arch/x86/kernel/entry_32.S

   1 /*
   2  *
   3  *  Copyright (C) 1991, 1992  Linus Torvalds
   4  */
   5
   6 /*
   7  * entry.S contains the system-call and fault low-level handling routines.
   8  * This also contains the timer-interrupt handler, as well as all interrupts
   9  * and faults that can result in a task-switch.
  10  *
  11  * NOTE: This code handles signal-recognition, which happens every time
  12  * after a timer-interrupt and after each system call.
  13  *
  14  * I changed all the .align's to 4 (16 byte alignment), as that's faster
  15  * on a 486.
  16  *
  17  * Stack layout in 'syscall_exit':
  18  *      ptrace needs to have all regs on the stack.
  19  *      if the order here is changed, it needs to be
  20  *      updated in fork.c:copy_process, signal.c:do_signal,
  21  *      ptrace.c and ptrace.h
  22  *
  23  *       0(%esp) - %ebx
  24  *       4(%esp) - %ecx
  25  *       8(%esp) - %edx
  26  *       C(%esp) - %esi
  27  *      10(%esp) - %edi
  28  *      14(%esp) - %ebp
  29  *      18(%esp) - %eax
  30  *      1C(%esp) - %ds
  31  *      20(%esp) - %es
  32  *      24(%esp) - %fs
  33  *      28(%esp) - %gs          saved iff !CONFIG_X86_32_LAZY_GS
  34  *      2C(%esp) - orig_eax
  35  *      30(%esp) - %eip
  36  *      34(%esp) - %cs
  37  *      38(%esp) - %eflags
  38  *      3C(%esp) - %oldesp
  39  *      40(%esp) - %oldss
  40  *
  41  * "current" is in register %ebx during any slow entries.
  42  */
  43
  44 #include <linux/linkage.h>
  45 #include <asm/thread_info.h>
  46 #include <asm/irqflags.h>
  47 #include <asm/errno.h>
  48 #include <asm/segment.h>
  49 #include <asm/smp.h>
  50 #include <asm/page_types.h>
  51 #include <asm/desc.h>
  52 #include <asm/percpu.h>
  53 #include <asm/dwarf2.h>
  54 #include <asm/processor-flags.h>
  55 #include <asm/ftrace.h>
  56 #include <asm/irq_vectors.h>
  57
  58 /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
  59 #include <linux/elf-em.h>
  60 #define AUDIT_ARCH_I386         (EM_386|__AUDIT_ARCH_LE)
  61 #define __AUDIT_ARCH_LE    0x40000000
  62
  63 #ifndef CONFIG_AUDITSYSCALL
  64 #define sysenter_audit  syscall_trace_entry
  65 #define sysexit_audit   syscall_exit_work
  66 #endif
  67
  68 /*
  69  * We use macros for low-level operations which need to be overridden
  70  * for paravirtualization.  The following will never clobber any registers:
  71  *   INTERRUPT_RETURN (aka. "iret")
  72  *   GET_CR0_INTO_EAX (aka. "movl %cr0, %eax")
  73  *   ENABLE_INTERRUPTS_SYSEXIT (aka "sti; sysexit").
  74  *
  75  * For DISABLE_INTERRUPTS/ENABLE_INTERRUPTS (aka "cli"/"sti"), you must
  76  * specify what registers can be overwritten (CLBR_NONE, CLBR_EAX/EDX/ECX/ANY).
  77  * Allowing a register to be clobbered can shrink the paravirt replacement
  78  * enough to patch inline, increasing performance.
  79  */
  80
  81 #define nr_syscalls ((syscall_table_size)/4)
  82
  83 #ifdef CONFIG_PREEMPT
  84 #define preempt_stop(clobbers)  DISABLE_INTERRUPTS(clobbers); TRACE_IRQS_OFF
  85 #else
  86 #define preempt_stop(clobbers)
  87 #define resume_kernel           restore_nocheck
  88 #endif
  89
  90 .macro TRACE_IRQS_IRET
  91 #ifdef CONFIG_TRACE_IRQFLAGS
  92         testl $X86_EFLAGS_IF,PT_EFLAGS(%esp)     # interrupts off?
  93         jz 1f
  94         TRACE_IRQS_ON
  95 1:
  96 #endif
  97 .endm
  98
  99 #ifdef CONFIG_VM86
 100 #define resume_userspace_sig    check_userspace
 101 #else
 102 #define resume_userspace_sig    resume_userspace
 103 #endif
 104
 105 /*
 106  * User gs save/restore
 107  *
 108  * %gs is used for userland TLS and kernel only uses it for stack
 109  * canary which is required to be at %gs:20 by gcc.  Read the comment
 110  * at the top of stackprotector.h for more info.
 111  *
 112  * Local labels 98 and 99 are used.
 113  */
 114 #ifdef CONFIG_X86_32_LAZY_GS
 115
 116  /* unfortunately push/pop can't be no-op */
 117 .macro PUSH_GS
 118         pushl $0
 119         CFI_ADJUST_CFA_OFFSET 4
 120 .endm
 121 .macro POP_GS pop=0
 122         addl $(4 + \pop), %esp
 123         CFI_ADJUST_CFA_OFFSET -(4 + \pop)
 124 .endm
 125 .macro POP_GS_EX
 126 .endm
 127
 128  /* all the rest are no-op */
 129 .macro PTGS_TO_GS
 130 .endm
 131 .macro PTGS_TO_GS_EX
 132 .endm
 133 .macro GS_TO_REG reg
 134 .endm
 135 .macro REG_TO_PTGS reg
 136 .endm
 137 .macro SET_KERNEL_GS reg
 138 .endm
 139
 140 #else   /* CONFIG_X86_32_LAZY_GS */
 141
 142 .macro PUSH_GS
 143         pushl %gs
 144         CFI_ADJUST_CFA_OFFSET 4
 145         /*CFI_REL_OFFSET gs, 0*/
 146 .endm
 147
 148 .macro POP_GS pop=0
 149 98:     popl %gs
 150         CFI_ADJUST_CFA_OFFSET -4
 151         /*CFI_RESTORE gs*/
 152   .if \pop <> 0
 153         add $\pop, %esp
 154         CFI_ADJUST_CFA_OFFSET -\pop
 155   .endif
 156 .endm
 157 .macro POP_GS_EX
 158 .pushsection .fixup, "ax"
 159 99:     movl $0, (%esp)
 160         jmp 98b
 161 .section __ex_table, "a"
 162         .align 4
 163         .long 98b, 99b
 164 .popsection
 165 .endm
 166
 167 .macro PTGS_TO_GS
 168 98:     mov PT_GS(%esp), %gs
 169 .endm
 170 .macro PTGS_TO_GS_EX
 171 .pushsection .fixup, "ax"
 172 99:     movl $0, PT_GS(%esp)
 173         jmp 98b
 174 .section __ex_table, "a"
 175         .align 4
 176         .long 98b, 99b
 177 .popsection
 178 .endm
 179
 180 .macro GS_TO_REG reg
 181         movl %gs, \reg
 182         /*CFI_REGISTER gs, \reg*/
 183 .endm
 184 .macro REG_TO_PTGS reg
 185         movl \reg, PT_GS(%esp)
 186         /*CFI_REL_OFFSET gs, PT_GS*/
 187 .endm
 188 .macro SET_KERNEL_GS reg
 189         movl $(__KERNEL_STACK_CANARY), \reg
 190         movl \reg, %gs
 191 .endm
 192
 193 #endif  /* CONFIG_X86_32_LAZY_GS */
 194
 195 .macro SAVE_ALL
 196         cld
 197         PUSH_GS
 198         pushl %fs
 199         CFI_ADJUST_CFA_OFFSET 4
 200         /*CFI_REL_OFFSET fs, 0;*/
 201         pushl %es
 202         CFI_ADJUST_CFA_OFFSET 4
 203         /*CFI_REL_OFFSET es, 0;*/
 204         pushl %ds
 205         CFI_ADJUST_CFA_OFFSET 4
 206         /*CFI_REL_OFFSET ds, 0;*/
 207         pushl %eax
 208         CFI_ADJUST_CFA_OFFSET 4
 209         CFI_REL_OFFSET eax, 0
 210         pushl %ebp
 211         CFI_ADJUST_CFA_OFFSET 4
 212         CFI_REL_OFFSET ebp, 0
 213         pushl %edi
 214         CFI_ADJUST_CFA_OFFSET 4
 215         CFI_REL_OFFSET edi, 0
 216         pushl %esi
 217         CFI_ADJUST_CFA_OFFSET 4
 218         CFI_REL_OFFSET esi, 0
 219         pushl %edx
 220         CFI_ADJUST_CFA_OFFSET 4
 221         CFI_REL_OFFSET edx, 0
 222         pushl %ecx
 223         CFI_ADJUST_CFA_OFFSET 4
 224         CFI_REL_OFFSET ecx, 0
 225         pushl %ebx
 226         CFI_ADJUST_CFA_OFFSET 4
 227         CFI_REL_OFFSET ebx, 0
 228         movl $(__USER_DS), %edx
 229         movl %edx, %ds
 230         movl %edx, %es
 231         movl $(__KERNEL_PERCPU), %edx
 232         movl %edx, %fs
 233         SET_KERNEL_GS %edx
 234 .endm
 235
 236 .macro RESTORE_INT_REGS
 237         popl %ebx
 238         CFI_ADJUST_CFA_OFFSET -4
 239         CFI_RESTORE ebx
 240         popl %ecx
 241         CFI_ADJUST_CFA_OFFSET -4
 242         CFI_RESTORE ecx
 243         popl %edx
 244         CFI_ADJUST_CFA_OFFSET -4
 245         CFI_RESTORE edx
 246         popl %esi
 247         CFI_ADJUST_CFA_OFFSET -4
 248         CFI_RESTORE esi
 249         popl %edi
 250         CFI_ADJUST_CFA_OFFSET -4
 251         CFI_RESTORE edi
 252         popl %ebp
 253         CFI_ADJUST_CFA_OFFSET -4
 254         CFI_RESTORE ebp
 255         popl %eax
 256         CFI_ADJUST_CFA_OFFSET -4
 257         CFI_RESTORE eax
 258 .endm
 259
 260 .macro RESTORE_REGS pop=0
 261         RESTORE_INT_REGS
 262 1:      popl %ds
 263         CFI_ADJUST_CFA_OFFSET -4
 264         /*CFI_RESTORE ds;*/
 265 2:      popl %es
 266         CFI_ADJUST_CFA_OFFSET -4
 267         /*CFI_RESTORE es;*/
 268 3:      popl %fs
 269         CFI_ADJUST_CFA_OFFSET -4
 270         /*CFI_RESTORE fs;*/
 271         POP_GS \pop
 272 .pushsection .fixup, "ax"
 273 4:      movl $0, (%esp)
 274         jmp 1b
 275 5:      movl $0, (%esp)
 276         jmp 2b
 277 6:      movl $0, (%esp)
 278         jmp 3b
 279 .section __ex_table, "a"
 280         .align 4
 281         .long 1b, 4b
 282         .long 2b, 5b
 283         .long 3b, 6b
 284 .popsection
 285         POP_GS_EX
 286 .endm
 287
 288 .macro RING0_INT_FRAME
 289         CFI_STARTPROC simple
 290         CFI_SIGNAL_FRAME
 291         CFI_DEF_CFA esp, 3*4
 292         /*CFI_OFFSET cs, -2*4;*/
 293         CFI_OFFSET eip, -3*4
 294 .endm
 295
 296 .macro RING0_EC_FRAME
 297         CFI_STARTPROC simple
 298         CFI_SIGNAL_FRAME
 299         CFI_DEF_CFA esp, 4*4
 300         /*CFI_OFFSET cs, -2*4;*/
 301         CFI_OFFSET eip, -3*4
 302 .endm
 303
 304 .macro RING0_PTREGS_FRAME
 305         CFI_STARTPROC simple
 306         CFI_SIGNAL_FRAME
 307         CFI_DEF_CFA esp, PT_OLDESP-PT_EBX
 308         /*CFI_OFFSET cs, PT_CS-PT_OLDESP;*/
 309         CFI_OFFSET eip, PT_EIP-PT_OLDESP
 310         /*CFI_OFFSET es, PT_ES-PT_OLDESP;*/
 311         /*CFI_OFFSET ds, PT_DS-PT_OLDESP;*/
 312         CFI_OFFSET eax, PT_EAX-PT_OLDESP
 313         CFI_OFFSET ebp, PT_EBP-PT_OLDESP
 314         CFI_OFFSET edi, PT_EDI-PT_OLDESP
 315         CFI_OFFSET esi, PT_ESI-PT_OLDESP
 316         CFI_OFFSET edx, PT_EDX-PT_OLDESP
 317         CFI_OFFSET ecx, PT_ECX-PT_OLDESP
 318         CFI_OFFSET ebx, PT_EBX-PT_OLDESP
 319 .endm
 320
 321 ENTRY(ret_from_fork)
 322         CFI_STARTPROC
 323         pushl %eax
 324         CFI_ADJUST_CFA_OFFSET 4
 325         call schedule_tail
 326         GET_THREAD_INFO(%ebp)
 327         popl %eax
 328         CFI_ADJUST_CFA_OFFSET -4
 329         pushl $0x0202                   # Reset kernel eflags
 330         CFI_ADJUST_CFA_OFFSET 4
 331         popfl
 332         CFI_ADJUST_CFA_OFFSET -4
 333         jmp syscall_exit
 334         CFI_ENDPROC
 335 END(ret_from_fork)
 336
 337 /*
 338  * Return to user mode is not as complex as all this looks,
 339  * but we want the default path for a system call return to
 340  * go as quickly as possible which is why some of this is
 341  * less clear than it otherwise should be.
 342  */
 343
 344         # userspace resumption stub bypassing syscall exit tracing
 345         ALIGN
 346         RING0_PTREGS_FRAME
 347 ret_from_exception:
 348         preempt_stop(CLBR_ANY)
 349 ret_from_intr:
 350         GET_THREAD_INFO(%ebp)
 351 check_userspace:
 352         movl PT_EFLAGS(%esp), %eax      # mix EFLAGS and CS
 353         movb PT_CS(%esp), %al
 354         andl $(X86_EFLAGS_VM | SEGMENT_RPL_MASK), %eax
 355         cmpl $USER_RPL, %eax
 356         jb resume_kernel                # not returning to v8086 or userspace
 357
 358 ENTRY(resume_userspace)
 359         LOCKDEP_SYS_EXIT
 360         DISABLE_INTERRUPTS(CLBR_ANY)    # make sure we don't miss an interrupt
 361                                         # setting need_resched or sigpending
 362                                         # between sampling and the iret
 363         TRACE_IRQS_OFF
 364         movl TI_flags(%ebp), %ecx
 365         andl $_TIF_WORK_MASK, %ecx      # is there any work to be done on
 366                                         # int/exception return?
 367         jne work_pending
 368         jmp restore_all
 369 END(ret_from_exception)
 370
 371 #ifdef CONFIG_PREEMPT
 372 ENTRY(resume_kernel)
 373         DISABLE_INTERRUPTS(CLBR_ANY)
 374         cmpl $0,TI_preempt_count(%ebp)  # non-zero preempt_count ?
 375         jnz restore_nocheck
 376 need_resched:
 377         movl TI_flags(%ebp), %ecx       # need_resched set ?
 378         testb $_TIF_NEED_RESCHED, %cl
 379         jz restore_all
 380         testl $X86_EFLAGS_IF,PT_EFLAGS(%esp)    # interrupts off (exception path) ?
 381         jz restore_all
 382         call preempt_schedule_irq
 383         jmp need_resched
 384 END(resume_kernel)
 385 #endif
 386         CFI_ENDPROC
 387
 388 /* SYSENTER_RETURN points to after the "sysenter" instruction in
 389    the vsyscall page.  See vsyscall-sysentry.S, which defines the symbol.  */
 390
 391         # sysenter call handler stub
 392 ENTRY(ia32_sysenter_target)
 393         CFI_STARTPROC simple
 394         CFI_SIGNAL_FRAME
 395         CFI_DEF_CFA esp, 0
 396         CFI_REGISTER esp, ebp
 397         movl TSS_sysenter_sp0(%esp),%esp
 398 sysenter_past_esp:
 399         /*
 400          * Interrupts are disabled here, but we can't trace it until
 401          * enough kernel state to call TRACE_IRQS_OFF can be called - but
 402          * we immediately enable interrupts at that point anyway.
 403          */
 404         pushl $(__USER_DS)
 405         CFI_ADJUST_CFA_OFFSET 4
 406         /*CFI_REL_OFFSET ss, 0*/
 407         pushl %ebp
 408         CFI_ADJUST_CFA_OFFSET 4
 409         CFI_REL_OFFSET esp, 0
 410         pushfl
 411         orl $X86_EFLAGS_IF, (%esp)
 412         CFI_ADJUST_CFA_OFFSET 4
 413         pushl $(__USER_CS)
 414         CFI_ADJUST_CFA_OFFSET 4
 415         /*CFI_REL_OFFSET cs, 0*/
 416         /*
 417          * Push current_thread_info()->sysenter_return to the stack.
 418          * A tiny bit of offset fixup is necessary - 4*4 means the 4 words
 419          * pushed above; +8 corresponds to copy_thread's esp0 setting.
 420          */
 421         pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp)
 422         CFI_ADJUST_CFA_OFFSET 4
 423         CFI_REL_OFFSET eip, 0
 424
 425         pushl %eax
 426         CFI_ADJUST_CFA_OFFSET 4
 427         SAVE_ALL
 428         ENABLE_INTERRUPTS(CLBR_NONE)
 429
 430 /*
 431  * Load the potential sixth argument from user stack.
 432  * Careful about security.
 433  */
 434         cmpl $__PAGE_OFFSET-3,%ebp
 435         jae syscall_fault
 436 1:      movl (%ebp),%ebp
 437         movl %ebp,PT_EBP(%esp)
 438 .section __ex_table,"a"
 439         .align 4
 440         .long 1b,syscall_fault
 441 .previous
 442
 443         GET_THREAD_INFO(%ebp)
 444
 445         testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
 446         jnz sysenter_audit
 447 sysenter_do_call:
 448         cmpl $(nr_syscalls), %eax
 449         jae syscall_badsys
 450         call *sys_call_table(,%eax,4)
 451         movl %eax,PT_EAX(%esp)
 452         LOCKDEP_SYS_EXIT
 453         DISABLE_INTERRUPTS(CLBR_ANY)
 454         TRACE_IRQS_OFF
 455         movl TI_flags(%ebp), %ecx
 456         testl $_TIF_ALLWORK_MASK, %ecx
 457         jne sysexit_audit
 458 sysenter_exit:
 459 /* if something modifies registers it must also disable sysexit */
 460         movl PT_EIP(%esp), %edx
 461         movl PT_OLDESP(%esp), %ecx
 462         xorl %ebp,%ebp
 463         TRACE_IRQS_ON
 464 1:      mov  PT_FS(%esp), %fs
 465         PTGS_TO_GS
 466         ENABLE_INTERRUPTS_SYSEXIT
 467
 468 #ifdef CONFIG_AUDITSYSCALL
 469 sysenter_audit:
 470         testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
 471         jnz syscall_trace_entry
 472         addl $4,%esp
 473         CFI_ADJUST_CFA_OFFSET -4
 474         /* %esi already in 8(%esp)         6th arg: 4th syscall arg */
 475         /* %edx already in 4(%esp)         5th arg: 3rd syscall arg */
 476         /* %ecx already in 0(%esp)         4th arg: 2nd syscall arg */
 477         movl %ebx,%ecx                  /* 3rd arg: 1st syscall arg */
 478         movl %eax,%edx                  /* 2nd arg: syscall number */
 479         movl $AUDIT_ARCH_I386,%eax      /* 1st arg: audit arch */
 480         call audit_syscall_entry
 481         pushl %ebx
 482         CFI_ADJUST_CFA_OFFSET 4
 483         movl PT_EAX(%esp),%eax          /* reload syscall number */
 484         jmp sysenter_do_call
 485
 486 sysexit_audit:
 487         testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %ecx
 488         jne syscall_exit_work
 489         TRACE_IRQS_ON
 490         ENABLE_INTERRUPTS(CLBR_ANY)
 491         movl %eax,%edx          /* second arg, syscall return value */
 492         cmpl $0,%eax            /* is it < 0? */
 493         setl %al                /* 1 if so, 0 if not */
 494         movzbl %al,%eax         /* zero-extend that */
 495         inc %eax /* first arg, 0->1(AUDITSC_SUCCESS), 1->2(AUDITSC_FAILURE) */
 496         call audit_syscall_exit
 497         DISABLE_INTERRUPTS(CLBR_ANY)
 498         TRACE_IRQS_OFF
 499         movl TI_flags(%ebp), %ecx
 500         testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %ecx
 501         jne syscall_exit_work
 502         movl PT_EAX(%esp),%eax  /* reload syscall return value */
 503         jmp sysenter_exit
 504 #endif
 505
 506         CFI_ENDPROC
 507 .pushsection .fixup,"ax"
 508 2:      movl $0,PT_FS(%esp)
 509         jmp 1b
 510 .section __ex_table,"a"
 511         .align 4
 512         .long 1b,2b
 513 .popsection
 514         PTGS_TO_GS_EX
 515 ENDPROC(ia32_sysenter_target)
 516
 517         # system call handler stub
 518 ENTRY(system_call)
 519         RING0_INT_FRAME                 # can't unwind into user space anyway
 520         pushl %eax                      # save orig_eax
 521         CFI_ADJUST_CFA_OFFSET 4
 522         SAVE_ALL
 523         GET_THREAD_INFO(%ebp)
 524                                         # system call tracing in operation / emulation
 525         testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
 526         jnz syscall_trace_entry
 527         cmpl $(nr_syscalls), %eax
 528         jae syscall_badsys
 529 syscall_call:
 530         call *sys_call_table(,%eax,4)
 531         movl %eax,PT_EAX(%esp)          # store the return value
 532 syscall_exit:
 533         LOCKDEP_SYS_EXIT
 534         DISABLE_INTERRUPTS(CLBR_ANY)    # make sure we don't miss an interrupt
 535                                         # setting need_resched or sigpending
 536                                         # between sampling and the iret
 537         TRACE_IRQS_OFF
 538         movl TI_flags(%ebp), %ecx
 539         testl $_TIF_ALLWORK_MASK, %ecx  # current->work
 540         jne syscall_exit_work
 541
 542 restore_all:
 543         movl PT_EFLAGS(%esp), %eax      # mix EFLAGS, SS and CS
 544         # Warning: PT_OLDSS(%esp) contains the wrong/random values if we
 545         # are returning to the kernel.
 546         # See comments in process.c:copy_thread() for details.
 547         movb PT_OLDSS(%esp), %ah
 548         movb PT_CS(%esp), %al
 549         andl $(X86_EFLAGS_VM | (SEGMENT_TI_MASK << 8) | SEGMENT_RPL_MASK), %eax
 550         cmpl $((SEGMENT_LDT << 8) | USER_RPL), %eax
 551         CFI_REMEMBER_STATE
 552         je ldt_ss                       # returning to user-space with LDT SS
 553 restore_nocheck:
 554         TRACE_IRQS_IRET
 555 restore_nocheck_notrace:
 556         RESTORE_REGS 4                  # skip orig_eax/error_code
 557         CFI_ADJUST_CFA_OFFSET -4
 558 irq_return:
 559         INTERRUPT_RETURN
 560 .section .fixup,"ax"
 561 ENTRY(iret_exc)
 562         pushl $0                        # no error code
 563         pushl $do_iret_error
 564         jmp error_code
 565 .previous
 566 .section __ex_table,"a"
 567         .align 4
 568         .long irq_return,iret_exc
 569 .previous
 570
 571         CFI_RESTORE_STATE
 572 ldt_ss:
 573         larl PT_OLDSS(%esp), %eax
 574         jnz restore_nocheck
 575         testl $0x00400000, %eax         # returning to 32bit stack?
 576         jnz restore_nocheck             # allright, normal return
 577
 578 #ifdef CONFIG_PARAVIRT
 579         /*
 580          * The kernel can't run on a non-flat stack if paravirt mode
 581          * is active.  Rather than try to fixup the high bits of
 582          * ESP, bypass this code entirely.  This may break DOSemu
 583          * and/or Wine support in a paravirt VM, although the option
 584          * is still available to implement the setting of the high
 585          * 16-bits in the INTERRUPT_RETURN paravirt-op.
 586          */
 587         cmpl $0, pv_info+PARAVIRT_enabled
 588         jne restore_nocheck
 589 #endif
 590
 591         /* If returning to userspace with 16bit stack,
 592          * try to fix the higher word of ESP, as the CPU
 593          * won't restore it.
 594          * This is an "official" bug of all the x86-compatible
 595          * CPUs, which we can try to work around to make
 596          * dosemu and wine happy. */
 597         movl PT_OLDESP(%esp), %eax
 598         movl %esp, %edx
 599         call patch_espfix_desc
 600         pushl $__ESPFIX_SS
 601         CFI_ADJUST_CFA_OFFSET 4
 602         pushl %eax
 603         CFI_ADJUST_CFA_OFFSET 4
 604         DISABLE_INTERRUPTS(CLBR_EAX)
 605         TRACE_IRQS_OFF
 606         lss (%esp), %esp
 607         CFI_ADJUST_CFA_OFFSET -8
 608         jmp restore_nocheck
 609         CFI_ENDPROC
 610 ENDPROC(system_call)
 611
 612         # perform work that needs to be done immediately before resumption
 613         ALIGN
 614         RING0_PTREGS_FRAME              # can't unwind into user space anyway
 615 work_pending:
 616         testb $_TIF_NEED_RESCHED, %cl
 617         jz work_notifysig
 618 work_resched:
 619         call schedule
 620         LOCKDEP_SYS_EXIT
 621         DISABLE_INTERRUPTS(CLBR_ANY)    # make sure we don't miss an interrupt
 622                                         # setting need_resched or sigpending
 623                                         # between sampling and the iret
 624         TRACE_IRQS_OFF
 625         movl TI_flags(%ebp), %ecx
 626         andl $_TIF_WORK_MASK, %ecx      # is there any work to be done other
 627                                         # than syscall tracing?
 628         jz restore_all
 629         testb $_TIF_NEED_RESCHED, %cl
 630         jnz work_resched
 631
 632 work_notifysig:                         # deal with pending signals and
 633                                         # notify-resume requests
 634 #ifdef CONFIG_VM86
 635         testl $X86_EFLAGS_VM, PT_EFLAGS(%esp)
 636         movl %esp, %eax
 637         jne work_notifysig_v86          # returning to kernel-space or
 638                                         # vm86-space
 639         xorl %edx, %edx
 640         call do_notify_resume
 641         jmp resume_userspace_sig
 642
 643         ALIGN
 644 work_notifysig_v86:
 645         pushl %ecx                      # save ti_flags for do_notify_resume
 646         CFI_ADJUST_CFA_OFFSET 4
 647         call save_v86_state             # %eax contains pt_regs pointer
 648         popl %ecx
 649         CFI_ADJUST_CFA_OFFSET -4
 650         movl %eax, %esp
 651 #else
 652         movl %esp, %eax
 653 #endif
 654         xorl %edx, %edx
 655         call do_notify_resume
 656         jmp resume_userspace_sig
 657 END(work_pending)
 658
 659         # perform syscall exit tracing
 660         ALIGN
 661 syscall_trace_entry:
 662         movl $-ENOSYS,PT_EAX(%esp)
 663         movl %esp, %eax
 664         call syscall_trace_enter
 665         /* What it returned is what we'll actually use.  */
 666         cmpl $(nr_syscalls), %eax
 667         jnae syscall_call
 668         jmp syscall_exit
 669 END(syscall_trace_entry)
 670
 671         # perform syscall exit tracing
 672         ALIGN
 673 syscall_exit_work:
 674         testl $_TIF_WORK_SYSCALL_EXIT, %ecx
 675         jz work_pending
 676         TRACE_IRQS_ON
 677         ENABLE_INTERRUPTS(CLBR_ANY)     # could let syscall_trace_leave() call
 678                                         # schedule() instead
 679         movl %esp, %eax
 680         call syscall_trace_leave
 681         jmp resume_userspace
 682 END(syscall_exit_work)
 683         CFI_ENDPROC
 684
 685         RING0_INT_FRAME                 # can't unwind into user space anyway
 686 syscall_fault:
 687         GET_THREAD_INFO(%ebp)
 688         movl $-EFAULT,PT_EAX(%esp)
 689         jmp resume_userspace
 690 END(syscall_fault)
 691
 692 syscall_badsys:
 693         movl $-ENOSYS,PT_EAX(%esp)
 694         jmp resume_userspace
 695 END(syscall_badsys)
 696         CFI_ENDPROC
 697
 698 /*
 699  * System calls that need a pt_regs pointer.
 700  */
 701 #define PTREGSCALL(name) \
 702         ALIGN; \
 703 ptregs_##name: \
 704         leal 4(%esp),%eax; \
 705         jmp sys_##name;
 706
 707 PTREGSCALL(iopl)
 708 PTREGSCALL(fork)
 709 PTREGSCALL(clone)
 710 PTREGSCALL(vfork)
 711 PTREGSCALL(execve)
 712 PTREGSCALL(sigaltstack)
 713 PTREGSCALL(sigreturn)
 714 PTREGSCALL(rt_sigreturn)
 715 PTREGSCALL(vm86)
 716 PTREGSCALL(vm86old)
 717
 718 .macro FIXUP_ESPFIX_STACK
 719         /* since we are on a wrong stack, we cant make it a C code :( */
 720         PER_CPU(gdt_page, %ebx)
 721         GET_DESC_BASE(GDT_ENTRY_ESPFIX_SS, %ebx, %eax, %ax, %al, %ah)
 722         addl %esp, %eax
 723         pushl $__KERNEL_DS
 724         CFI_ADJUST_CFA_OFFSET 4
 725         pushl %eax
 726         CFI_ADJUST_CFA_OFFSET 4
 727         lss (%esp), %esp
 728         CFI_ADJUST_CFA_OFFSET -8
 729 .endm
 730 .macro UNWIND_ESPFIX_STACK
 731         movl %ss, %eax
 732         /* see if on espfix stack */
 733         cmpw $__ESPFIX_SS, %ax
 734         jne 27f
 735         movl $__KERNEL_DS, %eax
 736         movl %eax, %ds
 737         movl %eax, %es
 738         /* switch to normal stack */
 739         FIXUP_ESPFIX_STACK
 740 27:
 741 .endm
 742
 743 /*
 744  * Build the entry stubs and pointer table with some assembler magic.
 745  * We pack 7 stubs into a single 32-byte chunk, which will fit in a
 746  * single cache line on all modern x86 implementations.
 747  */
 748 .section .init.rodata,"a"
 749 ENTRY(interrupt)
 750 .text
 751         .p2align 5
 752         .p2align CONFIG_X86_L1_CACHE_SHIFT
 753 ENTRY(irq_entries_start)
 754         RING0_INT_FRAME
 755 vector=FIRST_EXTERNAL_VECTOR
 756 .rept (NR_VECTORS-FIRST_EXTERNAL_VECTOR+6)/7
 757         .balign 32
 758   .rept 7
 759     .if vector < NR_VECTORS
 760       .if vector <> FIRST_EXTERNAL_VECTOR
 761         CFI_ADJUST_CFA_OFFSET -4
 762       .endif
 763 1:      pushl $(~vector+0x80)   /* Note: always in signed byte range */
 764         CFI_ADJUST_CFA_OFFSET 4
 765       .if ((vector-FIRST_EXTERNAL_VECTOR)%7) <> 6
 766         jmp 2f
 767       .endif
 768       .previous
 769         .long 1b
 770       .text
 771 vector=vector+1
 772     .endif
 773   .endr
 774 2:      jmp common_interrupt
 775 .endr
 776 END(irq_entries_start)
 777
 778 .previous
 779 END(interrupt)
 780 .previous
 781
 782 /*
 783  * the CPU automatically disables interrupts when executing an IRQ vector,
 784  * so IRQ-flags tracing has to follow that:
 785  */
 786         .p2align CONFIG_X86_L1_CACHE_SHIFT
 787 common_interrupt:
 788         addl $-0x80,(%esp)      /* Adjust vector into the [-256,-1] range */
 789         SAVE_ALL
 790         TRACE_IRQS_OFF
 791         movl %esp,%eax
 792         call do_IRQ
 793         jmp ret_from_intr
 794 ENDPROC(common_interrupt)
 795         CFI_ENDPROC
 796
 797 #define BUILD_INTERRUPT3(name, nr, fn)  \
 798 ENTRY(name)                             \
 799         RING0_INT_FRAME;                \
 800         pushl $~(nr);                   \
 801         CFI_ADJUST_CFA_OFFSET 4;        \
 802         SAVE_ALL;                       \
 803         TRACE_IRQS_OFF                  \
 804         movl %esp,%eax;                 \
 805         call fn;                        \
 806         jmp ret_from_intr;              \
 807         CFI_ENDPROC;                    \
 808 ENDPROC(name)
 809
 810 #define BUILD_INTERRUPT(name, nr)       BUILD_INTERRUPT3(name, nr, smp_##name)
 811
 812 /* The include is where all of the SMP etc. interrupts come from */
 813 #include <asm/entry_arch.h>
 814
 815 ENTRY(coprocessor_error)
 816         RING0_INT_FRAME
 817         pushl $0
 818         CFI_ADJUST_CFA_OFFSET 4
 819         pushl $do_coprocessor_error
 820         CFI_ADJUST_CFA_OFFSET 4
 821         jmp error_code
 822         CFI_ENDPROC
 823 END(coprocessor_error)
 824
 825 ENTRY(simd_coprocessor_error)
 826         RING0_INT_FRAME
 827         pushl $0
 828         CFI_ADJUST_CFA_OFFSET 4
 829         pushl $do_simd_coprocessor_error
 830         CFI_ADJUST_CFA_OFFSET 4
 831         jmp error_code
 832         CFI_ENDPROC
 833 END(simd_coprocessor_error)
 834
 835 ENTRY(device_not_available)
 836         RING0_INT_FRAME
 837         pushl $-1                       # mark this as an int
 838         CFI_ADJUST_CFA_OFFSET 4
 839         pushl $do_device_not_available
 840         CFI_ADJUST_CFA_OFFSET 4
 841         jmp error_code
 842         CFI_ENDPROC
 843 END(device_not_available)
 844
 845 #ifdef CONFIG_PARAVIRT
 846 ENTRY(native_iret)
 847         iret
 848 .section __ex_table,"a"
 849         .align 4
 850         .long native_iret, iret_exc
 851 .previous
 852 END(native_iret)
 853
 854 ENTRY(native_irq_enable_sysexit)
 855         sti
 856         sysexit
 857 END(native_irq_enable_sysexit)
 858 #endif
 859
 860 ENTRY(overflow)
 861         RING0_INT_FRAME
 862         pushl $0
 863         CFI_ADJUST_CFA_OFFSET 4
 864         pushl $do_overflow
 865         CFI_ADJUST_CFA_OFFSET 4
 866         jmp error_code
 867         CFI_ENDPROC
 868 END(overflow)
 869
 870 ENTRY(bounds)
 871         RING0_INT_FRAME
 872         pushl $0
 873         CFI_ADJUST_CFA_OFFSET 4
 874         pushl $do_bounds
 875         CFI_ADJUST_CFA_OFFSET 4
 876         jmp error_code
 877         CFI_ENDPROC
 878 END(bounds)
 879
 880 ENTRY(invalid_op)
 881         RING0_INT_FRAME
 882         pushl $0
 883         CFI_ADJUST_CFA_OFFSET 4
 884         pushl $do_invalid_op
 885         CFI_ADJUST_CFA_OFFSET 4
 886         jmp error_code
 887         CFI_ENDPROC
 888 END(invalid_op)
 889
 890 ENTRY(coprocessor_segment_overrun)
 891         RING0_INT_FRAME
 892         pushl $0
 893         CFI_ADJUST_CFA_OFFSET 4
 894         pushl $do_coprocessor_segment_overrun
 895         CFI_ADJUST_CFA_OFFSET 4
 896         jmp error_code
 897         CFI_ENDPROC
 898 END(coprocessor_segment_overrun)
 899
 900 ENTRY(invalid_TSS)
 901         RING0_EC_FRAME
 902         pushl $do_invalid_TSS
 903         CFI_ADJUST_CFA_OFFSET 4
 904         jmp error_code
 905         CFI_ENDPROC
 906 END(invalid_TSS)
 907
 908 ENTRY(segment_not_present)
 909         RING0_EC_FRAME
 910         pushl $do_segment_not_present
 911         CFI_ADJUST_CFA_OFFSET 4
 912         jmp error_code
 913         CFI_ENDPROC
 914 END(segment_not_present)
 915
 916 ENTRY(stack_segment)
 917         RING0_EC_FRAME
 918         pushl $do_stack_segment
 919         CFI_ADJUST_CFA_OFFSET 4
 920         jmp error_code
 921         CFI_ENDPROC
 922 END(stack_segment)
 923
 924 ENTRY(alignment_check)
 925         RING0_EC_FRAME
 926         pushl $do_alignment_check
 927         CFI_ADJUST_CFA_OFFSET 4
 928         jmp error_code
 929         CFI_ENDPROC
 930 END(alignment_check)
 931
 932 ENTRY(divide_error)
 933         RING0_INT_FRAME
 934         pushl $0                        # no error code
 935         CFI_ADJUST_CFA_OFFSET 4
 936         pushl $do_divide_error
 937         CFI_ADJUST_CFA_OFFSET 4
 938         jmp error_code
 939         CFI_ENDPROC
 940 END(divide_error)
 941
 942 #ifdef CONFIG_X86_MCE
 943 ENTRY(machine_check)
 944         RING0_INT_FRAME
 945         pushl $0
 946         CFI_ADJUST_CFA_OFFSET 4
 947         pushl machine_check_vector
 948         CFI_ADJUST_CFA_OFFSET 4
 949         jmp error_code
 950         CFI_ENDPROC
 951 END(machine_check)
 952 #endif
 953
 954 ENTRY(spurious_interrupt_bug)
 955         RING0_INT_FRAME
 956         pushl $0
 957         CFI_ADJUST_CFA_OFFSET 4
 958         pushl $do_spurious_interrupt_bug
 959         CFI_ADJUST_CFA_OFFSET 4
 960         jmp error_code
 961         CFI_ENDPROC
 962 END(spurious_interrupt_bug)
 963
 964 ENTRY(kernel_thread_helper)
 965         pushl $0                # fake return address for unwinder
 966         CFI_STARTPROC
 967         movl %edx,%eax
 968         push %edx
 969         CFI_ADJUST_CFA_OFFSET 4
 970         call *%ebx
 971         push %eax
 972         CFI_ADJUST_CFA_OFFSET 4
 973         call do_exit
 974         ud2                     # padding for call trace
 975         CFI_ENDPROC
 976 ENDPROC(kernel_thread_helper)
 977
 978 #ifdef CONFIG_XEN
 979 /* Xen doesn't set %esp to be precisely what the normal sysenter
 980    entrypoint expects, so fix it up before using the normal path. */
 981 ENTRY(xen_sysenter_target)
 982         RING0_INT_FRAME
 983         addl $5*4, %esp         /* remove xen-provided frame */
 984         CFI_ADJUST_CFA_OFFSET -5*4
 985         jmp sysenter_past_esp
 986         CFI_ENDPROC
 987
 988 ENTRY(xen_hypervisor_callback)
 989         CFI_STARTPROC
 990         pushl $0
 991         CFI_ADJUST_CFA_OFFSET 4
 992         SAVE_ALL
 993         TRACE_IRQS_OFF
 994
 995         /* Check to see if we got the event in the critical
 996            region in xen_iret_direct, after we've reenabled
 997            events and checked for pending events.  This simulates
 998            iret instruction's behaviour where it delivers a
 999            pending interrupt when enabling interrupts. */
1000         movl PT_EIP(%esp),%eax
1001         cmpl $xen_iret_start_crit,%eax
1002         jb   1f
1003         cmpl $xen_iret_end_crit,%eax
1004         jae  1f
1005
1006         jmp  xen_iret_crit_fixup
1007
1008 ENTRY(xen_do_upcall)
1009 1:      mov %esp, %eax
1010         call xen_evtchn_do_upcall
1011         jmp  ret_from_intr
1012         CFI_ENDPROC
1013 ENDPROC(xen_hypervisor_callback)
1014
1015 # Hypervisor uses this for application faults while it executes.
1016 # We get here for two reasons:
1017 #  1. Fault while reloading DS, ES, FS or GS
1018 #  2. Fault while executing IRET
1019 # Category 1 we fix up by reattempting the load, and zeroing the segment
1020 # register if the load fails.
1021 # Category 2 we fix up by jumping to do_iret_error. We cannot use the
1022 # normal Linux return path in this case because if we use the IRET hypercall
1023 # to pop the stack frame we end up in an infinite loop of failsafe callbacks.
1024 # We distinguish between categories by maintaining a status value in EAX.
1025 ENTRY(xen_failsafe_callback)
1026         CFI_STARTPROC
1027         pushl %eax
1028         CFI_ADJUST_CFA_OFFSET 4
1029         movl $1,%eax
1030 1:      mov 4(%esp),%ds
1031 2:      mov 8(%esp),%es
1032 3:      mov 12(%esp),%fs
1033 4:      mov 16(%esp),%gs
1034         testl %eax,%eax
1035         popl %eax
1036         CFI_ADJUST_CFA_OFFSET -4
1037         lea 16(%esp),%esp
1038         CFI_ADJUST_CFA_OFFSET -16
1039         jz 5f
1040         addl $16,%esp
1041         jmp iret_exc            # EAX != 0 => Category 2 (Bad IRET)
1042 5:      pushl $0                # EAX == 0 => Category 1 (Bad segment)
1043         CFI_ADJUST_CFA_OFFSET 4
1044         SAVE_ALL
1045         jmp ret_from_exception
1046         CFI_ENDPROC
1047
1048 .section .fixup,"ax"
1049 6:      xorl %eax,%eax
1050         movl %eax,4(%esp)
1051         jmp 1b
1052 7:      xorl %eax,%eax
1053         movl %eax,8(%esp)
1054         jmp 2b
1055 8:      xorl %eax,%eax
1056         movl %eax,12(%esp)
1057         jmp 3b
1058 9:      xorl %eax,%eax
1059         movl %eax,16(%esp)
1060         jmp 4b
1061 .previous
1062 .section __ex_table,"a"
1063         .align 4
1064         .long 1b,6b
1065         .long 2b,7b
1066         .long 3b,8b
1067         .long 4b,9b
1068 .previous
1069 ENDPROC(xen_failsafe_callback)
1070
1071 #endif  /* CONFIG_XEN */
1072
1073 #ifdef CONFIG_FUNCTION_TRACER
1074 #ifdef CONFIG_DYNAMIC_FTRACE
1075
1076 ENTRY(mcount)
1077         ret
1078 END(mcount)
1079
1080 ENTRY(ftrace_caller)
1081         cmpl $0, function_trace_stop
1082         jne  ftrace_stub
1083
1084         pushl %eax
1085         pushl %ecx
1086         pushl %edx
1087         movl 0xc(%esp), %eax
1088         movl 0x4(%ebp), %edx
1089         subl $MCOUNT_INSN_SIZE, %eax
1090
1091 .globl ftrace_call
1092 ftrace_call:
1093         call ftrace_stub
1094
1095         popl %edx
1096         popl %ecx
1097         popl %eax
1098 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
1099 .globl ftrace_graph_call
1100 ftrace_graph_call:
1101         jmp ftrace_stub
1102 #endif
1103
1104 .globl ftrace_stub
1105 ftrace_stub:
1106         ret
1107 END(ftrace_caller)
1108
1109 #else /* ! CONFIG_DYNAMIC_FTRACE */
1110
1111 ENTRY(mcount)
1112         cmpl $0, function_trace_stop
1113         jne  ftrace_stub
1114
1115         cmpl $ftrace_stub, ftrace_trace_function
1116         jnz trace
1117 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
1118         cmpl $ftrace_stub, ftrace_graph_return
1119         jnz ftrace_graph_caller
1120
1121         cmpl $ftrace_graph_entry_stub, ftrace_graph_entry
1122         jnz ftrace_graph_caller
1123 #endif
1124 .globl ftrace_stub
1125 ftrace_stub:
1126         ret
1127
1128         /* taken from glibc */
1129 trace:
1130         pushl %eax
1131         pushl %ecx
1132         pushl %edx
1133         movl 0xc(%esp), %eax
1134         movl 0x4(%ebp), %edx
1135         subl $MCOUNT_INSN_SIZE, %eax
1136
1137         call *ftrace_trace_function
1138
1139         popl %edx
1140         popl %ecx
1141         popl %eax
1142         jmp ftrace_stub
1143 END(mcount)
1144 #endif /* CONFIG_DYNAMIC_FTRACE */
1145 #endif /* CONFIG_FUNCTION_TRACER */
1146
1147 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
1148 ENTRY(ftrace_graph_caller)
1149         cmpl $0, function_trace_stop
1150         jne ftrace_stub
1151
1152         pushl %eax
1153         pushl %ecx
1154         pushl %edx
1155         movl 0xc(%esp), %edx
1156         lea 0x4(%ebp), %eax
1157         subl $MCOUNT_INSN_SIZE, %edx
1158         call prepare_ftrace_return
1159         popl %edx
1160         popl %ecx
1161         popl %eax
1162         ret
1163 END(ftrace_graph_caller)
1164
1165 .globl return_to_handler
1166 return_to_handler:
1167         pushl $0
1168         pushl %eax
1169         pushl %ecx
1170         pushl %edx
1171         call ftrace_return_to_handler
1172         movl %eax, 0xc(%esp)
1173         popl %edx
1174         popl %ecx
1175         popl %eax
1176         ret
1177 #endif
1178
1179 .section .rodata,"a"
1180 #include "syscall_table_32.S"
1181
1182 syscall_table_size=(.-sys_call_table)
1183
1184 /*
1185  * Some functions should be protected against kprobes
1186  */
1187         .pushsection .kprobes.text, "ax"
1188
1189 ENTRY(page_fault)
1190         RING0_EC_FRAME
1191         pushl $do_page_fault
1192         CFI_ADJUST_CFA_OFFSET 4
1193         ALIGN
1194 error_code:
1195         /* the function address is in %gs's slot on the stack */
1196         pushl %fs
1197         CFI_ADJUST_CFA_OFFSET 4
1198         /*CFI_REL_OFFSET fs, 0*/
1199         pushl %es
1200         CFI_ADJUST_CFA_OFFSET 4
1201         /*CFI_REL_OFFSET es, 0*/
1202         pushl %ds
1203         CFI_ADJUST_CFA_OFFSET 4
1204         /*CFI_REL_OFFSET ds, 0*/
1205         pushl %eax
1206         CFI_ADJUST_CFA_OFFSET 4
1207         CFI_REL_OFFSET eax, 0
1208         pushl %ebp
1209         CFI_ADJUST_CFA_OFFSET 4
1210         CFI_REL_OFFSET ebp, 0
1211         pushl %edi
1212         CFI_ADJUST_CFA_OFFSET 4
1213         CFI_REL_OFFSET edi, 0
1214         pushl %esi
1215         CFI_ADJUST_CFA_OFFSET 4
1216         CFI_REL_OFFSET esi, 0
1217         pushl %edx
1218         CFI_ADJUST_CFA_OFFSET 4
1219         CFI_REL_OFFSET edx, 0
1220         pushl %ecx
1221         CFI_ADJUST_CFA_OFFSET 4
1222         CFI_REL_OFFSET ecx, 0
1223         pushl %ebx
1224         CFI_ADJUST_CFA_OFFSET 4
1225         CFI_REL_OFFSET ebx, 0
1226         cld
1227         movl $(__KERNEL_PERCPU), %ecx
1228         movl %ecx, %fs
1229         UNWIND_ESPFIX_STACK
1230         GS_TO_REG %ecx
1231         movl PT_GS(%esp), %edi          # get the function address
1232         movl PT_ORIG_EAX(%esp), %edx    # get the error code
1233         movl $-1, PT_ORIG_EAX(%esp)     # no syscall to restart
1234         REG_TO_PTGS %ecx
1235         SET_KERNEL_GS %ecx
1236         movl $(__USER_DS), %ecx
1237         movl %ecx, %ds
1238         movl %ecx, %es
1239         TRACE_IRQS_OFF
1240         movl %esp,%eax                  # pt_regs pointer
1241         call *%edi
1242         jmp ret_from_exception
1243         CFI_ENDPROC
1244 END(page_fault)
1245
1246 /*
1247  * Debug traps and NMI can happen at the one SYSENTER instruction
1248  * that sets up the real kernel stack. Check here, since we can't
1249  * allow the wrong stack to be used.
1250  *
1251  * "TSS_sysenter_sp0+12" is because the NMI/debug handler will have
1252  * already pushed 3 words if it hits on the sysenter instruction:
1253  * eflags, cs and eip.
1254  *
1255  * We just load the right stack, and push the three (known) values
1256  * by hand onto the new stack - while updating the return eip past
1257  * the instruction that would have done it for sysenter.
1258  */
1259 .macro FIX_STACK offset ok label
1260         cmpw $__KERNEL_CS, 4(%esp)
1261         jne \ok
1262 \label:
1263         movl TSS_sysenter_sp0 + \offset(%esp), %esp
1264         CFI_DEF_CFA esp, 0
1265         CFI_UNDEFINED eip
1266         pushfl
1267         CFI_ADJUST_CFA_OFFSET 4
1268         pushl $__KERNEL_CS
1269         CFI_ADJUST_CFA_OFFSET 4
1270         pushl $sysenter_past_esp
1271         CFI_ADJUST_CFA_OFFSET 4
1272         CFI_REL_OFFSET eip, 0
1273 .endm
1274
1275 ENTRY(debug)
1276         RING0_INT_FRAME
1277         cmpl $ia32_sysenter_target,(%esp)
1278         jne debug_stack_correct
1279         FIX_STACK 12, debug_stack_correct, debug_esp_fix_insn
1280 debug_stack_correct:
1281         pushl $-1                       # mark this as an int
1282         CFI_ADJUST_CFA_OFFSET 4
1283         SAVE_ALL
1284         TRACE_IRQS_OFF
1285         xorl %edx,%edx                  # error code 0
1286         movl %esp,%eax                  # pt_regs pointer
1287         call do_debug
1288         jmp ret_from_exception
1289         CFI_ENDPROC
1290 END(debug)
1291
1292 /*
1293  * NMI is doubly nasty. It can happen _while_ we're handling
1294  * a debug fault, and the debug fault hasn't yet been able to
1295  * clear up the stack. So we first check whether we got  an
1296  * NMI on the sysenter entry path, but after that we need to
1297  * check whether we got an NMI on the debug path where the debug
1298  * fault happened on the sysenter path.
1299  */
1300 ENTRY(nmi)
1301         RING0_INT_FRAME
1302         pushl %eax
1303         CFI_ADJUST_CFA_OFFSET 4
1304         movl %ss, %eax
1305         cmpw $__ESPFIX_SS, %ax
1306         popl %eax
1307         CFI_ADJUST_CFA_OFFSET -4
1308         je nmi_espfix_stack
1309         cmpl $ia32_sysenter_target,(%esp)
1310         je nmi_stack_fixup
1311         pushl %eax
1312         CFI_ADJUST_CFA_OFFSET 4
1313         movl %esp,%eax
1314         /* Do not access memory above the end of our stack page,
1315          * it might not exist.
1316          */
1317         andl $(THREAD_SIZE-1),%eax
1318         cmpl $(THREAD_SIZE-20),%eax
1319         popl %eax
1320         CFI_ADJUST_CFA_OFFSET -4
1321         jae nmi_stack_correct
1322         cmpl $ia32_sysenter_target,12(%esp)
1323         je nmi_debug_stack_check
1324 nmi_stack_correct:
1325         /* We have a RING0_INT_FRAME here */
1326         pushl %eax
1327         CFI_ADJUST_CFA_OFFSET 4
1328         SAVE_ALL
1329         xorl %edx,%edx          # zero error code
1330         movl %esp,%eax          # pt_regs pointer
1331         call do_nmi
1332         jmp restore_nocheck_notrace
1333         CFI_ENDPROC
1334
1335 nmi_stack_fixup:
1336         RING0_INT_FRAME
1337         FIX_STACK 12, nmi_stack_correct, 1
1338         jmp nmi_stack_correct
1339
1340 nmi_debug_stack_check:
1341         /* We have a RING0_INT_FRAME here */
1342         cmpw $__KERNEL_CS,16(%esp)
1343         jne nmi_stack_correct
1344         cmpl $debug,(%esp)
1345         jb nmi_stack_correct
1346         cmpl $debug_esp_fix_insn,(%esp)
1347         ja nmi_stack_correct
1348         FIX_STACK 24, nmi_stack_correct, 1
1349         jmp nmi_stack_correct
1350
1351 nmi_espfix_stack:
1352         /* We have a RING0_INT_FRAME here.
1353          *
1354          * create the pointer to lss back
1355          */
1356         pushl %ss
1357         CFI_ADJUST_CFA_OFFSET 4
1358         pushl %esp
1359         CFI_ADJUST_CFA_OFFSET 4
1360         addl $4, (%esp)
1361         /* copy the iret frame of 12 bytes */
1362         .rept 3
1363         pushl 16(%esp)
1364         CFI_ADJUST_CFA_OFFSET 4
1365         .endr
1366         pushl %eax
1367         CFI_ADJUST_CFA_OFFSET 4
1368         SAVE_ALL
1369         FIXUP_ESPFIX_STACK              # %eax == %esp
1370         xorl %edx,%edx                  # zero error code
1371         call do_nmi
1372         RESTORE_REGS
1373         lss 12+4(%esp), %esp            # back to espfix stack
1374         CFI_ADJUST_CFA_OFFSET -24
1375         jmp irq_return
1376         CFI_ENDPROC
1377 END(nmi)
1378
1379 ENTRY(int3)
1380         RING0_INT_FRAME
1381         pushl $-1                       # mark this as an int
1382         CFI_ADJUST_CFA_OFFSET 4
1383         SAVE_ALL
1384         TRACE_IRQS_OFF
1385         xorl %edx,%edx          # zero error code
1386         movl %esp,%eax          # pt_regs pointer
1387         call do_int3
1388         jmp ret_from_exception
1389         CFI_ENDPROC
1390 END(int3)
1391
1392 ENTRY(general_protection)
1393         RING0_EC_FRAME
1394         pushl $do_general_protection
1395         CFI_ADJUST_CFA_OFFSET 4
1396         jmp error_code
1397         CFI_ENDPROC
1398 END(general_protection)
1399
1400 /*
1401  * End of kprobes section
1402  */
1403         .popsection