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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [arch/] [x86_64/] [boot/] [compressed/] [head.S] - Blame information for rev 1765

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/*
 *  linux/boot/head.S
 *
 *  Copyright (C) 1991, 1992, 1993  Linus Torvalds
 *
 *  $Id: head.S,v 1.1.1.1 2004-04-15 01:36:30 phoenix Exp $
 */
 
/*
 *  head.S contains the 32-bit startup code.
 *
 * NOTE!!! Startup happens at absolute address 0x00001000, which is also where
 * the page directory will exist. The startup code will be overwritten by
 * the page directory. [According to comments etc elsewhere on a compressed
 * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
 *
 * Page 0 is deliberately kept safe, since System Management Mode code in
 * laptops may need to access the BIOS data stored there.  This is also
 * useful for future device drivers that either access the BIOS via VM86
 * mode.
 */
 
/*
 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
 */
.code32
.text
 
#include 
#include 
 
        .code32
        .globl startup_32
 
startup_32:
        cld
        cli
        movl $(__KERNEL_DS),%eax
        movl %eax,%ds
        movl %eax,%es
        movl %eax,%fs
        movl %eax,%gs
 
        lss SYMBOL_NAME(stack_start),%esp
        xorl %eax,%eax
1:      incl %eax               # check that A20 really IS enabled
        movl %eax,0x000000      # loop forever if it isn't
        cmpl %eax,0x100000
        je 1b
 
/*
 * Initialize eflags.  Some BIOS's leave bits like NT set.  This would
 * confuse the debugger if this code is traced.
 * XXX - best to initialize before switching to protected mode.
 */
        pushl $0
        popfl
/*
 * Clear BSS
 */
        xorl %eax,%eax
        movl $ SYMBOL_NAME(_edata),%edi
        movl $ SYMBOL_NAME(_end),%ecx
        subl %edi,%ecx
        cld
        rep
        stosb
/*
 * Do the decompression, and jump to the new kernel..
 */
        subl $16,%esp   # place for structure on the stack
        movl %esp,%eax
        pushl %esi      # real mode pointer as second arg
        pushl %eax      # address of structure as first arg
        call SYMBOL_NAME(decompress_kernel)
        orl  %eax,%eax
        jnz  3f
        addl $8,%esp
        xorl %ebx,%ebx
        ljmp $(__KERNEL_CS), $0x100000
 
/*
 * We come here, if we were loaded high.
 * We need to move the move-in-place routine down to 0x1000
 * and then start it with the buffer addresses in registers,
 * which we got from the stack.
 */
3:
        movl %esi,%ebx
        movl $move_routine_start,%esi
        movl $0x1000,%edi
        movl $move_routine_end,%ecx
        subl %esi,%ecx
        addl $3,%ecx
        shrl $2,%ecx
        cld
        rep
        movsl
 
        popl %esi       # discard the address
        addl $4,%esp    # real mode pointer
        popl %esi       # low_buffer_start
        popl %ecx       # lcount
        popl %edx       # high_buffer_start
        popl %eax       # hcount
        movl $0x100000,%edi
        cli             # make sure we don't get interrupted
        ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine
 
/*
 * Routine (template) for moving the decompressed kernel in place,
 * if we were high loaded. This _must_ PIC-code !
 */
move_routine_start:
        movl %ecx,%ebp
        shrl $2,%ecx
        rep
        movsl
        movl %ebp,%ecx
        andl $3,%ecx
        rep
        movsb
        movl %edx,%esi
        movl %eax,%ecx  # NOTE: rep movsb won't move if %ecx == 0
        addl $3,%ecx
        shrl $2,%ecx
        rep
        movsl
        movl %ebx,%esi  # Restore setup pointer
        xorl %ebx,%ebx
        ljmp $(__KERNEL_CS), $0x100000
move_routine_end:
 
 
/* Stack for uncompression */
        .align 32
user_stack:
        .fill 4096,4,0
stack_start:
        .long user_stack+4096
        .word __KERNEL_DS
 

Line No.	Rev	Author	Line
1	1275	phoenix	`/*`
2			`* linux/boot/head.S`
3			`*`
4			`* Copyright (C) 1991, 1992, 1993 Linus Torvalds`
5			`*`
6			`* $Id: head.S,v 1.1.1.1 2004-04-15 01:36:30 phoenix Exp $`
7			`*/`
8
9			`/*`
10			`* head.S contains the 32-bit startup code.`
11			`*`
12			`* NOTE!!! Startup happens at absolute address 0x00001000, which is also where`
13			`* the page directory will exist. The startup code will be overwritten by`
14			`* the page directory. [According to comments etc elsewhere on a compressed`
15			`* kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]`
16			`*`
17			`* Page 0 is deliberately kept safe, since System Management Mode code in`
18			`* laptops may need to access the BIOS data stored there. This is also`
19			`* useful for future device drivers that either access the BIOS via VM86`
20			`* mode.`
21			`*/`
22
23			`/*`
24			`* High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996`
25			`*/`
26			`.code32`
27			`.text`
28
29			`#include`
30			`#include`
31
32			`.code32`
33			`.globl startup_32`
34
35			`startup_32:`
36			`cld`
37			`cli`
38			`movl $(__KERNEL_DS),%eax`
39			`movl %eax,%ds`
40			`movl %eax,%es`
41			`movl %eax,%fs`
42			`movl %eax,%gs`
43
44			`lss SYMBOL_NAME(stack_start),%esp`
45			`xorl %eax,%eax`
46			`1: incl %eax # check that A20 really IS enabled`
47			`movl %eax,0x000000 # loop forever if it isn't`
48			`cmpl %eax,0x100000`
49			`je 1b`
50
51			`/*`
52			`* Initialize eflags. Some BIOS's leave bits like NT set. This would`
53			`* confuse the debugger if this code is traced.`
54			`* XXX - best to initialize before switching to protected mode.`
55			`*/`
56			`pushl $0`
57			`popfl`
58			`/*`
59			`* Clear BSS`
60			`*/`
61			`xorl %eax,%eax`
62			`movl $ SYMBOL_NAME(_edata),%edi`
63			`movl $ SYMBOL_NAME(_end),%ecx`
64			`subl %edi,%ecx`
65			`cld`
66			`rep`
67			`stosb`
68			`/*`
69			`* Do the decompression, and jump to the new kernel..`
70			`*/`
71			`subl $16,%esp # place for structure on the stack`
72			`movl %esp,%eax`
73			`pushl %esi # real mode pointer as second arg`
74			`pushl %eax # address of structure as first arg`
75			`call SYMBOL_NAME(decompress_kernel)`
76			`orl %eax,%eax`
77			`jnz 3f`
78			`addl $8,%esp`
79			`xorl %ebx,%ebx`
80			`ljmp $(__KERNEL_CS), $0x100000`
81
82			`/*`
83			`* We come here, if we were loaded high.`
84			`* We need to move the move-in-place routine down to 0x1000`
85			`* and then start it with the buffer addresses in registers,`
86			`* which we got from the stack.`
87			`*/`
88			`3:`
89			`movl %esi,%ebx`
90			`movl $move_routine_start,%esi`
91			`movl $0x1000,%edi`
92			`movl $move_routine_end,%ecx`
93			`subl %esi,%ecx`
94			`addl $3,%ecx`
95			`shrl $2,%ecx`
96			`cld`
97			`rep`
98			`movsl`
99
100			`popl %esi # discard the address`
101			`addl $4,%esp # real mode pointer`
102			`popl %esi # low_buffer_start`
103			`popl %ecx # lcount`
104			`popl %edx # high_buffer_start`
105			`popl %eax # hcount`
106			`movl $0x100000,%edi`
107			`cli # make sure we don't get interrupted`
108			`ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine`
109
110			`/*`
111			`* Routine (template) for moving the decompressed kernel in place,`
112			`* if we were high loaded. This _must_ PIC-code !`
113			`*/`
114			`move_routine_start:`
115			`movl %ecx,%ebp`
116			`shrl $2,%ecx`
117			`rep`
118			`movsl`
119			`movl %ebp,%ecx`
120			`andl $3,%ecx`
121			`rep`
122			`movsb`
123			`movl %edx,%esi`
124			`movl %eax,%ecx # NOTE: rep movsb won't move if %ecx == 0`
125			`addl $3,%ecx`
126			`shrl $2,%ecx`
127			`rep`
128			`movsl`
129			`movl %ebx,%esi # Restore setup pointer`
130			`xorl %ebx,%ebx`
131			`ljmp $(__KERNEL_CS), $0x100000`
132			`move_routine_end:`
133
134
135			`/* Stack for uncompression */`
136			`.align 32`
137			`user_stack:`
138			`.fill 4096,4,0`
139			`stack_start:`
140			`.long user_stack+4096`
141			`.word __KERNEL_DS`
142

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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [arch/] [x86_64/] [boot/] [compressed/] [head.S] - Blame information for rev 1765