xref: /openbmc/linux/arch/x86/xen/xen-asm.S (revision f71a261a) 
1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Asm versions of Xen pv-ops, suitable for direct use.
4 *
5 * We only bother with direct forms (ie, vcpu in percpu data) of the
6 * operations here; the indirect forms are better handled in C.
7 */
8
9#include <asm/errno.h>
10#include <asm/asm-offsets.h>
11#include <asm/percpu.h>
12#include <asm/processor-flags.h>
13#include <asm/segment.h>
14#include <asm/thread_info.h>
15#include <asm/asm.h>
16#include <asm/frame.h>
17#include <asm/unwind_hints.h>
18
19#include <xen/interface/xen.h>
20
21#include <linux/init.h>
22#include <linux/linkage.h>
23#include <../entry/calling.h>
24
25.pushsection .noinstr.text, "ax"
26/*
27 * Disabling events is simply a matter of making the event mask
28 * non-zero.
29 */
30SYM_FUNC_START(xen_irq_disable_direct)
31	movb $1, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
32	RET
33SYM_FUNC_END(xen_irq_disable_direct)
34
35/*
36 * Force an event check by making a hypercall, but preserve regs
37 * before making the call.
38 */
39SYM_FUNC_START(check_events)
40	FRAME_BEGIN
41	push %rax
42	push %rcx
43	push %rdx
44	push %rsi
45	push %rdi
46	push %r8
47	push %r9
48	push %r10
49	push %r11
50	call xen_force_evtchn_callback
51	pop %r11
52	pop %r10
53	pop %r9
54	pop %r8
55	pop %rdi
56	pop %rsi
57	pop %rdx
58	pop %rcx
59	pop %rax
60	FRAME_END
61	RET
62SYM_FUNC_END(check_events)
63
64/*
65 * Enable events.  This clears the event mask and tests the pending
66 * event status with one and operation.  If there are pending events,
67 * then enter the hypervisor to get them handled.
68 */
69SYM_FUNC_START(xen_irq_enable_direct)
70	FRAME_BEGIN
71	/* Unmask events */
72	movb $0, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
73
74	/*
75	 * Preempt here doesn't matter because that will deal with any
76	 * pending interrupts.  The pending check may end up being run
77	 * on the wrong CPU, but that doesn't hurt.
78	 */
79
80	/* Test for pending */
81	testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
82	jz 1f
83
84	call check_events
851:
86	FRAME_END
87	RET
88SYM_FUNC_END(xen_irq_enable_direct)
89
90/*
91 * (xen_)save_fl is used to get the current interrupt enable status.
92 * Callers expect the status to be in X86_EFLAGS_IF, and other bits
93 * may be set in the return value.  We take advantage of this by
94 * making sure that X86_EFLAGS_IF has the right value (and other bits
95 * in that byte are 0), but other bits in the return value are
96 * undefined.  We need to toggle the state of the bit, because Xen and
97 * x86 use opposite senses (mask vs enable).
98 */
99SYM_FUNC_START(xen_save_fl_direct)
100	testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
101	setz %ah
102	addb %ah, %ah
103	RET
104SYM_FUNC_END(xen_save_fl_direct)
105
106SYM_FUNC_START(xen_read_cr2)
107	FRAME_BEGIN
108	_ASM_MOV PER_CPU_VAR(xen_vcpu), %_ASM_AX
109	_ASM_MOV XEN_vcpu_info_arch_cr2(%_ASM_AX), %_ASM_AX
110	FRAME_END
111	RET
112SYM_FUNC_END(xen_read_cr2);
113
114SYM_FUNC_START(xen_read_cr2_direct)
115	FRAME_BEGIN
116	_ASM_MOV PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_arch_cr2, %_ASM_AX
117	FRAME_END
118	RET
119SYM_FUNC_END(xen_read_cr2_direct);
120.popsection
121
122.macro xen_pv_trap name
123SYM_CODE_START(xen_\name)
124	UNWIND_HINT_EMPTY
125	ENDBR
126	pop %rcx
127	pop %r11
128	jmp  \name
129SYM_CODE_END(xen_\name)
130_ASM_NOKPROBE(xen_\name)
131.endm
132
133xen_pv_trap asm_exc_divide_error
134xen_pv_trap asm_xenpv_exc_debug
135xen_pv_trap asm_exc_int3
136xen_pv_trap asm_xenpv_exc_nmi
137xen_pv_trap asm_exc_overflow
138xen_pv_trap asm_exc_bounds
139xen_pv_trap asm_exc_invalid_op
140xen_pv_trap asm_exc_device_not_available
141xen_pv_trap asm_xenpv_exc_double_fault
142xen_pv_trap asm_exc_coproc_segment_overrun
143xen_pv_trap asm_exc_invalid_tss
144xen_pv_trap asm_exc_segment_not_present
145xen_pv_trap asm_exc_stack_segment
146xen_pv_trap asm_exc_general_protection
147xen_pv_trap asm_exc_page_fault
148xen_pv_trap asm_exc_spurious_interrupt_bug
149xen_pv_trap asm_exc_coprocessor_error
150xen_pv_trap asm_exc_alignment_check
151#ifdef CONFIG_X86_KERNEL_IBT
152xen_pv_trap asm_exc_control_protection
153#endif
154#ifdef CONFIG_X86_MCE
155xen_pv_trap asm_xenpv_exc_machine_check
156#endif /* CONFIG_X86_MCE */
157xen_pv_trap asm_exc_simd_coprocessor_error
158#ifdef CONFIG_IA32_EMULATION
159xen_pv_trap entry_INT80_compat
160#endif
161xen_pv_trap asm_exc_xen_unknown_trap
162xen_pv_trap asm_exc_xen_hypervisor_callback
163
164	__INIT
165SYM_CODE_START(xen_early_idt_handler_array)
166	i = 0
167	.rept NUM_EXCEPTION_VECTORS
168	UNWIND_HINT_EMPTY
169	ENDBR
170	pop %rcx
171	pop %r11
172	jmp early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE
173	i = i + 1
174	.fill xen_early_idt_handler_array + i*XEN_EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
175	.endr
176SYM_CODE_END(xen_early_idt_handler_array)
177	__FINIT
178
179hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
180/*
181 * Xen64 iret frame:
182 *
183 *	ss
184 *	rsp
185 *	rflags
186 *	cs
187 *	rip		<-- standard iret frame
188 *
189 *	flags
190 *
191 *	rcx		}
192 *	r11		}<-- pushed by hypercall page
193 * rsp->rax		}
194 */
195SYM_CODE_START(xen_iret)
196	UNWIND_HINT_EMPTY
197	ANNOTATE_NOENDBR
198	pushq $0
199	jmp hypercall_iret
200SYM_CODE_END(xen_iret)
201
202/*
203 * XEN pv doesn't use trampoline stack, PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is
204 * also the kernel stack.  Reusing swapgs_restore_regs_and_return_to_usermode()
205 * in XEN pv would cause %rsp to move up to the top of the kernel stack and
206 * leave the IRET frame below %rsp, which is dangerous to be corrupted if #NMI
207 * interrupts. And swapgs_restore_regs_and_return_to_usermode() pushing the IRET
208 * frame at the same address is useless.
209 */
210SYM_CODE_START(xenpv_restore_regs_and_return_to_usermode)
211	UNWIND_HINT_REGS
212	POP_REGS
213
214	/* stackleak_erase() can work safely on the kernel stack. */
215	STACKLEAK_ERASE_NOCLOBBER
216
217	addq	$8, %rsp	/* skip regs->orig_ax */
218	jmp xen_iret
219SYM_CODE_END(xenpv_restore_regs_and_return_to_usermode)
220
221/*
222 * Xen handles syscall callbacks much like ordinary exceptions, which
223 * means we have:
224 * - kernel gs
225 * - kernel rsp
226 * - an iret-like stack frame on the stack (including rcx and r11):
227 *	ss
228 *	rsp
229 *	rflags
230 *	cs
231 *	rip
232 *	r11
233 * rsp->rcx
234 */
235
236/* Normal 64-bit system call target */
237SYM_CODE_START(xen_syscall_target)
238	UNWIND_HINT_EMPTY
239	ENDBR
240	popq %rcx
241	popq %r11
242
243	/*
244	 * Neither Xen nor the kernel really knows what the old SS and
245	 * CS were.  The kernel expects __USER_DS and __USER_CS, so
246	 * report those values even though Xen will guess its own values.
247	 */
248	movq $__USER_DS, 4*8(%rsp)
249	movq $__USER_CS, 1*8(%rsp)
250
251	jmp entry_SYSCALL_64_after_hwframe
252SYM_CODE_END(xen_syscall_target)
253
254#ifdef CONFIG_IA32_EMULATION
255
256/* 32-bit compat syscall target */
257SYM_CODE_START(xen_syscall32_target)
258	UNWIND_HINT_EMPTY
259	ENDBR
260	popq %rcx
261	popq %r11
262
263	/*
264	 * Neither Xen nor the kernel really knows what the old SS and
265	 * CS were.  The kernel expects __USER32_DS and __USER32_CS, so
266	 * report those values even though Xen will guess its own values.
267	 */
268	movq $__USER32_DS, 4*8(%rsp)
269	movq $__USER32_CS, 1*8(%rsp)
270
271	jmp entry_SYSCALL_compat_after_hwframe
272SYM_CODE_END(xen_syscall32_target)
273
274/* 32-bit compat sysenter target */
275SYM_CODE_START(xen_sysenter_target)
276	UNWIND_HINT_EMPTY
277	ENDBR
278	/*
279	 * NB: Xen is polite and clears TF from EFLAGS for us.  This means
280	 * that we don't need to guard against single step exceptions here.
281	 */
282	popq %rcx
283	popq %r11
284
285	/*
286	 * Neither Xen nor the kernel really knows what the old SS and
287	 * CS were.  The kernel expects __USER32_DS and __USER32_CS, so
288	 * report those values even though Xen will guess its own values.
289	 */
290	movq $__USER32_DS, 4*8(%rsp)
291	movq $__USER32_CS, 1*8(%rsp)
292
293	jmp entry_SYSENTER_compat_after_hwframe
294SYM_CODE_END(xen_sysenter_target)
295
296#else /* !CONFIG_IA32_EMULATION */
297
298SYM_CODE_START(xen_syscall32_target)
299SYM_CODE_START(xen_sysenter_target)
300	UNWIND_HINT_EMPTY
301	ENDBR
302	lea 16(%rsp), %rsp	/* strip %rcx, %r11 */
303	mov $-ENOSYS, %rax
304	pushq $0
305	jmp hypercall_iret
306SYM_CODE_END(xen_sysenter_target)
307SYM_CODE_END(xen_syscall32_target)
308
309#endif	/* CONFIG_IA32_EMULATION */
310