Commit 56067812 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Linus Torvalds

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: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 34e00acc
...@@ -1987,6 +1987,10 @@ config MODVERSIONS ...@@ -1987,6 +1987,10 @@ config MODVERSIONS
make them incompatible with the kernel you are running. If make them incompatible with the kernel you are running. If
unsure, say N. unsure, say N.
config MODULE_REL_CRCS
bool
depends on MODVERSIONS
config MODULE_SRCVERSION_ALL config MODULE_SRCVERSION_ALL
bool "Source checksum for all modules" bool "Source checksum for all modules"
help help
......
...@@ -164,6 +164,7 @@ cmd_gensymtypes_c = \ ...@@ -164,6 +164,7 @@ cmd_gensymtypes_c = \
$(CPP) -D__GENKSYMS__ $(c_flags) $< | \ $(CPP) -D__GENKSYMS__ $(c_flags) $< | \
$(GENKSYMS) $(if $(1), -T $(2)) \ $(GENKSYMS) $(if $(1), -T $(2)) \
$(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX)) \ $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX)) \
$(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS)) \
$(if $(KBUILD_PRESERVE),-p) \ $(if $(KBUILD_PRESERVE),-p) \
-r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null)) -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
...@@ -337,6 +338,7 @@ cmd_gensymtypes_S = \ ...@@ -337,6 +338,7 @@ cmd_gensymtypes_S = \
$(CPP) -D__GENKSYMS__ $(c_flags) -xc - | \ $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | \
$(GENKSYMS) $(if $(1), -T $(2)) \ $(GENKSYMS) $(if $(1), -T $(2)) \
$(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX)) \ $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX)) \
$(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS)) \
$(if $(KBUILD_PRESERVE),-p) \ $(if $(KBUILD_PRESERVE),-p) \
-r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null)) -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
......
...@@ -44,7 +44,7 @@ char *cur_filename, *source_file; ...@@ -44,7 +44,7 @@ char *cur_filename, *source_file;
int in_source_file; int in_source_file;
static int flag_debug, flag_dump_defs, flag_reference, flag_dump_types, 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 const char *mod_prefix = "";
static int errors; static int errors;
...@@ -693,7 +693,10 @@ void export_symbol(const char *name) ...@@ -693,7 +693,10 @@ void export_symbol(const char *name)
fputs(">\n", debugfile); fputs(">\n", debugfile);
/* Used as a linker script. */ /* 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, ...) ...@@ -730,7 +733,7 @@ void error_with_pos(const char *fmt, ...)
static void genksyms_usage(void) 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__ #ifdef __GNU_LIBRARY__
" -s, --symbol-prefix Select symbol prefix\n" " -s, --symbol-prefix Select symbol prefix\n"
" -d, --debug Increment the debug level (repeatable)\n" " -d, --debug Increment the debug level (repeatable)\n"
...@@ -742,6 +745,7 @@ static void genksyms_usage(void) ...@@ -742,6 +745,7 @@ static void genksyms_usage(void)
" -q, --quiet Disable warnings (default)\n" " -q, --quiet Disable warnings (default)\n"
" -h, --help Print this message\n" " -h, --help Print this message\n"
" -V, --version Print the release version\n" " -V, --version Print the release version\n"
" -R, --relative-crc Emit section relative symbol CRCs\n"
#else /* __GNU_LIBRARY__ */ #else /* __GNU_LIBRARY__ */
" -s Select symbol prefix\n" " -s Select symbol prefix\n"
" -d Increment the debug level (repeatable)\n" " -d Increment the debug level (repeatable)\n"
...@@ -753,6 +757,7 @@ static void genksyms_usage(void) ...@@ -753,6 +757,7 @@ static void genksyms_usage(void)
" -q Disable warnings (default)\n" " -q Disable warnings (default)\n"
" -h Print this message\n" " -h Print this message\n"
" -V Print the release version\n" " -V Print the release version\n"
" -R Emit section relative symbol CRCs\n"
#endif /* __GNU_LIBRARY__ */ #endif /* __GNU_LIBRARY__ */
, stderr); , stderr);
} }
...@@ -774,13 +779,14 @@ int main(int argc, char **argv) ...@@ -774,13 +779,14 @@ int main(int argc, char **argv)
{"preserve", 0, 0, 'p'}, {"preserve", 0, 0, 'p'},
{"version", 0, 0, 'V'}, {"version", 0, 0, 'V'},
{"help", 0, 0, 'h'}, {"help", 0, 0, 'h'},
{"relative-crc", 0, 0, 'R'},
{0, 0, 0, 0} {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) &long_opts[0], NULL)) != EOF)
#else /* __GNU_LIBRARY__ */ #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__ */ #endif /* __GNU_LIBRARY__ */
switch (o) { switch (o) {
case 's': case 's':
...@@ -823,6 +829,9 @@ int main(int argc, char **argv) ...@@ -823,6 +829,9 @@ int main(int argc, char **argv)
case 'h': case 'h':
genksyms_usage(); genksyms_usage();
return 0; return 0;
case 'R':
flag_rel_crcs = 1;
break;
default: default:
genksyms_usage(); genksyms_usage();
return 1; return 1;
......
...@@ -219,6 +219,10 @@ static int symbol_valid(struct sym_entry *s) ...@@ -219,6 +219,10 @@ static int symbol_valid(struct sym_entry *s)
"_SDA2_BASE_", /* ppc */ "_SDA2_BASE_", /* ppc */
NULL }; NULL };
static char *special_prefixes[] = {
"__crc_", /* modversions */
NULL };
static char *special_suffixes[] = { static char *special_suffixes[] = {
"_veneer", /* arm */ "_veneer", /* arm */
"_from_arm", /* arm */ "_from_arm", /* arm */
...@@ -259,6 +263,14 @@ static int symbol_valid(struct sym_entry *s) ...@@ -259,6 +263,14 @@ static int symbol_valid(struct sym_entry *s)
if (strcmp(sym_name, special_symbols[i]) == 0) if (strcmp(sym_name, special_symbols[i]) == 0)
return 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++) { for (i = 0; special_suffixes[i]; i++) {
int l = strlen(sym_name) - strlen(special_suffixes[i]); int l = strlen(sym_name) - strlen(special_suffixes[i]);
......
...@@ -621,6 +621,16 @@ static void handle_modversions(struct module *mod, struct elf_info *info, ...@@ -621,6 +621,16 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
if (strncmp(symname, CRC_PFX, strlen(CRC_PFX)) == 0) { if (strncmp(symname, CRC_PFX, strlen(CRC_PFX)) == 0) {
is_crc = true; is_crc = true;
crc = (unsigned int) sym->st_value; 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, sym_update_crc(symname + strlen(CRC_PFX), mod, crc,
export); export);
} }
......
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