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1/*
2 * Compatibility mode system call entry point for x86-64.
3 *
4 * Copyright 2000-2002 Andi Kleen, SuSE Labs.
5 */
6#include "calling.h"
7#include <asm/asm-offsets.h>
8#include <asm/current.h>
9#include <asm/errno.h>
10#include <asm/ia32_unistd.h>
11#include <asm/thread_info.h>
12#include <asm/segment.h>
13#include <asm/irqflags.h>
14#include <asm/asm.h>
15#include <asm/smap.h>
16#include <linux/linkage.h>
17#include <linux/err.h>
18
19 .section .entry.text, "ax"
20
21/*
22 * 32-bit SYSENTER entry.
23 *
24 * 32-bit system calls through the vDSO's __kernel_vsyscall enter here
25 * on 64-bit kernels running on Intel CPUs.
26 *
27 * The SYSENTER instruction, in principle, should *only* occur in the
28 * vDSO. In practice, a small number of Android devices were shipped
29 * with a copy of Bionic that inlined a SYSENTER instruction. This
30 * never happened in any of Google's Bionic versions -- it only happened
31 * in a narrow range of Intel-provided versions.
32 *
33 * SYSENTER loads SS, RSP, CS, and RIP from previously programmed MSRs.
34 * IF and VM in RFLAGS are cleared (IOW: interrupts are off).
35 * SYSENTER does not save anything on the stack,
36 * and does not save old RIP (!!!), RSP, or RFLAGS.
37 *
38 * Arguments:
39 * eax system call number
40 * ebx arg1
41 * ecx arg2
42 * edx arg3
43 * esi arg4
44 * edi arg5
45 * ebp user stack
46 * 0(%ebp) arg6
47 */
48ENTRY(entry_SYSENTER_compat)
49 /* Interrupts are off on entry. */
50 SWAPGS_UNSAFE_STACK
51 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
52
53 /*
54 * User tracing code (ptrace or signal handlers) might assume that
55 * the saved RAX contains a 32-bit number when we're invoking a 32-bit
56 * syscall. Just in case the high bits are nonzero, zero-extend
57 * the syscall number. (This could almost certainly be deleted
58 * with no ill effects.)
59 */
60 movl %eax, %eax
61
62 /* Construct struct pt_regs on stack */
63 pushq $__USER32_DS /* pt_regs->ss */
64 pushq %rbp /* pt_regs->sp (stashed in bp) */
65
66 /*
67 * Push flags. This is nasty. First, interrupts are currently
68 * off, but we need pt_regs->flags to have IF set. Second, even
69 * if TF was set when SYSENTER started, it's clear by now. We fix
70 * that later using TIF_SINGLESTEP.
71 */
72 pushfq /* pt_regs->flags (except IF = 0) */
73 orl $X86_EFLAGS_IF, (%rsp) /* Fix saved flags */
74 pushq $__USER32_CS /* pt_regs->cs */
75 xorq %r8,%r8
76 pushq %r8 /* pt_regs->ip = 0 (placeholder) */
77 pushq %rax /* pt_regs->orig_ax */
78 pushq %rdi /* pt_regs->di */
79 pushq %rsi /* pt_regs->si */
80 pushq %rdx /* pt_regs->dx */
81 pushq %rcx /* pt_regs->cx */
82 pushq $-ENOSYS /* pt_regs->ax */
83 pushq %r8 /* pt_regs->r8 = 0 */
84 pushq %r8 /* pt_regs->r9 = 0 */
85 pushq %r8 /* pt_regs->r10 = 0 */
86 pushq %r8 /* pt_regs->r11 = 0 */
87 pushq %rbx /* pt_regs->rbx */
88 pushq %rbp /* pt_regs->rbp (will be overwritten) */
89 pushq %r8 /* pt_regs->r12 = 0 */
90 pushq %r8 /* pt_regs->r13 = 0 */
91 pushq %r8 /* pt_regs->r14 = 0 */
92 pushq %r8 /* pt_regs->r15 = 0 */
93 cld
94
95 /*
96 * SYSENTER doesn't filter flags, so we need to clear NT and AC
97 * ourselves. To save a few cycles, we can check whether
98 * either was set instead of doing an unconditional popfq.
99 * This needs to happen before enabling interrupts so that
100 * we don't get preempted with NT set.
101 *
102 * If TF is set, we will single-step all the way to here -- do_debug
103 * will ignore all the traps. (Yes, this is slow, but so is
104 * single-stepping in general. This allows us to avoid having
105 * a more complicated code to handle the case where a user program
106 * forces us to single-step through the SYSENTER entry code.)
107 *
108 * NB.: .Lsysenter_fix_flags is a label with the code under it moved
109 * out-of-line as an optimization: NT is unlikely to be set in the
110 * majority of the cases and instead of polluting the I$ unnecessarily,
111 * we're keeping that code behind a branch which will predict as
112 * not-taken and therefore its instructions won't be fetched.
113 */
114 testl $X86_EFLAGS_NT|X86_EFLAGS_AC|X86_EFLAGS_TF, EFLAGS(%rsp)
115 jnz .Lsysenter_fix_flags
116.Lsysenter_flags_fixed:
117
118 /*
119 * User mode is traced as though IRQs are on, and SYSENTER
120 * turned them off.
121 */
122 TRACE_IRQS_OFF
123
124 movq %rsp, %rdi
125 call do_fast_syscall_32
126 /* XEN PV guests always use IRET path */
127 ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
128 "jmp .Lsyscall_32_done", X86_FEATURE_XENPV
129 jmp sysret32_from_system_call
130
131.Lsysenter_fix_flags:
132 pushq $X86_EFLAGS_FIXED
133 popfq
134 jmp .Lsysenter_flags_fixed
135GLOBAL(__end_entry_SYSENTER_compat)
136ENDPROC(entry_SYSENTER_compat)
137
138/*
139 * 32-bit SYSCALL entry.
140 *
141 * 32-bit system calls through the vDSO's __kernel_vsyscall enter here
142 * on 64-bit kernels running on AMD CPUs.
143 *
144 * The SYSCALL instruction, in principle, should *only* occur in the
145 * vDSO. In practice, it appears that this really is the case.
146 * As evidence:
147 *
148 * - The calling convention for SYSCALL has changed several times without
149 * anyone noticing.
150 *
151 * - Prior to the in-kernel X86_BUG_SYSRET_SS_ATTRS fixup, anything
152 * user task that did SYSCALL without immediately reloading SS
153 * would randomly crash.
154 *
155 * - Most programmers do not directly target AMD CPUs, and the 32-bit
156 * SYSCALL instruction does not exist on Intel CPUs. Even on AMD
157 * CPUs, Linux disables the SYSCALL instruction on 32-bit kernels
158 * because the SYSCALL instruction in legacy/native 32-bit mode (as
159 * opposed to compat mode) is sufficiently poorly designed as to be
160 * essentially unusable.
161 *
162 * 32-bit SYSCALL saves RIP to RCX, clears RFLAGS.RF, then saves
163 * RFLAGS to R11, then loads new SS, CS, and RIP from previously
164 * programmed MSRs. RFLAGS gets masked by a value from another MSR
165 * (so CLD and CLAC are not needed). SYSCALL does not save anything on
166 * the stack and does not change RSP.
167 *
168 * Note: RFLAGS saving+masking-with-MSR happens only in Long mode
169 * (in legacy 32-bit mode, IF, RF and VM bits are cleared and that's it).
170 * Don't get confused: RFLAGS saving+masking depends on Long Mode Active bit
171 * (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes
172 * or target CS descriptor's L bit (SYSCALL does not read segment descriptors).
173 *
174 * Arguments:
175 * eax system call number
176 * ecx return address
177 * ebx arg1
178 * ebp arg2 (note: not saved in the stack frame, should not be touched)
179 * edx arg3
180 * esi arg4
181 * edi arg5
182 * esp user stack
183 * 0(%esp) arg6
184 */
185ENTRY(entry_SYSCALL_compat)
186 /* Interrupts are off on entry. */
187 SWAPGS_UNSAFE_STACK
188
189 /* Stash user ESP and switch to the kernel stack. */
190 movl %esp, %r8d
191 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
192
193 /* Zero-extending 32-bit regs, do not remove */
194 movl %eax, %eax
195
196 /* Construct struct pt_regs on stack */
197 pushq $__USER32_DS /* pt_regs->ss */
198 pushq %r8 /* pt_regs->sp */
199 pushq %r11 /* pt_regs->flags */
200 pushq $__USER32_CS /* pt_regs->cs */
201 pushq %rcx /* pt_regs->ip */
202 pushq %rax /* pt_regs->orig_ax */
203 pushq %rdi /* pt_regs->di */
204 pushq %rsi /* pt_regs->si */
205 pushq %rdx /* pt_regs->dx */
206 pushq %rbp /* pt_regs->cx (stashed in bp) */
207 pushq $-ENOSYS /* pt_regs->ax */
208 xorq %r8,%r8
209 pushq %r8 /* pt_regs->r8 = 0 */
210 pushq %r8 /* pt_regs->r9 = 0 */
211 pushq %r8 /* pt_regs->r10 = 0 */
212 pushq %r8 /* pt_regs->r11 = 0 */
213 pushq %rbx /* pt_regs->rbx */
214 pushq %rbp /* pt_regs->rbp (will be overwritten) */
215 pushq %r8 /* pt_regs->r12 = 0 */
216 pushq %r8 /* pt_regs->r13 = 0 */
217 pushq %r8 /* pt_regs->r14 = 0 */
218 pushq %r8 /* pt_regs->r15 = 0 */
219
220 /*
221 * User mode is traced as though IRQs are on, and SYSENTER
222 * turned them off.
223 */
224 TRACE_IRQS_OFF
225
226 movq %rsp, %rdi
227 call do_fast_syscall_32
228 /* XEN PV guests always use IRET path */
229 ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
230 "jmp .Lsyscall_32_done", X86_FEATURE_XENPV
231
232 /* Opportunistic SYSRET */
233sysret32_from_system_call:
234 TRACE_IRQS_ON /* User mode traces as IRQs on. */
235 movq RBX(%rsp), %rbx /* pt_regs->rbx */
236 movq RBP(%rsp), %rbp /* pt_regs->rbp */
237 movq EFLAGS(%rsp), %r11 /* pt_regs->flags (in r11) */
238 movq RIP(%rsp), %rcx /* pt_regs->ip (in rcx) */
239 addq $RAX, %rsp /* Skip r8-r15 */
240 popq %rax /* pt_regs->rax */
241 popq %rdx /* Skip pt_regs->cx */
242 popq %rdx /* pt_regs->dx */
243 popq %rsi /* pt_regs->si */
244 popq %rdi /* pt_regs->di */
245
246 /*
247 * USERGS_SYSRET32 does:
248 * GSBASE = user's GS base
249 * EIP = ECX
250 * RFLAGS = R11
251 * CS = __USER32_CS
252 * SS = __USER_DS
253 *
254 * ECX will not match pt_regs->cx, but we're returning to a vDSO
255 * trampoline that will fix up RCX, so this is okay.
256 *
257 * R12-R15 are callee-saved, so they contain whatever was in them
258 * when the system call started, which is already known to user
259 * code. We zero R8-R10 to avoid info leaks.
260 */
261 xorq %r8, %r8
262 xorq %r9, %r9
263 xorq %r10, %r10
264 movq RSP-ORIG_RAX(%rsp), %rsp
265 swapgs
266 sysretl
267END(entry_SYSCALL_compat)
268
269/*
270 * 32-bit legacy system call entry.
271 *
272 * 32-bit x86 Linux system calls traditionally used the INT $0x80
273 * instruction. INT $0x80 lands here.
274 *
275 * This entry point can be used by 32-bit and 64-bit programs to perform
276 * 32-bit system calls. Instances of INT $0x80 can be found inline in
277 * various programs and libraries. It is also used by the vDSO's
278 * __kernel_vsyscall fallback for hardware that doesn't support a faster
279 * entry method. Restarted 32-bit system calls also fall back to INT
280 * $0x80 regardless of what instruction was originally used to do the
281 * system call.
282 *
283 * This is considered a slow path. It is not used by most libc
284 * implementations on modern hardware except during process startup.
285 *
286 * Arguments:
287 * eax system call number
288 * ebx arg1
289 * ecx arg2
290 * edx arg3
291 * esi arg4
292 * edi arg5
293 * ebp arg6
294 */
295ENTRY(entry_INT80_compat)
296 /*
297 * Interrupts are off on entry.
298 */
299 PARAVIRT_ADJUST_EXCEPTION_FRAME
300 ASM_CLAC /* Do this early to minimize exposure */
301 SWAPGS
302
303 /*
304 * User tracing code (ptrace or signal handlers) might assume that
305 * the saved RAX contains a 32-bit number when we're invoking a 32-bit
306 * syscall. Just in case the high bits are nonzero, zero-extend
307 * the syscall number. (This could almost certainly be deleted
308 * with no ill effects.)
309 */
310 movl %eax, %eax
311
312 /* Construct struct pt_regs on stack (iret frame is already on stack) */
313 pushq %rax /* pt_regs->orig_ax */
314 pushq %rdi /* pt_regs->di */
315 pushq %rsi /* pt_regs->si */
316 pushq %rdx /* pt_regs->dx */
317 pushq %rcx /* pt_regs->cx */
318 pushq $-ENOSYS /* pt_regs->ax */
319 xorq %r8,%r8
320 pushq %r8 /* pt_regs->r8 = 0 */
321 pushq %r8 /* pt_regs->r9 = 0 */
322 pushq %r8 /* pt_regs->r10 = 0 */
323 pushq %r8 /* pt_regs->r11 = 0 */
324 pushq %rbx /* pt_regs->rbx */
325 pushq %rbp /* pt_regs->rbp */
326 pushq %r12 /* pt_regs->r12 */
327 pushq %r13 /* pt_regs->r13 */
328 pushq %r14 /* pt_regs->r14 */
329 pushq %r15 /* pt_regs->r15 */
330 cld
331
332 /*
333 * User mode is traced as though IRQs are on, and the interrupt
334 * gate turned them off.
335 */
336 TRACE_IRQS_OFF
337
338 movq %rsp, %rdi
339 call do_int80_syscall_32
340.Lsyscall_32_done:
341
342 /* Go back to user mode. */
343 TRACE_IRQS_ON
344 SWAPGS
345 jmp restore_regs_and_iret
346END(entry_INT80_compat)
347
348 ALIGN
349GLOBAL(stub32_clone)
350 /*
351 * The 32-bit clone ABI is: clone(..., int tls_val, int *child_tidptr).
352 * The 64-bit clone ABI is: clone(..., int *child_tidptr, int tls_val).
353 *
354 * The native 64-bit kernel's sys_clone() implements the latter,
355 * so we need to swap arguments here before calling it:
356 */
357 xchg %r8, %rcx
358 jmp sys_clone
1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Compatibility mode system call entry point for x86-64.
4 *
5 * Copyright 2000-2002 Andi Kleen, SuSE Labs.
6 */
7#include <asm/asm-offsets.h>
8#include <asm/current.h>
9#include <asm/errno.h>
10#include <asm/ia32_unistd.h>
11#include <asm/thread_info.h>
12#include <asm/segment.h>
13#include <asm/irqflags.h>
14#include <asm/asm.h>
15#include <asm/smap.h>
16#include <asm/nospec-branch.h>
17#include <linux/linkage.h>
18#include <linux/err.h>
19
20#include "calling.h"
21
22 .section .entry.text, "ax"
23
24/*
25 * 32-bit SYSENTER entry.
26 *
27 * 32-bit system calls through the vDSO's __kernel_vsyscall enter here
28 * on 64-bit kernels running on Intel CPUs.
29 *
30 * The SYSENTER instruction, in principle, should *only* occur in the
31 * vDSO. In practice, a small number of Android devices were shipped
32 * with a copy of Bionic that inlined a SYSENTER instruction. This
33 * never happened in any of Google's Bionic versions -- it only happened
34 * in a narrow range of Intel-provided versions.
35 *
36 * SYSENTER loads SS, RSP, CS, and RIP from previously programmed MSRs.
37 * IF and VM in RFLAGS are cleared (IOW: interrupts are off).
38 * SYSENTER does not save anything on the stack,
39 * and does not save old RIP (!!!), RSP, or RFLAGS.
40 *
41 * Arguments:
42 * eax system call number
43 * ebx arg1
44 * ecx arg2
45 * edx arg3
46 * esi arg4
47 * edi arg5
48 * ebp user stack
49 * 0(%ebp) arg6
50 */
51SYM_CODE_START(entry_SYSENTER_compat)
52 UNWIND_HINT_ENTRY
53 ENDBR
54 /* Interrupts are off on entry. */
55 swapgs
56
57 pushq %rax
58 SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
59 popq %rax
60
61 movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rsp
62
63 /* Construct struct pt_regs on stack */
64 pushq $__USER_DS /* pt_regs->ss */
65 pushq $0 /* pt_regs->sp = 0 (placeholder) */
66
67 /*
68 * Push flags. This is nasty. First, interrupts are currently
69 * off, but we need pt_regs->flags to have IF set. Second, if TS
70 * was set in usermode, it's still set, and we're singlestepping
71 * through this code. do_SYSENTER_32() will fix up IF.
72 */
73 pushfq /* pt_regs->flags (except IF = 0) */
74 pushq $__USER32_CS /* pt_regs->cs */
75 pushq $0 /* pt_regs->ip = 0 (placeholder) */
76SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL)
77
78 /*
79 * User tracing code (ptrace or signal handlers) might assume that
80 * the saved RAX contains a 32-bit number when we're invoking a 32-bit
81 * syscall. Just in case the high bits are nonzero, zero-extend
82 * the syscall number. (This could almost certainly be deleted
83 * with no ill effects.)
84 */
85 movl %eax, %eax
86
87 pushq %rax /* pt_regs->orig_ax */
88 PUSH_AND_CLEAR_REGS rax=$-ENOSYS
89 UNWIND_HINT_REGS
90
91 cld
92
93 IBRS_ENTER
94 UNTRAIN_RET
95
96 /*
97 * SYSENTER doesn't filter flags, so we need to clear NT and AC
98 * ourselves. To save a few cycles, we can check whether
99 * either was set instead of doing an unconditional popfq.
100 * This needs to happen before enabling interrupts so that
101 * we don't get preempted with NT set.
102 *
103 * If TF is set, we will single-step all the way to here -- do_debug
104 * will ignore all the traps. (Yes, this is slow, but so is
105 * single-stepping in general. This allows us to avoid having
106 * a more complicated code to handle the case where a user program
107 * forces us to single-step through the SYSENTER entry code.)
108 *
109 * NB.: .Lsysenter_fix_flags is a label with the code under it moved
110 * out-of-line as an optimization: NT is unlikely to be set in the
111 * majority of the cases and instead of polluting the I$ unnecessarily,
112 * we're keeping that code behind a branch which will predict as
113 * not-taken and therefore its instructions won't be fetched.
114 */
115 testl $X86_EFLAGS_NT|X86_EFLAGS_AC|X86_EFLAGS_TF, EFLAGS(%rsp)
116 jnz .Lsysenter_fix_flags
117.Lsysenter_flags_fixed:
118
119 movq %rsp, %rdi
120 call do_SYSENTER_32
121 /* XEN PV guests always use IRET path */
122 ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \
123 "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV
124 jmp sysret32_from_system_call
125
126.Lsysenter_fix_flags:
127 pushq $X86_EFLAGS_FIXED
128 popfq
129 jmp .Lsysenter_flags_fixed
130SYM_INNER_LABEL(__end_entry_SYSENTER_compat, SYM_L_GLOBAL)
131SYM_CODE_END(entry_SYSENTER_compat)
132
133/*
134 * 32-bit SYSCALL entry.
135 *
136 * 32-bit system calls through the vDSO's __kernel_vsyscall enter here
137 * on 64-bit kernels running on AMD CPUs.
138 *
139 * The SYSCALL instruction, in principle, should *only* occur in the
140 * vDSO. In practice, it appears that this really is the case.
141 * As evidence:
142 *
143 * - The calling convention for SYSCALL has changed several times without
144 * anyone noticing.
145 *
146 * - Prior to the in-kernel X86_BUG_SYSRET_SS_ATTRS fixup, anything
147 * user task that did SYSCALL without immediately reloading SS
148 * would randomly crash.
149 *
150 * - Most programmers do not directly target AMD CPUs, and the 32-bit
151 * SYSCALL instruction does not exist on Intel CPUs. Even on AMD
152 * CPUs, Linux disables the SYSCALL instruction on 32-bit kernels
153 * because the SYSCALL instruction in legacy/native 32-bit mode (as
154 * opposed to compat mode) is sufficiently poorly designed as to be
155 * essentially unusable.
156 *
157 * 32-bit SYSCALL saves RIP to RCX, clears RFLAGS.RF, then saves
158 * RFLAGS to R11, then loads new SS, CS, and RIP from previously
159 * programmed MSRs. RFLAGS gets masked by a value from another MSR
160 * (so CLD and CLAC are not needed). SYSCALL does not save anything on
161 * the stack and does not change RSP.
162 *
163 * Note: RFLAGS saving+masking-with-MSR happens only in Long mode
164 * (in legacy 32-bit mode, IF, RF and VM bits are cleared and that's it).
165 * Don't get confused: RFLAGS saving+masking depends on Long Mode Active bit
166 * (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes
167 * or target CS descriptor's L bit (SYSCALL does not read segment descriptors).
168 *
169 * Arguments:
170 * eax system call number
171 * ecx return address
172 * ebx arg1
173 * ebp arg2 (note: not saved in the stack frame, should not be touched)
174 * edx arg3
175 * esi arg4
176 * edi arg5
177 * esp user stack
178 * 0(%esp) arg6
179 */
180SYM_CODE_START(entry_SYSCALL_compat)
181 UNWIND_HINT_ENTRY
182 ENDBR
183 /* Interrupts are off on entry. */
184 swapgs
185
186 /* Stash user ESP */
187 movl %esp, %r8d
188
189 /* Use %rsp as scratch reg. User ESP is stashed in r8 */
190 SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp
191
192 /* Switch to the kernel stack */
193 movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rsp
194
195SYM_INNER_LABEL(entry_SYSCALL_compat_safe_stack, SYM_L_GLOBAL)
196 ANNOTATE_NOENDBR
197
198 /* Construct struct pt_regs on stack */
199 pushq $__USER_DS /* pt_regs->ss */
200 pushq %r8 /* pt_regs->sp */
201 pushq %r11 /* pt_regs->flags */
202 pushq $__USER32_CS /* pt_regs->cs */
203 pushq %rcx /* pt_regs->ip */
204SYM_INNER_LABEL(entry_SYSCALL_compat_after_hwframe, SYM_L_GLOBAL)
205 movl %eax, %eax /* discard orig_ax high bits */
206 pushq %rax /* pt_regs->orig_ax */
207 PUSH_AND_CLEAR_REGS rcx=%rbp rax=$-ENOSYS
208 UNWIND_HINT_REGS
209
210 IBRS_ENTER
211 UNTRAIN_RET
212
213 movq %rsp, %rdi
214 call do_fast_syscall_32
215 /* XEN PV guests always use IRET path */
216 ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \
217 "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV
218
219 /* Opportunistic SYSRET */
220sysret32_from_system_call:
221 /*
222 * We are not going to return to userspace from the trampoline
223 * stack. So let's erase the thread stack right now.
224 */
225 STACKLEAK_ERASE
226
227 IBRS_EXIT
228
229 movq RBX(%rsp), %rbx /* pt_regs->rbx */
230 movq RBP(%rsp), %rbp /* pt_regs->rbp */
231 movq EFLAGS(%rsp), %r11 /* pt_regs->flags (in r11) */
232 movq RIP(%rsp), %rcx /* pt_regs->ip (in rcx) */
233 addq $RAX, %rsp /* Skip r8-r15 */
234 popq %rax /* pt_regs->rax */
235 popq %rdx /* Skip pt_regs->cx */
236 popq %rdx /* pt_regs->dx */
237 popq %rsi /* pt_regs->si */
238 popq %rdi /* pt_regs->di */
239
240 /*
241 * USERGS_SYSRET32 does:
242 * GSBASE = user's GS base
243 * EIP = ECX
244 * RFLAGS = R11
245 * CS = __USER32_CS
246 * SS = __USER_DS
247 *
248 * ECX will not match pt_regs->cx, but we're returning to a vDSO
249 * trampoline that will fix up RCX, so this is okay.
250 *
251 * R12-R15 are callee-saved, so they contain whatever was in them
252 * when the system call started, which is already known to user
253 * code. We zero R8-R10 to avoid info leaks.
254 */
255 movq RSP-ORIG_RAX(%rsp), %rsp
256SYM_INNER_LABEL(entry_SYSRETL_compat_unsafe_stack, SYM_L_GLOBAL)
257 ANNOTATE_NOENDBR
258
259 /*
260 * The original userspace %rsp (RSP-ORIG_RAX(%rsp)) is stored
261 * on the process stack which is not mapped to userspace and
262 * not readable after we SWITCH_TO_USER_CR3. Delay the CR3
263 * switch until after after the last reference to the process
264 * stack.
265 *
266 * %r8/%r9 are zeroed before the sysret, thus safe to clobber.
267 */
268 SWITCH_TO_USER_CR3_NOSTACK scratch_reg=%r8 scratch_reg2=%r9
269
270 xorl %r8d, %r8d
271 xorl %r9d, %r9d
272 xorl %r10d, %r10d
273 swapgs
274 sysretl
275SYM_INNER_LABEL(entry_SYSRETL_compat_end, SYM_L_GLOBAL)
276 ANNOTATE_NOENDBR
277 int3
278SYM_CODE_END(entry_SYSCALL_compat)
279
280/*
281 * 32-bit legacy system call entry.
282 *
283 * 32-bit x86 Linux system calls traditionally used the INT $0x80
284 * instruction. INT $0x80 lands here.
285 *
286 * This entry point can be used by 32-bit and 64-bit programs to perform
287 * 32-bit system calls. Instances of INT $0x80 can be found inline in
288 * various programs and libraries. It is also used by the vDSO's
289 * __kernel_vsyscall fallback for hardware that doesn't support a faster
290 * entry method. Restarted 32-bit system calls also fall back to INT
291 * $0x80 regardless of what instruction was originally used to do the
292 * system call.
293 *
294 * This is considered a slow path. It is not used by most libc
295 * implementations on modern hardware except during process startup.
296 *
297 * Arguments:
298 * eax system call number
299 * ebx arg1
300 * ecx arg2
301 * edx arg3
302 * esi arg4
303 * edi arg5
304 * ebp arg6
305 */
306SYM_CODE_START(entry_INT80_compat)
307 UNWIND_HINT_ENTRY
308 ENDBR
309 /*
310 * Interrupts are off on entry.
311 */
312 ASM_CLAC /* Do this early to minimize exposure */
313 ALTERNATIVE "swapgs", "", X86_FEATURE_XENPV
314
315 /*
316 * User tracing code (ptrace or signal handlers) might assume that
317 * the saved RAX contains a 32-bit number when we're invoking a 32-bit
318 * syscall. Just in case the high bits are nonzero, zero-extend
319 * the syscall number. (This could almost certainly be deleted
320 * with no ill effects.)
321 */
322 movl %eax, %eax
323
324 /* switch to thread stack expects orig_ax and rdi to be pushed */
325 pushq %rax /* pt_regs->orig_ax */
326
327 /* Need to switch before accessing the thread stack. */
328 SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
329
330 /* In the Xen PV case we already run on the thread stack. */
331 ALTERNATIVE "", "jmp .Lint80_keep_stack", X86_FEATURE_XENPV
332
333 movq %rsp, %rax
334 movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rsp
335
336 pushq 5*8(%rax) /* regs->ss */
337 pushq 4*8(%rax) /* regs->rsp */
338 pushq 3*8(%rax) /* regs->eflags */
339 pushq 2*8(%rax) /* regs->cs */
340 pushq 1*8(%rax) /* regs->ip */
341 pushq 0*8(%rax) /* regs->orig_ax */
342.Lint80_keep_stack:
343
344 PUSH_AND_CLEAR_REGS rax=$-ENOSYS
345 UNWIND_HINT_REGS
346
347 cld
348
349 IBRS_ENTER
350 UNTRAIN_RET
351
352 movq %rsp, %rdi
353 call do_int80_syscall_32
354 jmp swapgs_restore_regs_and_return_to_usermode
355SYM_CODE_END(entry_INT80_compat)