1 /* 1 /*
2 * Startup glue code to uncompress the kernel !! 2 * linux/boot/head.S
3 * 3 *
4 * (C) 2017 Helge Deller <deller@gmx.de> !! 4 * Copyright (C) 1991, 1992, 1993 Linus Torvalds
5 */ 5 */
6 6
7 #include <linux/init.h> !! 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 * Page 0 is deliberately kept safe, since System Management Mode code in
>> 16 * laptops may need to access the BIOS data stored there. This is also
>> 17 * useful for future device drivers that either access the BIOS via VM86
>> 18 * mode.
>> 19 */
>> 20
>> 21 /*
>> 22 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
>> 23 */
>> 24 .text
>> 25
8 #include <linux/linkage.h> 26 #include <linux/linkage.h>
9 #include <asm/asm-offsets.h> !! 27 #include <asm/segment.h>
10 #include <asm/page.h> <<
11 #include <asm/psw.h> <<
12 #include <asm/pdc.h> <<
13 #include <asm/assembly.h> <<
14 #include "sizes.h" <<
15 <<
16 #define BOOTADDR(x) (x) <<
17 <<
18 #ifndef CONFIG_64BIT <<
19 .import $global$ /* for <<
20 #endif /*!CONFIG_64BIT*/ <<
21 <<
22 __HEAD <<
23 <<
24 ENTRY(startup) <<
25 .level PA_ASM_LEVEL <<
26 <<
27 #define PSW_W_SM 0x200 <<
28 #define PSW_W_BIT 36 <<
29 <<
30 ;! nuke the W bit, saving original val <<
31 .level 2.0 <<
32 rsm PSW_W_SM, %r1 <<
33 <<
34 .level 1.1 <<
35 extrw,u %r1, PSW_W_BIT-32, 1, %r1 <<
36 copy %r1, %arg0 <<
37 <<
38 /* Make sure sr4-sr7 are set to zero f <<
39 mtsp %r0,%sr4 <<
40 mtsp %r0,%sr5 <<
41 mtsp %r0,%sr6 <<
42 mtsp %r0,%sr7 <<
43 <<
44 /* Clear BSS */ <<
45 <<
46 .import _bss,data <<
47 .import _ebss,data <<
48 <<
49 load32 BOOTADDR(_bss),%r3 <<
50 load32 BOOTADDR(_ebss),%r4 <<
51 ldo FRAME_SIZE(%r4),%sp /* sta <<
52 $bss_loop: <<
53 cmpb,<<,n %r3,%r4,$bss_loop <<
54 stw,ma %r0,4(%r3) <<
55 <<
56 /* Initialize the global data pointer <<
57 loadgp <<
58 <<
59 /* arg0..arg4 were set by palo. */ <<
60 copy %arg1, %r6 /* com <<
61 copy %arg2, %r7 /* rd- <<
62 copy %arg3, %r8 /* rd- <<
63 load32 BOOTADDR(decompress_kernel),%r <<
64 <<
65 #ifdef CONFIG_64BIT <<
66 .level PA_ASM_LEVEL <<
67 ssm PSW_W_SM, %r0 /* set <<
68 depdi 0, 31, 32, %r3 <<
69 #endif <<
70 load32 BOOTADDR(startup_continue), %r <<
71 bv,n 0(%r3) <<
72 <<
73 startup_continue: <<
74 #ifdef CONFIG_64BIT <<
75 .level PA_ASM_LEVEL <<
76 rsm PSW_W_SM, %r0 /* cle <<
77 #endif <<
78 <<
79 load32 KERNEL_BINARY_TEXT_START, %arg <<
80 copy %r6, %arg1 /* com <<
81 copy %r7, %arg2 /* rd- <<
82 copy %r8, %arg3 /* rd- <<
83 28
84 bv,n 0(%ret0) !! 29 .globl startup_32
85 END(startup) !! 30
>> 31 startup_32:
>> 32 cld
>> 33 cli
>> 34 movl $(__BOOT_DS),%eax
>> 35 movl %eax,%ds
>> 36 movl %eax,%es
>> 37 movl %eax,%fs
>> 38 movl %eax,%gs
>> 39
>> 40 lss stack_start,%esp
>> 41 xorl %eax,%eax
>> 42 1: incl %eax # check that A20 really IS enabled
>> 43 movl %eax,0x000000 # loop forever if it isn't
>> 44 cmpl %eax,0x100000
>> 45 je 1b
>> 46
>> 47 /*
>> 48 * Initialize eflags. Some BIOS's leave bits like NT set. This would
>> 49 * confuse the debugger if this code is traced.
>> 50 * XXX - best to initialize before switching to protected mode.
>> 51 */
>> 52 pushl $0
>> 53 popfl
>> 54 /*
>> 55 * Clear BSS
>> 56 */
>> 57 xorl %eax,%eax
>> 58 movl $_edata,%edi
>> 59 movl $_end,%ecx
>> 60 subl %edi,%ecx
>> 61 cld
>> 62 rep
>> 63 stosb
>> 64 /*
>> 65 * Do the decompression, and jump to the new kernel..
>> 66 */
>> 67 subl $16,%esp # place for structure on the stack
>> 68 movl %esp,%eax
>> 69 pushl %esi # real mode pointer as second arg
>> 70 pushl %eax # address of structure as first arg
>> 71 call decompress_kernel
>> 72 orl %eax,%eax
>> 73 jnz 3f
>> 74 popl %esi # discard address
>> 75 popl %esi # real mode pointer
>> 76 xorl %ebx,%ebx
>> 77 ljmp $(__BOOT_CS), $0x100000
>> 78
>> 79 /*
>> 80 * We come here, if we were loaded high.
>> 81 * We need to move the move-in-place routine down to 0x1000
>> 82 * and then start it with the buffer addresses in registers,
>> 83 * which we got from the stack.
>> 84 */
>> 85 3:
>> 86 movl $move_routine_start,%esi
>> 87 movl $0x1000,%edi
>> 88 movl $move_routine_end,%ecx
>> 89 subl %esi,%ecx
>> 90 addl $3,%ecx
>> 91 shrl $2,%ecx
>> 92 cld
>> 93 rep
>> 94 movsl
>> 95
>> 96 popl %esi # discard the address
>> 97 popl %ebx # real mode pointer
>> 98 popl %esi # low_buffer_start
>> 99 popl %ecx # lcount
>> 100 popl %edx # high_buffer_start
>> 101 popl %eax # hcount
>> 102 movl $0x100000,%edi
>> 103 cli # make sure we don't get interrupted
>> 104 ljmp $(__BOOT_CS), $0x1000 # and jump to the move routine
>> 105
>> 106 /*
>> 107 * Routine (template) for moving the decompressed kernel in place,
>> 108 * if we were high loaded. This _must_ PIC-code !
>> 109 */
>> 110 move_routine_start:
>> 111 movl %ecx,%ebp
>> 112 shrl $2,%ecx
>> 113 rep
>> 114 movsl
>> 115 movl %ebp,%ecx
>> 116 andl $3,%ecx
>> 117 rep
>> 118 movsb
>> 119 movl %edx,%esi
>> 120 movl %eax,%ecx # NOTE: rep movsb won't move if %ecx == 0
>> 121 addl $3,%ecx
>> 122 shrl $2,%ecx
>> 123 rep
>> 124 movsl
>> 125 movl %ebx,%esi # Restore setup pointer
>> 126 xorl %ebx,%ebx
>> 127 ljmp $(__BOOT_CS), $0x100000
>> 128 move_routine_end:
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