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linux-vybrid_pu...
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arch
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x86
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kernel
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trampoline_32.S

trampoline_32.S 2.2 KB
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  1. /*
    2. 

  2.  *
    3. 

  3.  *	Trampoline.S	Derived from Setup.S by Linus Torvalds
    4. 

  4.  *
    5. 

  5.  *	4 Jan 1997 Michael Chastain: changed to gnu as.
    6. 

  6.  *
    7. 

  7.  *	This is only used for booting secondary CPUs in SMP machine
    8. 

  8.  *
    9. 

  9.  *	Entry: CS:IP point to the start of our code, we are 
    10. 

  10.  *	in real mode with no stack, but the rest of the 
    11. 

  11.  *	trampoline page to make our stack and everything else
    12. 

  12.  *	is a mystery.
    13. 

  13.  *
    14. 

  14.  *	We jump into arch/x86/kernel/head_32.S.
    15. 

  15.  *
    16. 

  16.  *	On entry to trampoline_data, the processor is in real mode
    17. 

  17.  *	with 16-bit addressing and 16-bit data.  CS has some value
    18. 

  18.  *	and IP is zero.  Thus, data addresses need to be absolute
    19. 

  19.  *	(no relocation) and are taken with regard to r_base.
    20. 

  20.  *
    21. 

  21.  *	If you work on this file, check the object module with
    22. 

  22.  *	objdump --reloc to make sure there are no relocation
    23. 

  23.  *	entries except for:
    24. 

  24.  *
    25. 

  25.  *	TYPE              VALUE
    26. 

  26.  *	R_386_32          startup_32_smp
    27. 

  27.  *	R_386_32          boot_gdt
    28. 

  28.  */
    29. 

  29. 

  30. #include <linux/linkage.h>
    31. 

  31. #include <linux/init.h>
    32. 

  32. #include <asm/segment.h>
    33. 

  33. #include <asm/page_types.h>
    34. 

  34. 

  35. /* We can free up trampoline after bootup if cpu hotplug is not supported. */
    36. 

  36. __CPUINITRODATA
    37. 

  37. .code16
    38. 

  38. 

  39. ENTRY(trampoline_data)
    40. 

  40. r_base = .
    41. 

  41. 	wbinvd			# Needed for NUMA-Q should be harmless for others
    42. 

  42. 	mov	%cs, %ax	# Code and data in the same place
    43. 

  43. 	mov	%ax, %ds
    44. 

  44. 

  45. 	cli			# We should be safe anyway
    46. 

  46. 

  47. 	movl	$0xA5A5A5A5, trampoline_data - r_base
    48. 

  48. 				# write marker for master knows we're running
    49. 

  49. 

  50. 	/* GDT tables in non default location kernel can be beyond 16MB and
    51. 

  51. 	 * lgdt will not be able to load the address as in real mode default
    52. 

  52. 	 * operand size is 16bit. Use lgdtl instead to force operand size
    53. 

  53. 	 * to 32 bit.
    54. 

  54. 	 */
    55. 

  55. 

  56. 	lidtl	boot_idt_descr - r_base	# load idt with 0, 0
    57. 

  57. 	lgdtl	boot_gdt_descr - r_base	# load gdt with whatever is appropriate
    58. 

  58. 

  59. 	xor	%ax, %ax
    60. 

  60. 	inc	%ax		# protected mode (PE) bit
    61. 

  61. 	lmsw	%ax		# into protected mode
    62. 

  62. 	# flush prefetch and jump to startup_32_smp in arch/i386/kernel/head.S
    63. 

  63. 	ljmpl	$__BOOT_CS, $(startup_32_smp-__PAGE_OFFSET)
    64. 

  64. 

  65. 	# These need to be in the same 64K segment as the above;
    66. 

  66. 	# hence we don't use the boot_gdt_descr defined in head.S
    67. 

  67. boot_gdt_descr:
    68. 

  68. 	.word	__BOOT_DS + 7			# gdt limit
    69. 

  69. 	.long	boot_gdt - __PAGE_OFFSET	# gdt base
    70. 

  70. 

  71. boot_idt_descr:
    72. 

  72. 	.word	0				# idt limit = 0
    73. 

  73. 	.long	0				# idt base = 0L
    74. 

  74. 

  75. .globl trampoline_end
    76. 

  76. trampoline_end:
    77.