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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.
arch/i386/kernel/machine_kexec.c | 59 -------------------------------------
arch/i386/kernel/relocate_kernel.S | 58 +++++++++++++++++++++++++++++++++---
2 files changed, 53 insertions(+), 64 deletions(-)
--- a/arch/i386/kernel/machine_kexec.c 2007-08-27 12:09:26.000000000 -0400
+++ b/arch/i386/kernel/machine_kexec.c 2007-08-27 14:02:11.000000000 -0400
@@ -29,48 +29,6 @@ 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 Xgt_desc_struct 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 Xgt_desc_struct 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
@@ -127,23 +85,6 @@ 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);
}
--- a/arch/i386/kernel/relocate_kernel.S 2007-08-27 12:09:26.000000000 -0400
+++ b/arch/i386/kernel/relocate_kernel.S 2007-08-27 14:01:24.000000000 -0400
@@ -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 */
|
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