lkml.org 
[lkml]   [2006]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[PATCH 02/02] kexec: Move segment code to assembly file (x86_64)
kexec: Move segment code to assembly file (x86_64)

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.

Signed-off-by: Magnus Damm <magnus@valinux.co.jp>
---

Applies to 2.6.19.

arch/x86_64/kernel/machine_kexec.c | 58 ----------------------------------
arch/x86_64/kernel/relocate_kernel.S | 50 ++++++++++++++++++++++++++---
2 files changed, 45 insertions(+), 63 deletions(-)

--- 0001/arch/x86_64/kernel/machine_kexec.c
+++ work/arch/x86_64/kernel/machine_kexec.c 2006-12-05 17:24:14.000000000 +0900
@@ -112,47 +112,6 @@ 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;
@@ -209,23 +168,6 @@ 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);
}
--- 0001/arch/x86_64/kernel/relocate_kernel.S
+++ work/arch/x86_64/kernel/relocate_kernel.S 2006-12-05 17:24:14.000000000 +0900
@@ -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 */
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2006-12-05 14:43    [W:0.039 / U:1.720 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site