156 lines
4.3 KiB
Diff
156 lines
4.3 KiB
Diff
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Subject: kexec: Move asm segment handling code to the assembly file (i386)
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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 (paralleling what's needed for 2.6.30 on x86-64)
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--- head-2010-01-19.orig/arch/x86/kernel/machine_kexec_32.c 2010-01-19 13:26:10.000000000 +0100
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+++ head-2010-01-19/arch/x86/kernel/machine_kexec_32.c 2010-01-19 14:51:07.000000000 +0100
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@@ -27,48 +27,6 @@
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#include <asm/cacheflush.h>
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#include <asm/debugreg.h>
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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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- /* ia32 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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- load_idt(&curidt);
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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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- /* ia32 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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- load_gdt(&curgdt);
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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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-#define __STR(X) #X
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-#define STR(X) __STR(X)
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-
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- __asm__ __volatile__ (
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- "\tljmp $"STR(__KERNEL_CS)",$1f\n"
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- "\t1:\n"
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- "\tmovl $"STR(__KERNEL_DS)",%%eax\n"
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- "\tmovl %%eax,%%ds\n"
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- "\tmovl %%eax,%%es\n"
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- "\tmovl %%eax,%%fs\n"
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- "\tmovl %%eax,%%gs\n"
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- "\tmovl %%eax,%%ss\n"
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- : : : "eax", "memory");
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-#undef STR
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-#undef __STR
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-}
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-
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static void machine_kexec_free_page_tables(struct kimage *image)
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{
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free_page((unsigned long)image->arch.pgd);
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@@ -228,24 +186,6 @@ 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_ptr((unsigned long)image->head,
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(unsigned long)page_list,
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--- head-2010-01-19.orig/arch/x86/kernel/relocate_kernel_32.S 2009-06-10 05:05:27.000000000 +0200
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+++ head-2010-01-19/arch/x86/kernel/relocate_kernel_32.S 2010-01-19 14:51:07.000000000 +0100
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@@ -87,14 +87,32 @@ relocate_kernel:
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movl PTR(PA_PGD)(%ebp), %eax
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movl %eax, %cr3
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+ /* setup idt */
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+ lidtl idt_48 - relocate_kernel(%edi)
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+
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+ /* setup gdt */
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+ leal gdt - relocate_kernel(%edi), %eax
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+ movl %eax, (gdt_48 - relocate_kernel) + 2(%edi)
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+ lgdtl gdt_48 - relocate_kernel(%edi)
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+
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+ /* setup data segment registers */
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+ mov $(gdt_ds - gdt), %eax
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+ mov %eax, %ds
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+ mov %eax, %es
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+ mov %eax, %fs
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+ mov %eax, %gs
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+ mov %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(%edi), %esp
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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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+ pushl $0
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+ pushl $(gdt_cs - gdt)
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movl %edi, %eax
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addl $(identity_mapped - relocate_kernel), %eax
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pushl %eax
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- ret
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+ iretl
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identity_mapped:
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/* store the start address on the stack */
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@@ -271,5 +289,22 @@ swap_pages:
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popl %ebp
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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 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */
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+gdt_ds:
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+ .quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */
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+gdt_end:
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+
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+gdt_48:
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+ .word gdt_end - gdt - 1 /* limit */
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+ .long 0 /* base - filled in by code above */
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+
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+idt_48:
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+ .word 0 /* limit */
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+ .long 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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