xref: /openbmc/linux/arch/x86/kernel/head_64.S (revision 6d99a79c) 
1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 *  linux/arch/x86/kernel/head_64.S -- start in 32bit and switch to 64bit
4 *
5 *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
6 *  Copyright (C) 2000 Pavel Machek <pavel@suse.cz>
7 *  Copyright (C) 2000 Karsten Keil <kkeil@suse.de>
8 *  Copyright (C) 2001,2002 Andi Kleen <ak@suse.de>
9 *  Copyright (C) 2005 Eric Biederman <ebiederm@xmission.com>
10 */
11
12
13#include <linux/linkage.h>
14#include <linux/threads.h>
15#include <linux/init.h>
16#include <asm/segment.h>
17#include <asm/pgtable.h>
18#include <asm/page.h>
19#include <asm/msr.h>
20#include <asm/cache.h>
21#include <asm/processor-flags.h>
22#include <asm/percpu.h>
23#include <asm/nops.h>
24#include "../entry/calling.h"
25#include <asm/export.h>
26#include <asm/nospec-branch.h>
27#include <asm/fixmap.h>
28
29#ifdef CONFIG_PARAVIRT_XXL
30#include <asm/asm-offsets.h>
31#include <asm/paravirt.h>
32#define GET_CR2_INTO(reg) GET_CR2_INTO_RAX ; movq %rax, reg
33#else
34#define GET_CR2_INTO(reg) movq %cr2, reg
35#define INTERRUPT_RETURN iretq
36#endif
37
38/* we are not able to switch in one step to the final KERNEL ADDRESS SPACE
39 * because we need identity-mapped pages.
40 *
41 */
42
43#define l4_index(x)	(((x) >> 39) & 511)
44#define pud_index(x)	(((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
45
46L4_PAGE_OFFSET = l4_index(__PAGE_OFFSET_BASE_L4)
47L4_START_KERNEL = l4_index(__START_KERNEL_map)
48
49L3_START_KERNEL = pud_index(__START_KERNEL_map)
50
51	.text
52	__HEAD
53	.code64
54	.globl startup_64
55startup_64:
56	UNWIND_HINT_EMPTY
57	/*
58	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
59	 * and someone has loaded an identity mapped page table
60	 * for us.  These identity mapped page tables map all of the
61	 * kernel pages and possibly all of memory.
62	 *
63	 * %rsi holds a physical pointer to real_mode_data.
64	 *
65	 * We come here either directly from a 64bit bootloader, or from
66	 * arch/x86/boot/compressed/head_64.S.
67	 *
68	 * We only come here initially at boot nothing else comes here.
69	 *
70	 * Since we may be loaded at an address different from what we were
71	 * compiled to run at we first fixup the physical addresses in our page
72	 * tables and then reload them.
73	 */
74
75	/* Set up the stack for verify_cpu(), similar to initial_stack below */
76	leaq	(__end_init_task - SIZEOF_PTREGS)(%rip), %rsp
77
78	/* Sanitize CPU configuration */
79	call verify_cpu
80
81	/*
82	 * Perform pagetable fixups. Additionally, if SME is active, encrypt
83	 * the kernel and retrieve the modifier (SME encryption mask if SME
84	 * is active) to be added to the initial pgdir entry that will be
85	 * programmed into CR3.
86	 */
87	leaq	_text(%rip), %rdi
88	pushq	%rsi
89	call	__startup_64
90	popq	%rsi
91
92	/* Form the CR3 value being sure to include the CR3 modifier */
93	addq	$(early_top_pgt - __START_KERNEL_map), %rax
94	jmp 1f
95ENTRY(secondary_startup_64)
96	UNWIND_HINT_EMPTY
97	/*
98	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
99	 * and someone has loaded a mapped page table.
100	 *
101	 * %rsi holds a physical pointer to real_mode_data.
102	 *
103	 * We come here either from startup_64 (using physical addresses)
104	 * or from trampoline.S (using virtual addresses).
105	 *
106	 * Using virtual addresses from trampoline.S removes the need
107	 * to have any identity mapped pages in the kernel page table
108	 * after the boot processor executes this code.
109	 */
110
111	/* Sanitize CPU configuration */
112	call verify_cpu
113
114	/*
115	 * Retrieve the modifier (SME encryption mask if SME is active) to be
116	 * added to the initial pgdir entry that will be programmed into CR3.
117	 */
118	pushq	%rsi
119	call	__startup_secondary_64
120	popq	%rsi
121
122	/* Form the CR3 value being sure to include the CR3 modifier */
123	addq	$(init_top_pgt - __START_KERNEL_map), %rax
1241:
125
126	/* Enable PAE mode, PGE and LA57 */
127	movl	$(X86_CR4_PAE | X86_CR4_PGE), %ecx
128#ifdef CONFIG_X86_5LEVEL
129	testl	$1, __pgtable_l5_enabled(%rip)
130	jz	1f
131	orl	$X86_CR4_LA57, %ecx
1321:
133#endif
134	movq	%rcx, %cr4
135
136	/* Setup early boot stage 4-/5-level pagetables. */
137	addq	phys_base(%rip), %rax
138	movq	%rax, %cr3
139
140	/* Ensure I am executing from virtual addresses */
141	movq	$1f, %rax
142	ANNOTATE_RETPOLINE_SAFE
143	jmp	*%rax
1441:
145	UNWIND_HINT_EMPTY
146
147	/* Check if nx is implemented */
148	movl	$0x80000001, %eax
149	cpuid
150	movl	%edx,%edi
151
152	/* Setup EFER (Extended Feature Enable Register) */
153	movl	$MSR_EFER, %ecx
154	rdmsr
155	btsl	$_EFER_SCE, %eax	/* Enable System Call */
156	btl	$20,%edi		/* No Execute supported? */
157	jnc     1f
158	btsl	$_EFER_NX, %eax
159	btsq	$_PAGE_BIT_NX,early_pmd_flags(%rip)
1601:	wrmsr				/* Make changes effective */
161
162	/* Setup cr0 */
163	movl	$CR0_STATE, %eax
164	/* Make changes effective */
165	movq	%rax, %cr0
166
167	/* Setup a boot time stack */
168	movq initial_stack(%rip), %rsp
169
170	/* zero EFLAGS after setting rsp */
171	pushq $0
172	popfq
173
174	/*
175	 * We must switch to a new descriptor in kernel space for the GDT
176	 * because soon the kernel won't have access anymore to the userspace
177	 * addresses where we're currently running on. We have to do that here
178	 * because in 32bit we couldn't load a 64bit linear address.
179	 */
180	lgdt	early_gdt_descr(%rip)
181
182	/* set up data segments */
183	xorl %eax,%eax
184	movl %eax,%ds
185	movl %eax,%ss
186	movl %eax,%es
187
188	/*
189	 * We don't really need to load %fs or %gs, but load them anyway
190	 * to kill any stale realmode selectors.  This allows execution
191	 * under VT hardware.
192	 */
193	movl %eax,%fs
194	movl %eax,%gs
195
196	/* Set up %gs.
197	 *
198	 * The base of %gs always points to the bottom of the irqstack
199	 * union.  If the stack protector canary is enabled, it is
200	 * located at %gs:40.  Note that, on SMP, the boot cpu uses
201	 * init data section till per cpu areas are set up.
202	 */
203	movl	$MSR_GS_BASE,%ecx
204	movl	initial_gs(%rip),%eax
205	movl	initial_gs+4(%rip),%edx
206	wrmsr
207
208	/* rsi is pointer to real mode structure with interesting info.
209	   pass it to C */
210	movq	%rsi, %rdi
211
212.Ljump_to_C_code:
213	/*
214	 * Jump to run C code and to be on a real kernel address.
215	 * Since we are running on identity-mapped space we have to jump
216	 * to the full 64bit address, this is only possible as indirect
217	 * jump.  In addition we need to ensure %cs is set so we make this
218	 * a far return.
219	 *
220	 * Note: do not change to far jump indirect with 64bit offset.
221	 *
222	 * AMD does not support far jump indirect with 64bit offset.
223	 * AMD64 Architecture Programmer's Manual, Volume 3: states only
224	 *	JMP FAR mem16:16 FF /5 Far jump indirect,
225	 *		with the target specified by a far pointer in memory.
226	 *	JMP FAR mem16:32 FF /5 Far jump indirect,
227	 *		with the target specified by a far pointer in memory.
228	 *
229	 * Intel64 does support 64bit offset.
230	 * Software Developer Manual Vol 2: states:
231	 *	FF /5 JMP m16:16 Jump far, absolute indirect,
232	 *		address given in m16:16
233	 *	FF /5 JMP m16:32 Jump far, absolute indirect,
234	 *		address given in m16:32.
235	 *	REX.W + FF /5 JMP m16:64 Jump far, absolute indirect,
236	 *		address given in m16:64.
237	 */
238	pushq	$.Lafter_lret	# put return address on stack for unwinder
239	xorl	%ebp, %ebp	# clear frame pointer
240	movq	initial_code(%rip), %rax
241	pushq	$__KERNEL_CS	# set correct cs
242	pushq	%rax		# target address in negative space
243	lretq
244.Lafter_lret:
245END(secondary_startup_64)
246
247#include "verify_cpu.S"
248
249#ifdef CONFIG_HOTPLUG_CPU
250/*
251 * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
252 * up already except stack. We just set up stack here. Then call
253 * start_secondary() via .Ljump_to_C_code.
254 */
255ENTRY(start_cpu0)
256	movq	initial_stack(%rip), %rsp
257	UNWIND_HINT_EMPTY
258	jmp	.Ljump_to_C_code
259ENDPROC(start_cpu0)
260#endif
261
262	/* Both SMP bootup and ACPI suspend change these variables */
263	__REFDATA
264	.balign	8
265	GLOBAL(initial_code)
266	.quad	x86_64_start_kernel
267	GLOBAL(initial_gs)
268	.quad	INIT_PER_CPU_VAR(irq_stack_union)
269	GLOBAL(initial_stack)
270	/*
271	 * The SIZEOF_PTREGS gap is a convention which helps the in-kernel
272	 * unwinder reliably detect the end of the stack.
273	 */
274	.quad  init_thread_union + THREAD_SIZE - SIZEOF_PTREGS
275	__FINITDATA
276
277	__INIT
278ENTRY(early_idt_handler_array)
279	i = 0
280	.rept NUM_EXCEPTION_VECTORS
281	.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
282		UNWIND_HINT_IRET_REGS
283		pushq $0	# Dummy error code, to make stack frame uniform
284	.else
285		UNWIND_HINT_IRET_REGS offset=8
286	.endif
287	pushq $i		# 72(%rsp) Vector number
288	jmp early_idt_handler_common
289	UNWIND_HINT_IRET_REGS
290	i = i + 1
291	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
292	.endr
293	UNWIND_HINT_IRET_REGS offset=16
294END(early_idt_handler_array)
295
296early_idt_handler_common:
297	/*
298	 * The stack is the hardware frame, an error code or zero, and the
299	 * vector number.
300	 */
301	cld
302
303	incl early_recursion_flag(%rip)
304
305	/* The vector number is currently in the pt_regs->di slot. */
306	pushq %rsi				/* pt_regs->si */
307	movq 8(%rsp), %rsi			/* RSI = vector number */
308	movq %rdi, 8(%rsp)			/* pt_regs->di = RDI */
309	pushq %rdx				/* pt_regs->dx */
310	pushq %rcx				/* pt_regs->cx */
311	pushq %rax				/* pt_regs->ax */
312	pushq %r8				/* pt_regs->r8 */
313	pushq %r9				/* pt_regs->r9 */
314	pushq %r10				/* pt_regs->r10 */
315	pushq %r11				/* pt_regs->r11 */
316	pushq %rbx				/* pt_regs->bx */
317	pushq %rbp				/* pt_regs->bp */
318	pushq %r12				/* pt_regs->r12 */
319	pushq %r13				/* pt_regs->r13 */
320	pushq %r14				/* pt_regs->r14 */
321	pushq %r15				/* pt_regs->r15 */
322	UNWIND_HINT_REGS
323
324	cmpq $14,%rsi		/* Page fault? */
325	jnz 10f
326	GET_CR2_INTO(%rdi)	/* Can clobber any volatile register if pv */
327	call early_make_pgtable
328	andl %eax,%eax
329	jz 20f			/* All good */
330
33110:
332	movq %rsp,%rdi		/* RDI = pt_regs; RSI is already trapnr */
333	call early_fixup_exception
334
33520:
336	decl early_recursion_flag(%rip)
337	jmp restore_regs_and_return_to_kernel
338END(early_idt_handler_common)
339
340	__INITDATA
341
342	.balign 4
343GLOBAL(early_recursion_flag)
344	.long 0
345
346#define NEXT_PAGE(name) \
347	.balign	PAGE_SIZE; \
348GLOBAL(name)
349
350#ifdef CONFIG_PAGE_TABLE_ISOLATION
351/*
352 * Each PGD needs to be 8k long and 8k aligned.  We do not
353 * ever go out to userspace with these, so we do not
354 * strictly *need* the second page, but this allows us to
355 * have a single set_pgd() implementation that does not
356 * need to worry about whether it has 4k or 8k to work
357 * with.
358 *
359 * This ensures PGDs are 8k long:
360 */
361#define PTI_USER_PGD_FILL	512
362/* This ensures they are 8k-aligned: */
363#define NEXT_PGD_PAGE(name) \
364	.balign 2 * PAGE_SIZE; \
365GLOBAL(name)
366#else
367#define NEXT_PGD_PAGE(name) NEXT_PAGE(name)
368#define PTI_USER_PGD_FILL	0
369#endif
370
371/* Automate the creation of 1 to 1 mapping pmd entries */
372#define PMDS(START, PERM, COUNT)			\
373	i = 0 ;						\
374	.rept (COUNT) ;					\
375	.quad	(START) + (i << PMD_SHIFT) + (PERM) ;	\
376	i = i + 1 ;					\
377	.endr
378
379	__INITDATA
380NEXT_PGD_PAGE(early_top_pgt)
381	.fill	512,8,0
382	.fill	PTI_USER_PGD_FILL,8,0
383
384NEXT_PAGE(early_dynamic_pgts)
385	.fill	512*EARLY_DYNAMIC_PAGE_TABLES,8,0
386
387	.data
388
389#if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
390NEXT_PGD_PAGE(init_top_pgt)
391	.quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
392	.org    init_top_pgt + L4_PAGE_OFFSET*8, 0
393	.quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
394	.org    init_top_pgt + L4_START_KERNEL*8, 0
395	/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
396	.quad   level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
397	.fill	PTI_USER_PGD_FILL,8,0
398
399NEXT_PAGE(level3_ident_pgt)
400	.quad	level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
401	.fill	511, 8, 0
402NEXT_PAGE(level2_ident_pgt)
403	/*
404	 * Since I easily can, map the first 1G.
405	 * Don't set NX because code runs from these pages.
406	 *
407	 * Note: This sets _PAGE_GLOBAL despite whether
408	 * the CPU supports it or it is enabled.  But,
409	 * the CPU should ignore the bit.
410	 */
411	PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
412#else
413NEXT_PGD_PAGE(init_top_pgt)
414	.fill	512,8,0
415	.fill	PTI_USER_PGD_FILL,8,0
416#endif
417
418#ifdef CONFIG_X86_5LEVEL
419NEXT_PAGE(level4_kernel_pgt)
420	.fill	511,8,0
421	.quad	level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
422#endif
423
424NEXT_PAGE(level3_kernel_pgt)
425	.fill	L3_START_KERNEL,8,0
426	/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
427	.quad	level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
428	.quad	level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
429
430NEXT_PAGE(level2_kernel_pgt)
431	/*
432	 * 512 MB kernel mapping. We spend a full page on this pagetable
433	 * anyway.
434	 *
435	 * The kernel code+data+bss must not be bigger than that.
436	 *
437	 * (NOTE: at +512MB starts the module area, see MODULES_VADDR.
438	 *  If you want to increase this then increase MODULES_VADDR
439	 *  too.)
440	 *
441	 *  This table is eventually used by the kernel during normal
442	 *  runtime.  Care must be taken to clear out undesired bits
443	 *  later, like _PAGE_RW or _PAGE_GLOBAL in some cases.
444	 */
445	PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
446		KERNEL_IMAGE_SIZE/PMD_SIZE)
447
448NEXT_PAGE(level2_fixmap_pgt)
449	.fill	(512 - 4 - FIXMAP_PMD_NUM),8,0
450	pgtno = 0
451	.rept (FIXMAP_PMD_NUM)
452	.quad level1_fixmap_pgt + (pgtno << PAGE_SHIFT) - __START_KERNEL_map \
453		+ _PAGE_TABLE_NOENC;
454	pgtno = pgtno + 1
455	.endr
456	/* 6 MB reserved space + a 2MB hole */
457	.fill	4,8,0
458
459NEXT_PAGE(level1_fixmap_pgt)
460	.rept (FIXMAP_PMD_NUM)
461	.fill	512,8,0
462	.endr
463
464#undef PMDS
465
466	.data
467	.align 16
468	.globl early_gdt_descr
469early_gdt_descr:
470	.word	GDT_ENTRIES*8-1
471early_gdt_descr_base:
472	.quad	INIT_PER_CPU_VAR(gdt_page)
473
474ENTRY(phys_base)
475	/* This must match the first entry in level2_kernel_pgt */
476	.quad   0x0000000000000000
477EXPORT_SYMBOL(phys_base)
478
479#include "../../x86/xen/xen-head.S"
480
481	__PAGE_ALIGNED_BSS
482NEXT_PAGE(empty_zero_page)
483	.skip PAGE_SIZE
484EXPORT_SYMBOL(empty_zero_page)
485
486