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1da177e4 1/*
54ad726c
IM
2 * Compatibility mode system call entry point for x86-64.
3 *
1da177e4 4 * Copyright 2000-2002 Andi Kleen, SuSE Labs.
54ad726c 5 */
d36f9479 6#include "calling.h"
e2d5df93 7#include <asm/asm-offsets.h>
1da177e4
LT
8#include <asm/current.h>
9#include <asm/errno.h>
54ad726c
IM
10#include <asm/ia32_unistd.h>
11#include <asm/thread_info.h>
1da177e4 12#include <asm/segment.h>
2601e64d 13#include <asm/irqflags.h>
1ce6f868 14#include <asm/asm.h>
63bcff2a 15#include <asm/smap.h>
1da177e4 16#include <linux/linkage.h>
d7e7528b 17#include <linux/err.h>
1da177e4 18
ea714547
JO
19 .section .entry.text, "ax"
20
1da177e4 21/*
54ad726c 22 * 32-bit SYSENTER instruction entry.
1da177e4 23 *
b87cf63e
DV
24 * SYSENTER loads ss, rsp, cs, and rip from previously programmed MSRs.
25 * IF and VM in rflags are cleared (IOW: interrupts are off).
26 * SYSENTER does not save anything on the stack,
27 * and does not save old rip (!!!) and rflags.
28 *
1da177e4 29 * Arguments:
b87cf63e
DV
30 * eax system call number
31 * ebx arg1
32 * ecx arg2
33 * edx arg3
34 * esi arg4
35 * edi arg5
36 * ebp user stack
37 * 0(%ebp) arg6
38 *
1da177e4 39 * This is purely a fast path. For anything complicated we use the int 0x80
b87cf63e 40 * path below. We set up a complete hardware stack frame to share code
1da177e4 41 * with the int 0x80 path.
b87cf63e 42 */
4c8cd0c5 43ENTRY(entry_SYSENTER_compat)
b611acf4 44 /* Interrupts are off on entry. */
a232e3d5 45 SWAPGS_UNSAFE_STACK
3a23208e 46 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
a232e3d5 47
a474e67c
AL
48 /*
49 * User tracing code (ptrace or signal handlers) might assume that
50 * the saved RAX contains a 32-bit number when we're invoking a 32-bit
51 * syscall. Just in case the high bits are nonzero, zero-extend
52 * the syscall number. (This could almost certainly be deleted
53 * with no ill effects.)
54 */
4ee8ec17
DV
55 movl %eax, %eax
56
4c9c0e91 57 /* Construct struct pt_regs on stack */
131484c8 58 pushq $__USER32_DS /* pt_regs->ss */
30bfa7b3 59 pushq %rbp /* pt_regs->sp (stashed in bp) */
b611acf4
AL
60
61 /*
62 * Push flags. This is nasty. First, interrupts are currently
63 * off, but we need pt_regs->flags to have IF set. Second, even
64 * if TF was set when SYSENTER started, it's clear by now. We fix
65 * that later using TIF_SINGLESTEP.
66 */
67 pushfq /* pt_regs->flags (except IF = 0) */
68 orl $X86_EFLAGS_IF, (%rsp) /* Fix saved flags */
a474e67c 69 ASM_CLAC /* Clear AC after saving FLAGS */
b611acf4 70
131484c8 71 pushq $__USER32_CS /* pt_regs->cs */
a474e67c
AL
72 xorq %r8,%r8
73 pushq %r8 /* pt_regs->ip = 0 (placeholder) */
131484c8
IM
74 pushq %rax /* pt_regs->orig_ax */
75 pushq %rdi /* pt_regs->di */
76 pushq %rsi /* pt_regs->si */
77 pushq %rdx /* pt_regs->dx */
30bfa7b3 78 pushq %rcx /* pt_regs->cx */
131484c8 79 pushq $-ENOSYS /* pt_regs->ax */
a474e67c
AL
80 pushq %r8 /* pt_regs->r8 = 0 */
81 pushq %r8 /* pt_regs->r9 = 0 */
82 pushq %r8 /* pt_regs->r10 = 0 */
83 pushq %r8 /* pt_regs->r11 = 0 */
84 pushq %rbx /* pt_regs->rbx */
30bfa7b3 85 pushq %rbp /* pt_regs->rbp (will be overwritten) */
a474e67c
AL
86 pushq %r8 /* pt_regs->r12 = 0 */
87 pushq %r8 /* pt_regs->r13 = 0 */
88 pushq %r8 /* pt_regs->r14 = 0 */
89 pushq %r8 /* pt_regs->r15 = 0 */
1da177e4 90 cld
4c9c0e91 91
8c7aa698
AL
92 /*
93 * Sysenter doesn't filter flags, so we need to clear NT
94 * ourselves. To save a few cycles, we can check whether
95 * NT was set instead of doing an unconditional popfq.
b611acf4
AL
96 * This needs to happen before enabling interrupts so that
97 * we don't get preempted with NT set.
374a3a39 98 *
f74acf0e 99 * NB.: .Lsysenter_fix_flags is a label with the code under it moved
374a3a39
BP
100 * out-of-line as an optimization: NT is unlikely to be set in the
101 * majority of the cases and instead of polluting the I$ unnecessarily,
102 * we're keeping that code behind a branch which will predict as
103 * not-taken and therefore its instructions won't be fetched.
8c7aa698 104 */
54ad726c 105 testl $X86_EFLAGS_NT, EFLAGS(%rsp)
f74acf0e
BP
106 jnz .Lsysenter_fix_flags
107.Lsysenter_flags_fixed:
8c7aa698 108
a474e67c
AL
109 /*
110 * User mode is traced as though IRQs are on, and SYSENTER
111 * turned them off.
112 */
113 TRACE_IRQS_OFF
e62a254a 114
a474e67c
AL
115 movq %rsp, %rdi
116 call do_fast_syscall_32
91e2eea9
BO
117 /* XEN PV guests always use IRET path */
118 ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
119 "jmp .Lsyscall_32_done", X86_FEATURE_XENPV
7841b408 120 jmp sysret32_from_system_call
1da177e4 121
f74acf0e 122.Lsysenter_fix_flags:
b611acf4 123 pushq $X86_EFLAGS_FIXED
131484c8 124 popfq
f74acf0e 125 jmp .Lsysenter_flags_fixed
4c8cd0c5 126ENDPROC(entry_SYSENTER_compat)
1da177e4
LT
127
128/*
54ad726c 129 * 32-bit SYSCALL instruction entry.
1da177e4 130 *
54ad726c 131 * 32-bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11,
b87cf63e
DV
132 * then loads new ss, cs, and rip from previously programmed MSRs.
133 * rflags gets masked by a value from another MSR (so CLD and CLAC
134 * are not needed). SYSCALL does not save anything on the stack
135 * and does not change rsp.
136 *
137 * Note: rflags saving+masking-with-MSR happens only in Long mode
54ad726c 138 * (in legacy 32-bit mode, IF, RF and VM bits are cleared and that's it).
b87cf63e
DV
139 * Don't get confused: rflags saving+masking depends on Long Mode Active bit
140 * (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes
141 * or target CS descriptor's L bit (SYSCALL does not read segment descriptors).
142 *
1da177e4 143 * Arguments:
b87cf63e
DV
144 * eax system call number
145 * ecx return address
146 * ebx arg1
147 * ebp arg2 (note: not saved in the stack frame, should not be touched)
148 * edx arg3
149 * esi arg4
150 * edi arg5
151 * esp user stack
152 * 0(%esp) arg6
b87cf63e 153 */
2cd23553 154ENTRY(entry_SYSCALL_compat)
a474e67c 155 /* Interrupts are off on entry. */
457da70e 156 SWAPGS_UNSAFE_STACK
e62a254a 157
a474e67c 158 /* Stash user ESP and switch to the kernel stack. */
54ad726c
IM
159 movl %esp, %r8d
160 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
a232e3d5 161
4ee8ec17 162 /* Zero-extending 32-bit regs, do not remove */
54ad726c 163 movl %eax, %eax
4ee8ec17 164
4c9c0e91 165 /* Construct struct pt_regs on stack */
131484c8
IM
166 pushq $__USER32_DS /* pt_regs->ss */
167 pushq %r8 /* pt_regs->sp */
168 pushq %r11 /* pt_regs->flags */
169 pushq $__USER32_CS /* pt_regs->cs */
170 pushq %rcx /* pt_regs->ip */
171 pushq %rax /* pt_regs->orig_ax */
172 pushq %rdi /* pt_regs->di */
173 pushq %rsi /* pt_regs->si */
174 pushq %rdx /* pt_regs->dx */
30bfa7b3 175 pushq %rbp /* pt_regs->cx (stashed in bp) */
131484c8 176 pushq $-ENOSYS /* pt_regs->ax */
a474e67c
AL
177 xorq %r8,%r8
178 pushq %r8 /* pt_regs->r8 = 0 */
179 pushq %r8 /* pt_regs->r9 = 0 */
180 pushq %r8 /* pt_regs->r10 = 0 */
181 pushq %r8 /* pt_regs->r11 = 0 */
182 pushq %rbx /* pt_regs->rbx */
30bfa7b3 183 pushq %rbp /* pt_regs->rbp (will be overwritten) */
a474e67c
AL
184 pushq %r8 /* pt_regs->r12 = 0 */
185 pushq %r8 /* pt_regs->r13 = 0 */
186 pushq %r8 /* pt_regs->r14 = 0 */
187 pushq %r8 /* pt_regs->r15 = 0 */
4c9c0e91 188
a474e67c
AL
189 /*
190 * User mode is traced as though IRQs are on, and SYSENTER
191 * turned them off.
192 */
193 TRACE_IRQS_OFF
194
195 movq %rsp, %rdi
196 call do_fast_syscall_32
91e2eea9
BO
197 /* XEN PV guests always use IRET path */
198 ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
199 "jmp .Lsyscall_32_done", X86_FEATURE_XENPV
7841b408
AL
200
201 /* Opportunistic SYSRET */
202sysret32_from_system_call:
203 TRACE_IRQS_ON /* User mode traces as IRQs on. */
204 movq RBX(%rsp), %rbx /* pt_regs->rbx */
205 movq RBP(%rsp), %rbp /* pt_regs->rbp */
206 movq EFLAGS(%rsp), %r11 /* pt_regs->flags (in r11) */
207 movq RIP(%rsp), %rcx /* pt_regs->ip (in rcx) */
208 addq $RAX, %rsp /* Skip r8-r15 */
209 popq %rax /* pt_regs->rax */
210 popq %rdx /* Skip pt_regs->cx */
211 popq %rdx /* pt_regs->dx */
212 popq %rsi /* pt_regs->si */
213 popq %rdi /* pt_regs->di */
214
215 /*
216 * USERGS_SYSRET32 does:
217 * GSBASE = user's GS base
218 * EIP = ECX
219 * RFLAGS = R11
220 * CS = __USER32_CS
221 * SS = __USER_DS
222 *
223 * ECX will not match pt_regs->cx, but we're returning to a vDSO
224 * trampoline that will fix up RCX, so this is okay.
225 *
226 * R12-R15 are callee-saved, so they contain whatever was in them
227 * when the system call started, which is already known to user
228 * code. We zero R8-R10 to avoid info leaks.
229 */
230 xorq %r8, %r8
231 xorq %r9, %r9
232 xorq %r10, %r10
233 movq RSP-ORIG_RAX(%rsp), %rsp
75ef8219
BO
234 swapgs
235 sysretl
2cd23553 236END(entry_SYSCALL_compat)
54ad726c 237
b87cf63e
DV
238/*
239 * Emulated IA32 system calls via int 0x80.
1da177e4 240 *
b87cf63e
DV
241 * Arguments:
242 * eax system call number
243 * ebx arg1
244 * ecx arg2
245 * edx arg3
246 * esi arg4
247 * edi arg5
248 * ebp arg6 (note: not saved in the stack frame, should not be touched)
1da177e4
LT
249 *
250 * Notes:
b87cf63e
DV
251 * Uses the same stack frame as the x86-64 version.
252 * All registers except eax must be saved (but ptrace may violate that).
1da177e4
LT
253 * Arguments are zero extended. For system calls that want sign extension and
254 * take long arguments a wrapper is needed. Most calls can just be called
255 * directly.
b87cf63e
DV
256 * Assumes it is only called from user space and entered with interrupts off.
257 */
1da177e4 258
2cd23553 259ENTRY(entry_INT80_compat)
2601e64d 260 /*
a232e3d5 261 * Interrupts are off on entry.
2601e64d 262 */
a232e3d5 263 PARAVIRT_ADJUST_EXCEPTION_FRAME
3d44d51b 264 ASM_CLAC /* Do this early to minimize exposure */
a232e3d5 265 SWAPGS
a232e3d5 266
ee08c6bd
AL
267 /*
268 * User tracing code (ptrace or signal handlers) might assume that
269 * the saved RAX contains a 32-bit number when we're invoking a 32-bit
270 * syscall. Just in case the high bits are nonzero, zero-extend
271 * the syscall number. (This could almost certainly be deleted
272 * with no ill effects.)
273 */
54ad726c 274 movl %eax, %eax
4ee8ec17 275
4c9c0e91 276 /* Construct struct pt_regs on stack (iret frame is already on stack) */
131484c8
IM
277 pushq %rax /* pt_regs->orig_ax */
278 pushq %rdi /* pt_regs->di */
279 pushq %rsi /* pt_regs->si */
280 pushq %rdx /* pt_regs->dx */
281 pushq %rcx /* pt_regs->cx */
282 pushq $-ENOSYS /* pt_regs->ax */
8169aff6
AL
283 xorq %r8,%r8
284 pushq %r8 /* pt_regs->r8 = 0 */
285 pushq %r8 /* pt_regs->r9 = 0 */
286 pushq %r8 /* pt_regs->r10 = 0 */
287 pushq %r8 /* pt_regs->r11 = 0 */
288 pushq %rbx /* pt_regs->rbx */
289 pushq %rbp /* pt_regs->rbp */
290 pushq %r12 /* pt_regs->r12 */
291 pushq %r13 /* pt_regs->r13 */
292 pushq %r14 /* pt_regs->r14 */
293 pushq %r15 /* pt_regs->r15 */
1da177e4 294 cld
54ad726c 295
73cbf687 296 /*
ee08c6bd
AL
297 * User mode is traced as though IRQs are on, and the interrupt
298 * gate turned them off.
73cbf687 299 */
ee08c6bd
AL
300 TRACE_IRQS_OFF
301
302 movq %rsp, %rdi
657c1eea 303 call do_syscall_32_irqs_off
a474e67c 304.Lsyscall_32_done:
ee08c6bd
AL
305
306 /* Go back to user mode. */
307 TRACE_IRQS_ON
308 SWAPGS
309 jmp restore_regs_and_iret
2cd23553 310END(entry_INT80_compat)
1da177e4 311
1d4b4b29
AV
312 ALIGN
313GLOBAL(stub32_clone)
5cdc683b 314 /*
7a5a9824
DV
315 * The 32-bit clone ABI is: clone(..., int tls_val, int *child_tidptr).
316 * The 64-bit clone ABI is: clone(..., int *child_tidptr, int tls_val).
317 *
318 * The native 64-bit kernel's sys_clone() implements the latter,
319 * so we need to swap arguments here before calling it:
5cdc683b 320 */
7a5a9824 321 xchg %r8, %rcx
8169aff6 322 jmp sys_clone