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Date: Thu, 21 Feb 2008 16:15:21 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>, Andi Kleen <ak@...e.de>,
Ian Campbell <ijc@...lion.org.uk>,
Matt Mackall <mpm@...enic.com>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] x86 : add init BSS sections
Init BSS sections are added for uninitialized init DATA sections to
reduce kernel image size.
Signed-off-by: Huang Ying <ying.huang@...el.com>
---
arch/x86/kernel/head64.c | 2 ++
arch/x86/kernel/head_32.S | 5 +++++
arch/x86/kernel/vmlinux_32.lds.S | 9 +++++++--
arch/x86/kernel/vmlinux_64.lds.S | 24 ++++++++++++++----------
include/asm-generic/sections.h | 1 +
include/linux/init.h | 1 +
6 files changed, 30 insertions(+), 12 deletions(-)
--- a/arch/x86/kernel/vmlinux_32.lds.S
+++ b/arch/x86/kernel/vmlinux_32.lds.S
@@ -189,10 +189,15 @@ SECTIONS
__per_cpu_end = .;
}
. = ALIGN(PAGE_SIZE);
- /* freed after init ends here */
.bss : AT(ADDR(.bss) - LOAD_OFFSET) {
- __init_end = .;
+ __init_bss_start = .;
+ *(.bss.init.page_aligned)
+ *(.bss.init)
+ . = ALIGN(4);
+ __init_bss_stop = .;
+ . = ALIGN(PAGE_SIZE);
+ __init_end = .; /* freed after init ends here */
__bss_start = .; /* BSS */
*(.bss.page_aligned)
*(.bss)
--- a/arch/x86/kernel/vmlinux_64.lds.S
+++ b/arch/x86/kernel/vmlinux_64.lds.S
@@ -150,6 +150,12 @@ SECTIONS
. = ALIGN(PAGE_SIZE);
__smp_alt_end = .;
+ . = ALIGN(PAGE_SIZE);
+ __nosave_begin = .;
+ .data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) { *(.data.nosave) }
+ . = ALIGN(PAGE_SIZE);
+ __nosave_end = .;
+
. = ALIGN(PAGE_SIZE); /* Init code and data */
__init_begin = .;
.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
@@ -219,17 +225,15 @@ SECTIONS
PERCPU(PAGE_SIZE)
- . = ALIGN(PAGE_SIZE);
- __init_end = .;
-
- . = ALIGN(PAGE_SIZE);
- __nosave_begin = .;
- .data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) { *(.data.nosave) }
- . = ALIGN(PAGE_SIZE);
- __nosave_end = .;
-
- __bss_start = .; /* BSS */
+ . = ALIGN(PAGE_SIZE); /* BSS */
.bss : AT(ADDR(.bss) - LOAD_OFFSET) {
+ __init_bss_start = .;
+ *(.bss.init.page_aligned)
+ *(.bss.init)
+ __init_bss_stop = .;
+ . = ALIGN(PAGE_SIZE);
+ __init_end = .;
+ __bss_start = .;
*(.bss.page_aligned)
*(.bss)
}
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -105,6 +105,11 @@ ENTRY(startup_32)
*/
cld
xorl %eax,%eax
+ movl $pa(__init_bss_start),%edi
+ movl $pa(__init_bss_stop), %ecx
+ subl %edi,%ecx
+ shrl $2,%ecx
+ rep ; stosl
movl $pa(__bss_start),%edi
movl $pa(__bss_stop),%ecx
subl %edi,%ecx
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -5,6 +5,7 @@
extern char _text[], _stext[], _etext[];
extern char _data[], _sdata[], _edata[];
+extern char __init_bss_start[], __init_bss_stop[];
extern char __bss_start[], __bss_stop[];
extern char __init_begin[], __init_end[];
extern char _sinittext[], _einittext[];
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -34,6 +34,8 @@ static void __init zap_identity_mappings
yet. */
static void __init clear_bss(void)
{
+ memset(__init_bss_start, 0, (unsigned long) __init_bss_stop -
+ (unsigned long) __init_bss_start);
memset(__bss_start, 0,
(unsigned long) __bss_stop - (unsigned long) __bss_start);
}
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -43,6 +43,7 @@
#define __init __section(.init.text) __cold
#define __initdata __section(.init.data)
#define __initconst __section(.init.rodata)
+#define __initbss __section(.bss.init)
#define __exitdata __section(.exit.data)
#define __exit_call __used __section(.exitcall.exit)
--
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