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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
1da177e4 LT |
2 | /* |
3 | * linux/boot/head.S | |
4 | * | |
5 | * Copyright (C) 1991, 1992, 1993 Linus Torvalds | |
6 | */ | |
7 | ||
8 | /* | |
9 | * head.S contains the 32-bit startup code. | |
10 | * | |
11 | * NOTE!!! Startup happens at absolute address 0x00001000, which is also where | |
12 | * the page directory will exist. The startup code will be overwritten by | |
13 | * the page directory. [According to comments etc elsewhere on a compressed | |
14 | * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC] | |
15 | * | |
5f64ec64 | 16 | * Page 0 is deliberately kept safe, since System Management Mode code in |
1da177e4 | 17 | * laptops may need to access the BIOS data stored there. This is also |
5f64ec64 | 18 | * useful for future device drivers that either access the BIOS via VM86 |
1da177e4 LT |
19 | * mode. |
20 | */ | |
21 | ||
22 | /* | |
23 | * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 | |
24 | */ | |
5f64ec64 | 25 | .text |
1da177e4 | 26 | |
1dc818c1 | 27 | #include <linux/init.h> |
1da177e4 LT |
28 | #include <linux/linkage.h> |
29 | #include <asm/segment.h> | |
0341c14d | 30 | #include <asm/page_types.h> |
e69f202d | 31 | #include <asm/boot.h> |
a24e7851 | 32 | #include <asm/asm-offsets.h> |
fb148d83 | 33 | #include <asm/bootparam.h> |
1da177e4 | 34 | |
6d92bc9d L |
35 | /* |
36 | * The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X | |
37 | * relocation to get the symbol address in PIC. When the compressed x86 | |
38 | * kernel isn't built as PIC, the linker optimizes R_386_GOT32X | |
39 | * relocations to their fixed symbol addresses. However, when the | |
40 | * compressed x86 kernel is loaded at a different address, it leads | |
41 | * to the following load failure: | |
42 | * | |
43 | * Failed to allocate space for phdrs | |
44 | * | |
45 | * during the decompression stage. | |
46 | * | |
47 | * If the compressed x86 kernel is relocatable at run-time, it should be | |
48 | * compiled with -fPIE, instead of -fPIC, if possible and should be built as | |
49 | * Position Independent Executable (PIE) so that linker won't optimize | |
50 | * R_386_GOT32X relocation to its fixed symbol address. Older | |
51 | * linkers generate R_386_32 relocations against locally defined symbols, | |
52 | * _bss, _ebss, _got and _egot, in PIE. It isn't wrong, just less | |
53 | * optimal than R_386_RELATIVE. But the x86 kernel fails to properly handle | |
54 | * R_386_32 relocations when relocating the kernel. To generate | |
55 | * R_386_RELATIVE relocations, we mark _bss, _ebss, _got and _egot as | |
56 | * hidden: | |
57 | */ | |
58 | .hidden _bss | |
59 | .hidden _ebss | |
60 | .hidden _got | |
61 | .hidden _egot | |
62 | ||
1dc818c1 | 63 | __HEAD |
cb425afd | 64 | ENTRY(startup_32) |
bd53147d | 65 | cld |
5f64ec64 PA |
66 | /* |
67 | * Test KEEP_SEGMENTS flag to see if the bootloader is asking | |
68 | * us to not reload segments | |
69 | */ | |
fb148d83 | 70 | testb $KEEP_SEGMENTS, BP_loadflags(%esi) |
5f64ec64 | 71 | jnz 1f |
a24e7851 | 72 | |
bd53147d | 73 | cli |
5f64ec64 PA |
74 | movl $__BOOT_DS, %eax |
75 | movl %eax, %ds | |
76 | movl %eax, %es | |
77 | movl %eax, %fs | |
78 | movl %eax, %gs | |
79 | movl %eax, %ss | |
bd53147d | 80 | 1: |
a24e7851 | 81 | |
5f64ec64 PA |
82 | /* |
83 | * Calculate the delta between where we were compiled to run | |
968de4f0 EB |
84 | * at and where we were actually loaded at. This can only be done |
85 | * with a short local call on x86. Nothing else will tell us what | |
86 | * address we are running at. The reserved chunk of the real-mode | |
85414b69 PA |
87 | * data at 0x1e4 (defined as a scratch field) are used as the stack |
88 | * for this calculation. Only 4 bytes are needed. | |
968de4f0 | 89 | */ |
5f64ec64 PA |
90 | leal (BP_scratch+4)(%esi), %esp |
91 | call 1f | |
92 | 1: popl %ebp | |
93 | subl $1b, %ebp | |
968de4f0 | 94 | |
5f64ec64 PA |
95 | /* |
96 | * %ebp contains the address we are loaded at by the boot loader and %ebx | |
e69f202d VG |
97 | * contains the address where we should move the kernel image temporarily |
98 | * for safe in-place decompression. | |
968de4f0 | 99 | */ |
e69f202d | 100 | |
968de4f0 | 101 | #ifdef CONFIG_RELOCATABLE |
5f64ec64 | 102 | movl %ebp, %ebx |
37ba7ab5 PA |
103 | movl BP_kernel_alignment(%esi), %eax |
104 | decl %eax | |
105 | addl %eax, %ebx | |
106 | notl %eax | |
107 | andl %eax, %ebx | |
8ab3820f KC |
108 | cmpl $LOAD_PHYSICAL_ADDR, %ebx |
109 | jge 1f | |
968de4f0 | 110 | #endif |
8ab3820f KC |
111 | movl $LOAD_PHYSICAL_ADDR, %ebx |
112 | 1: | |
968de4f0 | 113 | |
02a884c0 | 114 | /* Target address to relocate to for decompression */ |
974f221c YL |
115 | movl BP_init_size(%esi), %eax |
116 | subl $_end, %eax | |
117 | addl %eax, %ebx | |
968de4f0 | 118 | |
0a137736 PA |
119 | /* Set up the stack */ |
120 | leal boot_stack_end(%ebx), %esp | |
121 | ||
97541912 PA |
122 | /* Zero EFLAGS */ |
123 | pushl $0 | |
124 | popfl | |
125 | ||
5f64ec64 PA |
126 | /* |
127 | * Copy the compressed kernel to the end of our buffer | |
968de4f0 EB |
128 | * where decompression in place becomes safe. |
129 | */ | |
5f64ec64 | 130 | pushl %esi |
36d3793c PA |
131 | leal (_bss-4)(%ebp), %esi |
132 | leal (_bss-4)(%ebx), %edi | |
5b11f1ce | 133 | movl $(_bss - startup_32), %ecx |
36d3793c | 134 | shrl $2, %ecx |
968de4f0 | 135 | std |
36d3793c | 136 | rep movsl |
968de4f0 | 137 | cld |
5f64ec64 | 138 | popl %esi |
968de4f0 | 139 | |
1da177e4 | 140 | /* |
968de4f0 | 141 | * Jump to the relocated address. |
1da177e4 | 142 | */ |
5f64ec64 PA |
143 | leal relocated(%ebx), %eax |
144 | jmp *%eax | |
cb425afd CG |
145 | ENDPROC(startup_32) |
146 | ||
f4dee0bb JS |
147 | #ifdef CONFIG_EFI_STUB |
148 | /* | |
149 | * We don't need the return address, so set up the stack so efi_main() can find | |
150 | * its arguments. | |
151 | */ | |
152 | ENTRY(efi_pe_entry) | |
153 | add $0x4, %esp | |
154 | ||
155 | call 1f | |
156 | 1: popl %esi | |
157 | subl $1b, %esi | |
158 | ||
159 | popl %ecx | |
160 | movl %ecx, efi32_config(%esi) /* Handle */ | |
161 | popl %ecx | |
162 | movl %ecx, efi32_config+8(%esi) /* EFI System table pointer */ | |
163 | ||
164 | /* Relocate efi_config->call() */ | |
165 | leal efi32_config(%esi), %eax | |
166 | add %esi, 40(%eax) | |
167 | pushl %eax | |
168 | ||
169 | call make_boot_params | |
170 | cmpl $0, %eax | |
171 | je fail | |
172 | movl %esi, BP_code32_start(%eax) | |
173 | popl %ecx | |
174 | pushl %eax | |
175 | pushl %ecx | |
176 | jmp 2f /* Skip efi_config initialization */ | |
177 | ENDPROC(efi_pe_entry) | |
178 | ||
179 | ENTRY(efi32_stub_entry) | |
180 | add $0x4, %esp | |
181 | popl %ecx | |
182 | popl %edx | |
183 | ||
184 | call 1f | |
185 | 1: popl %esi | |
186 | subl $1b, %esi | |
187 | ||
188 | movl %ecx, efi32_config(%esi) /* Handle */ | |
189 | movl %edx, efi32_config+8(%esi) /* EFI System table pointer */ | |
190 | ||
191 | /* Relocate efi_config->call() */ | |
192 | leal efi32_config(%esi), %eax | |
193 | add %esi, 40(%eax) | |
194 | pushl %eax | |
195 | 2: | |
196 | call efi_main | |
197 | cmpl $0, %eax | |
198 | movl %eax, %esi | |
199 | jne 2f | |
200 | fail: | |
201 | /* EFI init failed, so hang. */ | |
202 | hlt | |
203 | jmp fail | |
204 | 2: | |
205 | movl BP_code32_start(%esi), %eax | |
206 | leal startup_32(%eax), %eax | |
207 | jmp *%eax | |
208 | ENDPROC(efi32_stub_entry) | |
209 | #endif | |
210 | ||
5f64ec64 | 211 | .text |
968de4f0 EB |
212 | relocated: |
213 | ||
1da177e4 | 214 | /* |
0a137736 | 215 | * Clear BSS (stack is currently empty) |
1da177e4 | 216 | */ |
5f64ec64 | 217 | xorl %eax, %eax |
5b11f1ce | 218 | leal _bss(%ebx), %edi |
5f64ec64 PA |
219 | leal _ebss(%ebx), %ecx |
220 | subl %edi, %ecx | |
36d3793c PA |
221 | shrl $2, %ecx |
222 | rep stosl | |
968de4f0 | 223 | |
f3670394 LT |
224 | /* |
225 | * Adjust our own GOT | |
226 | */ | |
227 | leal _got(%ebx), %edx | |
228 | leal _egot(%ebx), %ecx | |
229 | 1: | |
230 | cmpl %ecx, %edx | |
231 | jae 2f | |
232 | addl %ebx, (%edx) | |
233 | addl $4, %edx | |
234 | jmp 1b | |
235 | 2: | |
236 | ||
1da177e4 | 237 | /* |
c0402881 | 238 | * Do the extraction, and jump to the new kernel.. |
1da177e4 | 239 | */ |
c0402881 | 240 | /* push arguments for extract_kernel: */ |
e6023367 | 241 | pushl $z_output_len /* decompressed length, end of relocs */ |
974f221c YL |
242 | |
243 | movl BP_init_size(%esi), %eax | |
244 | subl $_end, %eax | |
245 | movl %ebx, %ebp | |
246 | subl %eax, %ebp | |
5f64ec64 | 247 | pushl %ebp /* output address */ |
974f221c | 248 | |
02a884c0 | 249 | pushl $z_input_len /* input_len */ |
5f64ec64 PA |
250 | leal input_data(%ebx), %eax |
251 | pushl %eax /* input_data */ | |
252 | leal boot_heap(%ebx), %eax | |
253 | pushl %eax /* heap area */ | |
254 | pushl %esi /* real mode pointer */ | |
c0402881 | 255 | call extract_kernel /* returns kernel location in %eax */ |
4d2d5424 | 256 | addl $24, %esp |
1da177e4 LT |
257 | |
258 | /* | |
c0402881 | 259 | * Jump to the extracted kernel. |
1da177e4 | 260 | */ |
5f64ec64 | 261 | xorl %ebx, %ebx |
8ab3820f | 262 | jmp *%eax |
968de4f0 | 263 | |
9cb0e394 | 264 | #ifdef CONFIG_EFI_STUB |
f3670394 | 265 | .data |
54b52d87 | 266 | efi32_config: |
a2cd2f3f | 267 | .fill 5,8,0 |
54b52d87 MF |
268 | .long efi_call_phys |
269 | .long 0 | |
270 | .byte 0 | |
3db4cafd | 271 | #endif |
54b52d87 | 272 | |
5f64ec64 PA |
273 | /* |
274 | * Stack and heap for uncompression | |
275 | */ | |
276 | .bss | |
277 | .balign 4 | |
7c539764 AH |
278 | boot_heap: |
279 | .fill BOOT_HEAP_SIZE, 1, 0 | |
280 | boot_stack: | |
281 | .fill BOOT_STACK_SIZE, 1, 0 | |
282 | boot_stack_end: |