src/patches/suse-2.6.27.25/patches.xen/linux-2.6.19-rc1-kexec-move_segment_code-x86_64.patch

   1 Subject: kexec: Move asm segment handling code to the assembly file (x86_64)
   2 From: http://xenbits.xensource.com/xen-unstable.hg (tip 13816)
   3 Patch-mainline: obsolete
   4
   5 This patch moves the idt, gdt, and segment handling code from machine_kexec.c
   6 to relocate_kernel.S.  The main reason behind this move is to avoid code
   7 duplication in the Xen hypervisor. With this patch all code required to kexec
   8 is put on the control page.
   9
  10 On top of that this patch also counts as a cleanup - I think it is much
  11 nicer to write assembly directly in assembly files than wrap inline assembly
  12 in C functions for no apparent reason.
  13
  14 Signed-off-by: Magnus Damm <magnus@valinux.co.jp>
  15 Acked-by: jbeulich@novell.com
  16 ---
  17
  18  Applies to 2.6.19-rc1.
  19
  20  machine_kexec.c   |   58 -----------------------------------------------------
  21  relocate_kernel.S |   50 +++++++++++++++++++++++++++++++++++++++++----
  22  2 files changed, 45 insertions(+), 63 deletions(-)
  23
  24 Index: head-2008-08-18/arch/x86/kernel/machine_kexec_64.c
  25 ===================================================================
  26 --- head-2008-08-18.orig/arch/x86/kernel/machine_kexec_64.c     2008-08-18 09:05:04.000000000 +0200
  27 +++ head-2008-08-18/arch/x86/kernel/machine_kexec_64.c  2008-08-18 10:13:08.000000000 +0200
  28 @@ -115,47 +115,6 @@ static int init_pgtable(struct kimage *i
  29         return init_level4_page(image, level4p, 0, max_pfn << PAGE_SHIFT);
  30  }
  31
  32 -static void set_idt(void *newidt, u16 limit)
  33 -{
  34 -       struct desc_ptr curidt;
  35 -
  36 -       /* x86-64 supports unaliged loads & stores */
  37 -       curidt.size    = limit;
  38 -       curidt.address = (unsigned long)newidt;
  39 -
  40 -       __asm__ __volatile__ (
  41 -               "lidtq %0\n"
  42 -               : : "m" (curidt)
  43 -               );
  44 -};
  45 -
  46 -
  47 -static void set_gdt(void *newgdt, u16 limit)
  48 -{
  49 -       struct desc_ptr curgdt;
  50 -
  51 -       /* x86-64 supports unaligned loads & stores */
  52 -       curgdt.size    = limit;
  53 -       curgdt.address = (unsigned long)newgdt;
  54 -
  55 -       __asm__ __volatile__ (
  56 -               "lgdtq %0\n"
  57 -               : : "m" (curgdt)
  58 -               );
  59 -};
  60 -
  61 -static void load_segments(void)
  62 -{
  63 -       __asm__ __volatile__ (
  64 -               "\tmovl %0,%%ds\n"
  65 -               "\tmovl %0,%%es\n"
  66 -               "\tmovl %0,%%ss\n"
  67 -               "\tmovl %0,%%fs\n"
  68 -               "\tmovl %0,%%gs\n"
  69 -               : : "a" (__KERNEL_DS) : "memory"
  70 -               );
  71 -}
  72 -
  73  int machine_kexec_prepare(struct kimage *image)
  74  {
  75         unsigned long start_pgtable;
  76 @@ -214,23 +173,6 @@ void machine_kexec(struct kimage *image)
  77         page_list[PA_TABLE_PAGE] =
  78           (unsigned long)__pa(page_address(image->control_code_page));
  79
  80 -       /* The segment registers are funny things, they have both a
  81 -        * visible and an invisible part.  Whenever the visible part is
  82 -        * set to a specific selector, the invisible part is loaded
  83 -        * with from a table in memory.  At no other time is the
  84 -        * descriptor table in memory accessed.
  85 -        *
  86 -        * I take advantage of this here by force loading the
  87 -        * segments, before I zap the gdt with an invalid value.
  88 -        */
  89 -       load_segments();
  90 -       /* The gdt & idt are now invalid.
  91 -        * If you want to load them you must set up your own idt & gdt.
  92 -        */
  93 -       set_gdt(phys_to_virt(0),0);
  94 -       set_idt(phys_to_virt(0),0);
  95 -
  96 -       /* now call it */
  97         relocate_kernel((unsigned long)image->head, (unsigned long)page_list,
  98                         image->start);
  99  }
 100 Index: head-2008-08-18/arch/x86/kernel/relocate_kernel_64.S
 101 ===================================================================
 102 --- head-2008-08-18.orig/arch/x86/kernel/relocate_kernel_64.S   2008-07-13 23:51:29.000000000 +0200
 103 +++ head-2008-08-18/arch/x86/kernel/relocate_kernel_64.S        2008-08-18 10:13:08.000000000 +0200
 104 @@ -160,13 +160,39 @@ relocate_new_kernel:
 105         movq    PTR(PA_PGD)(%rsi), %r9
 106         movq    %r9, %cr3
 107
 108 +       /* setup idt */
 109 +       movq    %r8, %rax
 110 +       addq    $(idt_80 - relocate_kernel), %rax
 111 +       lidtq   (%rax)
 112 +
 113 +       /* setup gdt */
 114 +       movq    %r8, %rax
 115 +       addq    $(gdt - relocate_kernel), %rax
 116 +       movq    %r8, %r9
 117 +       addq    $((gdt_80 - relocate_kernel) + 2), %r9
 118 +       movq    %rax, (%r9)
 119 +
 120 +       movq    %r8, %rax
 121 +       addq    $(gdt_80 - relocate_kernel), %rax
 122 +       lgdtq   (%rax)
 123 +
 124 +       /* setup data segment registers */
 125 +       xorl    %eax, %eax
 126 +       movl    %eax, %ds
 127 +       movl    %eax, %es
 128 +       movl    %eax, %fs
 129 +       movl    %eax, %gs
 130 +       movl    %eax, %ss
 131 +
 132         /* setup a new stack at the end of the physical control page */
 133         lea     PAGE_SIZE(%r8), %rsp
 134
 135 -       /* jump to identity mapped page */
 136 -       addq    $(identity_mapped - relocate_kernel), %r8
 137 -       pushq   %r8
 138 -       ret
 139 +       /* load new code segment and jump to identity mapped page */
 140 +       movq    %r8, %rax
 141 +       addq    $(identity_mapped - relocate_kernel), %rax
 142 +       pushq   $(gdt_cs - gdt)
 143 +       pushq   %rax
 144 +       lretq
 145
 146  identity_mapped:
 147         /* store the start address on the stack */
 148 @@ -262,5 +288,19 @@ identity_mapped:
 149         xorq    %r13, %r13
 150         xorq    %r14, %r14
 151         xorq    %r15, %r15
 152 -
 153         ret
 154 +
 155 +       .align  16
 156 +gdt:
 157 +       .quad   0x0000000000000000      /* NULL descriptor */
 158 +gdt_cs:
 159 +       .quad   0x00af9a000000ffff
 160 +gdt_end:
 161 +
 162 +gdt_80:
 163 +       .word   gdt_end - gdt - 1       /* limit */
 164 +       .quad   0                       /* base - filled in by code above */
 165 +
 166 +idt_80:
 167 +       .word   0                       /* limit */
 168 +       .quad   0                       /* base */