src/patches/suse-2.6.27.25/patches.xen/linux-2.6.19-rc1-kexec-move_segment_code-i386.patch

   1 Subject: kexec: Move asm segment handling code to the assembly file (i386)
   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   |   59 -----------------------------------------------------
  21  relocate_kernel.S |   58 +++++++++++++++++++++++++++++++++++++++++++++++-----
  22  2 files changed, 53 insertions(+), 64 deletions(-)
  23
  24 Index: head-2008-11-17/arch/x86/kernel/machine_kexec_32.c
  25 ===================================================================
  26 --- head-2008-11-17.orig/arch/x86/kernel/machine_kexec_32.c     2008-11-17 13:15:56.000000000 +0100
  27 +++ head-2008-11-17/arch/x86/kernel/machine_kexec_32.c  2008-11-17 13:38:03.000000000 +0100
  28 @@ -34,48 +34,6 @@ static u32 kexec_pmd1[1024] PAGE_ALIGNED
  29  static u32 kexec_pte0[1024] PAGE_ALIGNED;
  30  static u32 kexec_pte1[1024] PAGE_ALIGNED;
  31
  32 -static void set_idt(void *newidt, __u16 limit)
  33 -{
  34 -       struct desc_ptr curidt;
  35 -
  36 -       /* ia32 supports unaliged loads & stores */
  37 -       curidt.size    = limit;
  38 -       curidt.address = (unsigned long)newidt;
  39 -
  40 -       load_idt(&curidt);
  41 -}
  42 -
  43 -
  44 -static void set_gdt(void *newgdt, __u16 limit)
  45 -{
  46 -       struct desc_ptr curgdt;
  47 -
  48 -       /* ia32 supports unaligned loads & stores */
  49 -       curgdt.size    = limit;
  50 -       curgdt.address = (unsigned long)newgdt;
  51 -
  52 -       load_gdt(&curgdt);
  53 -}
  54 -
  55 -static void load_segments(void)
  56 -{
  57 -#define __STR(X) #X
  58 -#define STR(X) __STR(X)
  59 -
  60 -       __asm__ __volatile__ (
  61 -               "\tljmp $"STR(__KERNEL_CS)",$1f\n"
  62 -               "\t1:\n"
  63 -               "\tmovl $"STR(__KERNEL_DS)",%%eax\n"
  64 -               "\tmovl %%eax,%%ds\n"
  65 -               "\tmovl %%eax,%%es\n"
  66 -               "\tmovl %%eax,%%fs\n"
  67 -               "\tmovl %%eax,%%gs\n"
  68 -               "\tmovl %%eax,%%ss\n"
  69 -               ::: "eax", "memory");
  70 -#undef STR
  71 -#undef __STR
  72 -}
  73 -
  74  /*
  75   * A architecture hook called to validate the
  76   * proposed image and prepare the control pages
  77 @@ -167,23 +125,6 @@ void machine_kexec(struct kimage *image)
  78                 page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)
  79                                                 << PAGE_SHIFT);
  80
  81 -       /* The segment registers are funny things, they have both a
  82 -        * visible and an invisible part.  Whenever the visible part is
  83 -        * set to a specific selector, the invisible part is loaded
  84 -        * with from a table in memory.  At no other time is the
  85 -        * descriptor table in memory accessed.
  86 -        *
  87 -        * I take advantage of this here by force loading the
  88 -        * segments, before I zap the gdt with an invalid value.
  89 -        */
  90 -       load_segments();
  91 -       /* The gdt & idt are now invalid.
  92 -        * If you want to load them you must set up your own idt & gdt.
  93 -        */
  94 -       set_gdt(phys_to_virt(0),0);
  95 -       set_idt(phys_to_virt(0),0);
  96 -
  97 -       /* now call it */
  98         image->start = relocate_kernel_ptr((unsigned long)image->head,
  99                                            (unsigned long)page_list,
 100                                            image->start, cpu_has_pae,
 101 Index: head-2008-11-17/arch/x86/kernel/relocate_kernel_32.S
 102 ===================================================================
 103 --- head-2008-11-17.orig/arch/x86/kernel/relocate_kernel_32.S   2008-11-17 13:15:56.000000000 +0100
 104 +++ head-2008-11-17/arch/x86/kernel/relocate_kernel_32.S        2008-11-17 13:38:03.000000000 +0100
 105 @@ -199,14 +199,45 @@ relocate_new_kernel:
 106         movl    PTR(PA_PGD)(%ebp), %eax
 107         movl    %eax, %cr3
 108
 109 +       /* setup idt */
 110 +       movl    %edi, %eax
 111 +       addl    $(idt_48 - relocate_kernel), %eax
 112 +       lidtl   (%eax)
 113 +
 114 +       /* setup gdt */
 115 +       movl    %edi, %eax
 116 +       addl    $(gdt - relocate_kernel), %eax
 117 +       movl    %edi, %esi
 118 +       addl    $((gdt_48 - relocate_kernel) + 2), %esi
 119 +       movl    %eax, (%esi)
 120 +
 121 +       movl    %edi, %eax
 122 +       addl    $(gdt_48 - relocate_kernel), %eax
 123 +       lgdtl   (%eax)
 124 +
 125 +       /* setup data segment registers */
 126 +       mov     $(gdt_ds - gdt), %eax
 127 +       mov     %eax, %ds
 128 +       mov     %eax, %es
 129 +       mov     %eax, %fs
 130 +       mov     %eax, %gs
 131 +       mov     %eax, %ss
 132 +
 133         /* setup a new stack at the end of the physical control page */
 134         lea     PAGE_SIZE(%edi), %esp
 135
 136 -       /* jump to identity mapped page */
 137 -       movl    %edi, %eax
 138 -       addl    $(identity_mapped - relocate_kernel), %eax
 139 -       pushl   %eax
 140 -       ret
 141 +       /* load new code segment and jump to identity mapped page */
 142 +       movl    %edi, %esi
 143 +       xorl    %eax, %eax
 144 +       pushl   %eax
 145 +       pushl   %esi
 146 +       pushl   %eax
 147 +       movl    $(gdt_cs - gdt), %eax
 148 +       pushl   %eax
 149 +       movl    %edi, %eax
 150 +       addl    $(identity_mapped - relocate_kernel),%eax
 151 +       pushl   %eax
 152 +       iretl
 153
 154  identity_mapped:
 155         /* store the start address on the stack */
 156 @@ -378,5 +409,22 @@ swap_pages:
 157         popl    %ebp
 158         ret
 159
 160 +       .align  16
 161 +gdt:
 162 +       .quad   0x0000000000000000      /* NULL descriptor */
 163 +gdt_cs:
 164 +       .quad   0x00cf9a000000ffff      /* kernel 4GB code at 0x00000000 */
 165 +gdt_ds:
 166 +       .quad   0x00cf92000000ffff      /* kernel 4GB data at 0x00000000 */
 167 +gdt_end:
 168 +
 169 +gdt_48:
 170 +       .word   gdt_end - gdt - 1       /* limit */
 171 +       .long   0                       /* base - filled in by code above */
 172 +
 173 +idt_48:
 174 +       .word   0                       /* limit */
 175 +       .long   0                       /* base */
 176 +
 177         .globl kexec_control_code_size
 178  .set kexec_control_code_size, . - relocate_kernel