arch/x86/kernel/entry_64.S

   1 /*
   2  *  linux/arch/x86_64/entry.S
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *  Copyright (C) 2000, 2001, 2002  Andi Kleen SuSE Labs
   6  *  Copyright (C) 2000  Pavel Machek <pavel@suse.cz>
   7  */
   8
   9 /*
  10  * entry.S contains the system-call and fault low-level handling routines.
  11  *
  12  * NOTE: This code handles signal-recognition, which happens every time
  13  * after an interrupt and after each system call.
  14  *
  15  * Normal syscalls and interrupts don't save a full stack frame, this is
  16  * only done for syscall tracing, signals or fork/exec et.al.
  17  *
  18  * A note on terminology:
  19  * - top of stack: Architecture defined interrupt frame from SS to RIP
  20  * at the top of the kernel process stack.
  21  * - partial stack frame: partially saved registers upto R11.
  22  * - full stack frame: Like partial stack frame, but all register saved.
  23  *
  24  * Some macro usage:
  25  * - CFI macros are used to generate dwarf2 unwind information for better
  26  * backtraces. They don't change any code.
  27  * - SAVE_ALL/RESTORE_ALL - Save/restore all registers
  28  * - SAVE_ARGS/RESTORE_ARGS - Save/restore registers that C functions modify.
  29  * There are unfortunately lots of special cases where some registers
  30  * not touched. The macro is a big mess that should be cleaned up.
  31  * - SAVE_REST/RESTORE_REST - Handle the registers not saved by SAVE_ARGS.
  32  * Gives a full stack frame.
  33  * - ENTRY/END Define functions in the symbol table.
  34  * - FIXUP_TOP_OF_STACK/RESTORE_TOP_OF_STACK - Fix up the hardware stack
  35  * frame that is otherwise undefined after a SYSCALL
  36  * - TRACE_IRQ_* - Trace hard interrupt state for lock debugging.
  37  * - errorentry/paranoidentry/zeroentry - Define exception entry points.
  38  */
  39
  40 #include <linux/linkage.h>
  41 #include <asm/segment.h>
  42 #include <asm/cache.h>
  43 #include <asm/errno.h>
  44 #include <asm/dwarf2.h>
  45 #include <asm/calling.h>
  46 #include <asm/asm-offsets.h>
  47 #include <asm/msr.h>
  48 #include <asm/unistd.h>
  49 #include <asm/thread_info.h>
  50 #include <asm/hw_irq.h>
  51 #include <asm/page.h>
  52 #include <asm/irqflags.h>
  53 #include <asm/paravirt.h>
  54 #include <asm/ftrace.h>
  55 #include <asm/percpu.h>
  56
  57 /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
  58 #include <linux/elf-em.h>
  59 #define AUDIT_ARCH_X86_64       (EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
  60 #define __AUDIT_ARCH_64BIT 0x80000000
  61 #define __AUDIT_ARCH_LE    0x40000000
  62
  63         .code64
  64 #ifdef CONFIG_FUNCTION_TRACER
  65 #ifdef CONFIG_DYNAMIC_FTRACE
  66 ENTRY(mcount)
  67         retq
  68 END(mcount)
  69
  70 ENTRY(ftrace_caller)
  71         cmpl $0, function_trace_stop
  72         jne  ftrace_stub
  73
  74         MCOUNT_SAVE_FRAME
  75
  76         movq 0x38(%rsp), %rdi
  77         movq 8(%rbp), %rsi
  78         subq $MCOUNT_INSN_SIZE, %rdi
  79
  80 .globl ftrace_call
  81 ftrace_call:
  82         call ftrace_stub
  83
  84         MCOUNT_RESTORE_FRAME
  85
  86 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  87 .globl ftrace_graph_call
  88 ftrace_graph_call:
  89         jmp ftrace_stub
  90 #endif
  91
  92 .globl ftrace_stub
  93 ftrace_stub:
  94         retq
  95 END(ftrace_caller)
  96
  97 #else /* ! CONFIG_DYNAMIC_FTRACE */
  98 ENTRY(mcount)
  99         cmpl $0, function_trace_stop
 100         jne  ftrace_stub
 101
 102         cmpq $ftrace_stub, ftrace_trace_function
 103         jnz trace
 104
 105 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 106         cmpq $ftrace_stub, ftrace_graph_return
 107         jnz ftrace_graph_caller
 108
 109         cmpq $ftrace_graph_entry_stub, ftrace_graph_entry
 110         jnz ftrace_graph_caller
 111 #endif
 112
 113 .globl ftrace_stub
 114 ftrace_stub:
 115         retq
 116
 117 trace:
 118         MCOUNT_SAVE_FRAME
 119
 120         movq 0x38(%rsp), %rdi
 121         movq 8(%rbp), %rsi
 122         subq $MCOUNT_INSN_SIZE, %rdi
 123
 124         call   *ftrace_trace_function
 125
 126         MCOUNT_RESTORE_FRAME
 127
 128         jmp ftrace_stub
 129 END(mcount)
 130 #endif /* CONFIG_DYNAMIC_FTRACE */
 131 #endif /* CONFIG_FUNCTION_TRACER */
 132
 133 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 134 ENTRY(ftrace_graph_caller)
 135         cmpl $0, function_trace_stop
 136         jne ftrace_stub
 137
 138         MCOUNT_SAVE_FRAME
 139
 140         leaq 8(%rbp), %rdi
 141         movq 0x38(%rsp), %rsi
 142         subq $MCOUNT_INSN_SIZE, %rsi
 143
 144         call    prepare_ftrace_return
 145
 146         MCOUNT_RESTORE_FRAME
 147
 148         retq
 149 END(ftrace_graph_caller)
 150
 151
 152 .globl return_to_handler
 153 return_to_handler:
 154         subq  $80, %rsp
 155
 156         movq %rax, (%rsp)
 157         movq %rcx, 8(%rsp)
 158         movq %rdx, 16(%rsp)
 159         movq %rsi, 24(%rsp)
 160         movq %rdi, 32(%rsp)
 161         movq %r8, 40(%rsp)
 162         movq %r9, 48(%rsp)
 163         movq %r10, 56(%rsp)
 164         movq %r11, 64(%rsp)
 165
 166         call ftrace_return_to_handler
 167
 168         movq %rax, 72(%rsp)
 169         movq 64(%rsp), %r11
 170         movq 56(%rsp), %r10
 171         movq 48(%rsp), %r9
 172         movq 40(%rsp), %r8
 173         movq 32(%rsp), %rdi
 174         movq 24(%rsp), %rsi
 175         movq 16(%rsp), %rdx
 176         movq 8(%rsp), %rcx
 177         movq (%rsp), %rax
 178         addq $72, %rsp
 179         retq
 180 #endif
 181
 182
 183 #ifndef CONFIG_PREEMPT
 184 #define retint_kernel retint_restore_args
 185 #endif
 186
 187 #ifdef CONFIG_PARAVIRT
 188 ENTRY(native_usergs_sysret64)
 189         swapgs
 190         sysretq
 191 #endif /* CONFIG_PARAVIRT */
 192
 193
 194 .macro TRACE_IRQS_IRETQ offset=ARGOFFSET
 195 #ifdef CONFIG_TRACE_IRQFLAGS
 196         bt   $9,EFLAGS-\offset(%rsp)    /* interrupts off? */
 197         jnc  1f
 198         TRACE_IRQS_ON
 199 1:
 200 #endif
 201 .endm
 202
 203 /*
 204  * C code is not supposed to know about undefined top of stack. Every time
 205  * a C function with an pt_regs argument is called from the SYSCALL based
 206  * fast path FIXUP_TOP_OF_STACK is needed.
 207  * RESTORE_TOP_OF_STACK syncs the syscall state after any possible ptregs
 208  * manipulation.
 209  */
 210
 211         /* %rsp:at FRAMEEND */
 212         .macro FIXUP_TOP_OF_STACK tmp offset=0
 213         movq %gs:pda_oldrsp,\tmp
 214         movq \tmp,RSP+\offset(%rsp)
 215         movq $__USER_DS,SS+\offset(%rsp)
 216         movq $__USER_CS,CS+\offset(%rsp)
 217         movq $-1,RCX+\offset(%rsp)
 218         movq R11+\offset(%rsp),\tmp  /* get eflags */
 219         movq \tmp,EFLAGS+\offset(%rsp)
 220         .endm
 221
 222         .macro RESTORE_TOP_OF_STACK tmp offset=0
 223         movq RSP+\offset(%rsp),\tmp
 224         movq \tmp,%gs:pda_oldrsp
 225         movq EFLAGS+\offset(%rsp),\tmp
 226         movq \tmp,R11+\offset(%rsp)
 227         .endm
 228
 229         .macro FAKE_STACK_FRAME child_rip
 230         /* push in order ss, rsp, eflags, cs, rip */
 231         xorl %eax, %eax
 232         pushq $__KERNEL_DS /* ss */
 233         CFI_ADJUST_CFA_OFFSET   8
 234         /*CFI_REL_OFFSET        ss,0*/
 235         pushq %rax /* rsp */
 236         CFI_ADJUST_CFA_OFFSET   8
 237         CFI_REL_OFFSET  rsp,0
 238         pushq $X86_EFLAGS_IF /* eflags - interrupts on */
 239         CFI_ADJUST_CFA_OFFSET   8
 240         /*CFI_REL_OFFSET        rflags,0*/
 241         pushq $__KERNEL_CS /* cs */
 242         CFI_ADJUST_CFA_OFFSET   8
 243         /*CFI_REL_OFFSET        cs,0*/
 244         pushq \child_rip /* rip */
 245         CFI_ADJUST_CFA_OFFSET   8
 246         CFI_REL_OFFSET  rip,0
 247         pushq   %rax /* orig rax */
 248         CFI_ADJUST_CFA_OFFSET   8
 249         .endm
 250
 251         .macro UNFAKE_STACK_FRAME
 252         addq $8*6, %rsp
 253         CFI_ADJUST_CFA_OFFSET   -(6*8)
 254         .endm
 255
 256 /*
 257  * initial frame state for interrupts (and exceptions without error code)
 258  */
 259         .macro EMPTY_FRAME start=1 offset=0
 260         .if \start
 261         CFI_STARTPROC simple
 262         CFI_SIGNAL_FRAME
 263         CFI_DEF_CFA rsp,8+\offset
 264         .else
 265         CFI_DEF_CFA_OFFSET 8+\offset
 266         .endif
 267         .endm
 268
 269 /*
 270  * initial frame state for interrupts (and exceptions without error code)
 271  */
 272         .macro INTR_FRAME start=1 offset=0
 273         EMPTY_FRAME \start, SS+8+\offset-RIP
 274         /*CFI_REL_OFFSET ss, SS+\offset-RIP*/
 275         CFI_REL_OFFSET rsp, RSP+\offset-RIP
 276         /*CFI_REL_OFFSET rflags, EFLAGS+\offset-RIP*/
 277         /*CFI_REL_OFFSET cs, CS+\offset-RIP*/
 278         CFI_REL_OFFSET rip, RIP+\offset-RIP
 279         .endm
 280
 281 /*
 282  * initial frame state for exceptions with error code (and interrupts
 283  * with vector already pushed)
 284  */
 285         .macro XCPT_FRAME start=1 offset=0
 286         INTR_FRAME \start, RIP+\offset-ORIG_RAX
 287         /*CFI_REL_OFFSET orig_rax, ORIG_RAX-ORIG_RAX*/
 288         .endm
 289
 290 /*
 291  * frame that enables calling into C.
 292  */
 293         .macro PARTIAL_FRAME start=1 offset=0
 294         XCPT_FRAME \start, ORIG_RAX+\offset-ARGOFFSET
 295         CFI_REL_OFFSET rdi, RDI+\offset-ARGOFFSET
 296         CFI_REL_OFFSET rsi, RSI+\offset-ARGOFFSET
 297         CFI_REL_OFFSET rdx, RDX+\offset-ARGOFFSET
 298         CFI_REL_OFFSET rcx, RCX+\offset-ARGOFFSET
 299         CFI_REL_OFFSET rax, RAX+\offset-ARGOFFSET
 300         CFI_REL_OFFSET r8, R8+\offset-ARGOFFSET
 301         CFI_REL_OFFSET r9, R9+\offset-ARGOFFSET
 302         CFI_REL_OFFSET r10, R10+\offset-ARGOFFSET
 303         CFI_REL_OFFSET r11, R11+\offset-ARGOFFSET
 304         .endm
 305
 306 /*
 307  * frame that enables passing a complete pt_regs to a C function.
 308  */
 309         .macro DEFAULT_FRAME start=1 offset=0
 310         PARTIAL_FRAME \start, R11+\offset-R15
 311         CFI_REL_OFFSET rbx, RBX+\offset
 312         CFI_REL_OFFSET rbp, RBP+\offset
 313         CFI_REL_OFFSET r12, R12+\offset
 314         CFI_REL_OFFSET r13, R13+\offset
 315         CFI_REL_OFFSET r14, R14+\offset
 316         CFI_REL_OFFSET r15, R15+\offset
 317         .endm
 318
 319 /* save partial stack frame */
 320 ENTRY(save_args)
 321         XCPT_FRAME
 322         cld
 323         movq_cfi rdi, RDI+16-ARGOFFSET
 324         movq_cfi rsi, RSI+16-ARGOFFSET
 325         movq_cfi rdx, RDX+16-ARGOFFSET
 326         movq_cfi rcx, RCX+16-ARGOFFSET
 327         movq_cfi rax, RAX+16-ARGOFFSET
 328         movq_cfi  r8,  R8+16-ARGOFFSET
 329         movq_cfi  r9,  R9+16-ARGOFFSET
 330         movq_cfi r10, R10+16-ARGOFFSET
 331         movq_cfi r11, R11+16-ARGOFFSET
 332
 333         leaq -ARGOFFSET+16(%rsp),%rdi   /* arg1 for handler */
 334         movq_cfi rbp, 8         /* push %rbp */
 335         leaq 8(%rsp), %rbp              /* mov %rsp, %ebp */
 336         testl $3, CS(%rdi)
 337         je 1f
 338         SWAPGS
 339         /*
 340          * irqcount is used to check if a CPU is already on an interrupt stack
 341          * or not. While this is essentially redundant with preempt_count it is
 342          * a little cheaper to use a separate counter in the PDA (short of
 343          * moving irq_enter into assembly, which would be too much work)
 344          */
 345 1:      incl %gs:pda_irqcount
 346         jne 2f
 347         popq_cfi %rax                   /* move return address... */
 348         mov PER_CPU_VAR(irq_stack_ptr),%rsp
 349         EMPTY_FRAME 0
 350         pushq_cfi %rax                  /* ... to the new stack */
 351         /*
 352          * We entered an interrupt context - irqs are off:
 353          */
 354 2:      TRACE_IRQS_OFF
 355         ret
 356         CFI_ENDPROC
 357 END(save_args)
 358
 359 ENTRY(save_rest)
 360         PARTIAL_FRAME 1 REST_SKIP+8
 361         movq 5*8+16(%rsp), %r11 /* save return address */
 362         movq_cfi rbx, RBX+16
 363         movq_cfi rbp, RBP+16
 364         movq_cfi r12, R12+16
 365         movq_cfi r13, R13+16
 366         movq_cfi r14, R14+16
 367         movq_cfi r15, R15+16
 368         movq %r11, 8(%rsp)      /* return address */
 369         FIXUP_TOP_OF_STACK %r11, 16
 370         ret
 371         CFI_ENDPROC
 372 END(save_rest)
 373
 374 /* save complete stack frame */
 375 ENTRY(save_paranoid)
 376         XCPT_FRAME 1 RDI+8
 377         cld
 378         movq_cfi rdi, RDI+8
 379         movq_cfi rsi, RSI+8
 380         movq_cfi rdx, RDX+8
 381         movq_cfi rcx, RCX+8
 382         movq_cfi rax, RAX+8
 383         movq_cfi r8, R8+8
 384         movq_cfi r9, R9+8
 385         movq_cfi r10, R10+8
 386         movq_cfi r11, R11+8
 387         movq_cfi rbx, RBX+8
 388         movq_cfi rbp, RBP+8
 389         movq_cfi r12, R12+8
 390         movq_cfi r13, R13+8
 391         movq_cfi r14, R14+8
 392         movq_cfi r15, R15+8
 393         movl $1,%ebx
 394         movl $MSR_GS_BASE,%ecx
 395         rdmsr
 396         testl %edx,%edx
 397         js 1f   /* negative -> in kernel */
 398         SWAPGS
 399         xorl %ebx,%ebx
 400 1:      ret
 401         CFI_ENDPROC
 402 END(save_paranoid)
 403
 404 /*
 405  * A newly forked process directly context switches into this address.
 406  *
 407  * rdi: prev task we switched from
 408  */
 409 ENTRY(ret_from_fork)
 410         DEFAULT_FRAME
 411
 412         push kernel_eflags(%rip)
 413         CFI_ADJUST_CFA_OFFSET 8
 414         popf                                    # reset kernel eflags
 415         CFI_ADJUST_CFA_OFFSET -8
 416
 417         call schedule_tail                      # rdi: 'prev' task parameter
 418
 419         GET_THREAD_INFO(%rcx)
 420
 421         CFI_REMEMBER_STATE
 422         RESTORE_REST
 423
 424         testl $3, CS-ARGOFFSET(%rsp)            # from kernel_thread?
 425         je   int_ret_from_sys_call
 426
 427         testl $_TIF_IA32, TI_flags(%rcx)        # 32-bit compat task needs IRET
 428         jnz  int_ret_from_sys_call
 429
 430         RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
 431         jmp ret_from_sys_call                   # go to the SYSRET fastpath
 432
 433         CFI_RESTORE_STATE
 434         CFI_ENDPROC
 435 END(ret_from_fork)
 436
 437 /*
 438  * System call entry. Upto 6 arguments in registers are supported.
 439  *
 440  * SYSCALL does not save anything on the stack and does not change the
 441  * stack pointer.
 442  */
 443
 444 /*
 445  * Register setup:
 446  * rax  system call number
 447  * rdi  arg0
 448  * rcx  return address for syscall/sysret, C arg3
 449  * rsi  arg1
 450  * rdx  arg2
 451  * r10  arg3    (--> moved to rcx for C)
 452  * r8   arg4
 453  * r9   arg5
 454  * r11  eflags for syscall/sysret, temporary for C
 455  * r12-r15,rbp,rbx saved by C code, not touched.
 456  *
 457  * Interrupts are off on entry.
 458  * Only called from user space.
 459  *
 460  * XXX  if we had a free scratch register we could save the RSP into the stack frame
 461  *      and report it properly in ps. Unfortunately we haven't.
 462  *
 463  * When user can change the frames always force IRET. That is because
 464  * it deals with uncanonical addresses better. SYSRET has trouble
 465  * with them due to bugs in both AMD and Intel CPUs.
 466  */
 467
 468 ENTRY(system_call)
 469         CFI_STARTPROC   simple
 470         CFI_SIGNAL_FRAME
 471         CFI_DEF_CFA     rsp,KERNEL_STACK_OFFSET
 472         CFI_REGISTER    rip,rcx
 473         /*CFI_REGISTER  rflags,r11*/
 474         SWAPGS_UNSAFE_STACK
 475         /*
 476          * A hypervisor implementation might want to use a label
 477          * after the swapgs, so that it can do the swapgs
 478          * for the guest and jump here on syscall.
 479          */
 480 ENTRY(system_call_after_swapgs)
 481
 482         movq    %rsp,%gs:pda_oldrsp
 483         movq    PER_CPU_VAR(kernel_stack),%rsp
 484         /*
 485          * No need to follow this irqs off/on section - it's straight
 486          * and short:
 487          */
 488         ENABLE_INTERRUPTS(CLBR_NONE)
 489         SAVE_ARGS 8,1
 490         movq  %rax,ORIG_RAX-ARGOFFSET(%rsp)
 491         movq  %rcx,RIP-ARGOFFSET(%rsp)
 492         CFI_REL_OFFSET rip,RIP-ARGOFFSET
 493         GET_THREAD_INFO(%rcx)
 494         testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%rcx)
 495         jnz tracesys
 496 system_call_fastpath:
 497         cmpq $__NR_syscall_max,%rax
 498         ja badsys
 499         movq %r10,%rcx
 500         call *sys_call_table(,%rax,8)  # XXX:    rip relative
 501         movq %rax,RAX-ARGOFFSET(%rsp)
 502 /*
 503  * Syscall return path ending with SYSRET (fast path)
 504  * Has incomplete stack frame and undefined top of stack.
 505  */
 506 ret_from_sys_call:
 507         movl $_TIF_ALLWORK_MASK,%edi
 508         /* edi: flagmask */
 509 sysret_check:
 510         LOCKDEP_SYS_EXIT
 511         GET_THREAD_INFO(%rcx)
 512         DISABLE_INTERRUPTS(CLBR_NONE)
 513         TRACE_IRQS_OFF
 514         movl TI_flags(%rcx),%edx
 515         andl %edi,%edx
 516         jnz  sysret_careful
 517         CFI_REMEMBER_STATE
 518         /*
 519          * sysretq will re-enable interrupts:
 520          */
 521         TRACE_IRQS_ON
 522         movq RIP-ARGOFFSET(%rsp),%rcx
 523         CFI_REGISTER    rip,rcx
 524         RESTORE_ARGS 0,-ARG_SKIP,1
 525         /*CFI_REGISTER  rflags,r11*/
 526         movq    %gs:pda_oldrsp, %rsp
 527         USERGS_SYSRET64
 528
 529         CFI_RESTORE_STATE
 530         /* Handle reschedules */
 531         /* edx: work, edi: workmask */
 532 sysret_careful:
 533         bt $TIF_NEED_RESCHED,%edx
 534         jnc sysret_signal
 535         TRACE_IRQS_ON
 536         ENABLE_INTERRUPTS(CLBR_NONE)
 537         pushq %rdi
 538         CFI_ADJUST_CFA_OFFSET 8
 539         call schedule
 540         popq  %rdi
 541         CFI_ADJUST_CFA_OFFSET -8
 542         jmp sysret_check
 543
 544         /* Handle a signal */
 545 sysret_signal:
 546         TRACE_IRQS_ON
 547         ENABLE_INTERRUPTS(CLBR_NONE)
 548 #ifdef CONFIG_AUDITSYSCALL
 549         bt $TIF_SYSCALL_AUDIT,%edx
 550         jc sysret_audit
 551 #endif
 552         /* edx: work flags (arg3) */
 553         leaq -ARGOFFSET(%rsp),%rdi # &pt_regs -> arg1
 554         xorl %esi,%esi # oldset -> arg2
 555         SAVE_REST
 556         FIXUP_TOP_OF_STACK %r11
 557         call do_notify_resume
 558         RESTORE_TOP_OF_STACK %r11
 559         RESTORE_REST
 560         movl $_TIF_WORK_MASK,%edi
 561         /* Use IRET because user could have changed frame. This
 562            works because ptregscall_common has called FIXUP_TOP_OF_STACK. */
 563         DISABLE_INTERRUPTS(CLBR_NONE)
 564         TRACE_IRQS_OFF
 565         jmp int_with_check
 566
 567 badsys:
 568         movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
 569         jmp ret_from_sys_call
 570
 571 #ifdef CONFIG_AUDITSYSCALL
 572         /*
 573          * Fast path for syscall audit without full syscall trace.
 574          * We just call audit_syscall_entry() directly, and then
 575          * jump back to the normal fast path.
 576          */
 577 auditsys:
 578         movq %r10,%r9                   /* 6th arg: 4th syscall arg */
 579         movq %rdx,%r8                   /* 5th arg: 3rd syscall arg */
 580         movq %rsi,%rcx                  /* 4th arg: 2nd syscall arg */
 581         movq %rdi,%rdx                  /* 3rd arg: 1st syscall arg */
 582         movq %rax,%rsi                  /* 2nd arg: syscall number */
 583         movl $AUDIT_ARCH_X86_64,%edi    /* 1st arg: audit arch */
 584         call audit_syscall_entry
 585         LOAD_ARGS 0             /* reload call-clobbered registers */
 586         jmp system_call_fastpath
 587
 588         /*
 589          * Return fast path for syscall audit.  Call audit_syscall_exit()
 590          * directly and then jump back to the fast path with TIF_SYSCALL_AUDIT
 591          * masked off.
 592          */
 593 sysret_audit:
 594         movq %rax,%rsi          /* second arg, syscall return value */
 595         cmpq $0,%rax            /* is it < 0? */
 596         setl %al                /* 1 if so, 0 if not */
 597         movzbl %al,%edi         /* zero-extend that into %edi */
 598         inc %edi /* first arg, 0->1(AUDITSC_SUCCESS), 1->2(AUDITSC_FAILURE) */
 599         call audit_syscall_exit
 600         movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
 601         jmp sysret_check
 602 #endif  /* CONFIG_AUDITSYSCALL */
 603
 604         /* Do syscall tracing */
 605 tracesys:
 606 #ifdef CONFIG_AUDITSYSCALL
 607         testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%rcx)
 608         jz auditsys
 609 #endif
 610         SAVE_REST
 611         movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */
 612         FIXUP_TOP_OF_STACK %rdi
 613         movq %rsp,%rdi
 614         call syscall_trace_enter
 615         /*
 616          * Reload arg registers from stack in case ptrace changed them.
 617          * We don't reload %rax because syscall_trace_enter() returned
 618          * the value it wants us to use in the table lookup.
 619          */
 620         LOAD_ARGS ARGOFFSET, 1
 621         RESTORE_REST
 622         cmpq $__NR_syscall_max,%rax
 623         ja   int_ret_from_sys_call      /* RAX(%rsp) set to -ENOSYS above */
 624         movq %r10,%rcx  /* fixup for C */
 625         call *sys_call_table(,%rax,8)
 626         movq %rax,RAX-ARGOFFSET(%rsp)
 627         /* Use IRET because user could have changed frame */
 628
 629 /*
 630  * Syscall return path ending with IRET.
 631  * Has correct top of stack, but partial stack frame.
 632  */
 633         .globl int_ret_from_sys_call
 634         .globl int_with_check
 635 int_ret_from_sys_call:
 636         DISABLE_INTERRUPTS(CLBR_NONE)
 637         TRACE_IRQS_OFF
 638         testl $3,CS-ARGOFFSET(%rsp)
 639         je retint_restore_args
 640         movl $_TIF_ALLWORK_MASK,%edi
 641         /* edi: mask to check */
 642 int_with_check:
 643         LOCKDEP_SYS_EXIT_IRQ
 644         GET_THREAD_INFO(%rcx)
 645         movl TI_flags(%rcx),%edx
 646         andl %edi,%edx
 647         jnz   int_careful
 648         andl    $~TS_COMPAT,TI_status(%rcx)
 649         jmp   retint_swapgs
 650
 651         /* Either reschedule or signal or syscall exit tracking needed. */
 652         /* First do a reschedule test. */
 653         /* edx: work, edi: workmask */
 654 int_careful:
 655         bt $TIF_NEED_RESCHED,%edx
 656         jnc  int_very_careful
 657         TRACE_IRQS_ON
 658         ENABLE_INTERRUPTS(CLBR_NONE)
 659         pushq %rdi
 660         CFI_ADJUST_CFA_OFFSET 8
 661         call schedule
 662         popq %rdi
 663         CFI_ADJUST_CFA_OFFSET -8
 664         DISABLE_INTERRUPTS(CLBR_NONE)
 665         TRACE_IRQS_OFF
 666         jmp int_with_check
 667
 668         /* handle signals and tracing -- both require a full stack frame */
 669 int_very_careful:
 670         TRACE_IRQS_ON
 671         ENABLE_INTERRUPTS(CLBR_NONE)
 672         SAVE_REST
 673         /* Check for syscall exit trace */
 674         testl $_TIF_WORK_SYSCALL_EXIT,%edx
 675         jz int_signal
 676         pushq %rdi
 677         CFI_ADJUST_CFA_OFFSET 8
 678         leaq 8(%rsp),%rdi       # &ptregs -> arg1
 679         call syscall_trace_leave
 680         popq %rdi
 681         CFI_ADJUST_CFA_OFFSET -8
 682         andl $~(_TIF_WORK_SYSCALL_EXIT|_TIF_SYSCALL_EMU),%edi
 683         jmp int_restore_rest
 684
 685 int_signal:
 686         testl $_TIF_DO_NOTIFY_MASK,%edx
 687         jz 1f
 688         movq %rsp,%rdi          # &ptregs -> arg1
 689         xorl %esi,%esi          # oldset -> arg2
 690         call do_notify_resume
 691 1:      movl $_TIF_WORK_MASK,%edi
 692 int_restore_rest:
 693         RESTORE_REST
 694         DISABLE_INTERRUPTS(CLBR_NONE)
 695         TRACE_IRQS_OFF
 696         jmp int_with_check
 697         CFI_ENDPROC
 698 END(system_call)
 699
 700 /*
 701  * Certain special system calls that need to save a complete full stack frame.
 702  */
 703         .macro PTREGSCALL label,func,arg
 704 ENTRY(\label)
 705         PARTIAL_FRAME 1 8               /* offset 8: return address */
 706         subq $REST_SKIP, %rsp
 707         CFI_ADJUST_CFA_OFFSET REST_SKIP
 708         call save_rest
 709         DEFAULT_FRAME 0 8               /* offset 8: return address */
 710         leaq 8(%rsp), \arg      /* pt_regs pointer */
 711         call \func
 712         jmp ptregscall_common
 713         CFI_ENDPROC
 714 END(\label)
 715         .endm
 716
 717         PTREGSCALL stub_clone, sys_clone, %r8
 718         PTREGSCALL stub_fork, sys_fork, %rdi
 719         PTREGSCALL stub_vfork, sys_vfork, %rdi
 720         PTREGSCALL stub_sigaltstack, sys_sigaltstack, %rdx
 721         PTREGSCALL stub_iopl, sys_iopl, %rsi
 722
 723 ENTRY(ptregscall_common)
 724         DEFAULT_FRAME 1 8       /* offset 8: return address */
 725         RESTORE_TOP_OF_STACK %r11, 8
 726         movq_cfi_restore R15+8, r15
 727         movq_cfi_restore R14+8, r14
 728         movq_cfi_restore R13+8, r13
 729         movq_cfi_restore R12+8, r12
 730         movq_cfi_restore RBP+8, rbp
 731         movq_cfi_restore RBX+8, rbx
 732         ret $REST_SKIP          /* pop extended registers */
 733         CFI_ENDPROC
 734 END(ptregscall_common)
 735
 736 ENTRY(stub_execve)
 737         CFI_STARTPROC
 738         popq %r11
 739         CFI_ADJUST_CFA_OFFSET -8
 740         CFI_REGISTER rip, r11
 741         SAVE_REST
 742         FIXUP_TOP_OF_STACK %r11
 743         movq %rsp, %rcx
 744         call sys_execve
 745         RESTORE_TOP_OF_STACK %r11
 746         movq %rax,RAX(%rsp)
 747         RESTORE_REST
 748         jmp int_ret_from_sys_call
 749         CFI_ENDPROC
 750 END(stub_execve)
 751
 752 /*
 753  * sigreturn is special because it needs to restore all registers on return.
 754  * This cannot be done with SYSRET, so use the IRET return path instead.
 755  */
 756 ENTRY(stub_rt_sigreturn)
 757         CFI_STARTPROC
 758         addq $8, %rsp
 759         CFI_ADJUST_CFA_OFFSET   -8
 760         SAVE_REST
 761         movq %rsp,%rdi
 762         FIXUP_TOP_OF_STACK %r11
 763         call sys_rt_sigreturn
 764         movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
 765         RESTORE_REST
 766         jmp int_ret_from_sys_call
 767         CFI_ENDPROC
 768 END(stub_rt_sigreturn)
 769
 770 /*
 771  * Build the entry stubs and pointer table with some assembler magic.
 772  * We pack 7 stubs into a single 32-byte chunk, which will fit in a
 773  * single cache line on all modern x86 implementations.
 774  */
 775         .section .init.rodata,"a"
 776 ENTRY(interrupt)
 777         .text
 778         .p2align 5
 779         .p2align CONFIG_X86_L1_CACHE_SHIFT
 780 ENTRY(irq_entries_start)
 781         INTR_FRAME
 782 vector=FIRST_EXTERNAL_VECTOR
 783 .rept (NR_VECTORS-FIRST_EXTERNAL_VECTOR+6)/7
 784         .balign 32
 785   .rept 7
 786     .if vector < NR_VECTORS
 787       .if vector <> FIRST_EXTERNAL_VECTOR
 788         CFI_ADJUST_CFA_OFFSET -8
 789       .endif
 790 1:      pushq $(~vector+0x80)   /* Note: always in signed byte range */
 791         CFI_ADJUST_CFA_OFFSET 8
 792       .if ((vector-FIRST_EXTERNAL_VECTOR)%7) <> 6
 793         jmp 2f
 794       .endif
 795       .previous
 796         .quad 1b
 797       .text
 798 vector=vector+1
 799     .endif
 800   .endr
 801 2:      jmp common_interrupt
 802 .endr
 803         CFI_ENDPROC
 804 END(irq_entries_start)
 805
 806 .previous
 807 END(interrupt)
 808 .previous
 809
 810 /*
 811  * Interrupt entry/exit.
 812  *
 813  * Interrupt entry points save only callee clobbered registers in fast path.
 814  *
 815  * Entry runs with interrupts off.
 816  */
 817
 818 /* 0(%rsp): ~(interrupt number) */
 819         .macro interrupt func
 820         subq $10*8, %rsp
 821         CFI_ADJUST_CFA_OFFSET 10*8
 822         call save_args
 823         PARTIAL_FRAME 0
 824         call \func
 825         .endm
 826
 827         /*
 828          * The interrupt stubs push (~vector+0x80) onto the stack and
 829          * then jump to common_interrupt.
 830          */
 831         .p2align CONFIG_X86_L1_CACHE_SHIFT
 832 common_interrupt:
 833         XCPT_FRAME
 834         addq $-0x80,(%rsp)              /* Adjust vector to [-256,-1] range */
 835         interrupt do_IRQ
 836         /* 0(%rsp): oldrsp-ARGOFFSET */
 837 ret_from_intr:
 838         DISABLE_INTERRUPTS(CLBR_NONE)
 839         TRACE_IRQS_OFF
 840         decl %gs:pda_irqcount
 841         leaveq
 842         CFI_DEF_CFA_REGISTER    rsp
 843         CFI_ADJUST_CFA_OFFSET   -8
 844 exit_intr:
 845         GET_THREAD_INFO(%rcx)
 846         testl $3,CS-ARGOFFSET(%rsp)
 847         je retint_kernel
 848
 849         /* Interrupt came from user space */
 850         /*
 851          * Has a correct top of stack, but a partial stack frame
 852          * %rcx: thread info. Interrupts off.
 853          */
 854 retint_with_reschedule:
 855         movl $_TIF_WORK_MASK,%edi
 856 retint_check:
 857         LOCKDEP_SYS_EXIT_IRQ
 858         movl TI_flags(%rcx),%edx
 859         andl %edi,%edx
 860         CFI_REMEMBER_STATE
 861         jnz  retint_careful
 862
 863 retint_swapgs:          /* return to user-space */
 864         /*
 865          * The iretq could re-enable interrupts:
 866          */
 867         DISABLE_INTERRUPTS(CLBR_ANY)
 868         TRACE_IRQS_IRETQ
 869         SWAPGS
 870         jmp restore_args
 871
 872 retint_restore_args:    /* return to kernel space */
 873         DISABLE_INTERRUPTS(CLBR_ANY)
 874         /*
 875          * The iretq could re-enable interrupts:
 876          */
 877         TRACE_IRQS_IRETQ
 878 restore_args:
 879         RESTORE_ARGS 0,8,0
 880
 881 irq_return:
 882         INTERRUPT_RETURN
 883
 884         .section __ex_table, "a"
 885         .quad irq_return, bad_iret
 886         .previous
 887
 888 #ifdef CONFIG_PARAVIRT
 889 ENTRY(native_iret)
 890         iretq
 891
 892         .section __ex_table,"a"
 893         .quad native_iret, bad_iret
 894         .previous
 895 #endif
 896
 897         .section .fixup,"ax"
 898 bad_iret:
 899         /*
 900          * The iret traps when the %cs or %ss being restored is bogus.
 901          * We've lost the original trap vector and error code.
 902          * #GPF is the most likely one to get for an invalid selector.
 903          * So pretend we completed the iret and took the #GPF in user mode.
 904          *
 905          * We are now running with the kernel GS after exception recovery.
 906          * But error_entry expects us to have user GS to match the user %cs,
 907          * so swap back.
 908          */
 909         pushq $0
 910
 911         SWAPGS
 912         jmp general_protection
 913
 914         .previous
 915
 916         /* edi: workmask, edx: work */
 917 retint_careful:
 918         CFI_RESTORE_STATE
 919         bt    $TIF_NEED_RESCHED,%edx
 920         jnc   retint_signal
 921         TRACE_IRQS_ON
 922         ENABLE_INTERRUPTS(CLBR_NONE)
 923         pushq %rdi
 924         CFI_ADJUST_CFA_OFFSET   8
 925         call  schedule
 926         popq %rdi
 927         CFI_ADJUST_CFA_OFFSET   -8
 928         GET_THREAD_INFO(%rcx)
 929         DISABLE_INTERRUPTS(CLBR_NONE)
 930         TRACE_IRQS_OFF
 931         jmp retint_check
 932
 933 retint_signal:
 934         testl $_TIF_DO_NOTIFY_MASK,%edx
 935         jz    retint_swapgs
 936         TRACE_IRQS_ON
 937         ENABLE_INTERRUPTS(CLBR_NONE)
 938         SAVE_REST
 939         movq $-1,ORIG_RAX(%rsp)
 940         xorl %esi,%esi          # oldset
 941         movq %rsp,%rdi          # &pt_regs
 942         call do_notify_resume
 943         RESTORE_REST
 944         DISABLE_INTERRUPTS(CLBR_NONE)
 945         TRACE_IRQS_OFF
 946         GET_THREAD_INFO(%rcx)
 947         jmp retint_with_reschedule
 948
 949 #ifdef CONFIG_PREEMPT
 950         /* Returning to kernel space. Check if we need preemption */
 951         /* rcx:  threadinfo. interrupts off. */
 952 ENTRY(retint_kernel)
 953         cmpl $0,TI_preempt_count(%rcx)
 954         jnz  retint_restore_args
 955         bt  $TIF_NEED_RESCHED,TI_flags(%rcx)
 956         jnc  retint_restore_args
 957         bt   $9,EFLAGS-ARGOFFSET(%rsp)  /* interrupts off? */
 958         jnc  retint_restore_args
 959         call preempt_schedule_irq
 960         jmp exit_intr
 961 #endif
 962
 963         CFI_ENDPROC
 964 END(common_interrupt)
 965
 966 /*
 967  * APIC interrupts.
 968  */
 969 .macro apicinterrupt num sym do_sym
 970 ENTRY(\sym)
 971         INTR_FRAME
 972         pushq $~(\num)
 973         CFI_ADJUST_CFA_OFFSET 8
 974         interrupt \do_sym
 975         jmp ret_from_intr
 976         CFI_ENDPROC
 977 END(\sym)
 978 .endm
 979
 980 #ifdef CONFIG_SMP
 981 apicinterrupt IRQ_MOVE_CLEANUP_VECTOR \
 982         irq_move_cleanup_interrupt smp_irq_move_cleanup_interrupt
 983 #endif
 984
 985 apicinterrupt UV_BAU_MESSAGE \
 986         uv_bau_message_intr1 uv_bau_message_interrupt
 987 apicinterrupt LOCAL_TIMER_VECTOR \
 988         apic_timer_interrupt smp_apic_timer_interrupt
 989
 990 #ifdef CONFIG_SMP
 991 apicinterrupt INVALIDATE_TLB_VECTOR_START+0 \
 992         invalidate_interrupt0 smp_invalidate_interrupt
 993 apicinterrupt INVALIDATE_TLB_VECTOR_START+1 \
 994         invalidate_interrupt1 smp_invalidate_interrupt
 995 apicinterrupt INVALIDATE_TLB_VECTOR_START+2 \
 996         invalidate_interrupt2 smp_invalidate_interrupt
 997 apicinterrupt INVALIDATE_TLB_VECTOR_START+3 \
 998         invalidate_interrupt3 smp_invalidate_interrupt
 999 apicinterrupt INVALIDATE_TLB_VECTOR_START+4 \
1000         invalidate_interrupt4 smp_invalidate_interrupt
1001 apicinterrupt INVALIDATE_TLB_VECTOR_START+5 \
1002         invalidate_interrupt5 smp_invalidate_interrupt
1003 apicinterrupt INVALIDATE_TLB_VECTOR_START+6 \
1004         invalidate_interrupt6 smp_invalidate_interrupt
1005 apicinterrupt INVALIDATE_TLB_VECTOR_START+7 \
1006         invalidate_interrupt7 smp_invalidate_interrupt
1007 #endif
1008
1009 apicinterrupt THRESHOLD_APIC_VECTOR \
1010         threshold_interrupt mce_threshold_interrupt
1011 apicinterrupt THERMAL_APIC_VECTOR \
1012         thermal_interrupt smp_thermal_interrupt
1013
1014 #ifdef CONFIG_SMP
1015 apicinterrupt CALL_FUNCTION_SINGLE_VECTOR \
1016         call_function_single_interrupt smp_call_function_single_interrupt
1017 apicinterrupt CALL_FUNCTION_VECTOR \
1018         call_function_interrupt smp_call_function_interrupt
1019 apicinterrupt RESCHEDULE_VECTOR \
1020         reschedule_interrupt smp_reschedule_interrupt
1021 #endif
1022
1023 apicinterrupt ERROR_APIC_VECTOR \
1024         error_interrupt smp_error_interrupt
1025 apicinterrupt SPURIOUS_APIC_VECTOR \
1026         spurious_interrupt smp_spurious_interrupt
1027
1028 /*
1029  * Exception entry points.
1030  */
1031 .macro zeroentry sym do_sym
1032 ENTRY(\sym)
1033         INTR_FRAME
1034         PARAVIRT_ADJUST_EXCEPTION_FRAME
1035         pushq_cfi $-1           /* ORIG_RAX: no syscall to restart */
1036         subq $15*8,%rsp
1037         CFI_ADJUST_CFA_OFFSET 15*8
1038         call error_entry
1039         DEFAULT_FRAME 0
1040         movq %rsp,%rdi          /* pt_regs pointer */
1041         xorl %esi,%esi          /* no error code */
1042         call \do_sym
1043         jmp error_exit          /* %ebx: no swapgs flag */
1044         CFI_ENDPROC
1045 END(\sym)
1046 .endm
1047
1048 .macro paranoidzeroentry sym do_sym
1049 ENTRY(\sym)
1050         INTR_FRAME
1051         PARAVIRT_ADJUST_EXCEPTION_FRAME
1052         pushq $-1               /* ORIG_RAX: no syscall to restart */
1053         CFI_ADJUST_CFA_OFFSET 8
1054         subq $15*8, %rsp
1055         call save_paranoid
1056         TRACE_IRQS_OFF
1057         movq %rsp,%rdi          /* pt_regs pointer */
1058         xorl %esi,%esi          /* no error code */
1059         call \do_sym
1060         jmp paranoid_exit       /* %ebx: no swapgs flag */
1061         CFI_ENDPROC
1062 END(\sym)
1063 .endm
1064
1065 .macro paranoidzeroentry_ist sym do_sym ist
1066 ENTRY(\sym)
1067         INTR_FRAME
1068         PARAVIRT_ADJUST_EXCEPTION_FRAME
1069         pushq $-1               /* ORIG_RAX: no syscall to restart */
1070         CFI_ADJUST_CFA_OFFSET 8
1071         subq $15*8, %rsp
1072         call save_paranoid
1073         TRACE_IRQS_OFF
1074         movq %rsp,%rdi          /* pt_regs pointer */
1075         xorl %esi,%esi          /* no error code */
1076         PER_CPU(init_tss, %rbp)
1077         subq $EXCEPTION_STKSZ, TSS_ist + (\ist - 1) * 8(%rbp)
1078         call \do_sym
1079         addq $EXCEPTION_STKSZ, TSS_ist + (\ist - 1) * 8(%rbp)
1080         jmp paranoid_exit       /* %ebx: no swapgs flag */
1081         CFI_ENDPROC
1082 END(\sym)
1083 .endm
1084
1085 .macro errorentry sym do_sym
1086 ENTRY(\sym)
1087         XCPT_FRAME
1088         PARAVIRT_ADJUST_EXCEPTION_FRAME
1089         subq $15*8,%rsp
1090         CFI_ADJUST_CFA_OFFSET 15*8
1091         call error_entry
1092         DEFAULT_FRAME 0
1093         movq %rsp,%rdi                  /* pt_regs pointer */
1094         movq ORIG_RAX(%rsp),%rsi        /* get error code */
1095         movq $-1,ORIG_RAX(%rsp)         /* no syscall to restart */
1096         call \do_sym
1097         jmp error_exit                  /* %ebx: no swapgs flag */
1098         CFI_ENDPROC
1099 END(\sym)
1100 .endm
1101
1102         /* error code is on the stack already */
1103 .macro paranoiderrorentry sym do_sym
1104 ENTRY(\sym)
1105         XCPT_FRAME
1106         PARAVIRT_ADJUST_EXCEPTION_FRAME
1107         subq $15*8,%rsp
1108         CFI_ADJUST_CFA_OFFSET 15*8
1109         call save_paranoid
1110         DEFAULT_FRAME 0
1111         TRACE_IRQS_OFF
1112         movq %rsp,%rdi                  /* pt_regs pointer */
1113         movq ORIG_RAX(%rsp),%rsi        /* get error code */
1114         movq $-1,ORIG_RAX(%rsp)         /* no syscall to restart */
1115         call \do_sym
1116         jmp paranoid_exit               /* %ebx: no swapgs flag */
1117         CFI_ENDPROC
1118 END(\sym)
1119 .endm
1120
1121 zeroentry divide_error do_divide_error
1122 zeroentry overflow do_overflow
1123 zeroentry bounds do_bounds
1124 zeroentry invalid_op do_invalid_op
1125 zeroentry device_not_available do_device_not_available
1126 paranoiderrorentry double_fault do_double_fault
1127 zeroentry coprocessor_segment_overrun do_coprocessor_segment_overrun
1128 errorentry invalid_TSS do_invalid_TSS
1129 errorentry segment_not_present do_segment_not_present
1130 zeroentry spurious_interrupt_bug do_spurious_interrupt_bug
1131 zeroentry coprocessor_error do_coprocessor_error
1132 errorentry alignment_check do_alignment_check
1133 zeroentry simd_coprocessor_error do_simd_coprocessor_error
1134
1135         /* Reload gs selector with exception handling */
1136         /* edi:  new selector */
1137 ENTRY(native_load_gs_index)
1138         CFI_STARTPROC
1139         pushf
1140         CFI_ADJUST_CFA_OFFSET 8
1141         DISABLE_INTERRUPTS(CLBR_ANY | ~(CLBR_RDI))
1142         SWAPGS
1143 gs_change:
1144         movl %edi,%gs
1145 2:      mfence          /* workaround */
1146         SWAPGS
1147         popf
1148         CFI_ADJUST_CFA_OFFSET -8
1149         ret
1150         CFI_ENDPROC
1151 END(native_load_gs_index)
1152
1153         .section __ex_table,"a"
1154         .align 8
1155         .quad gs_change,bad_gs
1156         .previous
1157         .section .fixup,"ax"
1158         /* running with kernelgs */
1159 bad_gs:
1160         SWAPGS                  /* switch back to user gs */
1161         xorl %eax,%eax
1162         movl %eax,%gs
1163         jmp  2b
1164         .previous
1165
1166 /*
1167  * Create a kernel thread.
1168  *
1169  * C extern interface:
1170  *      extern long kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
1171  *
1172  * asm input arguments:
1173  *      rdi: fn, rsi: arg, rdx: flags
1174  */
1175 ENTRY(kernel_thread)
1176         CFI_STARTPROC
1177         FAKE_STACK_FRAME $child_rip
1178         SAVE_ALL
1179
1180         # rdi: flags, rsi: usp, rdx: will be &pt_regs
1181         movq %rdx,%rdi
1182         orq  kernel_thread_flags(%rip),%rdi
1183         movq $-1, %rsi
1184         movq %rsp, %rdx
1185
1186         xorl %r8d,%r8d
1187         xorl %r9d,%r9d
1188
1189         # clone now
1190         call do_fork
1191         movq %rax,RAX(%rsp)
1192         xorl %edi,%edi
1193
1194         /*
1195          * It isn't worth to check for reschedule here,
1196          * so internally to the x86_64 port you can rely on kernel_thread()
1197          * not to reschedule the child before returning, this avoids the need
1198          * of hacks for example to fork off the per-CPU idle tasks.
1199          * [Hopefully no generic code relies on the reschedule -AK]
1200          */
1201         RESTORE_ALL
1202         UNFAKE_STACK_FRAME
1203         ret
1204         CFI_ENDPROC
1205 END(kernel_thread)
1206
1207 ENTRY(child_rip)
1208         pushq $0                # fake return address
1209         CFI_STARTPROC
1210         /*
1211          * Here we are in the child and the registers are set as they were
1212          * at kernel_thread() invocation in the parent.
1213          */
1214         movq %rdi, %rax
1215         movq %rsi, %rdi
1216         call *%rax
1217         # exit
1218         mov %eax, %edi
1219         call do_exit
1220         ud2                     # padding for call trace
1221         CFI_ENDPROC
1222 END(child_rip)
1223
1224 /*
1225  * execve(). This function needs to use IRET, not SYSRET, to set up all state properly.
1226  *
1227  * C extern interface:
1228  *       extern long execve(char *name, char **argv, char **envp)
1229  *
1230  * asm input arguments:
1231  *      rdi: name, rsi: argv, rdx: envp
1232  *
1233  * We want to fallback into:
1234  *      extern long sys_execve(char *name, char **argv,char **envp, struct pt_regs *regs)
1235  *
1236  * do_sys_execve asm fallback arguments:
1237  *      rdi: name, rsi: argv, rdx: envp, rcx: fake frame on the stack
1238  */
1239 ENTRY(kernel_execve)
1240         CFI_STARTPROC
1241         FAKE_STACK_FRAME $0
1242         SAVE_ALL
1243         movq %rsp,%rcx
1244         call sys_execve
1245         movq %rax, RAX(%rsp)
1246         RESTORE_REST
1247         testq %rax,%rax
1248         je int_ret_from_sys_call
1249         RESTORE_ARGS
1250         UNFAKE_STACK_FRAME
1251         ret
1252         CFI_ENDPROC
1253 END(kernel_execve)
1254
1255 /* Call softirq on interrupt stack. Interrupts are off. */
1256 ENTRY(call_softirq)
1257         CFI_STARTPROC
1258         push %rbp
1259         CFI_ADJUST_CFA_OFFSET   8
1260         CFI_REL_OFFSET rbp,0
1261         mov  %rsp,%rbp
1262         CFI_DEF_CFA_REGISTER rbp
1263         incl %gs:pda_irqcount
1264         cmove PER_CPU_VAR(irq_stack_ptr),%rsp
1265         push  %rbp                      # backlink for old unwinder
1266         call __do_softirq
1267         leaveq
1268         CFI_DEF_CFA_REGISTER    rsp
1269         CFI_ADJUST_CFA_OFFSET   -8
1270         decl %gs:pda_irqcount
1271         ret
1272         CFI_ENDPROC
1273 END(call_softirq)
1274
1275 #ifdef CONFIG_XEN
1276 zeroentry xen_hypervisor_callback xen_do_hypervisor_callback
1277
1278 /*
1279  * A note on the "critical region" in our callback handler.
1280  * We want to avoid stacking callback handlers due to events occurring
1281  * during handling of the last event. To do this, we keep events disabled
1282  * until we've done all processing. HOWEVER, we must enable events before
1283  * popping the stack frame (can't be done atomically) and so it would still
1284  * be possible to get enough handler activations to overflow the stack.
1285  * Although unlikely, bugs of that kind are hard to track down, so we'd
1286  * like to avoid the possibility.
1287  * So, on entry to the handler we detect whether we interrupted an
1288  * existing activation in its critical region -- if so, we pop the current
1289  * activation and restart the handler using the previous one.
1290  */
1291 ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)
1292         CFI_STARTPROC
1293 /*
1294  * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
1295  * see the correct pointer to the pt_regs
1296  */
1297         movq %rdi, %rsp            # we don't return, adjust the stack frame
1298         CFI_ENDPROC
1299         DEFAULT_FRAME
1300 11:     incl %gs:pda_irqcount
1301         movq %rsp,%rbp
1302         CFI_DEF_CFA_REGISTER rbp
1303         cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
1304         pushq %rbp                      # backlink for old unwinder
1305         call xen_evtchn_do_upcall
1306         popq %rsp
1307         CFI_DEF_CFA_REGISTER rsp
1308         decl %gs:pda_irqcount
1309         jmp  error_exit
1310         CFI_ENDPROC
1311 END(do_hypervisor_callback)
1312
1313 /*
1314  * Hypervisor uses this for application faults while it executes.
1315  * We get here for two reasons:
1316  *  1. Fault while reloading DS, ES, FS or GS
1317  *  2. Fault while executing IRET
1318  * Category 1 we do not need to fix up as Xen has already reloaded all segment
1319  * registers that could be reloaded and zeroed the others.
1320  * Category 2 we fix up by killing the current process. We cannot use the
1321  * normal Linux return path in this case because if we use the IRET hypercall
1322  * to pop the stack frame we end up in an infinite loop of failsafe callbacks.
1323  * We distinguish between categories by comparing each saved segment register
1324  * with its current contents: any discrepancy means we in category 1.
1325  */
1326 ENTRY(xen_failsafe_callback)
1327         INTR_FRAME 1 (6*8)
1328         /*CFI_REL_OFFSET gs,GS*/
1329         /*CFI_REL_OFFSET fs,FS*/
1330         /*CFI_REL_OFFSET es,ES*/
1331         /*CFI_REL_OFFSET ds,DS*/
1332         CFI_REL_OFFSET r11,8
1333         CFI_REL_OFFSET rcx,0
1334         movw %ds,%cx
1335         cmpw %cx,0x10(%rsp)
1336         CFI_REMEMBER_STATE
1337         jne 1f
1338         movw %es,%cx
1339         cmpw %cx,0x18(%rsp)
1340         jne 1f
1341         movw %fs,%cx
1342         cmpw %cx,0x20(%rsp)
1343         jne 1f
1344         movw %gs,%cx
1345         cmpw %cx,0x28(%rsp)
1346         jne 1f
1347         /* All segments match their saved values => Category 2 (Bad IRET). */
1348         movq (%rsp),%rcx
1349         CFI_RESTORE rcx
1350         movq 8(%rsp),%r11
1351         CFI_RESTORE r11
1352         addq $0x30,%rsp
1353         CFI_ADJUST_CFA_OFFSET -0x30
1354         pushq_cfi $0    /* RIP */
1355         pushq_cfi %r11
1356         pushq_cfi %rcx
1357         jmp general_protection
1358         CFI_RESTORE_STATE
1359 1:      /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */
1360         movq (%rsp),%rcx
1361         CFI_RESTORE rcx
1362         movq 8(%rsp),%r11
1363         CFI_RESTORE r11
1364         addq $0x30,%rsp
1365         CFI_ADJUST_CFA_OFFSET -0x30
1366         pushq_cfi $0
1367         SAVE_ALL
1368         jmp error_exit
1369         CFI_ENDPROC
1370 END(xen_failsafe_callback)
1371
1372 #endif /* CONFIG_XEN */
1373
1374 /*
1375  * Some functions should be protected against kprobes
1376  */
1377         .pushsection .kprobes.text, "ax"
1378
1379 paranoidzeroentry_ist debug do_debug DEBUG_STACK
1380 paranoidzeroentry_ist int3 do_int3 DEBUG_STACK
1381 paranoiderrorentry stack_segment do_stack_segment
1382 errorentry general_protection do_general_protection
1383 errorentry page_fault do_page_fault
1384 #ifdef CONFIG_X86_MCE
1385 paranoidzeroentry machine_check do_machine_check
1386 #endif
1387
1388         /*
1389          * "Paranoid" exit path from exception stack.
1390          * Paranoid because this is used by NMIs and cannot take
1391          * any kernel state for granted.
1392          * We don't do kernel preemption checks here, because only
1393          * NMI should be common and it does not enable IRQs and
1394          * cannot get reschedule ticks.
1395          *
1396          * "trace" is 0 for the NMI handler only, because irq-tracing
1397          * is fundamentally NMI-unsafe. (we cannot change the soft and
1398          * hard flags at once, atomically)
1399          */
1400
1401         /* ebx: no swapgs flag */
1402 ENTRY(paranoid_exit)
1403         INTR_FRAME
1404         DISABLE_INTERRUPTS(CLBR_NONE)
1405         TRACE_IRQS_OFF
1406         testl %ebx,%ebx                         /* swapgs needed? */
1407         jnz paranoid_restore
1408         testl $3,CS(%rsp)
1409         jnz   paranoid_userspace
1410 paranoid_swapgs:
1411         TRACE_IRQS_IRETQ 0
1412         SWAPGS_UNSAFE_STACK
1413 paranoid_restore:
1414         RESTORE_ALL 8
1415         jmp irq_return
1416 paranoid_userspace:
1417         GET_THREAD_INFO(%rcx)
1418         movl TI_flags(%rcx),%ebx
1419         andl $_TIF_WORK_MASK,%ebx
1420         jz paranoid_swapgs
1421         movq %rsp,%rdi                  /* &pt_regs */
1422         call sync_regs
1423         movq %rax,%rsp                  /* switch stack for scheduling */
1424         testl $_TIF_NEED_RESCHED,%ebx
1425         jnz paranoid_schedule
1426         movl %ebx,%edx                  /* arg3: thread flags */
1427         TRACE_IRQS_ON
1428         ENABLE_INTERRUPTS(CLBR_NONE)
1429         xorl %esi,%esi                  /* arg2: oldset */
1430         movq %rsp,%rdi                  /* arg1: &pt_regs */
1431         call do_notify_resume
1432         DISABLE_INTERRUPTS(CLBR_NONE)
1433         TRACE_IRQS_OFF
1434         jmp paranoid_userspace
1435 paranoid_schedule:
1436         TRACE_IRQS_ON
1437         ENABLE_INTERRUPTS(CLBR_ANY)
1438         call schedule
1439         DISABLE_INTERRUPTS(CLBR_ANY)
1440         TRACE_IRQS_OFF
1441         jmp paranoid_userspace
1442         CFI_ENDPROC
1443 END(paranoid_exit)
1444
1445 /*
1446  * Exception entry point. This expects an error code/orig_rax on the stack.
1447  * returns in "no swapgs flag" in %ebx.
1448  */
1449 ENTRY(error_entry)
1450         XCPT_FRAME
1451         CFI_ADJUST_CFA_OFFSET 15*8
1452         /* oldrax contains error code */
1453         cld
1454         movq_cfi rdi, RDI+8
1455         movq_cfi rsi, RSI+8
1456         movq_cfi rdx, RDX+8
1457         movq_cfi rcx, RCX+8
1458         movq_cfi rax, RAX+8
1459         movq_cfi  r8,  R8+8
1460         movq_cfi  r9,  R9+8
1461         movq_cfi r10, R10+8
1462         movq_cfi r11, R11+8
1463         movq_cfi rbx, RBX+8
1464         movq_cfi rbp, RBP+8
1465         movq_cfi r12, R12+8
1466         movq_cfi r13, R13+8
1467         movq_cfi r14, R14+8
1468         movq_cfi r15, R15+8
1469         xorl %ebx,%ebx
1470         testl $3,CS+8(%rsp)
1471         je error_kernelspace
1472 error_swapgs:
1473         SWAPGS
1474 error_sti:
1475         TRACE_IRQS_OFF
1476         ret
1477         CFI_ENDPROC
1478
1479 /*
1480  * There are two places in the kernel that can potentially fault with
1481  * usergs. Handle them here. The exception handlers after iret run with
1482  * kernel gs again, so don't set the user space flag. B stepping K8s
1483  * sometimes report an truncated RIP for IRET exceptions returning to
1484  * compat mode. Check for these here too.
1485  */
1486 error_kernelspace:
1487         incl %ebx
1488         leaq irq_return(%rip),%rcx
1489         cmpq %rcx,RIP+8(%rsp)
1490         je error_swapgs
1491         movl %ecx,%ecx  /* zero extend */
1492         cmpq %rcx,RIP+8(%rsp)
1493         je error_swapgs
1494         cmpq $gs_change,RIP+8(%rsp)
1495         je error_swapgs
1496         jmp error_sti
1497 END(error_entry)
1498
1499
1500 /* ebx: no swapgs flag (1: don't need swapgs, 0: need it) */
1501 ENTRY(error_exit)
1502         DEFAULT_FRAME
1503         movl %ebx,%eax
1504         RESTORE_REST
1505         DISABLE_INTERRUPTS(CLBR_NONE)
1506         TRACE_IRQS_OFF
1507         GET_THREAD_INFO(%rcx)
1508         testl %eax,%eax
1509         jne retint_kernel
1510         LOCKDEP_SYS_EXIT_IRQ
1511         movl TI_flags(%rcx),%edx
1512         movl $_TIF_WORK_MASK,%edi
1513         andl %edi,%edx
1514         jnz retint_careful
1515         jmp retint_swapgs
1516         CFI_ENDPROC
1517 END(error_exit)
1518
1519
1520         /* runs on exception stack */
1521 ENTRY(nmi)
1522         INTR_FRAME
1523         PARAVIRT_ADJUST_EXCEPTION_FRAME
1524         pushq_cfi $-1
1525         subq $15*8, %rsp
1526         CFI_ADJUST_CFA_OFFSET 15*8
1527         call save_paranoid
1528         DEFAULT_FRAME 0
1529         /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
1530         movq %rsp,%rdi
1531         movq $-1,%rsi
1532         call do_nmi
1533 #ifdef CONFIG_TRACE_IRQFLAGS
1534         /* paranoidexit; without TRACE_IRQS_OFF */
1535         /* ebx: no swapgs flag */
1536         DISABLE_INTERRUPTS(CLBR_NONE)
1537         testl %ebx,%ebx                         /* swapgs needed? */
1538         jnz nmi_restore
1539         testl $3,CS(%rsp)
1540         jnz nmi_userspace
1541 nmi_swapgs:
1542         SWAPGS_UNSAFE_STACK
1543 nmi_restore:
1544         RESTORE_ALL 8
1545         jmp irq_return
1546 nmi_userspace:
1547         GET_THREAD_INFO(%rcx)
1548         movl TI_flags(%rcx),%ebx
1549         andl $_TIF_WORK_MASK,%ebx
1550         jz nmi_swapgs
1551         movq %rsp,%rdi                  /* &pt_regs */
1552         call sync_regs
1553         movq %rax,%rsp                  /* switch stack for scheduling */
1554         testl $_TIF_NEED_RESCHED,%ebx
1555         jnz nmi_schedule
1556         movl %ebx,%edx                  /* arg3: thread flags */
1557         ENABLE_INTERRUPTS(CLBR_NONE)
1558         xorl %esi,%esi                  /* arg2: oldset */
1559         movq %rsp,%rdi                  /* arg1: &pt_regs */
1560         call do_notify_resume
1561         DISABLE_INTERRUPTS(CLBR_NONE)
1562         jmp nmi_userspace
1563 nmi_schedule:
1564         ENABLE_INTERRUPTS(CLBR_ANY)
1565         call schedule
1566         DISABLE_INTERRUPTS(CLBR_ANY)
1567         jmp nmi_userspace
1568         CFI_ENDPROC
1569 #else
1570         jmp paranoid_exit
1571         CFI_ENDPROC
1572 #endif
1573 END(nmi)
1574
1575 ENTRY(ignore_sysret)
1576         CFI_STARTPROC
1577         mov $-ENOSYS,%eax
1578         sysret
1579         CFI_ENDPROC
1580 END(ignore_sysret)
1581
1582 /*
1583  * End of kprobes section
1584  */
1585         .popsection