151 lines
4.1 KiB
Diff
151 lines
4.1 KiB
Diff
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Subject: kexec: Move asm segment handling code to the assembly file (x86_64)
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From: http://xenbits.xensource.com/xen-unstable.hg (tip 13816)
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Patch-mainline: n/a
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This patch moves the idt, gdt, and segment handling code from machine_kexec.c
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to relocate_kernel.S. The main reason behind this move is to avoid code
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duplication in the Xen hypervisor. With this patch all code required to kexec
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is put on the control page.
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On top of that this patch also counts as a cleanup - I think it is much
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nicer to write assembly directly in assembly files than wrap inline assembly
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in C functions for no apparent reason.
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Signed-off-by: Magnus Damm <magnus@valinux.co.jp>
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Acked-by: jbeulich@novell.com
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Applies to 2.6.19-rc1.
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jb: fixed up register usage for 2.6.30 (bnc#545206)
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--- head-2010-04-15.orig/arch/x86/kernel/machine_kexec_64.c 2010-04-15 09:37:47.000000000 +0200
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+++ head-2010-04-15/arch/x86/kernel/machine_kexec_64.c 2010-04-15 09:38:56.000000000 +0200
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@@ -203,47 +203,6 @@ static int init_pgtable(struct kimage *i
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return init_transition_pgtable(image, level4p);
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}
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-static void set_idt(void *newidt, u16 limit)
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-{
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- struct desc_ptr curidt;
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-
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- /* x86-64 supports unaliged loads & stores */
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- curidt.size = limit;
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- curidt.address = (unsigned long)newidt;
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-
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- __asm__ __volatile__ (
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- "lidtq %0\n"
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- : : "m" (curidt)
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- );
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-};
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-
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-
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-static void set_gdt(void *newgdt, u16 limit)
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-{
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- struct desc_ptr curgdt;
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-
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- /* x86-64 supports unaligned loads & stores */
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- curgdt.size = limit;
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- curgdt.address = (unsigned long)newgdt;
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-
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- __asm__ __volatile__ (
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- "lgdtq %0\n"
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- : : "m" (curgdt)
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- );
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-};
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-
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-static void load_segments(void)
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-{
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- __asm__ __volatile__ (
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- "\tmovl %0,%%ds\n"
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- "\tmovl %0,%%es\n"
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- "\tmovl %0,%%ss\n"
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- "\tmovl %0,%%fs\n"
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- "\tmovl %0,%%gs\n"
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- : : "a" (__KERNEL_DS) : "memory"
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- );
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-}
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-
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int machine_kexec_prepare(struct kimage *image)
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{
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unsigned long start_pgtable;
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@@ -311,24 +270,6 @@ void machine_kexec(struct kimage *image)
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page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)
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<< PAGE_SHIFT);
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- /*
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- * The segment registers are funny things, they have both a
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- * visible and an invisible part. Whenever the visible part is
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- * set to a specific selector, the invisible part is loaded
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- * with from a table in memory. At no other time is the
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- * descriptor table in memory accessed.
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- *
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- * I take advantage of this here by force loading the
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- * segments, before I zap the gdt with an invalid value.
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- */
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- load_segments();
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- /*
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- * The gdt & idt are now invalid.
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- * If you want to load them you must set up your own idt & gdt.
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- */
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- set_gdt(phys_to_virt(0), 0);
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- set_idt(phys_to_virt(0), 0);
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-
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/* now call it */
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image->start = relocate_kernel((unsigned long)image->head,
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(unsigned long)page_list,
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--- head-2010-04-15.orig/arch/x86/kernel/relocate_kernel_64.S 2010-04-15 09:37:47.000000000 +0200
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+++ head-2010-04-15/arch/x86/kernel/relocate_kernel_64.S 2010-01-19 14:51:10.000000000 +0100
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@@ -91,13 +91,30 @@ relocate_kernel:
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/* Switch to the identity mapped page tables */
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movq %r9, %cr3
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+ /* setup idt */
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+ lidtq idt_80 - relocate_kernel(%r8)
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+
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+ /* setup gdt */
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+ leaq gdt - relocate_kernel(%r8), %rax
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+ movq %rax, (gdt_80 - relocate_kernel) + 2(%r8)
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+ lgdtq gdt_80 - relocate_kernel(%r8)
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+
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+ /* setup data segment registers */
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+ xorl %eax, %eax
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+ movl %eax, %ds
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+ movl %eax, %es
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+ movl %eax, %fs
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+ movl %eax, %gs
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+ movl %eax, %ss
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+
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/* setup a new stack at the end of the physical control page */
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lea PAGE_SIZE(%r8), %rsp
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- /* jump to identity mapped page */
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+ /* load new code segment and jump to identity mapped page */
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addq $(identity_mapped - relocate_kernel), %r8
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+ pushq $(gdt_cs - gdt)
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pushq %r8
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- ret
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+ lretq
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identity_mapped:
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/* store the start address on the stack */
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@@ -262,5 +279,20 @@ swap_pages:
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3:
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ret
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+ .align 16
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+gdt:
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+ .quad 0x0000000000000000 /* NULL descriptor */
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+gdt_cs:
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+ .quad 0x00af9a000000ffff
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+gdt_end:
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+
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+gdt_80:
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+ .word gdt_end - gdt - 1 /* limit */
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+ .quad 0 /* base - filled in by code above */
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+
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+idt_80:
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+ .word 0 /* limit */
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+ .quad 0 /* base */
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+
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.globl kexec_control_code_size
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.set kexec_control_code_size, . - relocate_kernel
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