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Commit 5b11f1ce authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x86, boot: straighten out ranges to copy/zero in compressed/head*.S 



Both on 32 and 64 bits, we copy all the way up to the end of bss,
except that on 64 bits there is a hack to avoid copying on top of the
page tables.  There is no point in copying bss at all, especially
since we are just about to zero it all anyway.

To clean up and unify the handling, we now do:

  - copy from startup_32 to _bss.
  - zero from _bss to _ebss.
  - the _ebss symbol is aligned to an 8-byte boundary.
  - the page tables are moved to a separate section.

Use _bss as the copy endpoint since _edata may be misaligned.

[ Impact: cleanup, trivial performance improvement ]

Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent b40d68d5

arch/x86/boot/compressed/head_32.S

+4 −4
Original line number Diff line number Diff line
@@ -93,9 +93,9 @@ ENTRY(startup_32) 
 * where decompression in place becomes safe.

 */

	pushl	%esi

	leal	_ebss(%ebp), %esi

	leal	_ebss(%ebx), %edi

	movl	$(_ebss - startup_32), %ecx

	leal	_bss(%ebp), %esi

	leal	_bss(%ebx), %edi

	movl	$(_bss - startup_32), %ecx

	std

	rep	movsb

	cld
@@ -125,7 +125,7 @@ relocated: 
 * Clear BSS

 */

	xorl	%eax, %eax

	leal	_edata(%ebx), %edi

	leal	_bss(%ebx), %edi

	leal	_ebss(%ebx), %ecx

	subl	%edi, %ecx

	cld

arch/x86/boot/compressed/head_64.S

+13 −5
Original line number Diff line number Diff line
@@ -253,9 +253,9 @@ ENTRY(startup_64) 
 * Copy the compressed kernel to the end of our buffer

 * where decompression in place becomes safe.

 */

	leaq	_end_before_pgt(%rip), %r8

	leaq	_end_before_pgt(%rbx), %r9

	movq	$_end_before_pgt /* - $startup_32 */, %rcx

	leaq	_bss(%rip), %r8

	leaq	_bss(%rbx), %r9

	movq	$_bss /* - $startup_32 */, %rcx

1:	subq	$8, %r8

	subq	$8, %r9

	movq	0(%r8), %rax
@@ -276,8 +276,8 @@ relocated: 
 * Clear BSS

 */

	xorq	%rax, %rax

	leaq    _edata(%rbx), %rdi

	leaq    _end_before_pgt(%rbx), %rcx

	leaq    _bss(%rbx), %rdi

	leaq    _ebss(%rbx), %rcx

	subq	%rdi, %rcx

	cld

	rep	stosb
@@ -329,3 +329,11 @@ boot_heap: 
boot_stack:

	.fill BOOT_STACK_SIZE, 1, 0

boot_stack_end:



/*

 * Space for page tables (not in .bss so not zeroed)

 */

	.section ".pgtable","a",@nobits

	.balign 4096

pgtable:

	.fill 6*4096, 1, 0

arch/x86/boot/compressed/vmlinux.lds.S

+12 −7
Original line number Diff line number Diff line
@@ -2,6 +2,8 @@ OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT) 


#undef i386



#include <asm/page_types.h>



#ifdef CONFIG_X86_64

OUTPUT_ARCH(i386:x86-64)

ENTRY(startup_64)
@@ -48,13 +50,16 @@ SECTIONS 
		*(.bss)

		*(.bss.*)

		*(COMMON)

#ifdef CONFIG_X86_64

		. = ALIGN(8);

		_end_before_pgt = . ;

		. = ALIGN(4096);

		pgtable = . ;

		. = . + 4096 * 6;

#endif

		. = ALIGN(8);	/* For convenience during zeroing */

		_ebss = .;

	}

#ifdef CONFIG_X86_64

       . = ALIGN(PAGE_SIZE);

       .pgtable : {

		_pgtable = . ;

		*(.pgtable)

		_epgtable = . ;

	}

#endif

	_end = .;

}