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[/] [or1k/] [trunk/] [uclinux/] [uClinux-2.0.x/] [arch/] [i386/] [boot/] [compressed/] [head.S] - Blame information for rev 1775

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/*
 *  linux/boot/head.S
 *
 *  Copyright (C) 1991, 1992, 1993  Linus Torvalds
 */
 
/*
 *  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]
 *
 * In SMP mode we keep this page safe. Really we ought to shuffle things and
 * put the trampoline here. - AC. An SMP trampoline enters with %cx holding
 * the stack base.
 *
 * 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
 */
.text
 
#define __ASSEMBLY__
#include 
#include 
 
        .globl startup_32
 
startup_32:
        cld
        cli
        movl $(KERNEL_DS),%eax
        mov %ax,%ds
        mov %ax,%es
        mov %ax,%fs
        mov %ax,%gs
#ifdef __SMP__
        orw %bx,%bx                     # What state are we in BX=1 for SMP
                                        # 0 for boot
        jz  2f                          # Initial boot
 
/*
 *      We are trampolining an SMP processor
 */
        mov %ax,%ss
        xorl %eax,%eax                  # Back to 0
        mov  %cx,%ax                    # SP low 16 bits
        movl %eax,%esp
        pushl 0                         # Clear NT
        popfl
        ljmp $(KERNEL_CS), $0x100000    # Into C and sanity
 
2:
#endif
        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
        pushl %esp      # address of structure as first arg
        call SYMBOL_NAME(decompress_kernel)
        orl  %eax,%eax
        jnz  3f
        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 $move_routine_start,%esi
        movl $0x1000,%edi
        movl $move_routine_end,%ecx
        subl %esi,%ecx
        cld
        rep
        movsb
 
        popl %esi       # discard the address
        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:
        rep
        movsb
        movl %edx,%esi
        movl %eax,%ecx  # NOTE: rep movsb won't move if %ecx == 0
        rep
        movsb
        xorl %ebx,%ebx
/*
 * Well, the kernel relies on %esp pointing into low mem,
 * with the decompressor loaded high this is no longer true,
 * so we set esp here.
 */
        mov  $0x90000,%esp
        ljmp $(KERNEL_CS), $0x100000
move_routine_end:

Line No.	Rev	Author	Line
1	199	simons	`/*`
2			`* linux/boot/head.S`
3			`*`
4			`* Copyright (C) 1991, 1992, 1993 Linus Torvalds`
5			`*/`
6
7			`/*`
8			`* head.S contains the 32-bit startup code.`
9			`*`
10			`* NOTE!!! Startup happens at absolute address 0x00001000, which is also where`
11			`* the page directory will exist. The startup code will be overwritten by`
12			`* the page directory. [According to comments etc elsewhere on a compressed`
13			`* kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]`
14			`*`
15			`* In SMP mode we keep this page safe. Really we ought to shuffle things and`
16			`* put the trampoline here. - AC. An SMP trampoline enters with %cx holding`
17			`* the stack base.`
18			`*`
19			`* Page 0 is deliberately kept safe, since System Management Mode code in`
20			`* laptops may need to access the BIOS data stored there. This is also`
21			`* useful for future device drivers that either access the BIOS via VM86`
22			`* mode.`
23			`*/`
24
25			`/*`
26			`* High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996`
27			`*/`
28			`.text`
29
30			`#define __ASSEMBLY__`
31			`#include`
32			`#include`
33
34			`.globl startup_32`
35
36			`startup_32:`
37			`cld`
38			`cli`
39			`movl $(KERNEL_DS),%eax`
40			`mov %ax,%ds`
41			`mov %ax,%es`
42			`mov %ax,%fs`
43			`mov %ax,%gs`
44			`#ifdef __SMP__`
45			`orw %bx,%bx # What state are we in BX=1 for SMP`
46			`# 0 for boot`
47			`jz 2f # Initial boot`
48
49			`/*`
50			`* We are trampolining an SMP processor`
51			`*/`
52			`mov %ax,%ss`
53			`xorl %eax,%eax # Back to 0`
54			`mov %cx,%ax # SP low 16 bits`
55			`movl %eax,%esp`
56			`pushl 0 # Clear NT`
57			`popfl`
58			`ljmp $(KERNEL_CS), $0x100000 # Into C and sanity`
59
60			`2:`
61			`#endif`
62			`lss SYMBOL_NAME(stack_start),%esp`
63			`xorl %eax,%eax`
64			`1: incl %eax # check that A20 really IS enabled`
65			`movl %eax,0x000000 # loop forever if it isn't`
66			`cmpl %eax,0x100000`
67			`je 1b`
68			`/*`
69			`* Initialize eflags. Some BIOS's leave bits like NT set. This would`
70			`* confuse the debugger if this code is traced.`
71			`* XXX - best to initialize before switching to protected mode.`
72			`*/`
73			`pushl $0`
74			`popfl`
75			`/*`
76			`* Clear BSS`
77			`*/`
78			`xorl %eax,%eax`
79			`movl $ SYMBOL_NAME(_edata),%edi`
80			`movl $ SYMBOL_NAME(_end),%ecx`
81			`subl %edi,%ecx`
82			`cld`
83			`rep`
84			`stosb`
85			`/*`
86			`* Do the decompression, and jump to the new kernel..`
87			`*/`
88			`subl $16,%esp # place for structure on the stack`
89			`pushl %esp # address of structure as first arg`
90			`call SYMBOL_NAME(decompress_kernel)`
91			`orl %eax,%eax`
92			`jnz 3f`
93			`xorl %ebx,%ebx`
94			`ljmp $(KERNEL_CS), $0x100000`
95
96			`/*`
97			`* We come here, if we were loaded high.`
98			`* We need to move the move-in-place routine down to 0x1000`
99			`* and then start it with the buffer addresses in registers,`
100			`* which we got from the stack.`
101			`*/`
102			`3:`
103			`movl $move_routine_start,%esi`
104			`movl $0x1000,%edi`
105			`movl $move_routine_end,%ecx`
106			`subl %esi,%ecx`
107			`cld`
108			`rep`
109			`movsb`
110
111			`popl %esi # discard the address`
112			`popl %esi # low_buffer_start`
113			`popl %ecx # lcount`
114			`popl %edx # high_buffer_start`
115			`popl %eax # hcount`
116			`movl $0x100000,%edi`
117			`cli # make sure we don't get interrupted`
118			`ljmp $(KERNEL_CS), $0x1000 # and jump to the move routine`
119
120			`/*`
121			`* Routine (template) for moving the decompressed kernel in place,`
122			`* if we were high loaded. This _must_ PIC-code !`
123			`*/`
124			`move_routine_start:`
125			`rep`
126			`movsb`
127			`movl %edx,%esi`
128			`movl %eax,%ecx # NOTE: rep movsb won't move if %ecx == 0`
129			`rep`
130			`movsb`
131			`xorl %ebx,%ebx`
132			`/*`
133			`* Well, the kernel relies on %esp pointing into low mem,`
134			`* with the decompressor loaded high this is no longer true,`
135			`* so we set esp here.`
136			`*/`
137			`mov $0x90000,%esp`
138			`ljmp $(KERNEL_CS), $0x100000`
139			`move_routine_end:`

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[/] [or1k/] [trunk/] [uclinux/] [uClinux-2.0.x/] [arch/] [i386/] [boot/] [compressed/] [head.S] - Blame information for rev 1775