summaryrefslogtreecommitdiff
path: root/arch/x86/ia32/ia32entry.S
blob: 2be23c734db5c2109b63227f86c1c880ee2ab8cb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
/*
 * Compatibility mode system call entry point for x86-64. 
 * 		
 * Copyright 2000-2002 Andi Kleen, SuSE Labs.
 */		 

#include <asm/calling.h>
#include <asm/asm-offsets.h>
#include <asm/current.h>
#include <asm/errno.h>
#include <asm/ia32_unistd.h>	
#include <asm/thread_info.h>	
#include <asm/segment.h>
#include <asm/irqflags.h>
#include <asm/asm.h>
#include <asm/smap.h>
#include <linux/linkage.h>
#include <linux/err.h>

/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
#include <linux/elf-em.h>
#define AUDIT_ARCH_I386		(EM_386|__AUDIT_ARCH_LE)
#define __AUDIT_ARCH_LE	   0x40000000

#ifndef CONFIG_AUDITSYSCALL
#define sysexit_audit ia32_ret_from_sys_call
#define sysretl_audit ia32_ret_from_sys_call
#endif

	.section .entry.text, "ax"

	/* clobbers %rax */
	.macro  CLEAR_RREGS _r9=rax
	xorl 	%eax,%eax
	movq	%rax,R11(%rsp)
	movq	%rax,R10(%rsp)
	movq	%\_r9,R9(%rsp)
	movq	%rax,R8(%rsp)
	.endm

	/*
	 * Reload arg registers from stack in case ptrace changed them.
	 * We don't reload %eax because syscall_trace_enter() returned
	 * the %rax value we should see.  Instead, we just truncate that
	 * value to 32 bits again as we did on entry from user mode.
	 * If it's a new value set by user_regset during entry tracing,
	 * this matches the normal truncation of the user-mode value.
	 * If it's -1 to make us punt the syscall, then (u32)-1 is still
	 * an appropriately invalid value.
	 */
	.macro LOAD_ARGS32 _r9=0
	.if \_r9
	movl R9(%rsp),%r9d
	.endif
	movl RCX(%rsp),%ecx
	movl RDX(%rsp),%edx
	movl RSI(%rsp),%esi
	movl RDI(%rsp),%edi
	movl %eax,%eax			/* zero extension */
	.endm
	

#ifdef CONFIG_PARAVIRT
ENTRY(native_usergs_sysret32)
	swapgs
	sysretl
ENDPROC(native_usergs_sysret32)
#endif

/*
 * 32bit SYSENTER instruction entry.
 *
 * SYSENTER loads ss, rsp, cs, and rip from previously programmed MSRs.
 * IF and VM in rflags are cleared (IOW: interrupts are off).
 * SYSENTER does not save anything on the stack,
 * and does not save old rip (!!!) and rflags.
 *
 * Arguments:
 * eax  system call number
 * ebx  arg1
 * ecx  arg2
 * edx  arg3
 * esi  arg4
 * edi  arg5
 * ebp  user stack
 * 0(%ebp) arg6
 *
 * This is purely a fast path. For anything complicated we use the int 0x80
 * path below. We set up a complete hardware stack frame to share code
 * with the int 0x80 path.
 */
ENTRY(ia32_sysenter_target)
	/*
	 * Interrupts are off on entry.
	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
	 * it is too small to ever cause noticeable irq latency.
	 */
	SWAPGS_UNSAFE_STACK
	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp
	ENABLE_INTERRUPTS(CLBR_NONE)

	/* Zero-extending 32-bit regs, do not remove */
	movl	%ebp, %ebp
	movl	%eax, %eax

	movl	ASM_THREAD_INFO(TI_sysenter_return, %rsp, 0), %r10d

	/* Construct struct pt_regs on stack */
	pushq	$__USER32_DS		/* pt_regs->ss */
	pushq	%rbp			/* pt_regs->sp */
	pushfq				/* pt_regs->flags */
	pushq	$__USER32_CS		/* pt_regs->cs */
	pushq	%r10 /* pt_regs->ip = thread_info->sysenter_return */
	pushq	%rax			/* pt_regs->orig_ax */
	pushq	%rdi			/* pt_regs->di */
	pushq	%rsi			/* pt_regs->si */
	pushq	%rdx			/* pt_regs->dx */
	pushq	%rcx			/* pt_regs->cx */
	pushq	$-ENOSYS		/* pt_regs->ax */
	cld
	sub	$(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */

	/*
	 * no need to do an access_ok check here because rbp has been
	 * 32bit zero extended
	 */
	ASM_STAC
1:	movl	(%rbp),%ebp
	_ASM_EXTABLE(1b,ia32_badarg)
	ASM_CLAC

	/*
	 * Sysenter doesn't filter flags, so we need to clear NT
	 * ourselves.  To save a few cycles, we can check whether
	 * NT was set instead of doing an unconditional popfq.
	 */
	testl $X86_EFLAGS_NT,EFLAGS(%rsp)
	jnz sysenter_fix_flags
sysenter_flags_fixed:

	orl     $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	testl   $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz  sysenter_tracesys

sysenter_do_call:
	/* 32bit syscall -> 64bit C ABI argument conversion */
	movl	%edi,%r8d	/* arg5 */
	movl	%ebp,%r9d	/* arg6 */
	xchg	%ecx,%esi	/* rsi:arg2, rcx:arg4 */
	movl	%ebx,%edi	/* arg1 */
	movl	%edx,%edx	/* arg3 (zero extension) */
sysenter_dispatch:
	cmpq	$(IA32_NR_syscalls-1),%rax
	ja	1f
	call	*ia32_sys_call_table(,%rax,8)
	movq	%rax,RAX(%rsp)
1:
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	testl	$_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz	sysexit_audit
sysexit_from_sys_call:
	/*
	 * NB: SYSEXIT is not obviously safe for 64-bit kernels -- an
	 * NMI between STI and SYSEXIT has poorly specified behavior,
	 * and and NMI followed by an IRQ with usergs is fatal.  So
	 * we just pretend we're using SYSEXIT but we really use
	 * SYSRETL instead.
	 *
	 * This code path is still called 'sysexit' because it pairs
	 * with 'sysenter' and it uses the SYSENTER calling convention.
	 */
	andl    $~TS_COMPAT,ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	movl	RIP(%rsp),%ecx		/* User %eip */
	RESTORE_RSI_RDI
	xorl	%edx,%edx		/* avoid info leaks */
	xorq	%r8,%r8
	xorq	%r9,%r9
	xorq	%r10,%r10
	movl	EFLAGS(%rsp),%r11d	/* User eflags */
	TRACE_IRQS_ON

	/*
	 * SYSRETL works even on Intel CPUs.  Use it in preference to SYSEXIT,
	 * since it avoids a dicey window with interrupts enabled.
	 */
	movl	RSP(%rsp),%esp

	/*
	 * USERGS_SYSRET32 does:
	 *  gsbase = user's gs base
	 *  eip = ecx
	 *  rflags = r11
	 *  cs = __USER32_CS
	 *  ss = __USER_DS
	 *
	 * The prologue set RIP(%rsp) to VDSO32_SYSENTER_RETURN, which does:
	 *
	 *  pop %ebp
	 *  pop %edx
	 *  pop %ecx
	 *
	 * Therefore, we invoke SYSRETL with EDX and R8-R10 zeroed to
	 * avoid info leaks.  R11 ends up with VDSO32_SYSENTER_RETURN's
	 * address (already known to user code), and R12-R15 are
	 * callee-saved and therefore don't contain any interesting
	 * kernel data.
	 */
	USERGS_SYSRET32

#ifdef CONFIG_AUDITSYSCALL
	.macro auditsys_entry_common
	movl %esi,%r8d			/* 5th arg: 4th syscall arg */
	movl %ecx,%r9d			/*swap with edx*/
	movl %edx,%ecx			/* 4th arg: 3rd syscall arg */
	movl %r9d,%edx			/* 3rd arg: 2nd syscall arg */
	movl %ebx,%esi			/* 2nd arg: 1st syscall arg */
	movl %eax,%edi			/* 1st arg: syscall number */
	call __audit_syscall_entry
	movl ORIG_RAX(%rsp),%eax	/* reload syscall number */
	movl %ebx,%edi			/* reload 1st syscall arg */
	movl RCX(%rsp),%esi	/* reload 2nd syscall arg */
	movl RDX(%rsp),%edx	/* reload 3rd syscall arg */
	movl RSI(%rsp),%ecx	/* reload 4th syscall arg */
	movl RDI(%rsp),%r8d	/* reload 5th syscall arg */
	.endm

	.macro auditsys_exit exit
	testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz ia32_ret_from_sys_call
	TRACE_IRQS_ON
	ENABLE_INTERRUPTS(CLBR_NONE)
	movl %eax,%esi		/* second arg, syscall return value */
	cmpl $-MAX_ERRNO,%eax	/* is it an error ? */
	jbe 1f
	movslq %eax, %rsi	/* if error sign extend to 64 bits */
1:	setbe %al		/* 1 if error, 0 if not */
	movzbl %al,%edi		/* zero-extend that into %edi */
	call __audit_syscall_exit
	movq RAX(%rsp),%rax	/* reload syscall return value */
	movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	testl %edi, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jz \exit
	CLEAR_RREGS
	jmp int_with_check
	.endm

sysenter_auditsys:
	auditsys_entry_common
	movl %ebp,%r9d			/* reload 6th syscall arg */
	jmp sysenter_dispatch

sysexit_audit:
	auditsys_exit sysexit_from_sys_call
#endif

sysenter_fix_flags:
	pushq $(X86_EFLAGS_IF|X86_EFLAGS_FIXED)
	popfq
	jmp sysenter_flags_fixed

sysenter_tracesys:
#ifdef CONFIG_AUDITSYSCALL
	testl	$(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jz	sysenter_auditsys
#endif
	SAVE_EXTRA_REGS
	CLEAR_RREGS
	movq	%rsp,%rdi        /* &pt_regs -> arg1 */
	call	syscall_trace_enter
	LOAD_ARGS32  /* reload args from stack in case ptrace changed it */
	RESTORE_EXTRA_REGS
	jmp	sysenter_do_call
ENDPROC(ia32_sysenter_target)

/*
 * 32bit SYSCALL instruction entry.
 *
 * 32bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11,
 * then loads new ss, cs, and rip from previously programmed MSRs.
 * rflags gets masked by a value from another MSR (so CLD and CLAC
 * are not needed). SYSCALL does not save anything on the stack
 * and does not change rsp.
 *
 * Note: rflags saving+masking-with-MSR happens only in Long mode
 * (in legacy 32bit mode, IF, RF and VM bits are cleared and that's it).
 * Don't get confused: rflags saving+masking depends on Long Mode Active bit
 * (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes
 * or target CS descriptor's L bit (SYSCALL does not read segment descriptors).
 *
 * Arguments:
 * eax  system call number
 * ecx  return address
 * ebx  arg1
 * ebp  arg2	(note: not saved in the stack frame, should not be touched)
 * edx  arg3
 * esi  arg4
 * edi  arg5
 * esp  user stack
 * 0(%esp) arg6
 *
 * This is purely a fast path. For anything complicated we use the int 0x80
 * path below. We set up a complete hardware stack frame to share code
 * with the int 0x80 path.
 */
ENTRY(ia32_cstar_target)
	/*
	 * Interrupts are off on entry.
	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
	 * it is too small to ever cause noticeable irq latency.
	 */
	SWAPGS_UNSAFE_STACK
	movl	%esp,%r8d
	movq	PER_CPU_VAR(cpu_current_top_of_stack),%rsp
	ENABLE_INTERRUPTS(CLBR_NONE)

	/* Zero-extending 32-bit regs, do not remove */
	movl	%eax,%eax

	/* Construct struct pt_regs on stack */
	pushq	$__USER32_DS		/* pt_regs->ss */
	pushq	%r8			/* pt_regs->sp */
	pushq	%r11			/* pt_regs->flags */
	pushq	$__USER32_CS		/* pt_regs->cs */
	pushq	%rcx			/* pt_regs->ip */
	pushq	%rax			/* pt_regs->orig_ax */
	pushq	%rdi			/* pt_regs->di */
	pushq	%rsi			/* pt_regs->si */
	pushq	%rdx			/* pt_regs->dx */
	pushq	%rbp			/* pt_regs->cx */
	movl	%ebp,%ecx
	pushq	$-ENOSYS		/* pt_regs->ax */
	sub	$(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */

	/*
	 * no need to do an access_ok check here because r8 has been
	 * 32bit zero extended
	 */
	ASM_STAC
1:	movl	(%r8),%r9d
	_ASM_EXTABLE(1b,ia32_badarg)
	ASM_CLAC
	orl     $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	testl   $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz   cstar_tracesys

cstar_do_call:
	/* 32bit syscall -> 64bit C ABI argument conversion */
	movl	%edi,%r8d	/* arg5 */
	/* r9 already loaded */	/* arg6 */
	xchg	%ecx,%esi	/* rsi:arg2, rcx:arg4 */
	movl	%ebx,%edi	/* arg1 */
	movl	%edx,%edx	/* arg3 (zero extension) */
cstar_dispatch:
	cmpq	$(IA32_NR_syscalls-1),%rax
	ja	1f
	call *ia32_sys_call_table(,%rax,8)
	movq %rax,RAX(%rsp)
1:
	DISABLE_INTERRUPTS(CLBR_NONE)
	TRACE_IRQS_OFF
	testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz sysretl_audit
sysretl_from_sys_call:
	andl $~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	RESTORE_RSI_RDI_RDX
	movl RIP(%rsp),%ecx
	movl EFLAGS(%rsp),%r11d
	xorq	%r10,%r10
	xorq	%r9,%r9
	xorq	%r8,%r8
	TRACE_IRQS_ON
	movl RSP(%rsp),%esp
	/*
	 * 64bit->32bit SYSRET restores eip from ecx,
	 * eflags from r11 (but RF and VM bits are forced to 0),
	 * cs and ss are loaded from MSRs.
	 * (Note: 32bit->32bit SYSRET is different: since r11
	 * does not exist, it merely sets eflags.IF=1).
	 *
	 * NB: On AMD CPUs with the X86_BUG_SYSRET_SS_ATTRS bug, the ss
	 * descriptor is not reinitialized.  This means that we must
	 * avoid SYSRET with SS == NULL, which could happen if we schedule,
	 * exit the kernel, and re-enter using an interrupt vector.  (All
	 * interrupt entries on x86_64 set SS to NULL.)  We prevent that
	 * from happening by reloading SS in __switch_to.
	 */
	USERGS_SYSRET32

#ifdef CONFIG_AUDITSYSCALL
cstar_auditsys:
	movl %r9d,R9(%rsp)	/* register to be clobbered by call */
	auditsys_entry_common
	movl R9(%rsp),%r9d	/* reload 6th syscall arg */
	jmp cstar_dispatch

sysretl_audit:
	auditsys_exit sysretl_from_sys_call
#endif

cstar_tracesys:
#ifdef CONFIG_AUDITSYSCALL
	testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jz cstar_auditsys
#endif
	xchgl %r9d,%ebp
	SAVE_EXTRA_REGS
	CLEAR_RREGS r9
	movq %rsp,%rdi        /* &pt_regs -> arg1 */
	call syscall_trace_enter
	LOAD_ARGS32 1	/* reload args from stack in case ptrace changed it */
	RESTORE_EXTRA_REGS
	xchgl %ebp,%r9d
	jmp cstar_do_call
END(ia32_cstar_target)
				
ia32_badarg:
	ASM_CLAC
	movq $-EFAULT,%rax
	jmp ia32_sysret

/*
 * Emulated IA32 system calls via int 0x80.
 *
 * Arguments:
 * eax  system call number
 * ebx  arg1
 * ecx  arg2
 * edx  arg3
 * esi  arg4
 * edi  arg5
 * ebp  arg6	(note: not saved in the stack frame, should not be touched)
 *
 * Notes:
 * Uses the same stack frame as the x86-64 version.
 * All registers except eax must be saved (but ptrace may violate that).
 * Arguments are zero extended. For system calls that want sign extension and
 * take long arguments a wrapper is needed. Most calls can just be called
 * directly.
 * Assumes it is only called from user space and entered with interrupts off.
 */

ENTRY(ia32_syscall)
	/*
	 * Interrupts are off on entry.
	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
	 * it is too small to ever cause noticeable irq latency.
	 */
	PARAVIRT_ADJUST_EXCEPTION_FRAME
	SWAPGS
	ENABLE_INTERRUPTS(CLBR_NONE)

	/* Zero-extending 32-bit regs, do not remove */
	movl	%eax,%eax

	/* Construct struct pt_regs on stack (iret frame is already on stack) */
	pushq	%rax			/* pt_regs->orig_ax */
	pushq	%rdi			/* pt_regs->di */
	pushq	%rsi			/* pt_regs->si */
	pushq	%rdx			/* pt_regs->dx */
	pushq	%rcx			/* pt_regs->cx */
	pushq	$-ENOSYS		/* pt_regs->ax */
	cld
	sub	$(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */

	orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
	testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
	jnz ia32_tracesys
ia32_do_call:
	/* 32bit syscall -> 64bit C ABI argument conversion */
	movl %edi,%r8d	/* arg5 */
	movl %ebp,%r9d	/* arg6 */
	xchg %ecx,%esi	/* rsi:arg2, rcx:arg4 */
	movl %ebx,%edi	/* arg1 */
	movl %edx,%edx	/* arg3 (zero extension) */
	cmpq	$(IA32_NR_syscalls-1),%rax
	ja	1f
	call *ia32_sys_call_table(,%rax,8) # xxx: rip relative
ia32_sysret:
	movq %rax,RAX(%rsp)
1:
ia32_ret_from_sys_call:
	CLEAR_RREGS
	jmp int_ret_from_sys_call

ia32_tracesys:
	SAVE_EXTRA_REGS
	CLEAR_RREGS
	movq %rsp,%rdi        /* &pt_regs -> arg1 */
	call syscall_trace_enter
	LOAD_ARGS32	/* reload args from stack in case ptrace changed it */
	RESTORE_EXTRA_REGS
	jmp ia32_do_call
END(ia32_syscall)

	.macro PTREGSCALL label, func
	ALIGN
GLOBAL(\label)
	leaq \func(%rip),%rax
	jmp  ia32_ptregs_common	
	.endm

	PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn
	PTREGSCALL stub32_sigreturn, sys32_sigreturn
	PTREGSCALL stub32_fork, sys_fork
	PTREGSCALL stub32_vfork, sys_vfork

	ALIGN
GLOBAL(stub32_clone)
	leaq sys_clone(%rip),%rax
	mov	%r8, %rcx
	jmp  ia32_ptregs_common	

	ALIGN
ia32_ptregs_common:
	SAVE_EXTRA_REGS 8
	call *%rax
	RESTORE_EXTRA_REGS 8
	ret
END(ia32_ptregs_common)