4 * Copyright (C) 1991, 1992, 1993 Linus Torvalds
8 * head.S contains the 32-bit startup code.
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]
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
22 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
27 #include <linux/init.h>
28 #include <linux/linkage.h>
29 #include <asm/segment.h>
32 #include <asm/processor-flags.h>
33 #include <asm/asm-offsets.h>
34 #include <asm/bootparam.h>
37 * Locally defined symbols should be marked hidden:
49 * 32bit entry is 0 and it is ABI so immutable!
50 * If we come here directly from a bootloader,
51 * kernel(text+data+bss+brk) ramdisk, zero_page, command line
52 * all need to be under the 4G limit.
56 * Test KEEP_SEGMENTS flag to see if the bootloader is asking
57 * us to not reload segments
59 testb $KEEP_SEGMENTS, BP_loadflags(%esi)
63 movl $(__BOOT_DS), %eax
70 * Calculate the delta between where we were compiled to run
71 * at and where we were actually loaded at. This can only be done
72 * with a short local call on x86. Nothing else will tell us what
73 * address we are running at. The reserved chunk of the real-mode
74 * data at 0x1e4 (defined as a scratch field) are used as the stack
75 * for this calculation. Only 4 bytes are needed.
77 leal (BP_scratch+4)(%esi), %esp
82 /* setup a stack and make sure cpu supports long mode. */
83 movl $boot_stack_end, %eax
92 * Compute the delta between where we were compiled to run at
93 * and where the code will actually run at.
95 * %ebp contains the address we are loaded at by the boot loader and %ebx
96 * contains the address where we should move the kernel image temporarily
97 * for safe in-place decompression.
100 #ifdef CONFIG_RELOCATABLE
102 movl BP_kernel_alignment(%esi), %eax
107 cmpl $LOAD_PHYSICAL_ADDR, %ebx
110 movl $LOAD_PHYSICAL_ADDR, %ebx
113 /* Target address to relocate to for decompression */
114 movl BP_init_size(%esi), %eax
119 * Prepare for entering 64 bit mode
122 /* Load new GDT with the 64bit segments using 32bit descriptor */
124 movl %eax, gdt+2(%ebp)
127 /* Enable PAE mode */
129 orl $X86_CR4_PAE, %eax
133 * Build early 4G boot pagetable
135 /* Initialize Page tables to 0 */
136 leal pgtable(%ebx), %edi
138 movl $(BOOT_INIT_PGT_SIZE/4), %ecx
142 leal pgtable + 0(%ebx), %edi
143 leal 0x1007 (%edi), %eax
147 leal pgtable + 0x1000(%ebx), %edi
148 leal 0x1007(%edi), %eax
150 1: movl %eax, 0x00(%edi)
151 addl $0x00001000, %eax
157 leal pgtable + 0x2000(%ebx), %edi
158 movl $0x00000183, %eax
160 1: movl %eax, 0(%edi)
161 addl $0x00200000, %eax
166 /* Enable the boot page tables */
167 leal pgtable(%ebx), %eax
170 /* Enable Long mode in EFER (Extended Feature Enable Register) */
173 btsl $_EFER_LME, %eax
176 /* After gdt is loaded */
179 movl $__BOOT_TSS, %eax
183 * Setup for the jump to 64bit mode
185 * When the jump is performend we will be in long mode but
186 * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1
187 * (and in turn EFER.LMA = 1). To jump into 64bit mode we use
188 * the new gdt/idt that has __KERNEL_CS with CS.L = 1.
189 * We place all of the values on our mini stack so lret can
190 * used to perform that far jump.
193 leal startup_64(%ebp), %eax
194 #ifdef CONFIG_EFI_MIXED
195 movl efi32_config(%ebp), %ebx
198 leal handover_entry(%ebp), %eax
203 /* Enter paged protected Mode, activating Long Mode */
204 movl $(X86_CR0_PG | X86_CR0_PE), %eax /* Enable Paging and Protected mode */
207 /* Jump from 32bit compatibility mode into 64bit mode. */
211 #ifdef CONFIG_EFI_MIXED
213 ENTRY(efi32_stub_entry)
214 add $0x4, %esp /* Discard return address */
219 leal (BP_scratch+4)(%esi), %esp
224 movl %ecx, efi32_config(%ebp)
225 movl %edx, efi32_config+8(%ebp)
226 sgdtl efi32_boot_gdt(%ebp)
228 leal efi32_config(%ebp), %eax
229 movl %eax, efi_config(%ebp)
233 btrl $X86_CR0_PG_BIT, %eax
237 ENDPROC(efi32_stub_entry)
244 * 64bit entry is 0x200 and it is ABI so immutable!
245 * We come here either from startup_32 or directly from a
247 * If we come here from a bootloader, kernel(text+data+bss+brk),
248 * ramdisk, zero_page, command line could be above 4G.
249 * We depend on an identity mapped page table being provided
250 * that maps our entire kernel(text+data+bss+brk), zero page
253 #ifdef CONFIG_EFI_STUB
255 * The entry point for the PE/COFF executable is efi_pe_entry, so
256 * only legacy boot loaders will execute this jmp.
261 movq %rcx, efi64_config(%rip) /* Handle */
262 movq %rdx, efi64_config+8(%rip) /* EFI System table pointer */
264 leaq efi64_config(%rip), %rax
265 movq %rax, efi_config(%rip)
272 * Relocate efi_config->call().
274 addq %rbp, efi64_config+32(%rip)
277 call make_boot_params
281 leaq startup_32(%rip), %rax
282 movl %eax, BP_code32_start(%rsi)
283 jmp 2f /* Skip the relocation */
291 * Relocate efi_config->call().
293 movq efi_config(%rip), %rax
296 movq efi_config(%rip), %rdi
302 /* EFI init failed, so hang. */
306 movl BP_code32_start(%esi), %eax
307 leaq preferred_addr(%rax), %rax
313 /* Setup data segments. */
322 * Compute the decompressed kernel start address. It is where
323 * we were loaded at aligned to a 2M boundary. %rbp contains the
324 * decompressed kernel start address.
326 * If it is a relocatable kernel then decompress and run the kernel
327 * from load address aligned to 2MB addr, otherwise decompress and
328 * run the kernel from LOAD_PHYSICAL_ADDR
330 * We cannot rely on the calculation done in 32-bit mode, since we
331 * may have been invoked via the 64-bit entry point.
334 /* Start with the delta to where the kernel will run at. */
335 #ifdef CONFIG_RELOCATABLE
336 leaq startup_32(%rip) /* - $startup_32 */, %rbp
337 movl BP_kernel_alignment(%rsi), %eax
342 cmpq $LOAD_PHYSICAL_ADDR, %rbp
345 movq $LOAD_PHYSICAL_ADDR, %rbp
348 /* Target address to relocate to for decompression */
349 movl BP_init_size(%rsi), %ebx
353 /* Set up the stack */
354 leaq boot_stack_end(%rbx), %rsp
361 * Copy the compressed kernel to the end of our buffer
362 * where decompression in place becomes safe.
365 leaq (_bss-8)(%rip), %rsi
366 leaq (_bss-8)(%rbx), %rdi
367 movq $_bss /* - $startup_32 */, %rcx
375 * Jump to the relocated address.
377 leaq relocated(%rbx), %rax
380 #ifdef CONFIG_EFI_STUB
382 ENTRY(efi64_stub_entry)
383 movq %rdi, efi64_config(%rip) /* Handle */
384 movq %rsi, efi64_config+8(%rip) /* EFI System table pointer */
386 leaq efi64_config(%rip), %rax
387 movq %rax, efi_config(%rip)
391 ENDPROC(efi64_stub_entry)
398 * Clear BSS (stack is currently empty)
401 leaq _bss(%rip), %rdi
402 leaq _ebss(%rip), %rcx
410 leaq _got(%rip), %rdx
411 leaq _egot(%rip), %rcx
421 * Do the extraction, and jump to the new kernel..
423 pushq %rsi /* Save the real mode argument */
424 movq %rsi, %rdi /* real mode address */
425 leaq boot_heap(%rip), %rsi /* malloc area for uncompression */
426 leaq input_data(%rip), %rdx /* input_data */
427 movl $z_input_len, %ecx /* input_len */
428 movq %rbp, %r8 /* output target address */
429 movq $z_output_len, %r9 /* decompressed length, end of relocs */
430 call extract_kernel /* returns kernel location in %rax */
434 * Jump to the decompressed kernel.
440 /* This isn't an x86-64 CPU so hang */
445 #include "../../kernel/verify_cpu.S"
452 .quad 0x0000000000000000 /* NULL descriptor */
453 .quad 0x00af9a000000ffff /* __KERNEL_CS */
454 .quad 0x00cf92000000ffff /* __KERNEL_DS */
455 .quad 0x0080890000000000 /* TS descriptor */
456 .quad 0x0000000000000000 /* TS continued */
459 #ifdef CONFIG_EFI_STUB
463 #ifdef CONFIG_EFI_MIXED
476 #endif /* CONFIG_EFI_STUB */
479 * Stack and heap for uncompression
484 .fill BOOT_HEAP_SIZE, 1, 0
486 .fill BOOT_STACK_SIZE, 1, 0
490 * Space for page tables (not in .bss so not zeroed)
492 .section ".pgtable","a",@nobits
495 .fill BOOT_PGT_SIZE, 1, 0