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1/* SPDX-License-Identifier: GPL-2.0 */
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 *
16 * Page 0 is deliberately kept safe, since System Management Mode code in
17 * laptops may need to access the BIOS data stored there. This is also
18 * useful for future device drivers that either access the BIOS via VM86
19 * mode.
20 */
21
22/*
23 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
24 */
25 .text
26
27#include <linux/init.h>
28#include <linux/linkage.h>
29#include <asm/segment.h>
30#include <asm/page_types.h>
31#include <asm/boot.h>
32#include <asm/asm-offsets.h>
33#include <asm/bootparam.h>
34
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
63 __HEAD
64ENTRY(startup_32)
65 cld
66 /*
67 * Test KEEP_SEGMENTS flag to see if the bootloader is asking
68 * us to not reload segments
69 */
70 testb $KEEP_SEGMENTS, BP_loadflags(%esi)
71 jnz 1f
72
73 cli
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
801:
81
82/*
83 * Calculate the delta between where we were compiled to run
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
87 * data at 0x1e4 (defined as a scratch field) are used as the stack
88 * for this calculation. Only 4 bytes are needed.
89 */
90 leal (BP_scratch+4)(%esi), %esp
91 call 1f
921: popl %ebp
93 subl $1b, %ebp
94
95/*
96 * %ebp contains the address we are loaded at by the boot loader and %ebx
97 * contains the address where we should move the kernel image temporarily
98 * for safe in-place decompression.
99 */
100
101#ifdef CONFIG_RELOCATABLE
102 movl %ebp, %ebx
103 movl BP_kernel_alignment(%esi), %eax
104 decl %eax
105 addl %eax, %ebx
106 notl %eax
107 andl %eax, %ebx
108 cmpl $LOAD_PHYSICAL_ADDR, %ebx
109 jge 1f
110#endif
111 movl $LOAD_PHYSICAL_ADDR, %ebx
1121:
113
114 /* Target address to relocate to for decompression */
115 movl BP_init_size(%esi), %eax
116 subl $_end, %eax
117 addl %eax, %ebx
118
119 /* Set up the stack */
120 leal boot_stack_end(%ebx), %esp
121
122 /* Zero EFLAGS */
123 pushl $0
124 popfl
125
126/*
127 * Copy the compressed kernel to the end of our buffer
128 * where decompression in place becomes safe.
129 */
130 pushl %esi
131 leal (_bss-4)(%ebp), %esi
132 leal (_bss-4)(%ebx), %edi
133 movl $(_bss - startup_32), %ecx
134 shrl $2, %ecx
135 std
136 rep movsl
137 cld
138 popl %esi
139
140/*
141 * Jump to the relocated address.
142 */
143 leal relocated(%ebx), %eax
144 jmp *%eax
145ENDPROC(startup_32)
146
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 */
152ENTRY(efi_pe_entry)
153 add $0x4, %esp
154
155 call 1f
1561: 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 */
177ENDPROC(efi_pe_entry)
178
179ENTRY(efi32_stub_entry)
180 add $0x4, %esp
181 popl %ecx
182 popl %edx
183
184 call 1f
1851: 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
1952:
196 call efi_main
197 cmpl $0, %eax
198 movl %eax, %esi
199 jne 2f
200fail:
201 /* EFI init failed, so hang. */
202 hlt
203 jmp fail
2042:
205 movl BP_code32_start(%esi), %eax
206 leal startup_32(%eax), %eax
207 jmp *%eax
208ENDPROC(efi32_stub_entry)
209#endif
210
211 .text
212relocated:
213
214/*
215 * Clear BSS (stack is currently empty)
216 */
217 xorl %eax, %eax
218 leal _bss(%ebx), %edi
219 leal _ebss(%ebx), %ecx
220 subl %edi, %ecx
221 shrl $2, %ecx
222 rep stosl
223
224/*
225 * Adjust our own GOT
226 */
227 leal _got(%ebx), %edx
228 leal _egot(%ebx), %ecx
2291:
230 cmpl %ecx, %edx
231 jae 2f
232 addl %ebx, (%edx)
233 addl $4, %edx
234 jmp 1b
2352:
236
237/*
238 * Do the extraction, and jump to the new kernel..
239 */
240 /* push arguments for extract_kernel: */
241 pushl $z_output_len /* decompressed length, end of relocs */
242
243 movl BP_init_size(%esi), %eax
244 subl $_end, %eax
245 movl %ebx, %ebp
246 subl %eax, %ebp
247 pushl %ebp /* output address */
248
249 pushl $z_input_len /* input_len */
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 */
255 call extract_kernel /* returns kernel location in %eax */
256 addl $24, %esp
257
258/*
259 * Jump to the extracted kernel.
260 */
261 xorl %ebx, %ebx
262 jmp *%eax
263
264#ifdef CONFIG_EFI_STUB
265 .data
266efi32_config:
267 .fill 5,8,0
268 .long efi_call_phys
269 .long 0
270 .byte 0
271#endif
272
273/*
274 * Stack and heap for uncompression
275 */
276 .bss
277 .balign 4
278boot_heap:
279 .fill BOOT_HEAP_SIZE, 1, 0
280boot_stack:
281 .fill BOOT_STACK_SIZE, 1, 0
282boot_stack_end:
283

Warning: That file was not part of the compilation database. It may have many parsing errors.