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Commit 275f5517 authored by Vivek Goyal's avatar Vivek Goyal Committed by Andi Kleen
Browse files

[PATCH] x86-64: wakeup.S misc cleanups 



o Various cleanups. One of the main purpose of cleanups is that make
  wakeup.S as close as possible to trampoline.S.

o Following are the changes
	- Indentations for comments.
	- Changed the gdt table to compact form and to resemble the
	  one in trampoline.S
	- Take the jump to 32bit from real mode using ljmpl. Makes code
	  more readable.
	- After enabling long mode, directly take a long jump for 64bit
	  mode. No need to take an extra jump to "reach_comaptibility_mode"
	- Stack is not used after real mode. So don't load stack in
 	  32 bit mode.
	- No need to enable PGE here.
	- No need to do extra EFER read, anyway we trash the read contents.
	- No need to enable system call (EFER_SCE). Anyway it will be
	  enabled when original EFER is restored.
	- No need to set MP, ET, NE, WP, AM bits in cr0. Very soon we will
  	  reload the original cr0 while restroing the processor state.

Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent 7db681d7

arch/x86_64/kernel/acpi/wakeup.S

+40 −72
Original line number Diff line number Diff line
@@ -32,7 +32,8 @@ wakeup_code: 
	movw	%cs, %ax

	movw	%ax, %ds		# Make ds:0 point to wakeup_start

	movw	%ax, %ss

	mov	$(wakeup_stack - wakeup_code), %sp		# Private stack is needed for ASUS board

					# Private stack is needed for ASUS board

	mov	$(wakeup_stack - wakeup_code), %sp



	pushl	$0			# Kill any dangerous flags

	popfl
@@ -75,9 +76,12 @@ wakeup_code: 
	jmp	1f

1:



	.byte 0x66, 0xea			# prefix + jmpi-opcode

	ljmpl   *(wakeup_32_vector - wakeup_code)



	.balign 4

wakeup_32_vector:

	.long   wakeup_32 - __START_KERNEL_map

	.word	__KERNEL_CS

	.word   __KERNEL32_CS, 0



	.code32

wakeup_32:
@@ -96,65 +100,50 @@ wakeup_32: 
	jnc	bogus_cpu

	movl	%edx,%edi

	

	movw	$__KERNEL_DS, %ax

	movw	%ax, %ds

	movw	%ax, %es

	movw	%ax, %fs

	movw	%ax, %gs

	movl	$__KERNEL_DS, %eax

	movl	%eax, %ds



	movw	$__KERNEL_DS, %ax	

	movw	%ax, %ss



	mov	$(wakeup_stack - __START_KERNEL_map), %esp

	movl	saved_magic - __START_KERNEL_map, %eax

	cmpl	$0x9abcdef0, %eax

	jne	bogus_32_magic



	movw	$0x0e00 + 'i', %ds:(0xb8012)

	movb	$0xa8, %al	;  outb %al, $0x80;



	/*

	 * Prepare for entering 64bits mode

	 */



	/* Enable PAE mode and PGE */

	/* Enable PAE */

	xorl	%eax, %eax

	btsl	$5, %eax

	btsl	$7, %eax

	movl	%eax, %cr4



	/* Setup early boot stage 4 level pagetables */

	movl	$(wakeup_level4_pgt - __START_KERNEL_map), %eax

	movl	%eax, %cr3



	/* Setup EFER (Extended Feature Enable Register) */

	movl	$MSR_EFER, %ecx

	rdmsr

	/* Fool rdmsr and reset %eax to avoid dependences */

	xorl	%eax, %eax

	/* Enable Long Mode */

	xorl    %eax, %eax

	btsl	$_EFER_LME, %eax

	/* Enable System Call */

	btsl	$_EFER_SCE, %eax



	/* No Execute supported? */

	btl	$20,%edi

	jnc     1f

	btsl	$_EFER_NX, %eax

1:	

				

	/* Make changes effective */

1:	movl    $MSR_EFER, %ecx

	xorl    %edx, %edx

	wrmsr

	wbinvd



	xorl	%eax, %eax

	btsl	$31, %eax			/* Enable paging and in turn activate Long Mode */

	btsl	$0, %eax			/* Enable protected mode */

	btsl	$1, %eax			/* Enable MP */

	btsl	$4, %eax			/* Enable ET */

	btsl	$5, %eax			/* Enable NE */

	btsl	$16, %eax			/* Enable WP */

	btsl	$18, %eax			/* Enable AM */



	/* Make changes effective */

	movl	%eax, %cr0



	/* At this point:

		CR4.PAE must be 1

		CS.L must be 0
@@ -162,11 +151,6 @@ wakeup_32: 
		Next instruction must be a branch

		This must be on identity-mapped page

	*/

	jmp	reach_compatibility_mode

reach_compatibility_mode:

	movw	$0x0e00 + 'i', %ds:(0xb8012)

	movb	$0xa8, %al	;  outb %al, $0x80; 	

		

	/*

	 * At this point we're in long mode but in 32bit compatibility mode

	 * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn
@@ -174,24 +158,19 @@ reach_compatibility_mode: 
	 * the new gdt/idt that has __KERNEL_CS with CS.L = 1.

	 */



	movw	$0x0e00 + 'n', %ds:(0xb8014)

	movb	$0xa9, %al	;  outb %al, $0x80

	

	/* Load new GDT with the 64bit segment using 32bit descriptor */

	movl	$(pGDT32 - __START_KERNEL_map), %eax

	lgdt	(%eax)



	movl    $(wakeup_jumpvector - __START_KERNEL_map), %eax

	/* Finally jump in 64bit mode */

	ljmp	*(%eax)

	ljmp	*(wakeup_long64_vector - __START_KERNEL_map)



wakeup_jumpvector:

	.balign 4

wakeup_long64_vector:

	.long   wakeup_long64 - __START_KERNEL_map

	.word	__KERNEL_CS

	.word   __KERNEL_CS, 0



.code64



	/*	Hooray, we are in Long 64-bit mode (but still running in low memory) */

	/* Hooray, we are in Long 64-bit mode (but still running in

	 * low memory)

	 */

wakeup_long64:

	/*

	 * We must switch to a new descriptor in kernel space for the GDT
@@ -201,6 +180,9 @@ wakeup_long64: 
	 */

	lgdt	cpu_gdt_descr - __START_KERNEL_map



	movw	$0x0e00 + 'n', %ds:(0xb8014)

	movb	$0xa9, %al	;  outb %al, $0x80



	movw	$0x0e00 + 'u', %ds:(0xb8016)

	

	nop
@@ -227,33 +209,19 @@ wakeup_long64: 


	.align	64	

gdta:

	/* Its good to keep gdt in sync with one in trampoline.S */

	.word	0, 0, 0, 0			# dummy



	.word	0, 0, 0, 0			# unused



	.word	0xFFFF				# 4Gb - (0x100000*0x1000 = 4Gb)

	.word	0				# base address = 0

	.word	0x9B00				# code read/exec. ??? Why I need 0x9B00 (as opposed to 0x9A00 in order for this to work?)

	.word	0x00CF				# granularity = 4096, 386

						#  (+5th nibble of limit)



	.word	0xFFFF				# 4Gb - (0x100000*0x1000 = 4Gb)

	.word	0				# base address = 0

	.word	0x9200				# data read/write

	.word	0x00CF				# granularity = 4096, 386

						#  (+5th nibble of limit)

# this is 64bit descriptor for code

	.word	0xFFFF

	.word	0

	.word	0x9A00				# code read/exec

	.word	0x00AF				# as above, but it is long mode and with D=0

	/* ??? Why I need the accessed bit set in order for this to work? */

	.quad   0x00cf9b000000ffff              # __KERNEL32_CS

	.quad   0x00af9b000000ffff              # __KERNEL_CS

	.quad   0x00cf93000000ffff              # __KERNEL_DS



idt_48a:

	.word	0				# idt limit = 0

	.word	0, 0				# idt base = 0L



gdt_48a:

	.word	0x8000				# gdt limit=2048,

	.word	0x800				# gdt limit=2048,

						#  256 GDT entries

	.word	0, 0				# gdt base (filled in later)