count++;
+
+	if (sec_mismatch_verbose)
+		report_extable_warnings(modname, elf, mismatch, r, sym,
+					fromsec, tosec);
+
+	if (match(tosec, mismatch->bad_tosec))
+		fatal("The relocation at %s+0x%lx references\n"
+		      "section \"%s\" which is black-listed.\n"
+		      "Something is seriously wrong and should be fixed.\n"
+		      "You might get more information about where this is\n"
+		      "coming from by using scripts/check_extable.sh %s\n",
+		      fromsec, (long)r->r_offset, tosec, modname);
+	else if (!is_executable_section(elf, get_secindex(elf, sym))) {
+		if (is_extable_fault_address(r))
+			fatal("The relocation at %s+0x%lx references\n"
+			      "section \"%s\" which is not executable, IOW\n"
+			      "it is not possible for the kernel to fault\n"
+			      "at that address.  Something is seriously wrong\n"
+			      "and should be fixed.\n",
+			      fromsec, (long)r->r_offset, tosec);
+		else
+			fatal("The relocation at %s+0x%lx references\n"
+			      "section \"%s\" which is not executable, IOW\n"
+			      "the kernel will fault if it ever tries to\n"
+			      "jump to it.  Something is seriously wrong\n"
+			      "and should be fixed.\n",
+			      fromsec, (long)r->r_offset, tosec);
+	}
+}
+
 static void check_section_mismatch(const char *modname, struct elf_info *elf,
 				   Elf_Rela *r, Elf_Sym *sym, const char *fromsec)
 {
@@ -1605,6 +1744,7 @@ static void section_rela(const char *modname, struct elf_info *elf,
 		/* Skip special sections */
 		if (is_shndx_special(sym->st_shndx))
 			continue;
+		find_extable_entry_size(fromsec, &r, start, rela);
 		check_section_mismatch(modname, elf, &r, sym, fromsec);
 	}
 }
@@ -1663,6 +1803,7 @@ static void section_rel(const char *modname, struct elf_info *elf,
 		/* Skip special sections */
 		if (is_shndx_special(sym->st_shndx))
 			continue;
+		find_extable_entry_size(fromsec, &r, start, rel);
 		check_section_mismatch(modname, elf, &r, sym, fromsec);
 	}
 }