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 * entry.S contains the system-call and fault low-level handling routines. 9 * 10 * Some of this is documented in Documentation/x86/entry_64.txt 11 * 12 * A note on terminology: 13 * - iret frame: Architecture defined interrupt frame from SS to RIP 14 * at the top of the kernel process stack. 15 * 16 * Some macro usage: 17 * - ENTRY/END: Define functions in the symbol table. 18 * - TRACE_IRQ_*: Trace hardirq state for lock debugging. 19 * - idtentry: Define exception entry points. 20 */ 21#include <linux/linkage.h> 22#include <asm/segment.h> 23#include <asm/cache.h> 24#include <asm/errno.h> 25#include "calling.h" 26#include <asm/asm-offsets.h> 27#include <asm/msr.h> 28#include <asm/unistd.h> 29#include <asm/thread_info.h> 30#include <asm/hw_irq.h> 31#include <asm/page_types.h> 32#include <asm/irqflags.h> 33#include <asm/paravirt.h> 34#include <asm/percpu.h> 35#include <asm/asm.h> 36#include <asm/smap.h> 37#include <asm/pgtable_types.h> 38#include <asm/export.h> 39#include <linux/err.h> 40 41/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */ 42#include <linux/elf-em.h> 43#define AUDIT_ARCH_X86_64 (EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE) 44#define __AUDIT_ARCH_64BIT 0x80000000 45#define __AUDIT_ARCH_LE 0x40000000 46 47.code64 48.section .entry.text, "ax" 49 50#ifdef CONFIG_PARAVIRT 51ENTRY(native_usergs_sysret64) 52 swapgs 53 sysretq 54ENDPROC(native_usergs_sysret64) 55#endif /* CONFIG_PARAVIRT */ 56 57.macro TRACE_IRQS_IRETQ 58#ifdef CONFIG_TRACE_IRQFLAGS 59 bt $9, EFLAGS(%rsp) /* interrupts off? */ 60 jnc 1f 61 TRACE_IRQS_ON 621: 63#endif 64.endm 65 66/* 67 * When dynamic function tracer is enabled it will add a breakpoint 68 * to all locations that it is about to modify, sync CPUs, update 69 * all the code, sync CPUs, then remove the breakpoints. In this time 70 * if lockdep is enabled, it might jump back into the debug handler 71 * outside the updating of the IST protection. (TRACE_IRQS_ON/OFF). 72 * 73 * We need to change the IDT table before calling TRACE_IRQS_ON/OFF to 74 * make sure the stack pointer does not get reset back to the top 75 * of the debug stack, and instead just reuses the current stack. 76 */ 77#if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_TRACE_IRQFLAGS) 78 79.macro TRACE_IRQS_OFF_DEBUG 80 call debug_stack_set_zero 81 TRACE_IRQS_OFF 82 call debug_stack_reset 83.endm 84 85.macro TRACE_IRQS_ON_DEBUG 86 call debug_stack_set_zero 87 TRACE_IRQS_ON 88 call debug_stack_reset 89.endm 90 91.macro TRACE_IRQS_IRETQ_DEBUG 92 bt $9, EFLAGS(%rsp) /* interrupts off? */ 93 jnc 1f 94 TRACE_IRQS_ON_DEBUG 951: 96.endm 97 98#else 99# define TRACE_IRQS_OFF_DEBUG TRACE_IRQS_OFF 100# define TRACE_IRQS_ON_DEBUG TRACE_IRQS_ON 101# define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ 102#endif 103 104/* 105 * 64-bit SYSCALL instruction entry. Up to 6 arguments in registers. 106 * 107 * This is the only entry point used for 64-bit system calls. The 108 * hardware interface is reasonably well designed and the register to 109 * argument mapping Linux uses fits well with the registers that are 110 * available when SYSCALL is used. 111 * 112 * SYSCALL instructions can be found inlined in libc implementations as 113 * well as some other programs and libraries. There are also a handful 114 * of SYSCALL instructions in the vDSO used, for example, as a 115 * clock_gettimeofday fallback. 116 * 117 * 64-bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11, 118 * then loads new ss, cs, and rip from previously programmed MSRs. 119 * rflags gets masked by a value from another MSR (so CLD and CLAC 120 * are not needed). SYSCALL does not save anything on the stack 121 * and does not change rsp. 122 * 123 * Registers on entry: 124 * rax system call number 125 * rcx return address 126 * r11 saved rflags (note: r11 is callee-clobbered register in C ABI) 127 * rdi arg0 128 * rsi arg1 129 * rdx arg2 130 * r10 arg3 (needs to be moved to rcx to conform to C ABI) 131 * r8 arg4 132 * r9 arg5 133 * (note: r12-r15, rbp, rbx are callee-preserved in C ABI) 134 * 135 * Only called from user space. 136 * 137 * When user can change pt_regs->foo always force IRET. That is because 138 * it deals with uncanonical addresses better. SYSRET has trouble 139 * with them due to bugs in both AMD and Intel CPUs. 140 */ 141 142ENTRY(entry_SYSCALL_64) 143 /* 144 * Interrupts are off on entry. 145 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON, 146 * it is too small to ever cause noticeable irq latency. 147 */ 148 SWAPGS_UNSAFE_STACK 149 /* 150 * A hypervisor implementation might want to use a label 151 * after the swapgs, so that it can do the swapgs 152 * for the guest and jump here on syscall. 153 */ 154GLOBAL(entry_SYSCALL_64_after_swapgs) 155 156 movq %rsp, PER_CPU_VAR(rsp_scratch) 157 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp 158 159 TRACE_IRQS_OFF 160 161 /* Construct struct pt_regs on stack */ 162 pushq $__USER_DS /* pt_regs->ss */ 163 pushq PER_CPU_VAR(rsp_scratch) /* pt_regs->sp */ 164 pushq %r11 /* pt_regs->flags */ 165 pushq $__USER_CS /* pt_regs->cs */ 166 pushq %rcx /* pt_regs->ip */ 167 pushq %rax /* pt_regs->orig_ax */ 168 pushq %rdi /* pt_regs->di */ 169 pushq %rsi /* pt_regs->si */ 170 pushq %rdx /* pt_regs->dx */ 171 pushq %rcx /* pt_regs->cx */ 172 pushq $-ENOSYS /* pt_regs->ax */ 173 pushq %r8 /* pt_regs->r8 */ 174 pushq %r9 /* pt_regs->r9 */ 175 pushq %r10 /* pt_regs->r10 */ 176 pushq %r11 /* pt_regs->r11 */ 177 sub $(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */ 178 179 /* 180 * If we need to do entry work or if we guess we'll need to do 181 * exit work, go straight to the slow path. 182 */ 183 movq PER_CPU_VAR(current_task), %r11 184 testl $_TIF_WORK_SYSCALL_ENTRY|_TIF_ALLWORK_MASK, TASK_TI_flags(%r11) 185 jnz entry_SYSCALL64_slow_path 186 187entry_SYSCALL_64_fastpath: 188 /* 189 * Easy case: enable interrupts and issue the syscall. If the syscall 190 * needs pt_regs, we'll call a stub that disables interrupts again 191 * and jumps to the slow path. 192 */ 193 TRACE_IRQS_ON 194 ENABLE_INTERRUPTS(CLBR_NONE) 195#if __SYSCALL_MASK == ~0 196 cmpq $__NR_syscall_max, %rax 197#else 198 andl $__SYSCALL_MASK, %eax 199 cmpl $__NR_syscall_max, %eax 200#endif 201 ja 1f /* return -ENOSYS (already in pt_regs->ax) */ 202 movq %r10, %rcx 203 204 /* 205 * This call instruction is handled specially in stub_ptregs_64. 206 * It might end up jumping to the slow path. If it jumps, RAX 207 * and all argument registers are clobbered. 208 */ 209 call *sys_call_table(, %rax, 8) 210.Lentry_SYSCALL_64_after_fastpath_call: 211 212 movq %rax, RAX(%rsp) 2131: 214 215 /* 216 * If we get here, then we know that pt_regs is clean for SYSRET64. 217 * If we see that no exit work is required (which we are required 218 * to check with IRQs off), then we can go straight to SYSRET64. 219 */ 220 DISABLE_INTERRUPTS(CLBR_NONE) 221 TRACE_IRQS_OFF 222 movq PER_CPU_VAR(current_task), %r11 223 testl $_TIF_ALLWORK_MASK, TASK_TI_flags(%r11) 224 jnz 1f 225 226 LOCKDEP_SYS_EXIT 227 TRACE_IRQS_ON /* user mode is traced as IRQs on */ 228 movq RIP(%rsp), %rcx 229 movq EFLAGS(%rsp), %r11 230 RESTORE_C_REGS_EXCEPT_RCX_R11 231 movq RSP(%rsp), %rsp 232 USERGS_SYSRET64 233 2341: 235 /* 236 * The fast path looked good when we started, but something changed 237 * along the way and we need to switch to the slow path. Calling 238 * raise(3) will trigger this, for example. IRQs are off. 239 */ 240 TRACE_IRQS_ON 241 ENABLE_INTERRUPTS(CLBR_NONE) 242 SAVE_EXTRA_REGS 243 movq %rsp, %rdi 244 call syscall_return_slowpath /* returns with IRQs disabled */ 245 jmp return_from_SYSCALL_64 246 247entry_SYSCALL64_slow_path: 248 /* IRQs are off. */ 249 SAVE_EXTRA_REGS 250 movq %rsp, %rdi 251 call do_syscall_64 /* returns with IRQs disabled */ 252 253return_from_SYSCALL_64: 254 RESTORE_EXTRA_REGS 255 TRACE_IRQS_IRETQ /* we're about to change IF */ 256 257 /* 258 * Try to use SYSRET instead of IRET if we're returning to 259 * a completely clean 64-bit userspace context. 260 */ 261 movq RCX(%rsp), %rcx 262 movq RIP(%rsp), %r11 263 cmpq %rcx, %r11 /* RCX == RIP */ 264 jne opportunistic_sysret_failed 265 266 /* 267 * On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP 268 * in kernel space. This essentially lets the user take over 269 * the kernel, since userspace controls RSP. 270 * 271 * If width of "canonical tail" ever becomes variable, this will need 272 * to be updated to remain correct on both old and new CPUs. 273 */ 274 .ifne __VIRTUAL_MASK_SHIFT - 47 275 .error "virtual address width changed -- SYSRET checks need update" 276 .endif 277 278 /* Change top 16 bits to be the sign-extension of 47th bit */ 279 shl $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx 280 sar $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx 281 282 /* If this changed %rcx, it was not canonical */ 283 cmpq %rcx, %r11 284 jne opportunistic_sysret_failed 285 286 cmpq $__USER_CS, CS(%rsp) /* CS must match SYSRET */ 287 jne opportunistic_sysret_failed 288 289 movq R11(%rsp), %r11 290 cmpq %r11, EFLAGS(%rsp) /* R11 == RFLAGS */ 291 jne opportunistic_sysret_failed 292 293 /* 294 * SYSCALL clears RF when it saves RFLAGS in R11 and SYSRET cannot 295 * restore RF properly. If the slowpath sets it for whatever reason, we 296 * need to restore it correctly. 297 * 298 * SYSRET can restore TF, but unlike IRET, restoring TF results in a 299 * trap from userspace immediately after SYSRET. This would cause an 300 * infinite loop whenever #DB happens with register state that satisfies 301 * the opportunistic SYSRET conditions. For example, single-stepping 302 * this user code: 303 * 304 * movq $stuck_here, %rcx 305 * pushfq 306 * popq %r11 307 * stuck_here: 308 * 309 * would never get past 'stuck_here'. 310 */ 311 testq $(X86_EFLAGS_RF|X86_EFLAGS_TF), %r11 312 jnz opportunistic_sysret_failed 313 314 /* nothing to check for RSP */ 315 316 cmpq $__USER_DS, SS(%rsp) /* SS must match SYSRET */ 317 jne opportunistic_sysret_failed 318 319 /* 320 * We win! This label is here just for ease of understanding 321 * perf profiles. Nothing jumps here. 322 */ 323syscall_return_via_sysret: 324 /* rcx and r11 are already restored (see code above) */ 325 RESTORE_C_REGS_EXCEPT_RCX_R11 326 movq RSP(%rsp), %rsp 327 USERGS_SYSRET64 328 329opportunistic_sysret_failed: 330 SWAPGS 331 jmp restore_c_regs_and_iret 332END(entry_SYSCALL_64) 333 334ENTRY(stub_ptregs_64) 335 /* 336 * Syscalls marked as needing ptregs land here. 337 * If we are on the fast path, we need to save the extra regs, 338 * which we achieve by trying again on the slow path. If we are on 339 * the slow path, the extra regs are already saved. 340 * 341 * RAX stores a pointer to the C function implementing the syscall. 342 * IRQs are on. 343 */ 344 cmpq $.Lentry_SYSCALL_64_after_fastpath_call, (%rsp) 345 jne 1f 346 347 /* 348 * Called from fast path -- disable IRQs again, pop return address 349 * and jump to slow path 350 */ 351 DISABLE_INTERRUPTS(CLBR_NONE) 352 TRACE_IRQS_OFF 353 popq %rax 354 jmp entry_SYSCALL64_slow_path 355 3561: 357 jmp *%rax /* Called from C */ 358END(stub_ptregs_64) 359 360.macro ptregs_stub func 361ENTRY(ptregs_\func) 362 leaq \func(%rip), %rax 363 jmp stub_ptregs_64 364END(ptregs_\func) 365.endm 366 367/* Instantiate ptregs_stub for each ptregs-using syscall */ 368#define __SYSCALL_64_QUAL_(sym) 369#define __SYSCALL_64_QUAL_ptregs(sym) ptregs_stub sym 370#define __SYSCALL_64(nr, sym, qual) __SYSCALL_64_QUAL_##qual(sym) 371#include <asm/syscalls_64.h> 372 373/* 374 * %rdi: prev task 375 * %rsi: next task 376 */ 377ENTRY(__switch_to_asm) 378 /* 379 * Save callee-saved registers 380 * This must match the order in inactive_task_frame 381 */ 382 pushq %rbp 383 pushq %rbx 384 pushq %r12 385 pushq %r13 386 pushq %r14 387 pushq %r15 388 389 /* switch stack */ 390 movq %rsp, TASK_threadsp(%rdi) 391 movq TASK_threadsp(%rsi), %rsp 392 393#ifdef CONFIG_CC_STACKPROTECTOR 394 movq TASK_stack_canary(%rsi), %rbx 395 movq %rbx, PER_CPU_VAR(irq_stack_union)+stack_canary_offset 396#endif 397 398 /* restore callee-saved registers */ 399 popq %r15 400 popq %r14 401 popq %r13 402 popq %r12 403 popq %rbx 404 popq %rbp 405 406 jmp __switch_to 407END(__switch_to_asm) 408 409/* 410 * A newly forked process directly context switches into this address. 411 * 412 * rax: prev task we switched from 413 * rbx: kernel thread func (NULL for user thread) 414 * r12: kernel thread arg 415 */ 416ENTRY(ret_from_fork) 417 movq %rax, %rdi 418 call schedule_tail /* rdi: 'prev' task parameter */ 419 420 testq %rbx, %rbx /* from kernel_thread? */ 421 jnz 1f /* kernel threads are uncommon */ 422 4232: 424 movq %rsp, %rdi 425 call syscall_return_slowpath /* returns with IRQs disabled */ 426 TRACE_IRQS_ON /* user mode is traced as IRQS on */ 427 SWAPGS 428 jmp restore_regs_and_iret 429 4301: 431 /* kernel thread */ 432 movq %r12, %rdi 433 call *%rbx 434 /* 435 * A kernel thread is allowed to return here after successfully 436 * calling do_execve(). Exit to userspace to complete the execve() 437 * syscall. 438 */ 439 movq $0, RAX(%rsp) 440 jmp 2b 441END(ret_from_fork) 442 443/* 444 * Build the entry stubs with some assembler magic. 445 * We pack 1 stub into every 8-byte block. 446 */ 447 .align 8 448ENTRY(irq_entries_start) 449 vector=FIRST_EXTERNAL_VECTOR 450 .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR) 451 pushq $(~vector+0x80) /* Note: always in signed byte range */ 452 vector=vector+1 453 jmp common_interrupt 454 .align 8 455 .endr 456END(irq_entries_start) 457 458/* 459 * Interrupt entry/exit. 460 * 461 * Interrupt entry points save only callee clobbered registers in fast path. 462 * 463 * Entry runs with interrupts off. 464 */ 465 466/* 0(%rsp): ~(interrupt number) */ 467 .macro interrupt func 468 cld 469 ALLOC_PT_GPREGS_ON_STACK 470 SAVE_C_REGS 471 SAVE_EXTRA_REGS 472 473 testb $3, CS(%rsp) 474 jz 1f 475 476 /* 477 * IRQ from user mode. Switch to kernel gsbase and inform context 478 * tracking that we're in kernel mode. 479 */ 480 SWAPGS 481 482 /* 483 * We need to tell lockdep that IRQs are off. We can't do this until 484 * we fix gsbase, and we should do it before enter_from_user_mode 485 * (which can take locks). Since TRACE_IRQS_OFF idempotent, 486 * the simplest way to handle it is to just call it twice if 487 * we enter from user mode. There's no reason to optimize this since 488 * TRACE_IRQS_OFF is a no-op if lockdep is off. 489 */ 490 TRACE_IRQS_OFF 491 492 CALL_enter_from_user_mode 493 4941: 495 /* 496 * Save previous stack pointer, optionally switch to interrupt stack. 497 * irq_count is used to check if a CPU is already on an interrupt stack 498 * or not. While this is essentially redundant with preempt_count it is 499 * a little cheaper to use a separate counter in the PDA (short of 500 * moving irq_enter into assembly, which would be too much work) 501 */ 502 movq %rsp, %rdi 503 incl PER_CPU_VAR(irq_count) 504 cmovzq PER_CPU_VAR(irq_stack_ptr), %rsp 505 pushq %rdi 506 /* We entered an interrupt context - irqs are off: */ 507 TRACE_IRQS_OFF 508 509 call \func /* rdi points to pt_regs */ 510 .endm 511 512 /* 513 * The interrupt stubs push (~vector+0x80) onto the stack and 514 * then jump to common_interrupt. 515 */ 516 .p2align CONFIG_X86_L1_CACHE_SHIFT 517common_interrupt: 518 ASM_CLAC 519 addq $-0x80, (%rsp) /* Adjust vector to [-256, -1] range */ 520 interrupt do_IRQ 521 /* 0(%rsp): old RSP */ 522ret_from_intr: 523 DISABLE_INTERRUPTS(CLBR_NONE) 524 TRACE_IRQS_OFF 525 decl PER_CPU_VAR(irq_count) 526 527 /* Restore saved previous stack */ 528 popq %rsp 529 530 testb $3, CS(%rsp) 531 jz retint_kernel 532 533 /* Interrupt came from user space */ 534GLOBAL(retint_user) 535 mov %rsp,%rdi 536 call prepare_exit_to_usermode 537 TRACE_IRQS_IRETQ 538 SWAPGS 539 jmp restore_regs_and_iret 540 541/* Returning to kernel space */ 542retint_kernel: 543#ifdef CONFIG_PREEMPT 544 /* Interrupts are off */ 545 /* Check if we need preemption */ 546 bt $9, EFLAGS(%rsp) /* were interrupts off? */ 547 jnc 1f 5480: cmpl $0, PER_CPU_VAR(__preempt_count) 549 jnz 1f 550 call preempt_schedule_irq 551 jmp 0b 5521: 553#endif 554 /* 555 * The iretq could re-enable interrupts: 556 */ 557 TRACE_IRQS_IRETQ 558 559/* 560 * At this label, code paths which return to kernel and to user, 561 * which come from interrupts/exception and from syscalls, merge. 562 */ 563GLOBAL(restore_regs_and_iret) 564 RESTORE_EXTRA_REGS 565restore_c_regs_and_iret: 566 RESTORE_C_REGS 567 REMOVE_PT_GPREGS_FROM_STACK 8 568 INTERRUPT_RETURN 569 570ENTRY(native_iret) 571 /* 572 * Are we returning to a stack segment from the LDT? Note: in 573 * 64-bit mode SS:RSP on the exception stack is always valid. 574 */ 575#ifdef CONFIG_X86_ESPFIX64 576 testb $4, (SS-RIP)(%rsp) 577 jnz native_irq_return_ldt 578#endif 579 580.global native_irq_return_iret 581native_irq_return_iret: 582 /* 583 * This may fault. Non-paranoid faults on return to userspace are 584 * handled by fixup_bad_iret. These include #SS, #GP, and #NP. 585 * Double-faults due to espfix64 are handled in do_double_fault. 586 * Other faults here are fatal. 587 */ 588 iretq 589 590#ifdef CONFIG_X86_ESPFIX64 591native_irq_return_ldt: 592 /* 593 * We are running with user GSBASE. All GPRs contain their user 594 * values. We have a percpu ESPFIX stack that is eight slots 595 * long (see ESPFIX_STACK_SIZE). espfix_waddr points to the bottom 596 * of the ESPFIX stack. 597 * 598 * We clobber RAX and RDI in this code. We stash RDI on the 599 * normal stack and RAX on the ESPFIX stack. 600 * 601 * The ESPFIX stack layout we set up looks like this: 602 * 603 * --- top of ESPFIX stack --- 604 * SS 605 * RSP 606 * RFLAGS 607 * CS 608 * RIP <-- RSP points here when we're done 609 * RAX <-- espfix_waddr points here 610 * --- bottom of ESPFIX stack --- 611 */ 612 613 pushq %rdi /* Stash user RDI */ 614 SWAPGS 615 movq PER_CPU_VAR(espfix_waddr), %rdi 616 movq %rax, (0*8)(%rdi) /* user RAX */ 617 movq (1*8)(%rsp), %rax /* user RIP */ 618 movq %rax, (1*8)(%rdi) 619 movq (2*8)(%rsp), %rax /* user CS */ 620 movq %rax, (2*8)(%rdi) 621 movq (3*8)(%rsp), %rax /* user RFLAGS */ 622 movq %rax, (3*8)(%rdi) 623 movq (5*8)(%rsp), %rax /* user SS */ 624 movq %rax, (5*8)(%rdi) 625 movq (4*8)(%rsp), %rax /* user RSP */ 626 movq %rax, (4*8)(%rdi) 627 /* Now RAX == RSP. */ 628 629 andl $0xffff0000, %eax /* RAX = (RSP & 0xffff0000) */ 630 popq %rdi /* Restore user RDI */ 631 632 /* 633 * espfix_stack[31:16] == 0. The page tables are set up such that 634 * (espfix_stack | (X & 0xffff0000)) points to a read-only alias of 635 * espfix_waddr for any X. That is, there are 65536 RO aliases of 636 * the same page. Set up RSP so that RSP[31:16] contains the 637 * respective 16 bits of the /userspace/ RSP and RSP nonetheless 638 * still points to an RO alias of the ESPFIX stack. 639 */ 640 orq PER_CPU_VAR(espfix_stack), %rax 641 SWAPGS 642 movq %rax, %rsp 643 644 /* 645 * At this point, we cannot write to the stack any more, but we can 646 * still read. 647 */ 648 popq %rax /* Restore user RAX */ 649 650 /* 651 * RSP now points to an ordinary IRET frame, except that the page 652 * is read-only and RSP[31:16] are preloaded with the userspace 653 * values. We can now IRET back to userspace. 654 */ 655 jmp native_irq_return_iret 656#endif 657END(common_interrupt) 658 659/* 660 * APIC interrupts. 661 */ 662.macro apicinterrupt3 num sym do_sym 663ENTRY(\sym) 664 ASM_CLAC 665 pushq $~(\num) 666.Lcommon_\sym: 667 interrupt \do_sym 668 jmp ret_from_intr 669END(\sym) 670.endm 671 672#ifdef CONFIG_TRACING 673#define trace(sym) trace_##sym 674#define smp_trace(sym) smp_trace_##sym 675 676.macro trace_apicinterrupt num sym 677apicinterrupt3 \num trace(\sym) smp_trace(\sym) 678.endm 679#else 680.macro trace_apicinterrupt num sym do_sym 681.endm 682#endif 683 684/* Make sure APIC interrupt handlers end up in the irqentry section: */ 685#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) 686# define PUSH_SECTION_IRQENTRY .pushsection .irqentry.text, "ax" 687# define POP_SECTION_IRQENTRY .popsection 688#else 689# define PUSH_SECTION_IRQENTRY 690# define POP_SECTION_IRQENTRY 691#endif 692 693.macro apicinterrupt num sym do_sym 694PUSH_SECTION_IRQENTRY 695apicinterrupt3 \num \sym \do_sym 696trace_apicinterrupt \num \sym 697POP_SECTION_IRQENTRY 698.endm 699 700#ifdef CONFIG_SMP 701apicinterrupt3 IRQ_MOVE_CLEANUP_VECTOR irq_move_cleanup_interrupt smp_irq_move_cleanup_interrupt 702apicinterrupt3 REBOOT_VECTOR reboot_interrupt smp_reboot_interrupt 703#endif 704 705#ifdef CONFIG_X86_UV 706apicinterrupt3 UV_BAU_MESSAGE uv_bau_message_intr1 uv_bau_message_interrupt 707#endif 708 709apicinterrupt LOCAL_TIMER_VECTOR apic_timer_interrupt smp_apic_timer_interrupt 710apicinterrupt X86_PLATFORM_IPI_VECTOR x86_platform_ipi smp_x86_platform_ipi 711 712#ifdef CONFIG_HAVE_KVM 713apicinterrupt3 POSTED_INTR_VECTOR kvm_posted_intr_ipi smp_kvm_posted_intr_ipi 714apicinterrupt3 POSTED_INTR_WAKEUP_VECTOR kvm_posted_intr_wakeup_ipi smp_kvm_posted_intr_wakeup_ipi 715#endif 716 717#ifdef CONFIG_X86_MCE_THRESHOLD 718apicinterrupt THRESHOLD_APIC_VECTOR threshold_interrupt smp_threshold_interrupt 719#endif 720 721#ifdef CONFIG_X86_MCE_AMD 722apicinterrupt DEFERRED_ERROR_VECTOR deferred_error_interrupt smp_deferred_error_interrupt 723#endif 724 725#ifdef CONFIG_X86_THERMAL_VECTOR 726apicinterrupt THERMAL_APIC_VECTOR thermal_interrupt smp_thermal_interrupt 727#endif 728 729#ifdef CONFIG_SMP 730apicinterrupt CALL_FUNCTION_SINGLE_VECTOR call_function_single_interrupt smp_call_function_single_interrupt 731apicinterrupt CALL_FUNCTION_VECTOR call_function_interrupt smp_call_function_interrupt 732apicinterrupt RESCHEDULE_VECTOR reschedule_interrupt smp_reschedule_interrupt 733#endif 734 735apicinterrupt ERROR_APIC_VECTOR error_interrupt smp_error_interrupt 736apicinterrupt SPURIOUS_APIC_VECTOR spurious_interrupt smp_spurious_interrupt 737 738#ifdef CONFIG_IRQ_WORK 739apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt 740#endif 741 742/* 743 * Exception entry points. 744 */ 745#define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss) + (TSS_ist + ((x) - 1) * 8) 746 747.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 748ENTRY(\sym) 749 /* Sanity check */ 750 .if \shift_ist != -1 && \paranoid == 0 751 .error "using shift_ist requires paranoid=1" 752 .endif 753 754 ASM_CLAC 755 PARAVIRT_ADJUST_EXCEPTION_FRAME 756 757 .ifeq \has_error_code 758 pushq $-1 /* ORIG_RAX: no syscall to restart */ 759 .endif 760 761 ALLOC_PT_GPREGS_ON_STACK 762 763 .if \paranoid 764 .if \paranoid == 1 765 testb $3, CS(%rsp) /* If coming from userspace, switch stacks */ 766 jnz 1f 767 .endif 768 call paranoid_entry 769 .else 770 call error_entry 771 .endif 772 /* returned flag: ebx=0: need swapgs on exit, ebx=1: don't need it */ 773 774 .if \paranoid 775 .if \shift_ist != -1 776 TRACE_IRQS_OFF_DEBUG /* reload IDT in case of recursion */ 777 .else 778 TRACE_IRQS_OFF 779 .endif 780 .endif 781 782 movq %rsp, %rdi /* pt_regs pointer */ 783 784 .if \has_error_code 785 movq ORIG_RAX(%rsp), %rsi /* get error code */ 786 movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */ 787 .else 788 xorl %esi, %esi /* no error code */ 789 .endif 790 791 .if \shift_ist != -1 792 subq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist) 793 .endif 794 795 call \do_sym 796 797 .if \shift_ist != -1 798 addq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist) 799 .endif 800 801 /* these procedures expect "no swapgs" flag in ebx */ 802 .if \paranoid 803 jmp paranoid_exit 804 .else 805 jmp error_exit 806 .endif 807 808 .if \paranoid == 1 809 /* 810 * Paranoid entry from userspace. Switch stacks and treat it 811 * as a normal entry. This means that paranoid handlers 812 * run in real process context if user_mode(regs). 813 */ 8141: 815 call error_entry 816 817 818 movq %rsp, %rdi /* pt_regs pointer */ 819 call sync_regs 820 movq %rax, %rsp /* switch stack */ 821 822 movq %rsp, %rdi /* pt_regs pointer */ 823 824 .if \has_error_code 825 movq ORIG_RAX(%rsp), %rsi /* get error code */ 826 movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */ 827 .else 828 xorl %esi, %esi /* no error code */ 829 .endif 830 831 call \do_sym 832 833 jmp error_exit /* %ebx: no swapgs flag */ 834 .endif 835END(\sym) 836.endm 837 838#ifdef CONFIG_TRACING 839.macro trace_idtentry sym do_sym has_error_code:req 840idtentry trace(\sym) trace(\do_sym) has_error_code=\has_error_code 841idtentry \sym \do_sym has_error_code=\has_error_code 842.endm 843#else 844.macro trace_idtentry sym do_sym has_error_code:req 845idtentry \sym \do_sym has_error_code=\has_error_code 846.endm 847#endif 848 849idtentry divide_error do_divide_error has_error_code=0 850idtentry overflow do_overflow has_error_code=0 851idtentry bounds do_bounds has_error_code=0 852idtentry invalid_op do_invalid_op has_error_code=0 853idtentry device_not_available do_device_not_available has_error_code=0 854idtentry double_fault do_double_fault has_error_code=1 paranoid=2 855idtentry coprocessor_segment_overrun do_coprocessor_segment_overrun has_error_code=0 856idtentry invalid_TSS do_invalid_TSS has_error_code=1 857idtentry segment_not_present do_segment_not_present has_error_code=1 858idtentry spurious_interrupt_bug do_spurious_interrupt_bug has_error_code=0 859idtentry coprocessor_error do_coprocessor_error has_error_code=0 860idtentry alignment_check do_alignment_check has_error_code=1 861idtentry simd_coprocessor_error do_simd_coprocessor_error has_error_code=0 862 863 864 /* 865 * Reload gs selector with exception handling 866 * edi: new selector 867 */ 868ENTRY(native_load_gs_index) 869 pushfq 870 DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI) 871 SWAPGS 872.Lgs_change: 873 movl %edi, %gs 8742: ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE 875 SWAPGS 876 popfq 877 ret 878END(native_load_gs_index) 879EXPORT_SYMBOL(native_load_gs_index) 880 881 _ASM_EXTABLE(.Lgs_change, bad_gs) 882 .section .fixup, "ax" 883 /* running with kernelgs */ 884bad_gs: 885 SWAPGS /* switch back to user gs */ 886.macro ZAP_GS 887 /* This can't be a string because the preprocessor needs to see it. */ 888 movl $__USER_DS, %eax 889 movl %eax, %gs 890.endm 891 ALTERNATIVE "", "ZAP_GS", X86_BUG_NULL_SEG 892 xorl %eax, %eax 893 movl %eax, %gs 894 jmp 2b 895 .previous 896 897/* Call softirq on interrupt stack. Interrupts are off. */ 898ENTRY(do_softirq_own_stack) 899 pushq %rbp 900 mov %rsp, %rbp 901 incl PER_CPU_VAR(irq_count) 902 cmove PER_CPU_VAR(irq_stack_ptr), %rsp 903 push %rbp /* frame pointer backlink */ 904 call __do_softirq 905 leaveq 906 decl PER_CPU_VAR(irq_count) 907 ret 908END(do_softirq_own_stack) 909 910#ifdef CONFIG_XEN 911idtentry xen_hypervisor_callback xen_do_hypervisor_callback has_error_code=0 912 913/* 914 * A note on the "critical region" in our callback handler. 915 * We want to avoid stacking callback handlers due to events occurring 916 * during handling of the last event. To do this, we keep events disabled 917 * until we've done all processing. HOWEVER, we must enable events before 918 * popping the stack frame (can't be done atomically) and so it would still 919 * be possible to get enough handler activations to overflow the stack. 920 * Although unlikely, bugs of that kind are hard to track down, so we'd 921 * like to avoid the possibility. 922 * So, on entry to the handler we detect whether we interrupted an 923 * existing activation in its critical region -- if so, we pop the current 924 * activation and restart the handler using the previous one. 925 */ 926ENTRY(xen_do_hypervisor_callback) /* do_hypervisor_callback(struct *pt_regs) */ 927 928/* 929 * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will 930 * see the correct pointer to the pt_regs 931 */ 932 movq %rdi, %rsp /* we don't return, adjust the stack frame */ 93311: incl PER_CPU_VAR(irq_count) 934 movq %rsp, %rbp 935 cmovzq PER_CPU_VAR(irq_stack_ptr), %rsp 936 pushq %rbp /* frame pointer backlink */ 937 call xen_evtchn_do_upcall 938 popq %rsp 939 decl PER_CPU_VAR(irq_count) 940#ifndef CONFIG_PREEMPT 941 call xen_maybe_preempt_hcall 942#endif 943 jmp error_exit 944END(xen_do_hypervisor_callback) 945 946/* 947 * Hypervisor uses this for application faults while it executes. 948 * We get here for two reasons: 949 * 1. Fault while reloading DS, ES, FS or GS 950 * 2. Fault while executing IRET 951 * Category 1 we do not need to fix up as Xen has already reloaded all segment 952 * registers that could be reloaded and zeroed the others. 953 * Category 2 we fix up by killing the current process. We cannot use the 954 * normal Linux return path in this case because if we use the IRET hypercall 955 * to pop the stack frame we end up in an infinite loop of failsafe callbacks. 956 * We distinguish between categories by comparing each saved segment register 957 * with its current contents: any discrepancy means we in category 1. 958 */ 959ENTRY(xen_failsafe_callback) 960 movl %ds, %ecx 961 cmpw %cx, 0x10(%rsp) 962 jne 1f 963 movl %es, %ecx 964 cmpw %cx, 0x18(%rsp) 965 jne 1f 966 movl %fs, %ecx 967 cmpw %cx, 0x20(%rsp) 968 jne 1f 969 movl %gs, %ecx 970 cmpw %cx, 0x28(%rsp) 971 jne 1f 972 /* All segments match their saved values => Category 2 (Bad IRET). */ 973 movq (%rsp), %rcx 974 movq 8(%rsp), %r11 975 addq $0x30, %rsp 976 pushq $0 /* RIP */ 977 pushq %r11 978 pushq %rcx 979 jmp general_protection 9801: /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */ 981 movq (%rsp), %rcx 982 movq 8(%rsp), %r11 983 addq $0x30, %rsp 984 pushq $-1 /* orig_ax = -1 => not a system call */ 985 ALLOC_PT_GPREGS_ON_STACK 986 SAVE_C_REGS 987 SAVE_EXTRA_REGS 988 jmp error_exit 989END(xen_failsafe_callback) 990 991apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ 992 xen_hvm_callback_vector xen_evtchn_do_upcall 993 994#endif /* CONFIG_XEN */ 995 996#if IS_ENABLED(CONFIG_HYPERV) 997apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ 998 hyperv_callback_vector hyperv_vector_handler 999#endif /* CONFIG_HYPERV */ 1000 1001idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK 1002idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK 1003idtentry stack_segment do_stack_segment has_error_code=1 1004 1005#ifdef CONFIG_XEN 1006idtentry xen_debug do_debug has_error_code=0 1007idtentry xen_int3 do_int3 has_error_code=0 1008idtentry xen_stack_segment do_stack_segment has_error_code=1 1009#endif 1010 1011idtentry general_protection do_general_protection has_error_code=1 1012trace_idtentry page_fault do_page_fault has_error_code=1 1013 1014#ifdef CONFIG_KVM_GUEST 1015idtentry async_page_fault do_async_page_fault has_error_code=1 1016#endif 1017 1018#ifdef CONFIG_X86_MCE 1019idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip) 1020#endif 1021 1022/* 1023 * Save all registers in pt_regs, and switch gs if needed. 1024 * Use slow, but surefire "are we in kernel?" check. 1025 * Return: ebx=0: need swapgs on exit, ebx=1: otherwise 1026 */ 1027ENTRY(paranoid_entry) 1028 cld 1029 SAVE_C_REGS 8 1030 SAVE_EXTRA_REGS 8 1031 movl $1, %ebx 1032 movl $MSR_GS_BASE, %ecx 1033 rdmsr 1034 testl %edx, %edx 1035 js 1f /* negative -> in kernel */ 1036 SWAPGS 1037 xorl %ebx, %ebx 10381: ret 1039END(paranoid_entry) 1040 1041/* 1042 * "Paranoid" exit path from exception stack. This is invoked 1043 * only on return from non-NMI IST interrupts that came 1044 * from kernel space. 1045 * 1046 * We may be returning to very strange contexts (e.g. very early 1047 * in syscall entry), so checking for preemption here would 1048 * be complicated. Fortunately, we there's no good reason 1049 * to try to handle preemption here. 1050 * 1051 * On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) 1052 */ 1053ENTRY(paranoid_exit) 1054 DISABLE_INTERRUPTS(CLBR_NONE) 1055 TRACE_IRQS_OFF_DEBUG 1056 testl %ebx, %ebx /* swapgs needed? */ 1057 jnz paranoid_exit_no_swapgs 1058 TRACE_IRQS_IRETQ 1059 SWAPGS_UNSAFE_STACK 1060 jmp paranoid_exit_restore 1061paranoid_exit_no_swapgs: 1062 TRACE_IRQS_IRETQ_DEBUG 1063paranoid_exit_restore: 1064 RESTORE_EXTRA_REGS 1065 RESTORE_C_REGS 1066 REMOVE_PT_GPREGS_FROM_STACK 8 1067 INTERRUPT_RETURN 1068END(paranoid_exit) 1069 1070/* 1071 * Save all registers in pt_regs, and switch gs if needed. 1072 * Return: EBX=0: came from user mode; EBX=1: otherwise 1073 */ 1074ENTRY(error_entry) 1075 cld 1076 SAVE_C_REGS 8 1077 SAVE_EXTRA_REGS 8 1078 xorl %ebx, %ebx 1079 testb $3, CS+8(%rsp) 1080 jz .Lerror_kernelspace 1081 1082 /* 1083 * We entered from user mode or we're pretending to have entered 1084 * from user mode due to an IRET fault. 1085 */ 1086 SWAPGS 1087 1088.Lerror_entry_from_usermode_after_swapgs: 1089 /* 1090 * We need to tell lockdep that IRQs are off. We can't do this until 1091 * we fix gsbase, and we should do it before enter_from_user_mode 1092 * (which can take locks). 1093 */ 1094 TRACE_IRQS_OFF 1095 CALL_enter_from_user_mode 1096 ret 1097 1098.Lerror_entry_done: 1099 TRACE_IRQS_OFF 1100 ret 1101 1102 /* 1103 * There are two places in the kernel that can potentially fault with 1104 * usergs. Handle them here. B stepping K8s sometimes report a 1105 * truncated RIP for IRET exceptions returning to compat mode. Check 1106 * for these here too. 1107 */ 1108.Lerror_kernelspace: 1109 incl %ebx 1110 leaq native_irq_return_iret(%rip), %rcx 1111 cmpq %rcx, RIP+8(%rsp) 1112 je .Lerror_bad_iret 1113 movl %ecx, %eax /* zero extend */ 1114 cmpq %rax, RIP+8(%rsp) 1115 je .Lbstep_iret 1116 cmpq $.Lgs_change, RIP+8(%rsp) 1117 jne .Lerror_entry_done 1118 1119 /* 1120 * hack: .Lgs_change can fail with user gsbase. If this happens, fix up 1121 * gsbase and proceed. We'll fix up the exception and land in 1122 * .Lgs_change's error handler with kernel gsbase. 1123 */ 1124 SWAPGS 1125 jmp .Lerror_entry_done 1126 1127.Lbstep_iret: 1128 /* Fix truncated RIP */ 1129 movq %rcx, RIP+8(%rsp) 1130 /* fall through */ 1131 1132.Lerror_bad_iret: 1133 /* 1134 * We came from an IRET to user mode, so we have user gsbase. 1135 * Switch to kernel gsbase: 1136 */ 1137 SWAPGS 1138 1139 /* 1140 * Pretend that the exception came from user mode: set up pt_regs 1141 * as if we faulted immediately after IRET and clear EBX so that 1142 * error_exit knows that we will be returning to user mode. 1143 */ 1144 mov %rsp, %rdi 1145 call fixup_bad_iret 1146 mov %rax, %rsp 1147 decl %ebx 1148 jmp .Lerror_entry_from_usermode_after_swapgs 1149END(error_entry) 1150 1151 1152/* 1153 * On entry, EBX is a "return to kernel mode" flag: 1154 * 1: already in kernel mode, don't need SWAPGS 1155 * 0: user gsbase is loaded, we need SWAPGS and standard preparation for return to usermode 1156 */ 1157ENTRY(error_exit) 1158 movl %ebx, %eax 1159 DISABLE_INTERRUPTS(CLBR_NONE) 1160 TRACE_IRQS_OFF 1161 testl %eax, %eax 1162 jnz retint_kernel 1163 jmp retint_user 1164END(error_exit) 1165 1166/* Runs on exception stack */ 1167ENTRY(nmi) 1168 /* 1169 * Fix up the exception frame if we're on Xen. 1170 * PARAVIRT_ADJUST_EXCEPTION_FRAME is guaranteed to push at most 1171 * one value to the stack on native, so it may clobber the rdx 1172 * scratch slot, but it won't clobber any of the important 1173 * slots past it. 1174 * 1175 * Xen is a different story, because the Xen frame itself overlaps 1176 * the "NMI executing" variable. 1177 */ 1178 PARAVIRT_ADJUST_EXCEPTION_FRAME 1179 1180 /* 1181 * We allow breakpoints in NMIs. If a breakpoint occurs, then 1182 * the iretq it performs will take us out of NMI context. 1183 * This means that we can have nested NMIs where the next 1184 * NMI is using the top of the stack of the previous NMI. We 1185 * can't let it execute because the nested NMI will corrupt the 1186 * stack of the previous NMI. NMI handlers are not re-entrant 1187 * anyway. 1188 * 1189 * To handle this case we do the following: 1190 * Check the a special location on the stack that contains 1191 * a variable that is set when NMIs are executing. 1192 * The interrupted task's stack is also checked to see if it 1193 * is an NMI stack. 1194 * If the variable is not set and the stack is not the NMI 1195 * stack then: 1196 * o Set the special variable on the stack 1197 * o Copy the interrupt frame into an "outermost" location on the 1198 * stack 1199 * o Copy the interrupt frame into an "iret" location on the stack 1200 * o Continue processing the NMI 1201 * If the variable is set or the previous stack is the NMI stack: 1202 * o Modify the "iret" location to jump to the repeat_nmi 1203 * o return back to the first NMI 1204 * 1205 * Now on exit of the first NMI, we first clear the stack variable 1206 * The NMI stack will tell any nested NMIs at that point that it is 1207 * nested. Then we pop the stack normally with iret, and if there was 1208 * a nested NMI that updated the copy interrupt stack frame, a 1209 * jump will be made to the repeat_nmi code that will handle the second 1210 * NMI. 1211 * 1212 * However, espfix prevents us from directly returning to userspace 1213 * with a single IRET instruction. Similarly, IRET to user mode 1214 * can fault. We therefore handle NMIs from user space like 1215 * other IST entries. 1216 */ 1217 1218 /* Use %rdx as our temp variable throughout */ 1219 pushq %rdx 1220 1221 testb $3, CS-RIP+8(%rsp) 1222 jz .Lnmi_from_kernel 1223 1224 /* 1225 * NMI from user mode. We need to run on the thread stack, but we 1226 * can't go through the normal entry paths: NMIs are masked, and 1227 * we don't want to enable interrupts, because then we'll end 1228 * up in an awkward situation in which IRQs are on but NMIs 1229 * are off. 1230 * 1231 * We also must not push anything to the stack before switching 1232 * stacks lest we corrupt the "NMI executing" variable. 1233 */ 1234 1235 SWAPGS_UNSAFE_STACK 1236 cld 1237 movq %rsp, %rdx 1238 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp 1239 pushq 5*8(%rdx) /* pt_regs->ss */ 1240 pushq 4*8(%rdx) /* pt_regs->rsp */ 1241 pushq 3*8(%rdx) /* pt_regs->flags */ 1242 pushq 2*8(%rdx) /* pt_regs->cs */ 1243 pushq 1*8(%rdx) /* pt_regs->rip */ 1244 pushq $-1 /* pt_regs->orig_ax */ 1245 pushq %rdi /* pt_regs->di */ 1246 pushq %rsi /* pt_regs->si */ 1247 pushq (%rdx) /* pt_regs->dx */ 1248 pushq %rcx /* pt_regs->cx */ 1249 pushq %rax /* pt_regs->ax */ 1250 pushq %r8 /* pt_regs->r8 */ 1251 pushq %r9 /* pt_regs->r9 */ 1252 pushq %r10 /* pt_regs->r10 */ 1253 pushq %r11 /* pt_regs->r11 */ 1254 pushq %rbx /* pt_regs->rbx */ 1255 pushq %rbp /* pt_regs->rbp */ 1256 pushq %r12 /* pt_regs->r12 */ 1257 pushq %r13 /* pt_regs->r13 */ 1258 pushq %r14 /* pt_regs->r14 */ 1259 pushq %r15 /* pt_regs->r15 */ 1260 1261 /* 1262 * At this point we no longer need to worry about stack damage 1263 * due to nesting -- we're on the normal thread stack and we're 1264 * done with the NMI stack. 1265 */ 1266 1267 movq %rsp, %rdi 1268 movq $-1, %rsi 1269 call do_nmi 1270 1271 /* 1272 * Return back to user mode. We must *not* do the normal exit 1273 * work, because we don't want to enable interrupts. Fortunately, 1274 * do_nmi doesn't modify pt_regs. 1275 */ 1276 SWAPGS 1277 jmp restore_c_regs_and_iret 1278 1279.Lnmi_from_kernel: 1280 /* 1281 * Here's what our stack frame will look like: 1282 * +---------------------------------------------------------+ 1283 * | original SS | 1284 * | original Return RSP | 1285 * | original RFLAGS | 1286 * | original CS | 1287 * | original RIP | 1288 * +---------------------------------------------------------+ 1289 * | temp storage for rdx | 1290 * +---------------------------------------------------------+ 1291 * | "NMI executing" variable | 1292 * +---------------------------------------------------------+ 1293 * | iret SS } Copied from "outermost" frame | 1294 * | iret Return RSP } on each loop iteration; overwritten | 1295 * | iret RFLAGS } by a nested NMI to force another | 1296 * | iret CS } iteration if needed. | 1297 * | iret RIP } | 1298 * +---------------------------------------------------------+ 1299 * | outermost SS } initialized in first_nmi; | 1300 * | outermost Return RSP } will not be changed before | 1301 * | outermost RFLAGS } NMI processing is done. | 1302 * | outermost CS } Copied to "iret" frame on each | 1303 * | outermost RIP } iteration. | 1304 * +---------------------------------------------------------+ 1305 * | pt_regs | 1306 * +---------------------------------------------------------+ 1307 * 1308 * The "original" frame is used by hardware. Before re-enabling 1309 * NMIs, we need to be done with it, and we need to leave enough 1310 * space for the asm code here. 1311 * 1312 * We return by executing IRET while RSP points to the "iret" frame. 1313 * That will either return for real or it will loop back into NMI 1314 * processing. 1315 * 1316 * The "outermost" frame is copied to the "iret" frame on each 1317 * iteration of the loop, so each iteration starts with the "iret" 1318 * frame pointing to the final return target. 1319 */ 1320 1321 /* 1322 * Determine whether we're a nested NMI. 1323 * 1324 * If we interrupted kernel code between repeat_nmi and 1325 * end_repeat_nmi, then we are a nested NMI. We must not 1326 * modify the "iret" frame because it's being written by 1327 * the outer NMI. That's okay; the outer NMI handler is 1328 * about to about to call do_nmi anyway, so we can just 1329 * resume the outer NMI. 1330 */ 1331 1332 movq $repeat_nmi, %rdx 1333 cmpq 8(%rsp), %rdx 1334 ja 1f 1335 movq $end_repeat_nmi, %rdx 1336 cmpq 8(%rsp), %rdx 1337 ja nested_nmi_out 13381: 1339 1340 /* 1341 * Now check "NMI executing". If it's set, then we're nested. 1342 * This will not detect if we interrupted an outer NMI just 1343 * before IRET. 1344 */ 1345 cmpl $1, -8(%rsp) 1346 je nested_nmi 1347 1348 /* 1349 * Now test if the previous stack was an NMI stack. This covers 1350 * the case where we interrupt an outer NMI after it clears 1351 * "NMI executing" but before IRET. We need to be careful, though: 1352 * there is one case in which RSP could point to the NMI stack 1353 * despite there being no NMI active: naughty userspace controls 1354 * RSP at the very beginning of the SYSCALL targets. We can 1355 * pull a fast one on naughty userspace, though: we program 1356 * SYSCALL to mask DF, so userspace cannot cause DF to be set 1357 * if it controls the kernel's RSP. We set DF before we clear 1358 * "NMI executing". 1359 */ 1360 lea 6*8(%rsp), %rdx 1361 /* Compare the NMI stack (rdx) with the stack we came from (4*8(%rsp)) */ 1362 cmpq %rdx, 4*8(%rsp) 1363 /* If the stack pointer is above the NMI stack, this is a normal NMI */ 1364 ja first_nmi 1365 1366 subq $EXCEPTION_STKSZ, %rdx 1367 cmpq %rdx, 4*8(%rsp) 1368 /* If it is below the NMI stack, it is a normal NMI */ 1369 jb first_nmi 1370 1371 /* Ah, it is within the NMI stack. */ 1372 1373 testb $(X86_EFLAGS_DF >> 8), (3*8 + 1)(%rsp) 1374 jz first_nmi /* RSP was user controlled. */ 1375 1376 /* This is a nested NMI. */ 1377 1378nested_nmi: 1379 /* 1380 * Modify the "iret" frame to point to repeat_nmi, forcing another 1381 * iteration of NMI handling. 1382 */ 1383 subq $8, %rsp 1384 leaq -10*8(%rsp), %rdx 1385 pushq $__KERNEL_DS 1386 pushq %rdx 1387 pushfq 1388 pushq $__KERNEL_CS 1389 pushq $repeat_nmi 1390 1391 /* Put stack back */ 1392 addq $(6*8), %rsp 1393 1394nested_nmi_out: 1395 popq %rdx 1396 1397 /* We are returning to kernel mode, so this cannot result in a fault. */ 1398 INTERRUPT_RETURN 1399 1400first_nmi: 1401 /* Restore rdx. */ 1402 movq (%rsp), %rdx 1403 1404 /* Make room for "NMI executing". */ 1405 pushq $0 1406 1407 /* Leave room for the "iret" frame */ 1408 subq $(5*8), %rsp 1409 1410 /* Copy the "original" frame to the "outermost" frame */ 1411 .rept 5 1412 pushq 11*8(%rsp) 1413 .endr 1414 1415 /* Everything up to here is safe from nested NMIs */ 1416 1417#ifdef CONFIG_DEBUG_ENTRY 1418 /* 1419 * For ease of testing, unmask NMIs right away. Disabled by 1420 * default because IRET is very expensive. 1421 */ 1422 pushq $0 /* SS */ 1423 pushq %rsp /* RSP (minus 8 because of the previous push) */ 1424 addq $8, (%rsp) /* Fix up RSP */ 1425 pushfq /* RFLAGS */ 1426 pushq $__KERNEL_CS /* CS */ 1427 pushq $1f /* RIP */ 1428 INTERRUPT_RETURN /* continues at repeat_nmi below */ 14291: 1430#endif 1431 1432repeat_nmi: 1433 /* 1434 * If there was a nested NMI, the first NMI's iret will return 1435 * here. But NMIs are still enabled and we can take another 1436 * nested NMI. The nested NMI checks the interrupted RIP to see 1437 * if it is between repeat_nmi and end_repeat_nmi, and if so 1438 * it will just return, as we are about to repeat an NMI anyway. 1439 * This makes it safe to copy to the stack frame that a nested 1440 * NMI will update. 1441 * 1442 * RSP is pointing to "outermost RIP". gsbase is unknown, but, if 1443 * we're repeating an NMI, gsbase has the same value that it had on 1444 * the first iteration. paranoid_entry will load the kernel 1445 * gsbase if needed before we call do_nmi. "NMI executing" 1446 * is zero. 1447 */ 1448 movq $1, 10*8(%rsp) /* Set "NMI executing". */ 1449 1450 /* 1451 * Copy the "outermost" frame to the "iret" frame. NMIs that nest 1452 * here must not modify the "iret" frame while we're writing to 1453 * it or it will end up containing garbage. 1454 */ 1455 addq $(10*8), %rsp 1456 .rept 5 1457 pushq -6*8(%rsp) 1458 .endr 1459 subq $(5*8), %rsp 1460end_repeat_nmi: 1461 1462 /* 1463 * Everything below this point can be preempted by a nested NMI. 1464 * If this happens, then the inner NMI will change the "iret" 1465 * frame to point back to repeat_nmi. 1466 */ 1467 pushq $-1 /* ORIG_RAX: no syscall to restart */ 1468 ALLOC_PT_GPREGS_ON_STACK 1469 1470 /* 1471 * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit 1472 * as we should not be calling schedule in NMI context. 1473 * Even with normal interrupts enabled. An NMI should not be 1474 * setting NEED_RESCHED or anything that normal interrupts and 1475 * exceptions might do. 1476 */ 1477 call paranoid_entry 1478 1479 /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */ 1480 movq %rsp, %rdi 1481 movq $-1, %rsi 1482 call do_nmi 1483 1484 testl %ebx, %ebx /* swapgs needed? */ 1485 jnz nmi_restore 1486nmi_swapgs: 1487 SWAPGS_UNSAFE_STACK 1488nmi_restore: 1489 RESTORE_EXTRA_REGS 1490 RESTORE_C_REGS 1491 1492 /* Point RSP at the "iret" frame. */ 1493 REMOVE_PT_GPREGS_FROM_STACK 6*8 1494 1495 /* 1496 * Clear "NMI executing". Set DF first so that we can easily 1497 * distinguish the remaining code between here and IRET from 1498 * the SYSCALL entry and exit paths. On a native kernel, we 1499 * could just inspect RIP, but, on paravirt kernels, 1500 * INTERRUPT_RETURN can translate into a jump into a 1501 * hypercall page. 1502 */ 1503 std 1504 movq $0, 5*8(%rsp) /* clear "NMI executing" */ 1505 1506 /* 1507 * INTERRUPT_RETURN reads the "iret" frame and exits the NMI 1508 * stack in a single instruction. We are returning to kernel 1509 * mode, so this cannot result in a fault. 1510 */ 1511 INTERRUPT_RETURN 1512END(nmi) 1513 1514ENTRY(ignore_sysret) 1515 mov $-ENOSYS, %eax 1516 sysret 1517END(ignore_sysret) 1518 1519ENTRY(rewind_stack_do_exit) 1520 /* Prevent any naive code from trying to unwind to our caller. */ 1521 xorl %ebp, %ebp 1522 1523 movq PER_CPU_VAR(cpu_current_top_of_stack), %rax 1524 leaq -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%rax), %rsp 1525 1526 call do_exit 15271: jmp 1b 1528END(rewind_stack_do_exit) 1529