2 * linux/arch/x86_64/kernel/head.S -- start in 32bit and switch to 64bit
4 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
5 * Copyright (C) 2000 Pavel Machek <pavel@suse.cz>
6 * Copyright (C) 2000 Karsten Keil <kkeil@suse.de>
7 * Copyright (C) 2001,2002 Andi Kleen <ak@suse.de>
11 #include <linux/linkage.h>
12 #include <linux/threads.h>
13 #include <linux/init.h>
15 #include <asm/segment.h>
16 #include <asm/pgtable.h>
19 #include <asm/cache.h>
21 /* we are not able to switch in one step to the final KERNEL ADRESS SPACE
22 * because we need identity-mapped pages on setup so define __START_KERNEL to
23 * 0x100000 for this stage
28 .section .bootstrap.text
31 /* %bx: 1 if coming from smp trampoline on secondary cpu */
35 * At this point the CPU runs in 32bit protected mode (CS.D = 1) with
36 * paging disabled and the point of this file is to switch to 64bit
37 * long mode with a kernel mapping for kerneland to jump into the
38 * kernel virtual addresses.
39 * There is no stack until we set one up.
42 /* Initialize the %ds segment register */
43 movl $__KERNEL_DS,%eax
46 /* Load new GDT with the 64bit segments using 32bit descriptor */
47 lgdt pGDT32 - __START_KERNEL_map
49 /* If the CPU doesn't support CPUID this will double fault.
50 * Unfortunately it is hard to check for CPUID without a stack.
53 /* Check if extended functions are implemented */
54 movl $0x80000000, %eax
56 cmpl $0x80000000, %eax
58 /* Check if long mode is implemented */
65 * Prepare for entering 64bits mode
73 /* Setup early boot stage 4 level pagetables */
74 movl $(boot_level4_pgt - __START_KERNEL_map), %eax
77 /* Setup EFER (Extended Feature Enable Register) */
81 /* Enable Long Mode */
84 /* Make changes effective */
88 btsl $31, %eax /* Enable paging and in turn activate Long Mode */
89 btsl $0, %eax /* Enable protected mode */
90 /* Make changes effective */
93 * At this point we're in long mode but in 32bit compatibility mode
94 * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn
95 * EFER.LMA = 1). Now we want to jump in 64bit mode, to do that we use
96 * the new gdt/idt that has __KERNEL_CS with CS.L = 1.
98 ljmp $__KERNEL_CS, $(startup_64 - __START_KERNEL_map)
104 ENTRY(secondary_startup_64)
105 /* We come here either from startup_32
106 * or directly from a 64bit bootloader.
107 * Since we may have come directly from a bootloader we
108 * reload the page tables here.
111 /* Enable PAE mode and PGE */
117 /* Setup early boot stage 4 level pagetables. */
118 movq $(boot_level4_pgt - __START_KERNEL_map), %rax
121 /* Check if nx is implemented */
122 movl $0x80000001, %eax
126 /* Setup EFER (Extended Feature Enable Register) */
130 /* Enable System Call */
131 btsl $_EFER_SCE, %eax
133 /* No Execute supported? */
138 /* Make changes effective */
142 #define CR0_PM 1 /* protected mode */
143 #define CR0_MP (1<<1)
144 #define CR0_ET (1<<4)
145 #define CR0_NE (1<<5)
146 #define CR0_WP (1<<16)
147 #define CR0_AM (1<<18)
148 #define CR0_PAGING (1<<31)
149 movl $CR0_PM|CR0_MP|CR0_ET|CR0_NE|CR0_WP|CR0_AM|CR0_PAGING,%eax
150 /* Make changes effective */
153 /* Setup a boot time stack */
154 movq init_rsp(%rip),%rsp
156 /* zero EFLAGS after setting rsp */
161 * We must switch to a new descriptor in kernel space for the GDT
162 * because soon the kernel won't have access anymore to the userspace
163 * addresses where we're currently running on. We have to do that here
164 * because in 32bit we couldn't load a 64bit linear address.
168 /* set up data segments. actually 0 would do too */
169 movl $__KERNEL_DS,%eax
175 * We don't really need to load %fs or %gs, but load them anyway
176 * to kill any stale realmode selectors. This allows execution
183 * Setup up a dummy PDA. this is just for some early bootup code
184 * that does in_interrupt()
186 movl $MSR_GS_BASE,%ecx
187 movq $empty_zero_page,%rax
192 /* esi is pointer to real mode structure with interesting info.
196 /* Finally jump to run C code and to be on real kernel address
197 * Since we are running on identity-mapped space we have to jump
198 * to the full 64bit address, this is only possible as indirect
199 * jump. In addition we need to ensure %cs is set so we make this
202 movq initial_code(%rip),%rax
203 pushq $0 # fake return address to stop unwinder
204 pushq $__KERNEL_CS # set correct cs
205 pushq %rax # target address in negative space
208 /* SMP bootup changes these two */
212 .quad x86_64_start_kernel
215 .quad init_thread_union+THREAD_SIZE-8
217 ENTRY(early_idt_handler)
218 cmpl $2,early_recursion_flag(%rip)
220 incl early_recursion_flag(%rip)
222 movq 8(%rsp),%rsi # get rip
225 leaq early_idt_msg(%rip),%rdi
227 cmpl $2,early_recursion_flag(%rip)
230 #ifdef CONFIG_KALLSYMS
231 leaq early_idt_ripmsg(%rip),%rdi
232 movq 8(%rsp),%rsi # get rip again
237 early_recursion_flag:
241 .asciz "PANIC: early exception rip %lx error %lx cr2 %lx\n"
247 /* This isn't an x86-64 CPU so hang */
254 .word gdt_end-cpu_gdt_table-1
255 .long cpu_gdt_table-__START_KERNEL_map
259 .long startup_64-__START_KERNEL_map
265 #define NEXT_PAGE(name) \
269 /* Automate the creation of 1 to 1 mapping pmd entries */
270 #define PMDS(START, PERM, COUNT) \
273 .quad (START) + (i << 21) + (PERM) ; \
277 NEXT_PAGE(init_level4_pgt)
278 /* This gets initialized in x86_64_start_kernel */
281 NEXT_PAGE(level3_ident_pgt)
282 .quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
285 NEXT_PAGE(level3_kernel_pgt)
287 /* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
288 .quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
291 NEXT_PAGE(level2_ident_pgt)
292 /* Since I easily can, map the first 1G.
293 * Don't set NX because code runs from these pages.
295 PMDS(0x0000000000000000, __PAGE_KERNEL_LARGE_EXEC, PTRS_PER_PMD)
297 NEXT_PAGE(level2_kernel_pgt)
298 /* 40MB kernel mapping. The kernel code cannot be bigger than that.
299 When you change this change KERNEL_TEXT_SIZE in page.h too. */
300 /* (2^48-(2*1024*1024*1024)-((2^39)*511)-((2^30)*510)) = 0 */
301 PMDS(0x0000000000000000, __PAGE_KERNEL_LARGE_EXEC|_PAGE_GLOBAL,
302 KERNEL_TEXT_SIZE/PMD_SIZE)
303 /* Module mapping starts here */
304 .fill (PTRS_PER_PMD - (KERNEL_TEXT_SIZE/PMD_SIZE)),8,0
311 #ifdef CONFIG_ACPI_SLEEP
313 ENTRY(wakeup_level4_pgt)
314 .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
316 /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
317 .quad level3_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
320 #ifndef CONFIG_HOTPLUG_CPU
324 * This default setting generates an ident mapping at address 0x100000
325 * and a mapping for the kernel that precisely maps virtual address
326 * 0xffffffff80000000 to physical address 0x000000. (always using
327 * 2Mbyte large pages provided by PAE mode)
330 ENTRY(boot_level4_pgt)
331 .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
333 .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
335 /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
336 .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
343 .word gdt_end-cpu_gdt_table-1
353 /* We need valid kernel segments for data and code in long mode too
354 * IRET will check the segment types kkeil 2000/10/28
355 * Also sysret mandates a special GDT layout
358 .section .data.page_aligned, "aw"
361 /* The TLS descriptors are currently at a different place compared to i386.
362 Hopefully nobody expects them at a fixed place (Wine?) */
365 .quad 0x0000000000000000 /* NULL descriptor */
366 .quad 0x00cf9b000000ffff /* __KERNEL32_CS */
367 .quad 0x00af9b000000ffff /* __KERNEL_CS */
368 .quad 0x00cf93000000ffff /* __KERNEL_DS */
369 .quad 0x00cffb000000ffff /* __USER32_CS */
370 .quad 0x00cff3000000ffff /* __USER_DS, __USER32_DS */
371 .quad 0x00affb000000ffff /* __USER_CS */
372 .quad 0x0 /* unused */
375 .quad 0,0,0 /* three TLS descriptors */
376 .quad 0x0000f40000000000 /* node/CPU stored in limit */
378 /* asm/segment.h:GDT_ENTRIES must match this */
379 /* This should be a multiple of the cache line size */
380 /* GDTs of other CPUs are now dynamically allocated */
382 /* zero the remaining page */
383 .fill PAGE_SIZE / 8 - GDT_ENTRIES,8,0
385 .section .bss, "aw", @nobits
386 .align L1_CACHE_BYTES
390 .section .bss.page_aligned, "aw", @nobits
392 ENTRY(empty_zero_page)