[PATCH 1/2] section garbage collection for i386

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* [PATCH 1/2] section garbage collection for i386
@ 2007-09-12 20:24 Denys Vlasenko
  2007-09-12 20:30 ` [PATCH 2/2] " Denys Vlasenko
  0 siblings, 1 reply; 3+ messages in thread
From: Denys Vlasenko @ 2007-09-12 20:24 UTC (permalink / raw)
  To: Sam Ravnborg; +Cc: linux-kernel

[-- Attachment #1: Type: text/plain, Size: 325 bytes --]

Hi Sam,

This patch is preparatory: it adds a few KEEP() directives where
I forgot them in previous patch set, adds comments which explains
places where KEEP() is definitely not needed, and fixes i386 vdso generation
in an "obviously safe" way.

Please apply.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
--
vda

[-- Attachment #2: linux-2.6.23-rc4.5.fixes.patch --]
[-- Type: text/x-diff, Size: 2329 bytes --]

diff -urpN linux-2.6.23-rc4.gc4/arch/i386/kernel/vsyscall.lds.S linux-2.6.23-rc4.gc5/arch/i386/kernel/vsyscall.lds.S
--- linux-2.6.23-rc4.gc4/arch/i386/kernel/vsyscall.lds.S	2007-07-09 00:32:17.000000000 +0100
+++ linux-2.6.23-rc4.gc5/arch/i386/kernel/vsyscall.lds.S	2007-09-12 19:47:17.000000000 +0100
@@ -23,10 +23,10 @@ SECTIONS
      is insufficient, ld -shared will barf.  Just increase it here.  */
   . = VDSO_PRELINK_asm + 0x400;
 
-  .text           : { *(.text) }		:text =0x90909090
+  .text           : { *(.text) *(.text.*) }	:text =0x90909090
   .note		  : { *(.note.*) }		:text :note
   .eh_frame_hdr   : { *(.eh_frame_hdr) }	:text :eh_frame_hdr
-  .eh_frame       : { KEEP (*(.eh_frame)) }	:text
+  .eh_frame       : { KEEP(*(.eh_frame)) }	:text
   .dynamic        : { *(.dynamic) }		:text :dynamic
   .useless        : {
   	*(.got.plt) *(.got)
diff -urpN linux-2.6.23-rc4.gc4/include/asm-generic/vmlinux.lds.h linux-2.6.23-rc4.gc5/include/asm-generic/vmlinux.lds.h
--- linux-2.6.23-rc4.gc4/include/asm-generic/vmlinux.lds.h	2007-09-12 19:46:32.000000000 +0100
+++ linux-2.6.23-rc4.gc5/include/asm-generic/vmlinux.lds.h	2007-09-12 19:47:17.000000000 +0100
@@ -169,6 +169,7 @@
 #define SCHED_TEXT							\
 		ALIGN_FUNCTION();					\
 		VMLINUX_SYMBOL(__sched_text_start) = .;			\
+		/* No need to KEEP */					\
 		*(.sched.text)						\
 		VMLINUX_SYMBOL(__sched_text_end) = .;
 
@@ -177,12 +178,14 @@
 #define LOCK_TEXT							\
 		ALIGN_FUNCTION();					\
 		VMLINUX_SYMBOL(__lock_text_start) = .;			\
+		/* No need to KEEP */					\
 		*(.spinlock.text)					\
 		VMLINUX_SYMBOL(__lock_text_end) = .;
 
 #define KPROBES_TEXT							\
 		ALIGN_FUNCTION();					\
 		VMLINUX_SYMBOL(__kprobes_text_start) = .;		\
+		/* No need to KEEP */					\
 		*(.kprobes.text)					\
 		VMLINUX_SYMBOL(__kprobes_text_end) = .;
 
@@ -228,14 +231,16 @@
 	. = ALIGN(8);							\
 	__bug_table : AT(ADDR(__bug_table) - LOAD_OFFSET) {		\
 		__start___bug_table = .;				\
-		*(__bug_table)						\
+		/* Support for BUG() */					\
+		KEEP(*(__bug_table))					\
 		__stop___bug_table = .;					\
 	}
 
 #define NOTES								\
 	.notes : AT(ADDR(.notes) - LOAD_OFFSET) {			\
 		VMLINUX_SYMBOL(__start_notes) = .;			\
-		*(.note.*)						\
+		/* For /sys/kernel/notes */				\
+		KEEP(*(.note.*))					\
 		VMLINUX_SYMBOL(__stop_notes) = .;			\
 	}
 

^ permalink raw reply	[flat|nested] 3+ messages in thread

* [PATCH 2/2] section garbage collection for i386
  2007-09-12 20:24 [PATCH 1/2] section garbage collection for i386 Denys Vlasenko
@ 2007-09-12 20:30 ` Denys Vlasenko
  2007-09-12 20:45   ` [PATCH 3/2] section garbage collection for i386 - BONUS TRACK Denys Vlasenko
  0 siblings, 1 reply; 3+ messages in thread
From: Denys Vlasenko @ 2007-09-12 20:30 UTC (permalink / raw)
  To: Sam Ravnborg; +Cc: linux-kernel

[-- Attachment #1: Type: text/plain, Size: 1658 bytes --]

Hi Sam,

This patch adds module linker script (completely analogous to x86_64),
and "minimally" fixes vmlinux linker script by adding KEEPs.
It also deleted an outdated comment and amends help text.

I got a few "section mismatch" warnings with .config which doesn't
show them (IIRC) on original kernel.

I took a look and I think that original kernel was actually in error
and these warnings are correct!

WARNING: vmlinux.o(.text.kmem_cache_create+0x32f): Section mismatch: reference to .init.refok.text:setup_cpu_cache (after 'kmem_cache_create')
WARNING: vmlinux.o(.text.vgacon_startup+0x2dd): Section mismatch: reference to .init.refok.text:vgacon_scrollback_startup (after 'vgacon_startup')
WARNING: vmlinux.o(.data.smp_ops+0x0): Section mismatch: reference to .init.text:native_smp_prepare_boot_cpu (after 'smp_ops')
WARNING: vmlinux.o(.data.smp_ops+0x4): Section mismatch: reference to .init.text:native_smp_prepare_cpus (after 'smp_ops')
WARNING: vmlinux.o(.data.smp_ops+0xc): Section mismatch: reference to .init.text:native_smp_cpus_done (after 'smp_ops')
WARNING: vmlinux.o(.data.vesafb_driver+0x0): Section mismatch: reference to .init.text:vesafb_probe (after 'vesafb_driver')
WARNING: vmlinux.o(.data.serial8250_console+0x20): Section mismatch: reference to .init.text:serial8250_console_setup (after 'serial8250_console')
WARNING: vmlinux.o(.data.dgrs_pci_driver+0x10): Section mismatch: reference to .init.text:dgrs_pci_probe (after 'dgrs_pci_driver')

Risk of this patch is analogous to last patch of first series -
run-tested and looks safe, but needs to go into -mm first.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
--
vda

[-- Attachment #2: linux-2.6.23-rc4.6.i386.patch --]
[-- Type: text/x-diff, Size: 9551 bytes --]

diff -urpN linux-2.6.23-rc4.gc5/arch/i386/kernel/modules.lds linux-2.6.23-rc4.gc6/arch/i386/kernel/modules.lds
--- linux-2.6.23-rc4.gc5/arch/i386/kernel/modules.lds	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.23-rc4.gc6/arch/i386/kernel/modules.lds	2007-09-12 19:49:10.000000000 +0100
@@ -0,0 +1,123 @@
+OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
+OUTPUT_ARCH(i386)
+
+/*
+This linker script is used if CONFIG_DISCARD_UNUSED_SECTIONS=y.
+We are trying to minimize number of sections in .ko file
+by coalescing .text.x, rodata.x, .data.x and bss.x input
+sections into one output section.
+
+This script may be usable without CONFIG_DISCARD_UNUSED_SECTIONS too.
+
+Kernel module loader (kernel/module.c) needs to see the following sections:
+
+.init*
+.exit*
+.gnu.linkonce.this_module
+.percpu.data
+.modinfo
+__ksymtab_gpl_future
+__ksymtab_gpl
+__ksymtab_unused_gpl
+__ksymtab_unused
+__ksymtab
+__kcrctab_gpl_future
+__kcrctab_gpl
+__kcrctab_unused_gpl
+__kcrctab_unused
+__kcrctab
+__param
+__ex_table
+__obsparm
+__versions
+.debug (?!)
+$ARCH_UNWIND_SECTION_NAME
+
+They must not be coalesced into sections with other names.
+
+*/
+
+SECTIONS
+{
+  /* ro, code */
+
+  /* .fixup and .altinstr_replacement work just fine
+   * without dedicated sections */
+  .text				: {
+				    *(SORT_BY_ALIGNMENT(.text*))
+				/* __ex_table points here */
+				    *(SORT_BY_ALIGNMENT(.fixup*))
+				/* .altinstructions points here */
+				    *(SORT_BY_ALIGNMENT(.altinstr_replacement*))
+				}
+  /* only if CONFIG_MODULE_UNLOAD */
+  .exit.text			: { *(SORT_BY_ALIGNMENT(.exit.text)) }
+  /* end CONFIG_MODULE_UNLOAD */
+
+  /* ro, data */
+
+  .rodata			: { *(SORT_BY_ALIGNMENT(.rodata*)) }
+  /* Kernel searches through this table when it needs to handle an exception */
+  __ex_table			: { *(__ex_table*) }
+  /* These two tables are not currently handled by in-kernel module loader,
+   * but likely will be in future kernels */
+  .altinstructions		: { *(.altinstructions*) }
+  .smp_locks			: { *(.smp_locks*) }
+  /* Used by depmod in order to generate modules.dep, modules.symbols */
+  __ksymtab_strings		: { *(SORT_BY_ALIGNMENT(__ksymtab_strings)) }
+  /* EXPORT_SYMBOLs exported in this module */
+  __ksymtab_gpl_future		: { *(__ksymtab_gpl_future) }
+  __ksymtab_gpl			: { *(__ksymtab_gpl) }
+  __ksymtab_unused_gpl		: { *(__ksymtab_unused_gpl) }
+  __ksymtab_unused		: { *(__ksymtab_unused) }
+  __ksymtab			: { *(__ksymtab) }
+  /* only if CONFIG_MODVERSIONS */
+  __kcrctab_gpl_future		: { *(__kcrctab_gpl_future) }
+  __kcrctab_gpl			: { *(__kcrctab_gpl) }
+  __kcrctab_unused_gpl		: { *(__kcrctab_unused_gpl) }
+  __kcrctab_unused		: { *(__kcrctab_unused) }
+  __kcrctab			: { *(__kcrctab) }
+  /* from *.mod.c: const struct modversion_info ____versions[] */
+  __versions			: { *(__versions) }
+  /* end CONFIG_MODVERSIONS */
+  __param			: { *(.__param) }
+  __obsparm			: { *(.__obsparm) }
+  /* from *.mod.c: const char __module_depends[] "depends=mod1,mod2" */
+  .modinfo			: { *(SORT_BY_ALIGNMENT(.modinfo)) }
+  /* ld segfaults if we give it --build-id and then discard this section */
+  .note.gnu.build-id		: { *(.note.gnu.build-id) }
+
+  /* rw, data */
+
+  .data				: {
+				    *(SORT_BY_ALIGNMENT(.cacheline_aligned.data))
+				    *(SORT_BY_ALIGNMENT(.data*))
+				    *(SORT_BY_ALIGNMENT(.read_mostly.data))
+				}
+  /* from *.mod.c: struct module __this_module */
+  .gnu.linkonce.this_module	: { *(.gnu.linkonce.this_module) }
+  /* only if CONFIG_SMP */
+  .percpu.data			: { *(SORT_BY_ALIGNMENT(.percpu.data)) }
+  /* end CONFIG_SMP */
+  /* only if CONFIG_MODULE_UNLOAD */
+  .exit.data			: { *(SORT_BY_ALIGNMENT(.exit.data)) }
+  /* end CONFIG_MODULE_UNLOAD */
+
+  /* rw, data initialized to 0 */
+
+  .bss				: { *(SORT_BY_ALIGNMENT(.bss*)) }
+
+  /* init code/data. discarded at the end of sys_init_module() */
+
+  .init.text			: { *(SORT_BY_ALIGNMENT(.init.text)) }
+  .init.data			: { *(SORT_BY_ALIGNMENT(.init.data)) }
+
+  /* Be bold and resist the temptation to pull junk "by default" */
+
+  /DISCARD/			: { *(*) }
+
+  /* If you are going to revive these, please add comment why it is needed */
+  /* .debug			: { *(.debug) } */
+  /* .comment			: { *(.comment) } */
+  /* .note.GNU-stack		: { *(.note.GNU-stack) } */
+}
diff -urpN linux-2.6.23-rc4.gc5/arch/i386/kernel/vmlinux.lds.S linux-2.6.23-rc4.gc6/arch/i386/kernel/vmlinux.lds.S
--- linux-2.6.23-rc4.gc5/arch/i386/kernel/vmlinux.lds.S	2007-09-12 19:46:32.000000000 +0100
+++ linux-2.6.23-rc4.gc6/arch/i386/kernel/vmlinux.lds.S	2007-09-12 19:51:42.000000000 +0100
@@ -32,7 +32,7 @@ SECTIONS
 
   .head.text : AT(ADDR(.head.text) - LOAD_OFFSET) {
   	_text = .;			/* Text and read-only data */
-	*(.head.text)
+	KEEP(*(.head.text))
   } :text = 0x9090
 
   /* read-only */
@@ -41,6 +41,7 @@ SECTIONS
 	SCHED_TEXT
 	LOCK_TEXT
 	KPROBES_TEXT
+	/* No need to KEEP - referenced by __ex_table */
 	*(.fixup)
 	*(.gnu.warning)
   	_etext = .;			/* End of text section */
@@ -49,7 +50,7 @@ SECTIONS
   . = ALIGN(16);		/* Exception table */
   __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
   	__start___ex_table = .;
-	 *(__ex_table)
+	KEEP(*(__ex_table))
   	__stop___ex_table = .;
   }
 
@@ -60,7 +61,8 @@ SECTIONS
   . = ALIGN(4);
   .tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) {
   	__tracedata_start = .;
-	*(.tracedata)
+	/* Resume debug tracing */
+	KEEP(*(.tracedata))
   	__tracedata_end = .;
   }
 
@@ -71,11 +73,12 @@ SECTIONS
   .data : AT(ADDR(.data) - LOAD_OFFSET) {	/* Data */
 	DATA_DATA
 	CONSTRUCTORS
-	} :data
+  } :data
 
   . = ALIGN(4096);
   .data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) {
   	__nosave_begin = .;
+	/* No need to KEEP */
 	*(.nosave.data)
   	. = ALIGN(4096);
   	__nosave_end = .;
@@ -108,19 +111,13 @@ SECTIONS
   . = ALIGN(4096);
   .smp_locks : AT(ADDR(.smp_locks) - LOAD_OFFSET) {
   	__smp_locks = .;
-	*(.smp_locks)
+	KEEP(*(.smp_locks))
 	__smp_locks_end = .;
   }
-  /* will be freed after init
-   * Following ALIGN() is required to make sure no other data falls on the
-   * same page where __smp_alt_end is pointing as that page might be freed
-   * after boot. Always make sure that ALIGN() directive is present after
-   * the section which contains __smp_alt_end.
-   */
-  . = ALIGN(4096);
 
-  /* will be freed after init */
-  . = ALIGN(4096);		/* Init code and data */
+  /* Will be freed after init */
+  /* Init code and data */
+  . = ALIGN(4096);
   .init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
   	__init_begin = .;
 	_sinittext = .;
@@ -131,7 +128,9 @@ SECTIONS
   . = ALIGN(16);
   .init.setup : AT(ADDR(.init.setup) - LOAD_OFFSET) {
   	__setup_start = .;
-	*(.init.setup)
+	/* __setup_param() macro produces these,
+	 * obsolete_checksetup() processes them */
+	KEEP(*(.init.setup))
   	__setup_end = .;
    }
   .initcall.init : AT(ADDR(.initcall.init) - LOAD_OFFSET) {
@@ -141,46 +140,50 @@ SECTIONS
   }
   .con_initcall.init : AT(ADDR(.con_initcall.init) - LOAD_OFFSET) {
   	__con_initcall_start = .;
-	*(.con_initcall.init)
+	KEEP(*(.con_initcall.init))
   	__con_initcall_end = .;
   }
   SECURITY_INIT
   . = ALIGN(4);
   .altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
   	__alt_instructions = .;
-	*(.altinstructions)
+	KEEP(*(.altinstructions))
 	__alt_instructions_end = .;
   }
   .altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) {
+	/* No need to KEEP - referenced by .altinstructions */
 	*(.altinstr_replacement)
   }
   . = ALIGN(4);
   .parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) {
   	__parainstructions = .;
-	*(.parainstructions)
+	KEEP(*(.parainstructions))
   	__parainstructions_end = .;
   }
-  /* .exit.text is discard at runtime, not link time, to deal with references
+  /* .exit.text is discarded at runtime, not link time, to deal with references
      from .altinstructions and .eh_frame */
   .exit.text : AT(ADDR(.exit.text) - LOAD_OFFSET) { *(.exit.text) }
   .exit.data : AT(ADDR(.exit.data) - LOAD_OFFSET) { *(.exit.data) }
+
 #if defined(CONFIG_BLK_DEV_INITRD)
   . = ALIGN(4096);
   .init.ramfs : AT(ADDR(.init.ramfs) - LOAD_OFFSET) {
 	__initramfs_start = .;
-	*(.init.ramfs)
+	KEEP(*(.init.ramfs))
 	__initramfs_end = .;
   }
 #endif
+
   . = ALIGN(4096);
-  .percpu.data  : AT(ADDR(.percpu.data) - LOAD_OFFSET) {
+  .percpu.data : AT(ADDR(.percpu.data) - LOAD_OFFSET) {
 	__per_cpu_start = .;
 	*(.percpu.data)
 	*(.percpu.shared_aligned.data)
 	__per_cpu_end = .;
   }
   . = ALIGN(4096);
-  /* freed after init ends here */
+
+  /* End of "freed after init" portion */
 	
   .bss : AT(ADDR(.bss) - LOAD_OFFSET) {
 	__init_end = .;
@@ -189,7 +192,7 @@ SECTIONS
          * we want to combine into bss, otherwise gcc does not set
          * 'nobits' flag for the section, and it cannot be merged into bss. */
 	*(.bss.k.page_aligned)
-	*(.bss)
+	*(SORT_BY_ALIGNMENT(.bss*))
 	. = ALIGN(4);
 	__bss_stop = .;
   	_end = . ;
@@ -201,7 +204,7 @@ SECTIONS
   /* Sections to be discarded */
   /DISCARD/ : {
 	*(.exitcall.exit)
-	}
+  }
 
   STABS_DEBUG
 
diff -urpN linux-2.6.23-rc4.gc5/init/Kconfig linux-2.6.23-rc4.gc6/init/Kconfig
--- linux-2.6.23-rc4.gc5/init/Kconfig	2007-09-12 19:46:32.000000000 +0100
+++ linux-2.6.23-rc4.gc6/init/Kconfig	2007-09-12 21:23:39.000000000 +0100
@@ -360,7 +360,7 @@ config DISCARD_UNUSED_SECTIONS
 	  and even then surprises are likely.
 
 	  This option also requires architecture-specific changes.
-	  Currently working architectures: x86_64
+	  Currently working architectures: x86_64, i386
 
 	  If unsure, say N.
 

^ permalink raw reply	[flat|nested] 3+ messages in thread

* [PATCH 3/2] section garbage collection for i386 - BONUS TRACK
  2007-09-12 20:30 ` [PATCH 2/2] " Denys Vlasenko
@ 2007-09-12 20:45   ` Denys Vlasenko
  0 siblings, 0 replies; 3+ messages in thread
From: Denys Vlasenko @ 2007-09-12 20:45 UTC (permalink / raw)
  To: Sam Ravnborg; +Cc: linux-kernel

[-- Attachment #1: Type: text/plain, Size: 8595 bytes --]

Hi Sam,

This patch makes i386 vmlinux linker script simpler
by minimizing number of generated sections.

For example, these sections:

 21 .init.text    000204a0  78701000  00701000  00502000  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 22 .init.data    000268db  787214a0  007214a0  005224a0  2**3
                  CONTENTS, ALLOC, LOAD, DATA
 23 .init.setup   00000654  78747d80  00747d80  00548d80  2**2
                  CONTENTS, ALLOC, LOAD, DATA
 24 .initcall.init 000004c4  787483d4  007483d4  005493d4  2**2
                  CONTENTS, ALLOC, LOAD, DATA
 25 .con_initcall.init 00000008  78748898  00748898  00549898  2**2
                  CONTENTS, ALLOC, LOAD, DATA
 26 .altinstructions 00009c23  787488a0  007488a0  005498a0  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 27 .altinstr_replacement 000027de  787524c3  007524c3  005534c3  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 28 .exit.text    00000f31  78754ca4  00754ca4  00555ca4  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 29 .init.ramfs   00000086  78756000  00756000  00557000  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA

code, data, data, data, rodata, code, code, data... -
doesn't look clean.

Can more sanely be grouped like this:

 15 .init.text    00023baf  78701000  00701000  00502000  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 16 .init.rodata  00009ca8  78725000  00725000  00526000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 17 .init.data    00027408  7872eca8  0072eca8  0052fca8  2**3
                  CONTENTS, ALLOC, LOAD, DATA

All in all, we have 20 sections instead of 32, and it still boots okay.


Full listing:


Before:

$ objdump -h
linux-2.6.23-rc4.gc6.t/vmlinux:     file format elf32-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .head.text    00000379  78200000  00200000  00001000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .text         003646da  78200380  00200380  00001380  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  2 __ex_table    00000ee8  78564a60  00564a60  00365a60  2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .notes        00000024  78565948  00565948  00366948  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  4 .rodata       000e85fe  78566000  00566000  00367000  2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  5 .pci_fixup    00000700  7864e600  0064e600  0044f600  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  6 __ksymtab     000057a0  7864ed00  0064ed00  0044fd00  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  7 __ksymtab_gpl 00001ac0  786544a0  006544a0  004554a0  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  8 __ksymtab_gpl_future 00000018  78655f60  00655f60  00456f60  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  9 __kcrctab     00002bd0  78655f78  00655f78  00456f78  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 10 __kcrctab_gpl 00000d60  78658b48  00658b48  00459b48  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 11 __kcrctab_gpl_future 0000000c  786598a8  006598a8  0045a8a8  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 12 __ksymtab_strings 00010d8b  786598b4  006598b4  0045a8b4  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 13 __param       00001838  7866a640  0066a640  0046b640  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 14 .data         0007fe99  7866c000  0066c000  0046d000  2**7
                  CONTENTS, ALLOC, LOAD, DATA
 15 .data_nosave  00001000  786ec000  006ec000  004ed000  2**12
                  CONTENTS, ALLOC, LOAD, DATA
 16 .page_aligned.data 00000800  786ed000  006ed000  004ee000  2**2
                  CONTENTS, ALLOC, LOAD, DATA
 17 .cacheline_aligned.data 0000a000  786ed800  006ed800  004ee800  2**7
                  CONTENTS, ALLOC, LOAD, DATA
 18 .read_mostly.data 000020d0  786f7800  006f7800  004f8800  2**7
                  CONTENTS, ALLOC, LOAD, DATA
 19 .init_task.data 00002000  786fa000  006fa000  004fb000  2**2
                  CONTENTS, ALLOC, LOAD, DATA
 20 .smp_locks    00004798  786fc000  006fc000  004fd000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 21 .init.text    000204a0  78701000  00701000  00502000  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 22 .init.data    000268db  787214a0  007214a0  005224a0  2**3
                  CONTENTS, ALLOC, LOAD, DATA
 23 .init.setup   00000654  78747d80  00747d80  00548d80  2**2
                  CONTENTS, ALLOC, LOAD, DATA
 24 .initcall.init 000004c4  787483d4  007483d4  005493d4  2**2
                  CONTENTS, ALLOC, LOAD, DATA
 25 .con_initcall.init 00000008  78748898  00748898  00549898  2**2
                  CONTENTS, ALLOC, LOAD, DATA
 26 .altinstructions 00009c23  787488a0  007488a0  005498a0  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 27 .altinstr_replacement 000027de  787524c3  007524c3  005534c3  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 28 .exit.text    00000f31  78754ca4  00754ca4  00555ca4  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 29 .init.ramfs   00000086  78756000  00756000  00557000  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 30 .percpu.data  00005f38  78757000  00757000  00558000  2**12
                  CONTENTS, ALLOC, LOAD, DATA
 31 .bss          00047000  7875d000  0075d000  0055df38  2**12
                  ALLOC
 32 .comment      00005004  00000000  00000000  0055df38  2**0
                  CONTENTS, READONLY


After:

linux-2.6.23-rc4.gc7.t/vmlinux:     file format elf32-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00364a5a  78200000  00200000  00001000  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 __ex_table    00000ee8  78564a60  00564a60  00365a60  2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  2 .notes        00000024  78565948  00565948  00366948  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  3 .rodata       000e8602  78566000  00566000  00367000  2**3
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .pci_fixup    00000700  7864e604  0064e604  0044f604  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  5 __ksymtab     000057a0  7864ed04  0064ed04  0044fd04  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  6 __ksymtab_gpl 00001ac0  786544a4  006544a4  004554a4  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  7 __ksymtab_gpl_future 00000018  78655f64  00655f64  00456f64  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  8 __kcrctab     00002bd0  78655f7c  00655f7c  00456f7c  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  9 __kcrctab_gpl 00000d60  78658b4c  00658b4c  00459b4c  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 10 __kcrctab_gpl_future 0000000c  786598ac  006598ac  0045a8ac  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 11 __ksymtab_strings 00010d8b  786598b8  006598b8  0045a8b8  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 12 __param       00001838  7866a644  0066a644  0046b644  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 13 .data         0008f7d0  7866c000  0066c000  0046d000  2**12
                  CONTENTS, ALLOC, LOAD, DATA
 14 .smp_locks    00004798  786fc000  006fc000  004fd000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 15 .init.text    00023baf  78701000  00701000  00502000  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
 16 .init.rodata  00009ca8  78725000  00725000  00526000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 17 .init.data    00027408  7872eca8  0072eca8  0052fca8  2**3
                  CONTENTS, ALLOC, LOAD, DATA
 18 .percpu.data  00005f38  78757000  00757000  00558000  2**12
                  CONTENTS, ALLOC, LOAD, DATA
 19 .bss          00047000  7875d000  0075d000  0055df38  2**12
                  ALLOC
 20 .comment      00005004  00000000  00000000  0055df38  2**0
                  CONTENTS, READONLY

Patch is run-tested.

It's purely cleanup work, it's not bringing any noticeable
size wins (well, maybe statistically it will have a bit less
alignment padding because I placed together a few page-aligned
chunks, but that's all).

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
--
vda

[-- Attachment #2: linux-2.6.23-rc4.7.i386part2.patch --]
[-- Type: text/x-diff, Size: 6591 bytes --]

diff -urpN linux-2.6.23-rc4.gc6/arch/i386/kernel/vmlinux.lds.S linux-2.6.23-rc4.gc7/arch/i386/kernel/vmlinux.lds.S
--- linux-2.6.23-rc4.gc6/arch/i386/kernel/vmlinux.lds.S	2007-09-12 19:51:42.000000000 +0100
+++ linux-2.6.23-rc4.gc7/arch/i386/kernel/vmlinux.lds.S	2007-09-12 21:10:38.000000000 +0100
@@ -6,7 +6,19 @@
  * at run time. Absolute symbols are not relocated. If symbol value should
  * change if kernel is relocated, make the symbol section relative
  * by putting it inside the section definition.
+ *
+ * Try to avoid creating output sections needlessly.
+ * Group pieces with same attributes (ro/rw, code/data,
+ * persistent/discarded-after-init) together in one section.
+ *
+ * Statistically, padding is smaller if input sections
+ * within output section are sorted by alignment in descending order.
+ *
+ * If you need to ALIGN a section, putting ALIGN immediately before section
+ * can result in smaller on-disk image than when you put it immeadiately
+ * after section's opening '{'.
  */
+
 #define LOAD_OFFSET __PAGE_OFFSET
 
 #include <asm-generic/vmlinux.lds.h>
@@ -18,6 +30,7 @@
 OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
 OUTPUT_ARCH(i386)
 ENTRY(phys_startup_32)
+
 jiffies = jiffies_64;
 
 PHDRS {
@@ -30,13 +43,11 @@ SECTIONS
   . = LOAD_OFFSET + LOAD_PHYSICAL_ADDR;
   phys_startup_32 = startup_32 - LOAD_OFFSET;
 
-  .head.text : AT(ADDR(.head.text) - LOAD_OFFSET) {
-  	_text = .;			/* Text and read-only data */
-	KEEP(*(.head.text))
-  } :text = 0x9090
-
   /* read-only */
   .text : AT(ADDR(.text) - LOAD_OFFSET) {
+	_text = .;			/* Text and read-only data */
+	KEEP(*(.head.text))
+
 	TEXT_TEXT
 	SCHED_TEXT
 	LOCK_TEXT
@@ -54,6 +65,7 @@ SECTIONS
   	__stop___ex_table = .;
   }
 
+  /* Hm? NOTES end up marked as CODE in vmlinux, but they are not. FIXME */
   NOTES :text :note
 
   BUG_TABLE :text
@@ -69,45 +81,39 @@ SECTIONS
   RODATA
 
   /* writeable */
-  . = ALIGN(4096);
+  . = ALIGN(THREAD_SIZE); /* at least 4k */
   .data : AT(ADDR(.data) - LOAD_OFFSET) {	/* Data */
-	DATA_DATA
-	CONSTRUCTORS
-  } :data
+	/* init_task */
+	*(.init_task.data)
 
-  . = ALIGN(4096);
-  .data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) {
+	. = ALIGN(4096);
+	*(.page_aligned.data)
+
+  	. = ALIGN(4096);
   	__nosave_begin = .;
 	/* No need to KEEP */
 	*(.nosave.data)
   	. = ALIGN(4096);
   	__nosave_end = .;
-  }
 
-  . = ALIGN(4096);
-  .page_aligned.data : AT(ADDR(.page_aligned.data) - LOAD_OFFSET) {
-	*(.page_aligned.data)
+	/* The IDT has to be page-aligned because of F0 0F bug */
 	*(.idt.data)
-  }
 
-  . = ALIGN(32);
-  .cacheline_aligned.data : AT(ADDR(.cacheline_aligned.data) - LOAD_OFFSET) {
+	DATA_DATA
+	CONSTRUCTORS
+
+	. = ALIGN(32);
 	*(.cacheline_aligned.data)
-  }
 
-  /* rarely changed data like cpu maps */
-  . = ALIGN(32);
-  .read_mostly.data : AT(ADDR(.read_mostly.data) - LOAD_OFFSET) {
+	/* rarely changed data like cpu maps */
+	. = ALIGN(32);
 	*(.read_mostly.data)
-	_edata = .;		/* End of data section */
-  }
 
-  . = ALIGN(THREAD_SIZE);	/* init_task */
-  .init_task.data : AT(ADDR(.init_task.data) - LOAD_OFFSET) {
-	*(.init_task.data)
-  }
+	_edata = .;
+  } :data
+
+  /* Might get freed after init */
 
-  /* might get freed after init */
   . = ALIGN(4096);
   .smp_locks : AT(ADDR(.smp_locks) - LOAD_OFFSET) {
   	__smp_locks = .;
@@ -116,75 +122,80 @@ SECTIONS
   }
 
   /* Will be freed after init */
-  /* Init code and data */
+
   . = ALIGN(4096);
   .init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
   	__init_begin = .;
 	_sinittext = .;
 	*(.init.text)
 	_einittext = .;
+
+	/* No need to KEEP - referenced by .altinstructions */
+	*(.altinstr_replacement)
+
+	/* .exit.text is discarded at runtime, not link time, to deal with references
+	   from .altinstructions and .eh_frame */
+	*(.exit.text)
+  }
+
+  /* ro, code */
+  SECURITY_INIT
+
+#if defined(CONFIG_BLK_DEV_INITRD)
+  /* ALIGN outside section may make on-disk image smaller */
+  . = ALIGN(4096);
+#endif
+  .init.rodata : AT(ADDR(.init.rodata) - LOAD_OFFSET) {
+#if defined(CONFIG_BLK_DEV_INITRD)
+	__initramfs_start = .;
+	KEEP(*(.init.ramfs))
+	__initramfs_end = .;
+#endif
+	. = ALIGN(4);
+  	__alt_instructions = .;
+	KEEP(*(.altinstructions))
+	__alt_instructions_end = .;
+
+	. = ALIGN(4);
+  	__parainstructions = .;
+	KEEP(*(.parainstructions))
+  	__parainstructions_end = .;
   }
-  .init.data : AT(ADDR(.init.data) - LOAD_OFFSET) { *(.init.data) }
-  . = ALIGN(16);
-  .init.setup : AT(ADDR(.init.setup) - LOAD_OFFSET) {
+
+  .init.data : AT(ADDR(.init.data) - LOAD_OFFSET) {
+	*(.init.data)
+
+	. = ALIGN(16);
   	__setup_start = .;
 	/* __setup_param() macro produces these,
 	 * obsolete_checksetup() processes them */
 	KEEP(*(.init.setup))
   	__setup_end = .;
-   }
-  .initcall.init : AT(ADDR(.initcall.init) - LOAD_OFFSET) {
+
   	__initcall_start = .;
 	INITCALLS
   	__initcall_end = .;
-  }
-  .con_initcall.init : AT(ADDR(.con_initcall.init) - LOAD_OFFSET) {
+
   	__con_initcall_start = .;
 	KEEP(*(.con_initcall.init))
   	__con_initcall_end = .;
-  }
-  SECURITY_INIT
-  . = ALIGN(4);
-  .altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
-  	__alt_instructions = .;
-	KEEP(*(.altinstructions))
-	__alt_instructions_end = .;
-  }
-  .altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) {
-	/* No need to KEEP - referenced by .altinstructions */
-	*(.altinstr_replacement)
-  }
-  . = ALIGN(4);
-  .parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) {
-  	__parainstructions = .;
-	KEEP(*(.parainstructions))
-  	__parainstructions_end = .;
-  }
-  /* .exit.text is discarded at runtime, not link time, to deal with references
-     from .altinstructions and .eh_frame */
-  .exit.text : AT(ADDR(.exit.text) - LOAD_OFFSET) { *(.exit.text) }
-  .exit.data : AT(ADDR(.exit.data) - LOAD_OFFSET) { *(.exit.data) }
 
-#if defined(CONFIG_BLK_DEV_INITRD)
-  . = ALIGN(4096);
-  .init.ramfs : AT(ADDR(.init.ramfs) - LOAD_OFFSET) {
-	__initramfs_start = .;
-	KEEP(*(.init.ramfs))
-	__initramfs_end = .;
+	/* TODO: can .exit.data be discarded at link time? */
+	*(.exit.data)
   }
-#endif
 
   . = ALIGN(4096);
   .percpu.data : AT(ADDR(.percpu.data) - LOAD_OFFSET) {
 	__per_cpu_start = .;
-	*(.percpu.data)
+	*(SORT_BY_ALIGNMENT(.percpu.data))
+	/* Dont move in front of .percpu.data, .percpu.data contains page-aligned stuff */
 	*(.percpu.shared_aligned.data)
 	__per_cpu_end = .;
   }
-  . = ALIGN(4096);
 
   /* End of "freed after init" portion */
 	
+  . = ALIGN(4096);
   .bss : AT(ADDR(.bss) - LOAD_OFFSET) {
 	__init_end = .;
 	__bss_start = .;		/* BSS */

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2007-09-12 20:46 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2007-09-12 20:24 [PATCH 1/2] section garbage collection for i386 Denys Vlasenko
2007-09-12 20:30 ` [PATCH 2/2] " Denys Vlasenko
2007-09-12 20:45   ` [PATCH 3/2] section garbage collection for i386 - BONUS TRACK Denys Vlasenko

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