kernel26-xen/patches-2.6.25-r1/1001-2.6.25-xen-linux-2.6.19-rc1-kexec-move_segment_code-i386.patch

Subject: kexec: Move asm segment handling code to the assembly file (i386)
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   |   59 -----------------------------------------------------
 relocate_kernel.S |   58 +++++++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 53 insertions(+), 64 deletions(-)

Index: head-2008-02-26/arch/x86/kernel/machine_kexec_32.c
===================================================================
--- head-2008-02-26.orig/arch/x86/kernel/machine_kexec_32.c	2008-02-26 11:43:15.000000000 +0100
+++ head-2008-02-26/arch/x86/kernel/machine_kexec_32.c	2008-02-26 11:45:10.000000000 +0100
@@ -30,48 +30,6 @@ static u32 kexec_pmd1[1024] PAGE_ALIGNED
 static u32 kexec_pte0[1024] PAGE_ALIGNED;
 static u32 kexec_pte1[1024] PAGE_ALIGNED;
 
-static void set_idt(void *newidt, __u16 limit)
-{
-	struct desc_ptr curidt;
-
-	/* ia32 supports unaliged loads & stores */
-	curidt.size    = limit;
-	curidt.address = (unsigned long)newidt;
-
-	load_idt(&curidt);
-};
-
-
-static void set_gdt(void *newgdt, __u16 limit)
-{
-	struct desc_ptr curgdt;
-
-	/* ia32 supports unaligned loads & stores */
-	curgdt.size    = limit;
-	curgdt.address = (unsigned long)newgdt;
-
-	load_gdt(&curgdt);
-};
-
-static void load_segments(void)
-{
-#define __STR(X) #X
-#define STR(X) __STR(X)
-
-	__asm__ __volatile__ (
-		"\tljmp $"STR(__KERNEL_CS)",$1f\n"
-		"\t1:\n"
-		"\tmovl $"STR(__KERNEL_DS)",%%eax\n"
-		"\tmovl %%eax,%%ds\n"
-		"\tmovl %%eax,%%es\n"
-		"\tmovl %%eax,%%fs\n"
-		"\tmovl %%eax,%%gs\n"
-		"\tmovl %%eax,%%ss\n"
-		::: "eax", "memory");
-#undef STR
-#undef __STR
-}
-
 /*
  * A architecture hook called to validate the
  * proposed image and prepare the control pages
@@ -128,23 +86,6 @@ NORET_TYPE void machine_kexec(struct kim
 	page_list[PA_PTE_1] = __pa(kexec_pte1);
 	page_list[VA_PTE_1] = (unsigned long)kexec_pte1;
 
-	/* 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, cpu_has_pae);
 }
Index: head-2008-02-26/arch/x86/kernel/relocate_kernel_32.S
===================================================================
--- head-2008-02-26.orig/arch/x86/kernel/relocate_kernel_32.S	2008-01-24 23:58:37.000000000 +0100
+++ head-2008-02-26/arch/x86/kernel/relocate_kernel_32.S	2008-02-26 11:45:10.000000000 +0100
@@ -154,14 +154,45 @@ relocate_new_kernel:
 	movl	PTR(PA_PGD)(%ebp), %eax
 	movl	%eax, %cr3
 
+	/* setup idt */
+	movl	%edi, %eax
+	addl	$(idt_48 - relocate_kernel), %eax
+	lidtl	(%eax)
+
+	/* setup gdt */
+	movl	%edi, %eax
+	addl	$(gdt - relocate_kernel), %eax
+	movl	%edi, %esi
+	addl	$((gdt_48 - relocate_kernel) + 2), %esi
+	movl	%eax, (%esi)
+
+	movl	%edi, %eax
+	addl	$(gdt_48 - relocate_kernel), %eax
+	lgdtl	(%eax)
+
+	/* setup data segment registers */
+	mov	$(gdt_ds - gdt), %eax
+	mov	%eax, %ds
+	mov	%eax, %es
+	mov	%eax, %fs
+	mov	%eax, %gs
+	mov	%eax, %ss
+
 	/* setup a new stack at the end of the physical control page */
 	lea	4096(%edi), %esp
 
-	/* jump to identity mapped page */
-	movl    %edi, %eax
-	addl    $(identity_mapped - relocate_kernel), %eax
-	pushl   %eax
-	ret
+	/* load new code segment and jump to identity mapped page */
+	movl	%edi, %esi
+	xorl	%eax, %eax
+	pushl	%eax
+	pushl	%esi
+	pushl	%eax
+	movl	$(gdt_cs - gdt), %eax
+	pushl	%eax
+	movl	%edi, %eax
+	addl	$(identity_mapped - relocate_kernel),%eax
+	pushl	%eax
+	iretl
 
 identity_mapped:
 	/* store the start address on the stack */
@@ -250,3 +281,20 @@ identity_mapped:
 	xorl    %edi, %edi
 	xorl    %ebp, %ebp
 	ret
+
+	.align	16
+gdt:
+	.quad	0x0000000000000000	/* NULL descriptor */
+gdt_cs:
+	.quad	0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
+gdt_ds:
+	.quad	0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
+gdt_end:
+
+gdt_48:
+	.word	gdt_end - gdt - 1	/* limit */
+	.long	0			/* base - filled in by code above */
+
+idt_48:
+	.word	0			/* limit */
+	.long	0			/* base */
1	niro	609	Subject: kexec: Move asm segment handling code to the assembly file (i386)
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 \| 59 -----------------------------------------------------
21			relocate_kernel.S \| 58 +++++++++++++++++++++++++++++++++++++++++++++++-----
22			2 files changed, 53 insertions(+), 64 deletions(-)
23
24			Index: head-2008-02-26/arch/x86/kernel/machine_kexec_32.c
25			===================================================================
26			--- head-2008-02-26.orig/arch/x86/kernel/machine_kexec_32.c 2008-02-26 11:43:15.000000000 +0100
27			+++ head-2008-02-26/arch/x86/kernel/machine_kexec_32.c 2008-02-26 11:45:10.000000000 +0100
28			@@ -30,48 +30,6 @@ static u32 kexec_pmd1[1024] PAGE_ALIGNED
29			static u32 kexec_pte0[1024] PAGE_ALIGNED;
30			static u32 kexec_pte1[1024] PAGE_ALIGNED;
31
32			-static void set_idt(void *newidt, __u16 limit)
33			-{
34			- struct desc_ptr curidt;
35			-
36			- /* ia32 supports unaliged loads & stores */
37			- curidt.size = limit;
38			- curidt.address = (unsigned long)newidt;
39			-
40			- load_idt(&curidt);
41			-};
42			-
43			-
44			-static void set_gdt(void *newgdt, __u16 limit)
45			-{
46			- struct desc_ptr curgdt;
47			-
48			- /* ia32 supports unaligned loads & stores */
49			- curgdt.size = limit;
50			- curgdt.address = (unsigned long)newgdt;
51			-
52			- load_gdt(&curgdt);
53			-};
54			-
55			-static void load_segments(void)
56			-{
57			-#define __STR(X) #X
58			-#define STR(X) __STR(X)
59			-
60			- __asm__ __volatile__ (
61			- "\tljmp $"STR(__KERNEL_CS)",$1f\n"
62			- "\t1:\n"
63			- "\tmovl $"STR(__KERNEL_DS)",%%eax\n"
64			- "\tmovl %%eax,%%ds\n"
65			- "\tmovl %%eax,%%es\n"
66			- "\tmovl %%eax,%%fs\n"
67			- "\tmovl %%eax,%%gs\n"
68			- "\tmovl %%eax,%%ss\n"
69			- ::: "eax", "memory");
70			-#undef STR
71			-#undef __STR
72			-}
73			-
74			/*
75			* A architecture hook called to validate the
76			* proposed image and prepare the control pages
77			@@ -128,23 +86,6 @@ NORET_TYPE void machine_kexec(struct kim
78			page_list[PA_PTE_1] = __pa(kexec_pte1);
79			page_list[VA_PTE_1] = (unsigned long)kexec_pte1;
80
81			- /* The segment registers are funny things, they have both a
82			- * visible and an invisible part. Whenever the visible part is
83			- * set to a specific selector, the invisible part is loaded
84			- * with from a table in memory. At no other time is the
85			- * descriptor table in memory accessed.
86			- *
87			- * I take advantage of this here by force loading the
88			- * segments, before I zap the gdt with an invalid value.
89			- */
90			- load_segments();
91			- /* The gdt & idt are now invalid.
92			- * If you want to load them you must set up your own idt & gdt.
93			- */
94			- set_gdt(phys_to_virt(0),0);
95			- set_idt(phys_to_virt(0),0);
96			-
97			- /* now call it */
98			relocate_kernel((unsigned long)image->head, (unsigned long)page_list,
99			image->start, cpu_has_pae);
100			}
101			Index: head-2008-02-26/arch/x86/kernel/relocate_kernel_32.S
102			===================================================================
103			--- head-2008-02-26.orig/arch/x86/kernel/relocate_kernel_32.S 2008-01-24 23:58:37.000000000 +0100
104			+++ head-2008-02-26/arch/x86/kernel/relocate_kernel_32.S 2008-02-26 11:45:10.000000000 +0100
105			@@ -154,14 +154,45 @@ relocate_new_kernel:
106			movl PTR(PA_PGD)(%ebp), %eax
107			movl %eax, %cr3
108
109			+ /* setup idt */
110			+ movl %edi, %eax
111			+ addl $(idt_48 - relocate_kernel), %eax
112			+ lidtl (%eax)
113			+
114			+ /* setup gdt */
115			+ movl %edi, %eax
116			+ addl $(gdt - relocate_kernel), %eax
117			+ movl %edi, %esi
118			+ addl $((gdt_48 - relocate_kernel) + 2), %esi
119			+ movl %eax, (%esi)
120			+
121			+ movl %edi, %eax
122			+ addl $(gdt_48 - relocate_kernel), %eax
123			+ lgdtl (%eax)
124			+
125			+ /* setup data segment registers */
126			+ mov $(gdt_ds - gdt), %eax
127			+ mov %eax, %ds
128			+ mov %eax, %es
129			+ mov %eax, %fs
130			+ mov %eax, %gs
131			+ mov %eax, %ss
132			+
133			/* setup a new stack at the end of the physical control page */
134			lea 4096(%edi), %esp
135
136			- /* jump to identity mapped page */
137			- movl %edi, %eax
138			- addl $(identity_mapped - relocate_kernel), %eax
139			- pushl %eax
140			- ret
141			+ /* load new code segment and jump to identity mapped page */
142			+ movl %edi, %esi
143			+ xorl %eax, %eax
144			+ pushl %eax
145			+ pushl %esi
146			+ pushl %eax
147			+ movl $(gdt_cs - gdt), %eax
148			+ pushl %eax
149			+ movl %edi, %eax
150			+ addl $(identity_mapped - relocate_kernel),%eax
151			+ pushl %eax
152			+ iretl
153
154			identity_mapped:
155			/* store the start address on the stack */
156			@@ -250,3 +281,20 @@ identity_mapped:
157			xorl %edi, %edi
158			xorl %ebp, %ebp
159			ret
160			+
161			+ .align 16
162			+gdt:
163			+ .quad 0x0000000000000000 /* NULL descriptor */
164			+gdt_cs:
165			+ .quad 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */
166			+gdt_ds:
167			+ .quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */
168			+gdt_end:
169			+
170			+gdt_48:
171			+ .word gdt_end - gdt - 1 /* limit */
172			+ .long 0 /* base - filled in by code above */
173			+
174			+idt_48:
175			+ .word 0 /* limit */
176			+ .long 0 /* base */