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Date: Tue, 30 Jun 2009 12:51:52 +0100
From: "Jan Beulich" <JBeulich@...ell.com>
To: "Ingo Molnar" <mingo@...e.hu>, <tony.luck@...el.com>,
"Thomas Gleixner" <tglx@...utronix.de>,
"Rusty Russell" <rusty@...tcorp.com.au>, <hpa@...or.com>
Cc: <linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] reduce export symbol CRC table size on 64-bit archs
Since these CRCs are really only 32-bit quantities, there's no need to
store them in 64-bit slots. Since, however, gcc doesn't allow
respective initializations, asm() constructs get used to create the CRC
tables (and its for that reason that the patch only makes x86-64 and
ia64 utilize that functionality, as I can't verify this doesn't break
in some subtle way elsewhere).
Observed size reduction (x86-64):
- 16k kernel resident size
- 2k module resident size
- 1M vmlinux image size
If the asm() construct could be extended to all architectures, and if
modpost would guarantee generation of CRCs for all exported, then
the __crc_* symbols wouldn't need to be declared weak anymore, could
hence remain local to the exporting object. By adding
-Wa,-strip-local-absolute to the second compilation step the __crc_*
symbols could even be prevented from making it into any object file at
all.
Signed-off-by: Jan Beulich <jbeulich@...ell.com>
---
arch/ia64/include/asm/module.h | 2 ++
arch/x86/include/asm/module.h | 1 +
include/linux/module.h | 41 ++++++++++++++++++++++++++---------------
include/linux/moduleparam.h | 10 +++++++++-
kernel/module.c | 26 +++++++++++++-------------
scripts/genksyms/genksyms.c | 16 ++++++++--------
6 files changed, 59 insertions(+), 37 deletions(-)
--- linux-2.6.31-rc1/arch/ia64/include/asm/module.h 2009-06-10 05:05:27.000000000 +0200
+++ 2.6.31-rc1-module-crc-int/arch/ia64/include/asm/module.h 2009-04-27 12:12:50.000000000 +0200
@@ -39,4 +39,6 @@ struct mod_arch_specific {
#define ARCH_SHF_SMALL SHF_IA_64_SHORT
+#define ARCH_ASM_KSYM_CRC data4
+
#endif /* _ASM_IA64_MODULE_H */
--- linux-2.6.31-rc1/arch/x86/include/asm/module.h 2008-12-25 00:26:37.000000000 +0100
+++ 2.6.31-rc1-module-crc-int/arch/x86/include/asm/module.h 2009-04-27 12:12:50.000000000 +0200
@@ -15,6 +15,7 @@ struct mod_arch_specific {};
#endif
#ifdef CONFIG_X86_64
+#define ARCH_ASM_KSYM_CRC .long
/* X86_64 does not define MODULE_PROC_FAMILY */
#elif defined CONFIG_M386
#define MODULE_PROC_FAMILY "386 "
--- linux-2.6.31-rc1/include/linux/module.h 2009-06-26 17:50:00.000000000 +0200
+++ 2.6.31-rc1-module-crc-int/include/linux/module.h 2009-04-27 12:15:26.000000000 +0200
@@ -19,8 +19,6 @@
#include <linux/tracepoint.h>
#include <asm/local.h>
-#include <asm/module.h>
-
/* Not Yet Implemented */
#define MODULE_SUPPORTED_DEVICE(name)
@@ -39,7 +37,7 @@ struct kernel_symbol
struct modversion_info
{
- unsigned long crc;
+ ksym_crc_t crc;
char name[MODULE_NAME_LEN];
};
@@ -175,17 +173,30 @@ void *__symbol_get_gpl(const char *symbo
#define symbol_get(x) ((typeof(&x))(__symbol_get(MODULE_SYMBOL_PREFIX #x)))
#ifndef __GENKSYMS__
-#ifdef CONFIG_MODVERSIONS
+#define __KSTRTAB(sym) __kstrtab_##sym
+#ifndef CONFIG_MODVERSIONS
+#define __CRC_SYMBOL(sym, sec)
+#elif !defined(ARCH_ASM_KSYM_CRC) || defined(CC_PTR_CAST_INT)
/* Mark the CRC weak since genksyms apparently decides not to
* generate a checksums for some symbols */
#define __CRC_SYMBOL(sym, sec) \
extern void *__crc_##sym __attribute__((weak)); \
- static const unsigned long __kcrctab_##sym \
+ static const ksym_crc_t __kcrctab_##sym \
__used \
__attribute__((section("__kcrctab" sec), unused)) \
- = (unsigned long) &__crc_##sym;
+ = (ksym_crc_t) (unsigned long) &__crc_##sym;
#else
-#define __CRC_SYMBOL(sym, sec)
+#define __CRC_SYMBOL(sym, sec) \
+ extern const char __Kstrtab_##sym[] \
+ __asm__("__kstrtab_" #sym "\n\t" \
+ ".section __kcrctab" sec ",\"a\"\n\t" \
+ ".weak __crc_" #sym "\n\t" \
+ __stringify(ARCH_ASM_KSYM_CRC) " __crc_" #sym "\n\t" \
+ ".previous"); \
+ static const char __kstrtab_##sym[] \
+ __used __attribute__((__unused__));
+#undef __KSTRTAB
+#define __KSTRTAB(sym) __Kstrtab_##sym
#endif
/* For every exported symbol, place a struct in the __ksymtab section */
@@ -198,7 +209,7 @@ void *__symbol_get_gpl(const char *symbo
static const struct kernel_symbol __ksymtab_##sym \
__used \
__attribute__((section("__ksymtab" sec), unused)) \
- = { (unsigned long)&sym, __kstrtab_##sym }
+ = { (unsigned long)&sym, __KSTRTAB(sym) }
#define EXPORT_SYMBOL(sym) \
__EXPORT_SYMBOL(sym, "")
@@ -246,7 +257,7 @@ struct module
/* Exported symbols */
const struct kernel_symbol *syms;
- const unsigned long *crcs;
+ const ksym_crc_t *crcs;
unsigned int num_syms;
/* Kernel parameters. */
@@ -256,23 +267,23 @@ struct module
/* GPL-only exported symbols. */
unsigned int num_gpl_syms;
const struct kernel_symbol *gpl_syms;
- const unsigned long *gpl_crcs;
+ const ksym_crc_t *gpl_crcs;
#ifdef CONFIG_UNUSED_SYMBOLS
/* unused exported symbols. */
const struct kernel_symbol *unused_syms;
- const unsigned long *unused_crcs;
+ const ksym_crc_t *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 ksym_crc_t *unused_gpl_crcs;
#endif
/* symbols that will be GPL-only in the near future. */
const struct kernel_symbol *gpl_future_syms;
- const unsigned long *gpl_future_crcs;
+ const ksym_crc_t *gpl_future_crcs;
unsigned int num_gpl_future_syms;
/* Exception table */
@@ -406,7 +417,7 @@ struct module *find_module(const char *n
struct symsearch {
const struct kernel_symbol *start, *stop;
- const unsigned long *crcs;
+ const ksym_crc_t *crcs;
enum {
NOT_GPL_ONLY,
GPL_ONLY,
@@ -418,7 +429,7 @@ struct symsearch {
/* Search for an exported symbol by name. */
const struct kernel_symbol *find_symbol(const char *name,
struct module **owner,
- const unsigned long **crc,
+ const ksym_crc_t **crc,
bool gplok,
bool warn);
--- linux-2.6.31-rc1/include/linux/moduleparam.h 2009-06-26 17:50:00.000000000 +0200
+++ 2.6.31-rc1-module-crc-int/include/linux/moduleparam.h 2009-04-27 12:12:50.000000000 +0200
@@ -5,6 +5,8 @@
#include <linux/stringify.h>
#include <linux/kernel.h>
+#include <asm/module.h>
+
/* You can override this manually, but generally this should match the
module name. */
#ifdef MODULE
@@ -13,8 +15,14 @@
#define MODULE_PARAM_PREFIX KBUILD_MODNAME "."
#endif
+#ifdef ARCH_ASM_KSYM_CRC
+typedef unsigned int ksym_crc_t;
+#else
+typedef unsigned long ksym_crc_t;
+#endif
+
/* Chosen so that structs with an unsigned long line up. */
-#define MAX_PARAM_PREFIX_LEN (64 - sizeof(unsigned long))
+#define MAX_PARAM_PREFIX_LEN (64 - sizeof(ksym_crc_t))
#ifdef MODULE
#define ___module_cat(a,b) __mod_ ## a ## b
--- linux-2.6.31-rc1/kernel/module.c 2009-06-26 17:50:00.000000000 +0200
+++ 2.6.31-rc1-module-crc-int/kernel/module.c 2009-04-27 12:16:40.000000000 +0200
@@ -174,16 +174,16 @@ extern const struct kernel_symbol __star
extern const struct kernel_symbol __stop___ksymtab_gpl_future[];
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 ksym_crc_t __start___kcrctab[];
+extern const ksym_crc_t __start___kcrctab_gpl[];
+extern const ksym_crc_t __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 ksym_crc_t __start___kcrctab_unused[];
+extern const ksym_crc_t __start___kcrctab_unused_gpl[];
#endif
#ifndef CONFIG_MODVERSIONS
@@ -276,7 +276,7 @@ struct find_symbol_arg {
/* Output */
struct module *owner;
- const unsigned long *crc;
+ const ksym_crc_t *crc;
const struct kernel_symbol *sym;
};
@@ -326,7 +326,7 @@ static bool find_symbol_in_section(const
* (optional) module which owns it */
const struct kernel_symbol *find_symbol(const char *name,
struct module **owner,
- const unsigned long **crc,
+ const ksym_crc_t **crc,
bool gplok,
bool warn)
{
@@ -1024,7 +1024,7 @@ static int check_version(Elf_Shdr *sechd
unsigned int versindex,
const char *symname,
struct module *mod,
- const unsigned long *crc)
+ const ksym_crc_t *crc)
{
unsigned int i, num_versions;
struct modversion_info *versions;
@@ -1047,8 +1047,8 @@ static int check_version(Elf_Shdr *sechd
if (versions[i].crc == *crc)
return 1;
- DEBUGP("Found checksum %lX vs module %lX\n",
- *crc, versions[i].crc);
+ DEBUGP("Found checksum %X vs module %X\n",
+ (unsigned int)*crc, (unsigned int)versions[i].crc);
goto bad_version;
}
@@ -1066,7 +1066,7 @@ static inline int check_modstruct_versio
unsigned int versindex,
struct module *mod)
{
- const unsigned long *crc;
+ const ksym_crc_t *crc;
if (!find_symbol("module_layout", NULL, &crc, true, false))
BUG();
@@ -1088,7 +1088,7 @@ static inline int check_version(Elf_Shdr
unsigned int versindex,
const char *symname,
struct module *mod,
- const unsigned long *crc)
+ const ksym_crc_t *crc)
{
return 1;
}
@@ -1116,7 +1116,7 @@ static const struct kernel_symbol *resol
{
struct module *owner;
const struct kernel_symbol *sym;
- const unsigned long *crc;
+ const ksym_crc_t *crc;
sym = find_symbol(name, &owner, &crc,
!(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
--- linux-2.6.31-rc1/scripts/genksyms/genksyms.c 2009-03-24 00:12:14.000000000 +0100
+++ 2.6.31-rc1-module-crc-int/scripts/genksyms/genksyms.c 2009-04-27 12:12:50.000000000 +0200
@@ -119,19 +119,19 @@ static const unsigned int crctab32[] = {
0x2d02ef8dU
};
-static unsigned long partial_crc32_one(unsigned char c, unsigned long crc)
+static unsigned int partial_crc32_one(unsigned char c, unsigned int crc)
{
return crctab32[(crc ^ c) & 0xff] ^ (crc >> 8);
}
-static unsigned long partial_crc32(const char *s, unsigned long crc)
+static unsigned int partial_crc32(const char *s, unsigned int crc)
{
while (*s)
crc = partial_crc32_one(*s++, crc);
return crc;
}
-static unsigned long crc32(const char *s)
+static unsigned int crc32(const char *s)
{
return partial_crc32(s, 0xffffffff) ^ 0xffffffff;
}
@@ -149,7 +149,7 @@ static enum symbol_type map_to_ns(enum s
struct symbol *find_symbol(const char *name, enum symbol_type ns)
{
- unsigned long h = crc32(name) % HASH_BUCKETS;
+ unsigned int h = crc32(name) % HASH_BUCKETS;
struct symbol *sym;
for (sym = symtab[h]; sym; sym = sym->hash_next)
@@ -180,7 +180,7 @@ struct symbol *__add_symbol(const char *
struct string_list *defn, int is_extern,
int is_reference)
{
- unsigned long h = crc32(name) % HASH_BUCKETS;
+ unsigned int h = crc32(name) % HASH_BUCKETS;
struct symbol *sym;
enum symbol_status status = STATUS_UNCHANGED;
@@ -433,7 +433,7 @@ static void print_list(FILE * f, struct
}
}
-static unsigned long expand_and_crc_sym(struct symbol *sym, unsigned long crc)
+static unsigned int expand_and_crc_sym(struct symbol *sym, unsigned int crc)
{
struct string_list *list = sym->defn;
struct string_list **e, **b;
@@ -569,7 +569,7 @@ void export_symbol(const char *name)
if (!sym)
error_with_pos("export undefined symbol %s", name);
else {
- unsigned long crc;
+ unsigned int crc;
int has_changed = 0;
if (flag_dump_defs)
@@ -611,7 +611,7 @@ 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("%s__crc_%s = %#08x ;\n", mod_prefix, name, crc);
}
}
--
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