kernel26-xen/patches-2.6.25-r1/1002-2.6.25-xen-linux-2.6.19-rc1-kexec-move_segment_code-x86_64.patch

Subject: kexec: Move asm segment handling code to the assembly file (x86_64)
From: http://xenbits.xensource.com/xen-unstable.hg (tip 13816)
Patch-mainline: obsolete

This patch moves the idt, gdt, and segment handling code from machine_kexec.c
to relocate_kernel.S.  The main reason behind this move is to avoid code 
duplication in the Xen hypervisor. With this patch all code required to kexec
is put on the control page.

On top of that this patch also counts as a cleanup - I think it is much
nicer to write assembly directly in assembly files than wrap inline assembly
in C functions for no apparent reason.

Signed-off-by: Magnus Damm <magnus@valinux.co.jp>
Acked-by: jbeulich@novell.com
---

 Applies to 2.6.19-rc1.

 machine_kexec.c   |   58 -----------------------------------------------------
 relocate_kernel.S |   50 +++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 45 insertions(+), 63 deletions(-)

Index: head-2007-11-30/arch/x86/kernel/machine_kexec_64.c
===================================================================
--- head-2007-11-30.orig/arch/x86/kernel/machine_kexec_64.c	2007-11-30 13:39:59.000000000 +0100
+++ head-2007-11-30/arch/x86/kernel/machine_kexec_64.c	2007-11-30 13:41:59.000000000 +0100
@@ -113,47 +113,6 @@ static int init_pgtable(struct kimage *i
  	return init_level4_page(image, level4p, 0, end_pfn << PAGE_SHIFT);
 }
 
-static void set_idt(void *newidt, u16 limit)
-{
-	struct desc_ptr curidt;
-
-	/* x86-64 supports unaliged loads & stores */
-	curidt.size    = limit;
-	curidt.address = (unsigned long)newidt;
-
-	__asm__ __volatile__ (
-		"lidtq %0\n"
-		: : "m" (curidt)
-		);
-};
-
-
-static void set_gdt(void *newgdt, u16 limit)
-{
-	struct desc_ptr curgdt;
-
-	/* x86-64 supports unaligned loads & stores */
-	curgdt.size    = limit;
-	curgdt.address = (unsigned long)newgdt;
-
-	__asm__ __volatile__ (
-		"lgdtq %0\n"
-		: : "m" (curgdt)
-		);
-};
-
-static void load_segments(void)
-{
-	__asm__ __volatile__ (
-		"\tmovl %0,%%ds\n"
-		"\tmovl %0,%%es\n"
-		"\tmovl %0,%%ss\n"
-		"\tmovl %0,%%fs\n"
-		"\tmovl %0,%%gs\n"
-		: : "a" (__KERNEL_DS) : "memory"
-		);
-}
-
 int machine_kexec_prepare(struct kimage *image)
 {
 	unsigned long start_pgtable;
@@ -210,23 +169,6 @@ NORET_TYPE void machine_kexec(struct kim
 	page_list[PA_TABLE_PAGE] =
 	  (unsigned long)__pa(page_address(image->control_code_page));
 
-	/* The segment registers are funny things, they have both a
-	 * visible and an invisible part.  Whenever the visible part is
-	 * set to a specific selector, the invisible part is loaded
-	 * with from a table in memory.  At no other time is the
-	 * descriptor table in memory accessed.
-	 *
-	 * I take advantage of this here by force loading the
-	 * segments, before I zap the gdt with an invalid value.
-	 */
-	load_segments();
-	/* The gdt & idt are now invalid.
-	 * If you want to load them you must set up your own idt & gdt.
-	 */
-	set_gdt(phys_to_virt(0),0);
-	set_idt(phys_to_virt(0),0);
-
-	/* now call it */
 	relocate_kernel((unsigned long)image->head, (unsigned long)page_list,
 			image->start);
 }
Index: head-2007-11-30/arch/x86/kernel/relocate_kernel_64.S
===================================================================
--- head-2007-11-30.orig/arch/x86/kernel/relocate_kernel_64.S	2007-11-30 13:39:59.000000000 +0100
+++ head-2007-11-30/arch/x86/kernel/relocate_kernel_64.S	2007-11-30 13:42:10.000000000 +0100
@@ -159,13 +159,39 @@ relocate_new_kernel:
 	movq	PTR(PA_PGD)(%rsi), %r9
 	movq	%r9, %cr3
 
+	/* setup idt */
+	movq    %r8, %rax
+	addq    $(idt_80 - relocate_kernel), %rax
+	lidtq   (%rax)
+
+	/* setup gdt */
+	movq    %r8, %rax
+	addq    $(gdt - relocate_kernel), %rax
+	movq    %r8, %r9
+	addq    $((gdt_80 - relocate_kernel) + 2), %r9
+	movq    %rax, (%r9)
+
+	movq    %r8, %rax
+	addq    $(gdt_80 - relocate_kernel), %rax
+	lgdtq   (%rax)
+
+	/* setup data segment registers */
+	xorl	%eax, %eax
+	movl    %eax, %ds
+	movl    %eax, %es
+	movl    %eax, %fs
+	movl    %eax, %gs
+	movl    %eax, %ss
+
 	/* setup a new stack at the end of the physical control page */
 	lea	4096(%r8), %rsp
 
-	/* jump to identity mapped page */
-	addq	$(identity_mapped - relocate_kernel), %r8
-	pushq	%r8
-	ret
+	/* load new code segment and jump to identity mapped page */
+	movq	%r8, %rax
+	addq    $(identity_mapped - relocate_kernel), %rax
+	pushq	$(gdt_cs - gdt)
+	pushq	%rax
+	lretq
 
 identity_mapped:
 	/* store the start address on the stack */
@@ -272,5 +298,19 @@ identity_mapped:
 	xorq	%r13, %r13
 	xorq	%r14, %r14
 	xorq	%r15, %r15
-
 	ret
+
+	.align  16
+gdt:
+	.quad	0x0000000000000000	/* NULL descriptor */
+gdt_cs:
+	.quad   0x00af9a000000ffff
+gdt_end:
+
+gdt_80:
+	.word	gdt_end - gdt - 1	/* limit */
+	.quad	0			/* base - filled in by code above */
+
+idt_80:
+	.word	0			/* limit */
+	.quad	0			/* base */
1	niro	609	Subject: kexec: Move asm segment handling code to the assembly file (x86_64)
2			From: http://xenbits.xensource.com/xen-unstable.hg (tip 13816)
3			Patch-mainline: obsolete
4
5			This patch moves the idt, gdt, and segment handling code from machine_kexec.c
6			to relocate_kernel.S. The main reason behind this move is to avoid code
7			duplication in the Xen hypervisor. With this patch all code required to kexec
8			is put on the control page.
9
10			On top of that this patch also counts as a cleanup - I think it is much
11			nicer to write assembly directly in assembly files than wrap inline assembly
12			in C functions for no apparent reason.
13
14			Signed-off-by: Magnus Damm <magnus@valinux.co.jp>
15			Acked-by: jbeulich@novell.com
16			---
17
18			Applies to 2.6.19-rc1.
19
20			machine_kexec.c \| 58 -----------------------------------------------------
21			relocate_kernel.S \| 50 +++++++++++++++++++++++++++++++++++++++++----
22			2 files changed, 45 insertions(+), 63 deletions(-)
23
24			Index: head-2007-11-30/arch/x86/kernel/machine_kexec_64.c
25			===================================================================
26			--- head-2007-11-30.orig/arch/x86/kernel/machine_kexec_64.c 2007-11-30 13:39:59.000000000 +0100
27			+++ head-2007-11-30/arch/x86/kernel/machine_kexec_64.c 2007-11-30 13:41:59.000000000 +0100
28			@@ -113,47 +113,6 @@ static int init_pgtable(struct kimage *i
29			return init_level4_page(image, level4p, 0, end_pfn << PAGE_SHIFT);
30			}
31
32			-static void set_idt(void *newidt, u16 limit)
33			-{
34			- struct desc_ptr curidt;
35			-
36			- /* x86-64 supports unaliged loads & stores */
37			- curidt.size = limit;
38			- curidt.address = (unsigned long)newidt;
39			-
40			- __asm__ __volatile__ (
41			- "lidtq %0\n"
42			- : : "m" (curidt)
43			- );
44			-};
45			-
46			-
47			-static void set_gdt(void *newgdt, u16 limit)
48			-{
49			- struct desc_ptr curgdt;
50			-
51			- /* x86-64 supports unaligned loads & stores */
52			- curgdt.size = limit;
53			- curgdt.address = (unsigned long)newgdt;
54			-
55			- __asm__ __volatile__ (
56			- "lgdtq %0\n"
57			- : : "m" (curgdt)
58			- );
59			-};
60			-
61			-static void load_segments(void)
62			-{
63			- __asm__ __volatile__ (
64			- "\tmovl %0,%%ds\n"
65			- "\tmovl %0,%%es\n"
66			- "\tmovl %0,%%ss\n"
67			- "\tmovl %0,%%fs\n"
68			- "\tmovl %0,%%gs\n"
69			- : : "a" (__KERNEL_DS) : "memory"
70			- );
71			-}
72			-
73			int machine_kexec_prepare(struct kimage *image)
74			{
75			unsigned long start_pgtable;
76			@@ -210,23 +169,6 @@ NORET_TYPE void machine_kexec(struct kim
77			page_list[PA_TABLE_PAGE] =
78			(unsigned long)__pa(page_address(image->control_code_page));
79
80			- /* The segment registers are funny things, they have both a
81			- * visible and an invisible part. Whenever the visible part is
82			- * set to a specific selector, the invisible part is loaded
83			- * with from a table in memory. At no other time is the
84			- * descriptor table in memory accessed.
85			- *
86			- * I take advantage of this here by force loading the
87			- * segments, before I zap the gdt with an invalid value.
88			- */
89			- load_segments();
90			- /* The gdt & idt are now invalid.
91			- * If you want to load them you must set up your own idt & gdt.
92			- */
93			- set_gdt(phys_to_virt(0),0);
94			- set_idt(phys_to_virt(0),0);
95			-
96			- /* now call it */
97			relocate_kernel((unsigned long)image->head, (unsigned long)page_list,
98			image->start);
99			}
100			Index: head-2007-11-30/arch/x86/kernel/relocate_kernel_64.S
101			===================================================================
102			--- head-2007-11-30.orig/arch/x86/kernel/relocate_kernel_64.S 2007-11-30 13:39:59.000000000 +0100
103			+++ head-2007-11-30/arch/x86/kernel/relocate_kernel_64.S 2007-11-30 13:42:10.000000000 +0100
104			@@ -159,13 +159,39 @@ relocate_new_kernel:
105			movq PTR(PA_PGD)(%rsi), %r9
106			movq %r9, %cr3
107
108			+ /* setup idt */
109			+ movq %r8, %rax
110			+ addq $(idt_80 - relocate_kernel), %rax
111			+ lidtq (%rax)
112			+
113			+ /* setup gdt */
114			+ movq %r8, %rax
115			+ addq $(gdt - relocate_kernel), %rax
116			+ movq %r8, %r9
117			+ addq $((gdt_80 - relocate_kernel) + 2), %r9
118			+ movq %rax, (%r9)
119			+
120			+ movq %r8, %rax
121			+ addq $(gdt_80 - relocate_kernel), %rax
122			+ lgdtq (%rax)
123			+
124			+ /* setup data segment registers */
125			+ xorl %eax, %eax
126			+ movl %eax, %ds
127			+ movl %eax, %es
128			+ movl %eax, %fs
129			+ movl %eax, %gs
130			+ movl %eax, %ss
131			+
132			/* setup a new stack at the end of the physical control page */
133			lea 4096(%r8), %rsp
134
135			- /* jump to identity mapped page */
136			- addq $(identity_mapped - relocate_kernel), %r8
137			- pushq %r8
138			- ret
139			+ /* load new code segment and jump to identity mapped page */
140			+ movq %r8, %rax
141			+ addq $(identity_mapped - relocate_kernel), %rax
142			+ pushq $(gdt_cs - gdt)
143			+ pushq %rax
144			+ lretq
145
146			identity_mapped:
147			/* store the start address on the stack */
148			@@ -272,5 +298,19 @@ identity_mapped:
149			xorq %r13, %r13
150			xorq %r14, %r14
151			xorq %r15, %r15
152			-
153			ret
154			+
155			+ .align 16
156			+gdt:
157			+ .quad 0x0000000000000000 /* NULL descriptor */
158			+gdt_cs:
159			+ .quad 0x00af9a000000ffff
160			+gdt_end:
161			+
162			+gdt_80:
163			+ .word gdt_end - gdt - 1 /* limit */
164			+ .quad 0 /* base - filled in by code above */
165			+
166			+idt_80:
167			+ .word 0 /* limit */
168			+ .quad 0 /* base */