kbuild: modversions: add infrastructure for emitting relative CRCs
This add the kbuild infrastructure that will allow architectures to emit vmlinux symbol CRCs as 32-bit offsets to another location in the kernel where the actual value is stored. This works around problems with CRCs being mistaken for relocatable symbols on kernels that self relocate at runtime (i.e., powerpc with CONFIG_RELOCATABLE=y) For the kbuild side of things, this comes down to the following: - introducing a Kconfig symbol MODULE_REL_CRCS - adding a -R switch to genksyms to instruct it to emit the CRC symbols as references into the .rodata section - making modpost distinguish such references from absolute CRC symbols by the section index (SHN_ABS) - making kallsyms disregard non-absolute symbols with a __crc_ prefix Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ard Biesheuvel
Linus Torvalds
Родитель
34e00accf6
Коммит
56067812d5
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@ -1987,6 +1987,10 @@ config MODVERSIONS
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make them incompatible with the kernel you are running. If
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unsure, say N.
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config MODULE_REL_CRCS
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bool
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depends on MODVERSIONS
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config MODULE_SRCVERSION_ALL
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bool "Source checksum for all modules"
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help
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@ -164,6 +164,7 @@ cmd_gensymtypes_c = \
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$(CPP) -D__GENKSYMS__ $(c_flags) $< | \
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$(GENKSYMS) $(if $(1), -T $(2)) \
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$(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX)) \
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$(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS)) \
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$(if $(KBUILD_PRESERVE),-p) \
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-r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
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@ -337,6 +338,7 @@ cmd_gensymtypes_S = \
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$(CPP) -D__GENKSYMS__ $(c_flags) -xc - | \
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$(GENKSYMS) $(if $(1), -T $(2)) \
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$(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX)) \
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$(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS)) \
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$(if $(KBUILD_PRESERVE),-p) \
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-r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
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@ -44,7 +44,7 @@ char *cur_filename, *source_file;
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int in_source_file;
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static int flag_debug, flag_dump_defs, flag_reference, flag_dump_types,
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flag_preserve, flag_warnings;
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flag_preserve, flag_warnings, flag_rel_crcs;
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static const char *mod_prefix = "";
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static int errors;
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@ -693,7 +693,10 @@ void export_symbol(const char *name)
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fputs(">\n", debugfile);
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/* Used as a linker script. */
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printf("%s__crc_%s = 0x%08lx ;\n", mod_prefix, name, crc);
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printf(!flag_rel_crcs ? "%s__crc_%s = 0x%08lx;\n" :
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"SECTIONS { .rodata : ALIGN(4) { "
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"%s__crc_%s = .; LONG(0x%08lx); } }\n",
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mod_prefix, name, crc);
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}
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}
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@ -730,7 +733,7 @@ void error_with_pos(const char *fmt, ...)
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static void genksyms_usage(void)
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{
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fputs("Usage:\n" "genksyms [-adDTwqhV] > /path/to/.tmp_obj.ver\n" "\n"
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fputs("Usage:\n" "genksyms [-adDTwqhVR] > /path/to/.tmp_obj.ver\n" "\n"
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#ifdef __GNU_LIBRARY__
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" -s, --symbol-prefix Select symbol prefix\n"
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" -d, --debug Increment the debug level (repeatable)\n"
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@ -742,6 +745,7 @@ static void genksyms_usage(void)
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" -q, --quiet Disable warnings (default)\n"
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" -h, --help Print this message\n"
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" -V, --version Print the release version\n"
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" -R, --relative-crc Emit section relative symbol CRCs\n"
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#else /* __GNU_LIBRARY__ */
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" -s Select symbol prefix\n"
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" -d Increment the debug level (repeatable)\n"
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@ -753,6 +757,7 @@ static void genksyms_usage(void)
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" -q Disable warnings (default)\n"
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" -h Print this message\n"
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" -V Print the release version\n"
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" -R Emit section relative symbol CRCs\n"
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#endif /* __GNU_LIBRARY__ */
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, stderr);
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}
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@ -774,13 +779,14 @@ int main(int argc, char **argv)
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{"preserve", 0, 0, 'p'},
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{"version", 0, 0, 'V'},
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{"help", 0, 0, 'h'},
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{"relative-crc", 0, 0, 'R'},
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{0, 0, 0, 0}
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};
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while ((o = getopt_long(argc, argv, "s:dwqVDr:T:ph",
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while ((o = getopt_long(argc, argv, "s:dwqVDr:T:phR",
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&long_opts[0], NULL)) != EOF)
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#else /* __GNU_LIBRARY__ */
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while ((o = getopt(argc, argv, "s:dwqVDr:T:ph")) != EOF)
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while ((o = getopt(argc, argv, "s:dwqVDr:T:phR")) != EOF)
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#endif /* __GNU_LIBRARY__ */
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switch (o) {
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case 's':
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@ -823,6 +829,9 @@ int main(int argc, char **argv)
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case 'h':
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genksyms_usage();
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return 0;
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case 'R':
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flag_rel_crcs = 1;
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break;
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default:
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genksyms_usage();
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return 1;
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@ -219,6 +219,10 @@ static int symbol_valid(struct sym_entry *s)
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"_SDA2_BASE_", /* ppc */
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NULL };
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static char *special_prefixes[] = {
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"__crc_", /* modversions */
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NULL };
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static char *special_suffixes[] = {
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"_veneer", /* arm */
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"_from_arm", /* arm */
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@ -259,6 +263,14 @@ static int symbol_valid(struct sym_entry *s)
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if (strcmp(sym_name, special_symbols[i]) == 0)
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return 0;
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for (i = 0; special_prefixes[i]; i++) {
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int l = strlen(special_prefixes[i]);
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if (l <= strlen(sym_name) &&
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strncmp(sym_name, special_prefixes[i], l) == 0)
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return 0;
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}
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for (i = 0; special_suffixes[i]; i++) {
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int l = strlen(sym_name) - strlen(special_suffixes[i]);
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@ -621,6 +621,16 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
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if (strncmp(symname, CRC_PFX, strlen(CRC_PFX)) == 0) {
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is_crc = true;
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crc = (unsigned int) sym->st_value;
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if (sym->st_shndx != SHN_UNDEF && sym->st_shndx != SHN_ABS) {
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unsigned int *crcp;
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/* symbol points to the CRC in the ELF object */
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crcp = (void *)info->hdr + sym->st_value +
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info->sechdrs[sym->st_shndx].sh_offset -
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(info->hdr->e_type != ET_REL ?
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info->sechdrs[sym->st_shndx].sh_addr : 0);
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crc = *crcp;
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}
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sym_update_crc(symname + strlen(CRC_PFX), mod, crc,
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export);
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}
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