Merge branch 'modversions' (modversions fixes for powerpc from Ard)

Merge kcrctab entry fixes from Ard Biesheuvel:
 "This is a followup to [0] 'modversions: redefine kcrctab entries as
  relative CRC pointers', but since relative CRC pointers do not work in
  modules, and are actually only needed by powerpc with
  CONFIG_RELOCATABLE=y, I have made it a Kconfig selectable feature
  instead.

  First it introduces the MODULE_REL_CRCS Kconfig symbol, and adds the
  kbuild handling of it, i.e., modpost, genksyms and kallsyms.

  Then it switches all architectures to 32-bit CRC entries in kcrctab,
  where all architectures except powerpc with CONFIG_RELOCATABLE=y use
  absolute ELF symbol references as before"

[0] http://marc.info/?l=linux-arch&m=148493613415294&w=2

* emailed patches from Ard Biesheuvel:
  module: unify absolute krctab definitions for 32-bit and 64-bit
  modversions: treat symbol CRCs as 32 bit quantities
  kbuild: modversions: add infrastructure for emitting relative CRCs

arch/powerpc/Kconfig

@@ -484,6 +484,7 @@ config RELOCATABLE
 	bool "Build a relocatable kernel"
 	depends on (PPC64 && !COMPILE_TEST) || (FLATMEM && (44x || FSL_BOOKE))
 	select NONSTATIC_KERNEL
+	select MODULE_REL_CRCS if MODVERSIONS
 	help
 	  This builds a kernel image that is capable of running at the
 	  location the kernel is loaded at. For ppc32, there is no any

arch/powerpc/include/asm/module.h

@@ -90,9 +90,5 @@ static inline int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sec
 }
 #endif
 
-#if defined(CONFIG_MODVERSIONS) && defined(CONFIG_PPC64)
-#define ARCH_RELOCATES_KCRCTAB
-#define reloc_start PHYSICAL_START
-#endif
 #endif /* __KERNEL__ */
 #endif	/* _ASM_POWERPC_MODULE_H */

arch/powerpc/kernel/module_64.c

@@ -286,14 +286,6 @@ static void dedotify_versions(struct modversion_info *vers,
 	for (end = (void *)vers + size; vers < end; vers++)
 		if (vers->name[0] == '.') {
 			memmove(vers->name, vers->name+1, strlen(vers->name));
-#ifdef ARCH_RELOCATES_KCRCTAB
-			/* The TOC symbol has no CRC computed. To avoid CRC
-			 * check failing, we must force it to the expected
-			 * value (see CRC check in module.c).
-			 */
-			if (!strcmp(vers->name, "TOC."))
-				vers->crc = -(unsigned long)reloc_start;
-#endif
 		}
 }
 

include/asm-generic/export.h

@@ -9,18 +9,15 @@
 #ifndef KSYM_ALIGN
 #define KSYM_ALIGN 8
 #endif
-#ifndef KCRC_ALIGN
-#define KCRC_ALIGN 8
-#endif
 #else
 #define __put .long
 #ifndef KSYM_ALIGN
 #define KSYM_ALIGN 4
 #endif
+#endif
 #ifndef KCRC_ALIGN
 #define KCRC_ALIGN 4
 #endif
-#endif
 
 #ifdef CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX
 #define KSYM(name) _##name
@@ -52,7 +49,11 @@ KSYM(__kstrtab_\name):
 	.section ___kcrctab\sec+\name,"a"
 	.balign KCRC_ALIGN
 KSYM(__kcrctab_\name):
-	__put KSYM(__crc_\name)
+#if defined(CONFIG_MODULE_REL_CRCS)
+	.long KSYM(__crc_\name) - .
+#else
+	.long KSYM(__crc_\name)
+#endif
 	.weak KSYM(__crc_\name)
 	.previous
 #endif

include/linux/export.h

@@ -43,12 +43,19 @@ extern struct module __this_module;
 #ifdef CONFIG_MODVERSIONS
 /* Mark the CRC weak since genksyms apparently decides not to
  * generate a checksums for some symbols */
+#if defined(CONFIG_MODULE_REL_CRCS)
 #define __CRC_SYMBOL(sym, sec)						\
-	extern __visible void *__crc_##sym __attribute__((weak));	\
-	static const unsigned long __kcrctab_##sym			\
-	__used								\
-	__attribute__((section("___kcrctab" sec "+" #sym), used))	\
-	= (unsigned long) &__crc_##sym;
+	asm("	.section \"___kcrctab" sec "+" #sym "\", \"a\"	\n"	\
+	    "	.weak	" VMLINUX_SYMBOL_STR(__crc_##sym) "	\n"	\
+	    "	.long	" VMLINUX_SYMBOL_STR(__crc_##sym) " - .	\n"	\
+	    "	.previous					\n");
+#else
+#define __CRC_SYMBOL(sym, sec)						\
+	asm("	.section \"___kcrctab" sec "+" #sym "\", \"a\"	\n"	\
+	    "	.weak	" VMLINUX_SYMBOL_STR(__crc_##sym) "	\n"	\
+	    "	.long	" VMLINUX_SYMBOL_STR(__crc_##sym) "	\n"	\
+	    "	.previous					\n");
+#endif
 #else
 #define __CRC_SYMBOL(sym, sec)
 #endif

include/linux/module.h

@@ -346,7 +346,7 @@ struct module {
 
 	/* Exported symbols */
 	const struct kernel_symbol *syms;
-	const unsigned long *crcs;
+	const s32 *crcs;
 	unsigned int num_syms;
 
 	/* Kernel parameters. */
@@ -359,18 +359,18 @@ struct module {
 	/* GPL-only exported symbols. */
 	unsigned int num_gpl_syms;
 	const struct kernel_symbol *gpl_syms;
-	const unsigned long *gpl_crcs;
+	const s32 *gpl_crcs;
 
 #ifdef CONFIG_UNUSED_SYMBOLS
 	/* unused exported symbols. */
 	const struct kernel_symbol *unused_syms;
-	const unsigned long *unused_crcs;
+	const s32 *unused_crcs;
 	unsigned int num_unused_syms;
 
 	/* GPL-only, unused exported symbols. */
 	unsigned int num_unused_gpl_syms;
 	const struct kernel_symbol *unused_gpl_syms;
-	const unsigned long *unused_gpl_crcs;
+	const s32 *unused_gpl_crcs;
 #endif
 
 #ifdef CONFIG_MODULE_SIG
@@ -382,7 +382,7 @@ struct module {
 
 	/* symbols that will be GPL-only in the near future. */
 	const struct kernel_symbol *gpl_future_syms;
-	const unsigned long *gpl_future_crcs;
+	const s32 *gpl_future_crcs;
 	unsigned int num_gpl_future_syms;
 
 	/* Exception table */
@@ -523,7 +523,7 @@ struct module *find_module(const char *name);
 
 struct symsearch {
 	const struct kernel_symbol *start, *stop;
-	const unsigned long *crcs;
+	const s32 *crcs;
 	enum {
 		NOT_GPL_ONLY,
 		GPL_ONLY,
@@ -539,7 +539,7 @@ struct symsearch {
  */
 const struct kernel_symbol *find_symbol(const char *name,
 					struct module **owner,
-					const unsigned long **crc,
+					const s32 **crc,
 					bool gplok,
 					bool warn);
 

init/Kconfig

@@ -1987,6 +1987,10 @@ config MODVERSIONS
 	  make them incompatible with the kernel you are running.  If
 	  unsure, say N.
 
+config MODULE_REL_CRCS
+	bool
+	depends on MODVERSIONS
+
 config MODULE_SRCVERSION_ALL
 	bool "Source checksum for all modules"
 	help

kernel/module.c

@@ -389,16 +389,16 @@ extern const struct kernel_symbol __start___ksymtab_gpl[];
 extern const struct kernel_symbol __stop___ksymtab_gpl[];
 extern const struct kernel_symbol __start___ksymtab_gpl_future[];
 extern const struct kernel_symbol __stop___ksymtab_gpl_future[];
-extern const unsigned long __start___kcrctab[];
-extern const unsigned long __start___kcrctab_gpl[];
-extern const unsigned long __start___kcrctab_gpl_future[];
+extern const s32 __start___kcrctab[];
+extern const s32 __start___kcrctab_gpl[];
+extern const s32 __start___kcrctab_gpl_future[];
 #ifdef CONFIG_UNUSED_SYMBOLS
 extern const struct kernel_symbol __start___ksymtab_unused[];
 extern const struct kernel_symbol __stop___ksymtab_unused[];
 extern const struct kernel_symbol __start___ksymtab_unused_gpl[];
 extern const struct kernel_symbol __stop___ksymtab_unused_gpl[];
-extern const unsigned long __start___kcrctab_unused[];
-extern const unsigned long __start___kcrctab_unused_gpl[];
+extern const s32 __start___kcrctab_unused[];
+extern const s32 __start___kcrctab_unused_gpl[];
 #endif
 
 #ifndef CONFIG_MODVERSIONS
@@ -497,7 +497,7 @@ struct find_symbol_arg {
 
 	/* Output */
 	struct module *owner;
-	const unsigned long *crc;
+	const s32 *crc;
 	const struct kernel_symbol *sym;
 };
 
@@ -563,7 +563,7 @@ static bool find_symbol_in_section(const struct symsearch *syms,
  * (optional) module which owns it.  Needs preempt disabled or module_mutex. */
 const struct kernel_symbol *find_symbol(const char *name,
 					struct module **owner,
-					const unsigned long **crc,
+					const s32 **crc,
 					bool gplok,
 					bool warn)
 {
@@ -1249,23 +1249,17 @@ static int try_to_force_load(struct module *mod, const char *reason)
 }
 
 #ifdef CONFIG_MODVERSIONS
-/* If the arch applies (non-zero) relocations to kernel kcrctab, unapply it. */
-static unsigned long maybe_relocated(unsigned long crc,
-				     const struct module *crc_owner)
+
+static u32 resolve_rel_crc(const s32 *crc)
 {
-#ifdef ARCH_RELOCATES_KCRCTAB
-	if (crc_owner == NULL)
-		return crc - (unsigned long)reloc_start;
-#endif
-	return crc;
+	return *(u32 *)((void *)crc + *crc);
 }
 
 static int check_version(Elf_Shdr *sechdrs,
 			 unsigned int versindex,
 			 const char *symname,
 			 struct module *mod,
-			 const unsigned long *crc,
-			 const struct module *crc_owner)
+			 const s32 *crc)
 {
 	unsigned int i, num_versions;
 	struct modversion_info *versions;
@@ -1283,13 +1277,19 @@ static int check_version(Elf_Shdr *sechdrs,
 		/ sizeof(struct modversion_info);
 
 	for (i = 0; i < num_versions; i++) {
+		u32 crcval;
+
 		if (strcmp(versions[i].name, symname) != 0)
 			continue;
 
-		if (versions[i].crc == maybe_relocated(*crc, crc_owner))
+		if (IS_ENABLED(CONFIG_MODULE_REL_CRCS))
+			crcval = resolve_rel_crc(crc);
+		else
+			crcval = *crc;
+		if (versions[i].crc == crcval)
 			return 1;
-		pr_debug("Found checksum %lX vs module %lX\n",
-		       maybe_relocated(*crc, crc_owner), versions[i].crc);
+		pr_debug("Found checksum %X vs module %lX\n",
+			 crcval, versions[i].crc);
 		goto bad_version;
 	}
 
@@ -1307,7 +1307,7 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
 					  unsigned int versindex,
 					  struct module *mod)
 {
-	const unsigned long *crc;
+	const s32 *crc;
 
 	/*
 	 * Since this should be found in kernel (which can't be removed), no
@@ -1321,8 +1321,7 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
 	}
 	preempt_enable();
 	return check_version(sechdrs, versindex,
-			     VMLINUX_SYMBOL_STR(module_layout), mod, crc,
-			     NULL);
+			     VMLINUX_SYMBOL_STR(module_layout), mod, crc);
 }
 
 /* First part is kernel version, which we ignore if module has crcs. */
@@ -1340,8 +1339,7 @@ static inline int check_version(Elf_Shdr *sechdrs,
 				unsigned int versindex,
 				const char *symname,
 				struct module *mod,
-				const unsigned long *crc,
-				const struct module *crc_owner)
+				const s32 *crc)
 {
 	return 1;
 }
@@ -1368,7 +1366,7 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
 {
 	struct module *owner;
 	const struct kernel_symbol *sym;
-	const unsigned long *crc;
+	const s32 *crc;
 	int err;
 
 	/*
@@ -1383,8 +1381,7 @@ static const struct kernel_symbol *resolve_symbol(struct module *mod,
 	if (!sym)
 		goto unlock;
 
-	if (!check_version(info->sechdrs, info->index.vers, name, mod, crc,
-			   owner)) {
+	if (!check_version(info->sechdrs, info->index.vers, name, mod, crc)) {
 		sym = ERR_PTR(-EINVAL);
 		goto getname;
 	}

scripts/Makefile.build

@@ -164,6 +164,7 @@ cmd_gensymtypes_c =                                                         \
     $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
     $(GENKSYMS) $(if $(1), -T $(2))                                         \
      $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX))             \
+     $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
      $(if $(KBUILD_PRESERVE),-p)                                            \
      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 
@@ -337,6 +338,7 @@ cmd_gensymtypes_S =                                                         \
     $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
     $(GENKSYMS) $(if $(1), -T $(2))                                         \
      $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX))             \
+     $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
      $(if $(KBUILD_PRESERVE),-p)                                            \
      -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
 

scripts/genksyms/genksyms.c

@@ -44,7 +44,7 @@ char *cur_filename, *source_file;
 int in_source_file;
 
 static int flag_debug, flag_dump_defs, flag_reference, flag_dump_types,
-	   flag_preserve, flag_warnings;
+	   flag_preserve, flag_warnings, flag_rel_crcs;
 static const char *mod_prefix = "";
 
 static int errors;
@@ -693,7 +693,10 @@ void export_symbol(const char *name)
 			fputs(">\n", debugfile);
 
 		/* Used as a linker script. */
-		printf("%s__crc_%s = 0x%08lx ;\n", mod_prefix, name, crc);
+		printf(!flag_rel_crcs ? "%s__crc_%s = 0x%08lx;\n" :
+		       "SECTIONS { .rodata : ALIGN(4) { "
+		       "%s__crc_%s = .; LONG(0x%08lx); } }\n",
+		       mod_prefix, name, crc);
 	}
 }
 
@@ -730,7 +733,7 @@ void error_with_pos(const char *fmt, ...)
 
 static void genksyms_usage(void)
 {
-	fputs("Usage:\n" "genksyms [-adDTwqhV] > /path/to/.tmp_obj.ver\n" "\n"
+	fputs("Usage:\n" "genksyms [-adDTwqhVR] > /path/to/.tmp_obj.ver\n" "\n"
 #ifdef __GNU_LIBRARY__
 	      "  -s, --symbol-prefix   Select symbol prefix\n"
 	      "  -d, --debug           Increment the debug level (repeatable)\n"
@@ -742,6 +745,7 @@ static void genksyms_usage(void)
 	      "  -q, --quiet           Disable warnings (default)\n"
 	      "  -h, --help            Print this message\n"
 	      "  -V, --version         Print the release version\n"
+	      "  -R, --relative-crc    Emit section relative symbol CRCs\n"
 #else				/* __GNU_LIBRARY__ */
 	      "  -s                    Select symbol prefix\n"
 	      "  -d                    Increment the debug level (repeatable)\n"
@@ -753,6 +757,7 @@ static void genksyms_usage(void)
 	      "  -q                    Disable warnings (default)\n"
 	      "  -h                    Print this message\n"
 	      "  -V                    Print the release version\n"
+	      "  -R                    Emit section relative symbol CRCs\n"
 #endif				/* __GNU_LIBRARY__ */
 	      , stderr);
 }
@@ -774,13 +779,14 @@ int main(int argc, char **argv)
 		{"preserve", 0, 0, 'p'},
 		{"version", 0, 0, 'V'},
 		{"help", 0, 0, 'h'},
+		{"relative-crc", 0, 0, 'R'},
 		{0, 0, 0, 0}
 	};
 
-	while ((o = getopt_long(argc, argv, "s:dwqVDr:T:ph",
+	while ((o = getopt_long(argc, argv, "s:dwqVDr:T:phR",
 				&long_opts[0], NULL)) != EOF)
 #else				/* __GNU_LIBRARY__ */
-	while ((o = getopt(argc, argv, "s:dwqVDr:T:ph")) != EOF)
+	while ((o = getopt(argc, argv, "s:dwqVDr:T:phR")) != EOF)
 #endif				/* __GNU_LIBRARY__ */
 		switch (o) {
 		case 's':
@@ -823,6 +829,9 @@ int main(int argc, char **argv)
 		case 'h':
 			genksyms_usage();
 			return 0;
+		case 'R':
+			flag_rel_crcs = 1;
+			break;
 		default:
 			genksyms_usage();
 			return 1;

scripts/kallsyms.c

@@ -219,6 +219,10 @@ static int symbol_valid(struct sym_entry *s)
 		"_SDA2_BASE_",		/* ppc */
 		NULL };
 
+	static char *special_prefixes[] = {
+		"__crc_",		/* modversions */
+		NULL };
+
 	static char *special_suffixes[] = {
 		"_veneer",		/* arm */
 		"_from_arm",		/* arm */
@@ -259,6 +263,14 @@ static int symbol_valid(struct sym_entry *s)
 		if (strcmp(sym_name, special_symbols[i]) == 0)
 			return 0;
 
+	for (i = 0; special_prefixes[i]; i++) {
+		int l = strlen(special_prefixes[i]);
+
+		if (l <= strlen(sym_name) &&
+		    strncmp(sym_name, special_prefixes[i], l) == 0)
+			return 0;
+	}
+
 	for (i = 0; special_suffixes[i]; i++) {
 		int l = strlen(sym_name) - strlen(special_suffixes[i]);
 

scripts/mod/modpost.c

@@ -621,6 +621,16 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
 	if (strncmp(symname, CRC_PFX, strlen(CRC_PFX)) == 0) {
 		is_crc = true;
 		crc = (unsigned int) sym->st_value;
+		if (sym->st_shndx != SHN_UNDEF && sym->st_shndx != SHN_ABS) {
+			unsigned int *crcp;
+
+			/* symbol points to the CRC in the ELF object */
+			crcp = (void *)info->hdr + sym->st_value +
+			       info->sechdrs[sym->st_shndx].sh_offset -
+			       (info->hdr->e_type != ET_REL ?
+				info->sechdrs[sym->st_shndx].sh_addr : 0);
+			crc = *crcp;
+		}
 		sym_update_crc(symname + strlen(CRC_PFX), mod, crc,
 				export);
 	}