--- /dev/null
+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-2008-08-18/arch/x86/kernel/machine_kexec_64.c
+===================================================================
+--- head-2008-08-18.orig/arch/x86/kernel/machine_kexec_64.c 2008-08-18 09:05:04.000000000 +0200
++++ head-2008-08-18/arch/x86/kernel/machine_kexec_64.c 2008-08-18 10:13:08.000000000 +0200
+@@ -115,47 +115,6 @@ static int init_pgtable(struct kimage *i
+ return init_level4_page(image, level4p, 0, max_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;
+@@ -214,23 +173,6 @@ void machine_kexec(struct kimage *image)
+ 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-2008-08-18/arch/x86/kernel/relocate_kernel_64.S
+===================================================================
+--- head-2008-08-18.orig/arch/x86/kernel/relocate_kernel_64.S 2008-07-13 23:51:29.000000000 +0200
++++ head-2008-08-18/arch/x86/kernel/relocate_kernel_64.S 2008-08-18 10:13:08.000000000 +0200
+@@ -160,13 +160,39 @@ 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 PAGE_SIZE(%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 */
+@@ -262,5 +288,19 @@ 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 */
projects / people / pmueller / ipfire-2.x.git / blobdiff