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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * linux/boot/head.S | |
3 | * | |
4 | * Copyright (C) 1991, 1992, 1993 Linus Torvalds | |
1da177e4 LT |
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 | * 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 | /* | |
f4549448 | 22 | * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 |
1da177e4 | 23 | */ |
b40d68d5 PA |
24 | .code32 |
25 | .text | |
1da177e4 LT |
26 | |
27 | #include <linux/linkage.h> | |
28 | #include <asm/segment.h> | |
0341c14d JF |
29 | #include <asm/pgtable_types.h> |
30 | #include <asm/page_types.h> | |
7c539764 | 31 | #include <asm/boot.h> |
1ab60e0f | 32 | #include <asm/msr.h> |
e83e31f4 | 33 | #include <asm/processor-flags.h> |
bd53147d | 34 | #include <asm/asm-offsets.h> |
1da177e4 | 35 | |
b40d68d5 | 36 | .section ".text.head" |
1da177e4 | 37 | .code32 |
2d4eeecb | 38 | ENTRY(startup_32) |
1da177e4 | 39 | cld |
b40d68d5 PA |
40 | /* |
41 | * Test KEEP_SEGMENTS flag to see if the bootloader is asking | |
42 | * us to not reload segments | |
43 | */ | |
bd53147d EB |
44 | testb $(1<<6), BP_loadflags(%esi) |
45 | jnz 1f | |
46 | ||
1da177e4 | 47 | cli |
1ab60e0f VG |
48 | movl $(__KERNEL_DS), %eax |
49 | movl %eax, %ds | |
50 | movl %eax, %es | |
51 | movl %eax, %ss | |
bd53147d | 52 | 1: |
1ab60e0f | 53 | |
b40d68d5 PA |
54 | /* |
55 | * Calculate the delta between where we were compiled to run | |
1ab60e0f VG |
56 | * at and where we were actually loaded at. This can only be done |
57 | * with a short local call on x86. Nothing else will tell us what | |
58 | * address we are running at. The reserved chunk of the real-mode | |
85414b69 PA |
59 | * data at 0x1e4 (defined as a scratch field) are used as the stack |
60 | * for this calculation. Only 4 bytes are needed. | |
1ab60e0f | 61 | */ |
bd2a3698 | 62 | leal (BP_scratch+4)(%esi), %esp |
1ab60e0f VG |
63 | call 1f |
64 | 1: popl %ebp | |
65 | subl $1b, %ebp | |
66 | ||
a4831e08 | 67 | /* setup a stack and make sure cpu supports long mode. */ |
7c539764 | 68 | movl $boot_stack_end, %eax |
a4831e08 VG |
69 | addl %ebp, %eax |
70 | movl %eax, %esp | |
71 | ||
72 | call verify_cpu | |
73 | testl %eax, %eax | |
74 | jnz no_longmode | |
75 | ||
b40d68d5 PA |
76 | /* |
77 | * Compute the delta between where we were compiled to run at | |
1ab60e0f | 78 | * and where the code will actually run at. |
b40d68d5 PA |
79 | * |
80 | * %ebp contains the address we are loaded at by the boot loader and %ebx | |
1ab60e0f VG |
81 | * contains the address where we should move the kernel image temporarily |
82 | * for safe in-place decompression. | |
83 | */ | |
84 | ||
85 | #ifdef CONFIG_RELOCATABLE | |
86 | movl %ebp, %ebx | |
31422c51 AK |
87 | addl $(PMD_PAGE_SIZE -1), %ebx |
88 | andl $PMD_PAGE_MASK, %ebx | |
1ab60e0f VG |
89 | #else |
90 | movl $CONFIG_PHYSICAL_START, %ebx | |
91 | #endif | |
92 | ||
93 | /* Replace the compressed data size with the uncompressed size */ | |
94 | subl input_len(%ebp), %ebx | |
95 | movl output_len(%ebp), %eax | |
96 | addl %eax, %ebx | |
97 | /* Add 8 bytes for every 32K input block */ | |
98 | shrl $12, %eax | |
99 | addl %eax, %ebx | |
100 | /* Add 32K + 18 bytes of extra slack and align on a 4K boundary */ | |
101 | addl $(32768 + 18 + 4095), %ebx | |
102 | andl $~4095, %ebx | |
1da177e4 LT |
103 | |
104 | /* | |
1ab60e0f | 105 | * Prepare for entering 64 bit mode |
1da177e4 | 106 | */ |
1ab60e0f VG |
107 | |
108 | /* Load new GDT with the 64bit segments using 32bit descriptor */ | |
109 | leal gdt(%ebp), %eax | |
110 | movl %eax, gdt+2(%ebp) | |
111 | lgdt gdt(%ebp) | |
112 | ||
113 | /* Enable PAE mode */ | |
114 | xorl %eax, %eax | |
e83e31f4 | 115 | orl $(X86_CR4_PAE), %eax |
1ab60e0f VG |
116 | movl %eax, %cr4 |
117 | ||
118 | /* | |
119 | * Build early 4G boot pagetable | |
120 | */ | |
b40d68d5 | 121 | /* Initialize Page tables to 0 */ |
1ab60e0f VG |
122 | leal pgtable(%ebx), %edi |
123 | xorl %eax, %eax | |
124 | movl $((4096*6)/4), %ecx | |
125 | rep stosl | |
126 | ||
127 | /* Build Level 4 */ | |
128 | leal pgtable + 0(%ebx), %edi | |
129 | leal 0x1007 (%edi), %eax | |
130 | movl %eax, 0(%edi) | |
131 | ||
132 | /* Build Level 3 */ | |
133 | leal pgtable + 0x1000(%ebx), %edi | |
134 | leal 0x1007(%edi), %eax | |
135 | movl $4, %ecx | |
136 | 1: movl %eax, 0x00(%edi) | |
137 | addl $0x00001000, %eax | |
138 | addl $8, %edi | |
139 | decl %ecx | |
140 | jnz 1b | |
141 | ||
142 | /* Build Level 2 */ | |
143 | leal pgtable + 0x2000(%ebx), %edi | |
144 | movl $0x00000183, %eax | |
145 | movl $2048, %ecx | |
146 | 1: movl %eax, 0(%edi) | |
147 | addl $0x00200000, %eax | |
148 | addl $8, %edi | |
149 | decl %ecx | |
150 | jnz 1b | |
151 | ||
152 | /* Enable the boot page tables */ | |
153 | leal pgtable(%ebx), %eax | |
154 | movl %eax, %cr3 | |
155 | ||
156 | /* Enable Long mode in EFER (Extended Feature Enable Register) */ | |
157 | movl $MSR_EFER, %ecx | |
158 | rdmsr | |
159 | btsl $_EFER_LME, %eax | |
160 | wrmsr | |
161 | ||
b40d68d5 PA |
162 | /* |
163 | * Setup for the jump to 64bit mode | |
1ab60e0f VG |
164 | * |
165 | * When the jump is performend we will be in long mode but | |
166 | * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1 | |
167 | * (and in turn EFER.LMA = 1). To jump into 64bit mode we use | |
168 | * the new gdt/idt that has __KERNEL_CS with CS.L = 1. | |
169 | * We place all of the values on our mini stack so lret can | |
170 | * used to perform that far jump. | |
171 | */ | |
172 | pushl $__KERNEL_CS | |
173 | leal startup_64(%ebp), %eax | |
174 | pushl %eax | |
175 | ||
176 | /* Enter paged protected Mode, activating Long Mode */ | |
e83e31f4 | 177 | movl $(X86_CR0_PG | X86_CR0_PE), %eax /* Enable Paging and Protected mode */ |
1ab60e0f VG |
178 | movl %eax, %cr0 |
179 | ||
180 | /* Jump from 32bit compatibility mode into 64bit mode. */ | |
181 | lret | |
2d4eeecb | 182 | ENDPROC(startup_32) |
1ab60e0f | 183 | |
a4831e08 VG |
184 | no_longmode: |
185 | /* This isn't an x86-64 CPU so hang */ | |
186 | 1: | |
187 | hlt | |
188 | jmp 1b | |
189 | ||
250c2277 | 190 | #include "../../kernel/verify_cpu_64.S" |
a4831e08 | 191 | |
b40d68d5 PA |
192 | /* |
193 | * Be careful here startup_64 needs to be at a predictable | |
1ab60e0f VG |
194 | * address so I can export it in an ELF header. Bootloaders |
195 | * should look at the ELF header to find this address, as | |
196 | * it may change in the future. | |
197 | */ | |
198 | .code64 | |
a4831e08 | 199 | .org 0x200 |
1ab60e0f | 200 | ENTRY(startup_64) |
b40d68d5 PA |
201 | /* |
202 | * We come here either from startup_32 or directly from a | |
1ab60e0f VG |
203 | * 64bit bootloader. If we come here from a bootloader we depend on |
204 | * an identity mapped page table being provied that maps our | |
205 | * entire text+data+bss and hopefully all of memory. | |
206 | */ | |
207 | ||
208 | /* Setup data segments. */ | |
209 | xorl %eax, %eax | |
210 | movl %eax, %ds | |
211 | movl %eax, %es | |
212 | movl %eax, %ss | |
08da5a2c ZA |
213 | movl %eax, %fs |
214 | movl %eax, %gs | |
215 | lldt %ax | |
216 | movl $0x20, %eax | |
217 | ltr %ax | |
1ab60e0f | 218 | |
b40d68d5 PA |
219 | /* |
220 | * Compute the decompressed kernel start address. It is where | |
1ab60e0f VG |
221 | * we were loaded at aligned to a 2M boundary. %rbp contains the |
222 | * decompressed kernel start address. | |
223 | * | |
224 | * If it is a relocatable kernel then decompress and run the kernel | |
225 | * from load address aligned to 2MB addr, otherwise decompress and | |
226 | * run the kernel from CONFIG_PHYSICAL_START | |
227 | */ | |
228 | ||
229 | /* Start with the delta to where the kernel will run at. */ | |
230 | #ifdef CONFIG_RELOCATABLE | |
231 | leaq startup_32(%rip) /* - $startup_32 */, %rbp | |
31422c51 AK |
232 | addq $(PMD_PAGE_SIZE - 1), %rbp |
233 | andq $PMD_PAGE_MASK, %rbp | |
1ab60e0f VG |
234 | movq %rbp, %rbx |
235 | #else | |
236 | movq $CONFIG_PHYSICAL_START, %rbp | |
237 | movq %rbp, %rbx | |
238 | #endif | |
239 | ||
240 | /* Replace the compressed data size with the uncompressed size */ | |
241 | movl input_len(%rip), %eax | |
242 | subq %rax, %rbx | |
243 | movl output_len(%rip), %eax | |
244 | addq %rax, %rbx | |
245 | /* Add 8 bytes for every 32K input block */ | |
246 | shrq $12, %rax | |
247 | addq %rax, %rbx | |
248 | /* Add 32K + 18 bytes of extra slack and align on a 4K boundary */ | |
249 | addq $(32768 + 18 + 4095), %rbx | |
250 | andq $~4095, %rbx | |
251 | ||
0a137736 PA |
252 | /* Set up the stack */ |
253 | leaq boot_stack_end(%rbx), %rsp | |
254 | ||
255 | /* Zero EFLAGS */ | |
256 | pushq $0 | |
257 | popfq | |
258 | ||
b40d68d5 PA |
259 | /* |
260 | * Copy the compressed kernel to the end of our buffer | |
1ab60e0f VG |
261 | * where decompression in place becomes safe. |
262 | */ | |
5b11f1ce PA |
263 | leaq _bss(%rip), %r8 |
264 | leaq _bss(%rbx), %r9 | |
265 | movq $_bss /* - $startup_32 */, %rcx | |
1ab60e0f VG |
266 | 1: subq $8, %r8 |
267 | subq $8, %r9 | |
268 | movq 0(%r8), %rax | |
269 | movq %rax, 0(%r9) | |
270 | subq $8, %rcx | |
271 | jnz 1b | |
272 | ||
273 | /* | |
274 | * Jump to the relocated address. | |
275 | */ | |
276 | leaq relocated(%rbx), %rax | |
277 | jmp *%rax | |
278 | ||
b40d68d5 | 279 | .text |
1ab60e0f VG |
280 | relocated: |
281 | ||
1da177e4 | 282 | /* |
0a137736 | 283 | * Clear BSS (stack is currently empty) |
1da177e4 | 284 | */ |
1ab60e0f | 285 | xorq %rax, %rax |
5b11f1ce PA |
286 | leaq _bss(%rbx), %rdi |
287 | leaq _ebss(%rbx), %rcx | |
1ab60e0f | 288 | subq %rdi, %rcx |
1da177e4 | 289 | cld |
b40d68d5 | 290 | rep stosb |
1ab60e0f | 291 | |
1da177e4 LT |
292 | /* |
293 | * Do the decompression, and jump to the new kernel.. | |
294 | */ | |
1ab60e0f VG |
295 | pushq %rsi # Save the real mode argument |
296 | movq %rsi, %rdi # real mode address | |
7c539764 | 297 | leaq boot_heap(%rip), %rsi # malloc area for uncompression |
1ab60e0f VG |
298 | leaq input_data(%rip), %rdx # input_data |
299 | movl input_len(%rip), %eax | |
300 | movq %rax, %rcx # input_len | |
301 | movq %rbp, %r8 # output | |
302 | call decompress_kernel | |
303 | popq %rsi | |
1da177e4 | 304 | |
1da177e4 | 305 | /* |
1ab60e0f | 306 | * Jump to the decompressed kernel. |
1da177e4 | 307 | */ |
1ab60e0f | 308 | jmp *%rbp |
1da177e4 | 309 | |
1ab60e0f VG |
310 | .data |
311 | gdt: | |
312 | .word gdt_end - gdt | |
313 | .long gdt | |
314 | .word 0 | |
315 | .quad 0x0000000000000000 /* NULL descriptor */ | |
316 | .quad 0x00af9a000000ffff /* __KERNEL_CS */ | |
317 | .quad 0x00cf92000000ffff /* __KERNEL_DS */ | |
08da5a2c ZA |
318 | .quad 0x0080890000000000 /* TS descriptor */ |
319 | .quad 0x0000000000000000 /* TS continued */ | |
1ab60e0f | 320 | gdt_end: |
7c539764 | 321 | |
b40d68d5 PA |
322 | /* |
323 | * Stack and heap for uncompression | |
324 | */ | |
325 | .bss | |
326 | .balign 4 | |
7c539764 AH |
327 | boot_heap: |
328 | .fill BOOT_HEAP_SIZE, 1, 0 | |
329 | boot_stack: | |
330 | .fill BOOT_STACK_SIZE, 1, 0 | |
331 | boot_stack_end: | |
5b11f1ce PA |
332 | |
333 | /* | |
334 | * Space for page tables (not in .bss so not zeroed) | |
335 | */ | |
336 | .section ".pgtable","a",@nobits | |
337 | .balign 4096 | |
338 | pgtable: | |
339 | .fill 6*4096, 1, 0 |