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 | 89 | #else |
40b387a8 | 90 | movl $LOAD_PHYSICAL_ADDR, %ebx |
1ab60e0f VG |
91 | #endif |
92 | ||
02a884c0 PA |
93 | /* Target address to relocate to for decompression */ |
94 | addl $z_extract_offset, %ebx | |
1da177e4 LT |
95 | |
96 | /* | |
1ab60e0f | 97 | * Prepare for entering 64 bit mode |
1da177e4 | 98 | */ |
1ab60e0f VG |
99 | |
100 | /* Load new GDT with the 64bit segments using 32bit descriptor */ | |
101 | leal gdt(%ebp), %eax | |
102 | movl %eax, gdt+2(%ebp) | |
103 | lgdt gdt(%ebp) | |
104 | ||
105 | /* Enable PAE mode */ | |
106 | xorl %eax, %eax | |
e83e31f4 | 107 | orl $(X86_CR4_PAE), %eax |
1ab60e0f VG |
108 | movl %eax, %cr4 |
109 | ||
110 | /* | |
111 | * Build early 4G boot pagetable | |
112 | */ | |
b40d68d5 | 113 | /* Initialize Page tables to 0 */ |
1ab60e0f VG |
114 | leal pgtable(%ebx), %edi |
115 | xorl %eax, %eax | |
116 | movl $((4096*6)/4), %ecx | |
117 | rep stosl | |
118 | ||
119 | /* Build Level 4 */ | |
120 | leal pgtable + 0(%ebx), %edi | |
121 | leal 0x1007 (%edi), %eax | |
122 | movl %eax, 0(%edi) | |
123 | ||
124 | /* Build Level 3 */ | |
125 | leal pgtable + 0x1000(%ebx), %edi | |
126 | leal 0x1007(%edi), %eax | |
127 | movl $4, %ecx | |
128 | 1: movl %eax, 0x00(%edi) | |
129 | addl $0x00001000, %eax | |
130 | addl $8, %edi | |
131 | decl %ecx | |
132 | jnz 1b | |
133 | ||
134 | /* Build Level 2 */ | |
135 | leal pgtable + 0x2000(%ebx), %edi | |
136 | movl $0x00000183, %eax | |
137 | movl $2048, %ecx | |
138 | 1: movl %eax, 0(%edi) | |
139 | addl $0x00200000, %eax | |
140 | addl $8, %edi | |
141 | decl %ecx | |
142 | jnz 1b | |
143 | ||
144 | /* Enable the boot page tables */ | |
145 | leal pgtable(%ebx), %eax | |
146 | movl %eax, %cr3 | |
147 | ||
148 | /* Enable Long mode in EFER (Extended Feature Enable Register) */ | |
149 | movl $MSR_EFER, %ecx | |
150 | rdmsr | |
151 | btsl $_EFER_LME, %eax | |
152 | wrmsr | |
153 | ||
b40d68d5 PA |
154 | /* |
155 | * Setup for the jump to 64bit mode | |
1ab60e0f VG |
156 | * |
157 | * When the jump is performend we will be in long mode but | |
158 | * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1 | |
159 | * (and in turn EFER.LMA = 1). To jump into 64bit mode we use | |
160 | * the new gdt/idt that has __KERNEL_CS with CS.L = 1. | |
161 | * We place all of the values on our mini stack so lret can | |
162 | * used to perform that far jump. | |
163 | */ | |
164 | pushl $__KERNEL_CS | |
165 | leal startup_64(%ebp), %eax | |
166 | pushl %eax | |
167 | ||
168 | /* Enter paged protected Mode, activating Long Mode */ | |
e83e31f4 | 169 | movl $(X86_CR0_PG | X86_CR0_PE), %eax /* Enable Paging and Protected mode */ |
1ab60e0f VG |
170 | movl %eax, %cr0 |
171 | ||
172 | /* Jump from 32bit compatibility mode into 64bit mode. */ | |
173 | lret | |
2d4eeecb | 174 | ENDPROC(startup_32) |
1ab60e0f | 175 | |
a4831e08 VG |
176 | no_longmode: |
177 | /* This isn't an x86-64 CPU so hang */ | |
178 | 1: | |
179 | hlt | |
180 | jmp 1b | |
181 | ||
250c2277 | 182 | #include "../../kernel/verify_cpu_64.S" |
a4831e08 | 183 | |
b40d68d5 PA |
184 | /* |
185 | * Be careful here startup_64 needs to be at a predictable | |
1ab60e0f VG |
186 | * address so I can export it in an ELF header. Bootloaders |
187 | * should look at the ELF header to find this address, as | |
188 | * it may change in the future. | |
189 | */ | |
190 | .code64 | |
a4831e08 | 191 | .org 0x200 |
1ab60e0f | 192 | ENTRY(startup_64) |
b40d68d5 PA |
193 | /* |
194 | * We come here either from startup_32 or directly from a | |
1ab60e0f VG |
195 | * 64bit bootloader. If we come here from a bootloader we depend on |
196 | * an identity mapped page table being provied that maps our | |
197 | * entire text+data+bss and hopefully all of memory. | |
198 | */ | |
199 | ||
200 | /* Setup data segments. */ | |
201 | xorl %eax, %eax | |
202 | movl %eax, %ds | |
203 | movl %eax, %es | |
204 | movl %eax, %ss | |
08da5a2c ZA |
205 | movl %eax, %fs |
206 | movl %eax, %gs | |
207 | lldt %ax | |
208 | movl $0x20, %eax | |
209 | ltr %ax | |
1ab60e0f | 210 | |
b40d68d5 PA |
211 | /* |
212 | * Compute the decompressed kernel start address. It is where | |
1ab60e0f VG |
213 | * we were loaded at aligned to a 2M boundary. %rbp contains the |
214 | * decompressed kernel start address. | |
215 | * | |
216 | * If it is a relocatable kernel then decompress and run the kernel | |
217 | * from load address aligned to 2MB addr, otherwise decompress and | |
40b387a8 | 218 | * run the kernel from LOAD_PHYSICAL_ADDR |
02a884c0 PA |
219 | * |
220 | * We cannot rely on the calculation done in 32-bit mode, since we | |
221 | * may have been invoked via the 64-bit entry point. | |
1ab60e0f VG |
222 | */ |
223 | ||
224 | /* Start with the delta to where the kernel will run at. */ | |
225 | #ifdef CONFIG_RELOCATABLE | |
226 | leaq startup_32(%rip) /* - $startup_32 */, %rbp | |
31422c51 AK |
227 | addq $(PMD_PAGE_SIZE - 1), %rbp |
228 | andq $PMD_PAGE_MASK, %rbp | |
1ab60e0f VG |
229 | movq %rbp, %rbx |
230 | #else | |
40b387a8 | 231 | movq $LOAD_PHYSICAL_ADDR, %rbp |
1ab60e0f VG |
232 | movq %rbp, %rbx |
233 | #endif | |
234 | ||
02a884c0 PA |
235 | /* Target address to relocate to for decompression */ |
236 | leaq z_extract_offset(%rbp), %rbx | |
1ab60e0f | 237 | |
0a137736 PA |
238 | /* Set up the stack */ |
239 | leaq boot_stack_end(%rbx), %rsp | |
240 | ||
241 | /* Zero EFLAGS */ | |
242 | pushq $0 | |
243 | popfq | |
244 | ||
b40d68d5 PA |
245 | /* |
246 | * Copy the compressed kernel to the end of our buffer | |
1ab60e0f VG |
247 | * where decompression in place becomes safe. |
248 | */ | |
36d3793c PA |
249 | pushq %rsi |
250 | leaq (_bss-8)(%rip), %rsi | |
251 | leaq (_bss-8)(%rbx), %rdi | |
5b11f1ce | 252 | movq $_bss /* - $startup_32 */, %rcx |
36d3793c PA |
253 | shrq $3, %rcx |
254 | std | |
255 | rep movsq | |
256 | cld | |
257 | popq %rsi | |
1ab60e0f VG |
258 | |
259 | /* | |
260 | * Jump to the relocated address. | |
261 | */ | |
262 | leaq relocated(%rbx), %rax | |
263 | jmp *%rax | |
264 | ||
b40d68d5 | 265 | .text |
1ab60e0f VG |
266 | relocated: |
267 | ||
1da177e4 | 268 | /* |
0a137736 | 269 | * Clear BSS (stack is currently empty) |
1da177e4 | 270 | */ |
36d3793c PA |
271 | xorl %eax, %eax |
272 | leaq _bss(%rip), %rdi | |
273 | leaq _ebss(%rip), %rcx | |
1ab60e0f | 274 | subq %rdi, %rcx |
36d3793c PA |
275 | shrq $3, %rcx |
276 | rep stosq | |
1ab60e0f | 277 | |
1da177e4 LT |
278 | /* |
279 | * Do the decompression, and jump to the new kernel.. | |
280 | */ | |
02a884c0 PA |
281 | pushq %rsi /* Save the real mode argument */ |
282 | movq %rsi, %rdi /* real mode address */ | |
283 | leaq boot_heap(%rip), %rsi /* malloc area for uncompression */ | |
284 | leaq input_data(%rip), %rdx /* input_data */ | |
285 | movl $z_input_len, %ecx /* input_len */ | |
286 | movq %rbp, %r8 /* output target address */ | |
1ab60e0f VG |
287 | call decompress_kernel |
288 | popq %rsi | |
1da177e4 | 289 | |
1da177e4 | 290 | /* |
1ab60e0f | 291 | * Jump to the decompressed kernel. |
1da177e4 | 292 | */ |
1ab60e0f | 293 | jmp *%rbp |
1da177e4 | 294 | |
1ab60e0f VG |
295 | .data |
296 | gdt: | |
297 | .word gdt_end - gdt | |
298 | .long gdt | |
299 | .word 0 | |
300 | .quad 0x0000000000000000 /* NULL descriptor */ | |
301 | .quad 0x00af9a000000ffff /* __KERNEL_CS */ | |
302 | .quad 0x00cf92000000ffff /* __KERNEL_DS */ | |
08da5a2c ZA |
303 | .quad 0x0080890000000000 /* TS descriptor */ |
304 | .quad 0x0000000000000000 /* TS continued */ | |
1ab60e0f | 305 | gdt_end: |
7c539764 | 306 | |
b40d68d5 PA |
307 | /* |
308 | * Stack and heap for uncompression | |
309 | */ | |
310 | .bss | |
311 | .balign 4 | |
7c539764 AH |
312 | boot_heap: |
313 | .fill BOOT_HEAP_SIZE, 1, 0 | |
314 | boot_stack: | |
315 | .fill BOOT_STACK_SIZE, 1, 0 | |
316 | boot_stack_end: | |
5b11f1ce PA |
317 | |
318 | /* | |
319 | * Space for page tables (not in .bss so not zeroed) | |
320 | */ | |
321 | .section ".pgtable","a",@nobits | |
322 | .balign 4096 | |
323 | pgtable: | |
324 | .fill 6*4096, 1, 0 |