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Date: Tue, 30 Jun 2009 13:18:57 +0100
From: "Jan Beulich" <JBeulich@...ell.com>
To: <sam@...nborg.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] reduce kallsyms table size on 64-bit arch-s
Some architectures (the patch carries it out for x86-64) can reduce the
kallsyms pointer table's size by half through the use of relative 32-
bit pointers. Since the kallsyms tables get created as assembly files
anyway, the adjustment is strait forward and only requires a little bit
of abstraction at the consuming side.
Further, independent of architecture, kallsyms_num_syms and
kallsyms_markers[] can use 32-bit types.
Signed-off-by: Jan Beulich <jbeulich@...ell.com>
---
arch/x86/Kconfig | 1 +
init/Kconfig | 3 +++
kernel/kallsyms.c | 31 +++++++++++++++++++++----------
scripts/kallsyms.c | 19 ++++++++++++++++---
4 files changed, 41 insertions(+), 13 deletions(-)
--- linux-2.6.31-rc1/arch/x86/Kconfig 2009-06-26 17:49:41.000000000 +0200
+++ 2.6.31-rc1-kallsyms-reduce-size/arch/x86/Kconfig 2009-04-29 15:59:50.000000000 +0200
@@ -14,6 +14,7 @@ config X86_32
config X86_64
def_bool 64BIT
+ select KALLSYMS_RELATIVE_POINTERS if KALLSYMS
### Arch settings
config X86
--- linux-2.6.31-rc1/init/Kconfig 2009-06-26 17:50:00.000000000 +0200
+++ 2.6.31-rc1-kallsyms-reduce-size/init/Kconfig 2009-04-27 12:04:03.000000000 +0200
@@ -802,6 +802,9 @@ config KALLSYMS_ALL
Say N.
+config KALLSYMS_RELATIVE_POINTERS
+ bool
+
config KALLSYMS_EXTRA_PASS
bool "Do an extra kallsyms pass"
depends on KALLSYMS
--- linux-2.6.31-rc1/kernel/kallsyms.c 2009-06-26 17:50:00.000000000 +0200
+++ 2.6.31-rc1-kallsyms-reduce-size/kernel/kallsyms.c 2009-06-30 11:11:22.000000000 +0200
@@ -34,20 +34,27 @@
* These will be re-linked against their real values
* during the second link stage.
*/
+#ifdef CONFIG_KALLSYMS_RELATIVE_POINTERS
+extern const signed int kallsyms_offsets[] __attribute__((weak));
+#define kallsyms_address(idx) ((unsigned long)_text + kallsyms_offsets[idx])
+#else
extern const unsigned long kallsyms_addresses[] __attribute__((weak));
+#define kallsyms_address(idx) kallsyms_addresses[idx]
+#endif
+
extern const u8 kallsyms_names[] __attribute__((weak));
/*
* Tell the compiler that the count isn't in the small data section if the arch
* has one (eg: FRV).
*/
-extern const unsigned long kallsyms_num_syms
+extern const unsigned int kallsyms_num_syms
__attribute__((weak, section(".rodata")));
extern const u8 kallsyms_token_table[] __attribute__((weak));
extern const u16 kallsyms_token_index[] __attribute__((weak));
-extern const unsigned long kallsyms_markers[] __attribute__((weak));
+extern const unsigned int kallsyms_markers[] __attribute__((weak));
static inline int is_kernel_inittext(unsigned long addr)
{
@@ -176,7 +183,7 @@ unsigned long kallsyms_lookup_name(const
off = kallsyms_expand_symbol(off, namebuf);
if (strcmp(namebuf, name) == 0)
- return kallsyms_addresses[i];
+ return kallsyms_address(i);
}
return module_kallsyms_lookup_name(name);
}
@@ -192,7 +199,7 @@ int kallsyms_on_each_symbol(int (*fn)(vo
for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
off = kallsyms_expand_symbol(off, namebuf);
- ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
+ ret = fn(data, namebuf, NULL, kallsyms_address(i));
if (ret != 0)
return ret;
}
@@ -208,7 +215,11 @@ static unsigned long get_symbol_pos(unsi
unsigned long i, low, high, mid;
/* This kernel should never had been booted. */
+#ifdef CONFIG_KALLSYMS_RELATIVE_POINTERS
+ BUG_ON(!kallsyms_offsets);
+#else
BUG_ON(!kallsyms_addresses);
+#endif
/* Do a binary search on the sorted kallsyms_addresses array. */
low = 0;
@@ -216,7 +227,7 @@ static unsigned long get_symbol_pos(unsi
while (high - low > 1) {
mid = low + (high - low) / 2;
- if (kallsyms_addresses[mid] <= addr)
+ if (kallsyms_address(mid) <= addr)
low = mid;
else
high = mid;
@@ -226,15 +237,15 @@ static unsigned long get_symbol_pos(unsi
* Search for the first aliased symbol. Aliased
* symbols are symbols with the same address.
*/
- while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
+ while (low && kallsyms_address(low-1) == kallsyms_address(low))
--low;
- symbol_start = kallsyms_addresses[low];
+ symbol_start = kallsyms_address(low);
/* Search for next non-aliased symbol. */
for (i = low + 1; i < kallsyms_num_syms; i++) {
- if (kallsyms_addresses[i] > symbol_start) {
- symbol_end = kallsyms_addresses[i];
+ if (kallsyms_address(i) > symbol_start) {
+ symbol_end = kallsyms_address(i);
break;
}
}
@@ -401,7 +412,7 @@ static unsigned long get_ksymbol_core(st
unsigned off = iter->nameoff;
iter->module_name[0] = '\0';
- iter->value = kallsyms_addresses[iter->pos];
+ iter->value = kallsyms_address(iter->pos);
iter->type = kallsyms_get_symbol_type(off);
--- linux-2.6.31-rc1/scripts/kallsyms.c 2009-06-26 17:50:01.000000000 +0200
+++ 2.6.31-rc1-kallsyms-reduce-size/scripts/kallsyms.c 2009-04-27 12:04:03.000000000 +0200
@@ -295,7 +295,8 @@ static void write_src(void)
char buf[KSYM_NAME_LEN];
printf("#include <asm/types.h>\n");
- printf("#if BITS_PER_LONG == 64\n");
+ printf("#if BITS_PER_LONG == 64"
+ " && !defined(CONFIG_KALLSYMS_RELATIVE_POINTERS)\n");
printf("#define PTR .quad\n");
printf("#define ALGN .align 8\n");
printf("#else\n");
@@ -312,7 +313,12 @@ static void write_src(void)
* .o files. This prevents .tmp_kallsyms.o or any other
* object from referencing them.
*/
+ printf("#ifdef CONFIG_KALLSYMS_RELATIVE_POINTERS\n");
+ output_label("kallsyms_offsets");
+ printf("#define _text\n");
+ printf("#else\n");
output_label("kallsyms_addresses");
+ printf("#endif\n");
for (i = 0; i < table_cnt; i++) {
if (toupper(table[i].sym[0]) != 'A') {
if (_text <= table[i].addr)
@@ -322,13 +328,20 @@ static void write_src(void)
printf("\tPTR\t_text - %#llx\n",
_text - table[i].addr);
} else {
+ printf("#if BITS_PER_LONG > 32"
+ " && defined(CONFIG_KALLSYMS_RELATIVE_POINTERS)\n");
+ printf("\t.err /* Absolute symbols not allowed on "
+ "this architecture, found '%s' */\n",
+ table[i].sym + 1);
+ printf("#else\n");
printf("\tPTR\t%#llx\n", table[i].addr);
+ printf("#endif\n");
}
}
printf("\n");
output_label("kallsyms_num_syms");
- printf("\tPTR\t%d\n", table_cnt);
+ printf("\t.long\t%u\n", table_cnt);
printf("\n");
/* table of offset markers, that give the offset in the compressed stream
@@ -357,7 +370,7 @@ static void write_src(void)
output_label("kallsyms_markers");
for (i = 0; i < ((table_cnt + 255) >> 8); i++)
- printf("\tPTR\t%d\n", markers[i]);
+ printf("\t.long\t%u\n", markers[i]);
printf("\n");
free(markers);
--
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