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 <linux/err.h> 39 40/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */ 41#include <linux/elf-em.h> 42#define AUDIT_ARCH_X86_64 (EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE) 43#define __AUDIT_ARCH_64BIT 0x80000000 44#define __AUDIT_ARCH_LE 0x40000000 45 46.code64 47.section .entry.text, "ax" 48 49#ifdef CONFIG_PARAVIRT 50ENTRY(native_usergs_sysret64) 51 swapgs 52 sysretq 53ENDPROC(native_usergs_sysret64) 54#endif /* CONFIG_PARAVIRT */ 55 56.macro TRACE_IRQS_IRETQ 57#ifdef CONFIG_TRACE_IRQFLAGS 58 bt $9, EFLAGS(%rsp) /* interrupts off? */ 59 jnc 1f 60 TRACE_IRQS_ON 611: 62#endif 63.endm 64 65/* 66 * When dynamic function tracer is enabled it will add a breakpoint 67 * to all locations that it is about to modify, sync CPUs, update 68 * all the code, sync CPUs, then remove the breakpoints. In this time 69 * if lockdep is enabled, it might jump back into the debug handler 70 * outside the updating of the IST protection. (TRACE_IRQS_ON/OFF). 71 * 72 * We need to change the IDT table before calling TRACE_IRQS_ON/OFF to 73 * make sure the stack pointer does not get reset back to the top 74 * of the debug stack, and instead just reuses the current stack. 75 */ 76#if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_TRACE_IRQFLAGS) 77 78.macro TRACE_IRQS_OFF_DEBUG 79 call debug_stack_set_zero 80 TRACE_IRQS_OFF 81 call debug_stack_reset 82.endm 83 84.macro TRACE_IRQS_ON_DEBUG 85 call debug_stack_set_zero 86 TRACE_IRQS_ON 87 call debug_stack_reset 88.endm 89 90.macro TRACE_IRQS_IRETQ_DEBUG 91 bt $9, EFLAGS(%rsp) /* interrupts off? */ 92 jnc 1f 93 TRACE_IRQS_ON_DEBUG 941: 95.endm 96 97#else 98# define TRACE_IRQS_OFF_DEBUG TRACE_IRQS_OFF 99# define TRACE_IRQS_ON_DEBUG TRACE_IRQS_ON 100# define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ 101#endif 102 103/* 104 * 64-bit SYSCALL instruction entry. Up to 6 arguments in registers. 105 * 106 * This is the only entry point used for 64-bit system calls. The 107 * hardware interface is reasonably well designed and the register to 108 * argument mapping Linux uses fits well with the registers that are 109 * available when SYSCALL is used. 110 * 111 * SYSCALL instructions can be found inlined in libc implementations as 112 * well as some other programs and libraries. There are also a handful 113 * of SYSCALL instructions in the vDSO used, for example, as a 114 * clock_gettimeofday fallback. 115 * 116 * 64-bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11, 117 * then loads new ss, cs, and rip from previously programmed MSRs. 118 * rflags gets masked by a value from another MSR (so CLD and CLAC 119 * are not needed). SYSCALL does not save anything on the stack 120 * and does not change rsp. 121 * 122 * Registers on entry: 123 * rax system call number 124 * rcx return address 125 * r11 saved rflags (note: r11 is callee-clobbered register in C ABI) 126 * rdi arg0 127 * rsi arg1 128 * rdx arg2 129 * r10 arg3 (needs to be moved to rcx to conform to C ABI) 130 * r8 arg4 131 * r9 arg5 132 * (note: r12-r15, rbp, rbx are callee-preserved in C ABI) 133 * 134 * Only called from user space. 135 * 136 * When user can change pt_regs->foo always force IRET. That is because 137 * it deals with uncanonical addresses better. SYSRET has trouble 138 * with them due to bugs in both AMD and Intel CPUs. 139 */ 140 141ENTRY(entry_SYSCALL_64) 142 /* 143 * Interrupts are off on entry. 144 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON, 145 * it is too small to ever cause noticeable irq latency. 146 */ 147 SWAPGS_UNSAFE_STACK 148 /* 149 * A hypervisor implementation might want to use a label 150 * after the swapgs, so that it can do the swapgs 151 * for the guest and jump here on syscall. 152 */ 153GLOBAL(entry_SYSCALL_64_after_swapgs) 154 155 movq %rsp, PER_CPU_VAR(rsp_scratch) 156 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp 157 158 TRACE_IRQS_OFF 159 160 /* Construct struct pt_regs on stack */ 161 pushq $__USER_DS /* pt_regs->ss */ 162 pushq PER_CPU_VAR(rsp_scratch) /* pt_regs->sp */ 163 pushq %r11 /* pt_regs->flags */ 164 pushq $__USER_CS /* pt_regs->cs */ 165 pushq %rcx /* pt_regs->ip */ 166 pushq %rax /* pt_regs->orig_ax */ 167 pushq %rdi /* pt_regs->di */ 168 pushq %rsi /* pt_regs->si */ 169 pushq %rdx /* pt_regs->dx */ 170 pushq %rcx /* pt_regs->cx */ 171 pushq $-ENOSYS /* pt_regs->ax */ 172 pushq %r8 /* pt_regs->r8 */ 173 pushq %r9 /* pt_regs->r9 */ 174 pushq %r10 /* pt_regs->r10 */ 175 pushq %r11 /* pt_regs->r11 */ 176 sub $(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */ 177 178 /* 179 * If we need to do entry work or if we guess we'll need to do 180 * exit work, go straight to the slow path. 181 */ 182 movq PER_CPU_VAR(current_task), %r11 183 testl $_TIF_WORK_SYSCALL_ENTRY|_TIF_ALLWORK_MASK, TASK_TI_flags(%r11) 184 jnz entry_SYSCALL64_slow_path 185 186entry_SYSCALL_64_fastpath: 187 /* 188 * Easy case: enable interrupts and issue the syscall. If the syscall 189 * needs pt_regs, we'll call a stub that disables interrupts again 190 * and jumps to the slow path. 191 */ 192 TRACE_IRQS_ON 193 ENABLE_INTERRUPTS(CLBR_NONE) 194#if __SYSCALL_MASK == ~0 195 cmpq $__NR_syscall_max, %rax 196#else 197 andl $__SYSCALL_MASK, %eax 198 cmpl $__NR_syscall_max, %eax 199#endif 200 ja 1f /* return -ENOSYS (already in pt_regs->ax) */ 201 movq %r10, %rcx 202 203 /* 204 * This call instruction is handled specially in stub_ptregs_64. 205 * It might end up jumping to the slow path. If it jumps, RAX 206 * and all argument registers are clobbered. 207 */ 208 call *sys_call_table(, %rax, 8) 209.Lentry_SYSCALL_64_after_fastpath_call: 210 211 movq %rax, RAX(%rsp) 2121: 213 214 /* 215 * If we get here, then we know that pt_regs is clean for SYSRET64. 216 * If we see that no exit work is required (which we are required 217 * to check with IRQs off), then we can go straight to SYSRET64. 218 */ 219 DISABLE_INTERRUPTS(CLBR_NONE) 220 TRACE_IRQS_OFF 221 movq PER_CPU_VAR(current_task), %r11 222 testl $_TIF_ALLWORK_MASK, TASK_TI_flags(%r11) 223 jnz 1f 224 225 LOCKDEP_SYS_EXIT 226 TRACE_IRQS_ON /* user mode is traced as IRQs on */ 227 movq RIP(%rsp), %rcx 228 movq EFLAGS(%rsp), %r11 229 RESTORE_C_REGS_EXCEPT_RCX_R11 230 movq RSP(%rsp), %rsp 231 USERGS_SYSRET64 232 2331: 234 /* 235 * The fast path looked good when we started, but something changed 236 * along the way and we need to switch to the slow path. Calling 237 * raise(3) will trigger this, for example. IRQs are off. 238 */ 239 TRACE_IRQS_ON 240 ENABLE_INTERRUPTS(CLBR_NONE) 241 SAVE_EXTRA_REGS 242 movq %rsp, %rdi 243 call syscall_return_slowpath /* returns with IRQs disabled */ 244 jmp return_from_SYSCALL_64 245 246entry_SYSCALL64_slow_path: 247 /* IRQs are off. */ 248 SAVE_EXTRA_REGS 249 movq %rsp, %rdi 250 call do_syscall_64 /* returns with IRQs disabled */ 251 252return_from_SYSCALL_64: 253 RESTORE_EXTRA_REGS 254 TRACE_IRQS_IRETQ /* we're about to change IF */ 255 256 /* 257 * Try to use SYSRET instead of IRET if we're returning to 258 * a completely clean 64-bit userspace context. 259 */ 260 movq RCX(%rsp), %rcx 261 movq RIP(%rsp), %r11 262 cmpq %rcx, %r11 /* RCX == RIP */ 263 jne opportunistic_sysret_failed 264 265 /* 266 * On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP 267 * in kernel space. This essentially lets the user take over 268 * the kernel, since userspace controls RSP. 269 * 270 * If width of "canonical tail" ever becomes variable, this will need 271 * to be updated to remain correct on both old and new CPUs. 272 */ 273 .ifne __VIRTUAL_MASK_SHIFT - 47 274 .error "virtual address width changed -- SYSRET checks need update" 275 .endif 276 277 /* Change top 16 bits to be the sign-extension of 47th bit */ 278 shl $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx 279 sar $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx 280 281 /* If this changed %rcx, it was not canonical */ 282 cmpq %rcx, %r11 283 jne opportunistic_sysret_failed 284 285 cmpq $__USER_CS, CS(%rsp) /* CS must match SYSRET */ 286 jne opportunistic_sysret_failed 287 288 movq R11(%rsp), %r11 289 cmpq %r11, EFLAGS(%rsp) /* R11 == RFLAGS */ 290 jne opportunistic_sysret_failed 291 292 /* 293 * SYSCALL clears RF when it saves RFLAGS in R11 and SYSRET cannot 294 * restore RF properly. If the slowpath sets it for whatever reason, we 295 * need to restore it correctly. 296 * 297 * SYSRET can restore TF, but unlike IRET, restoring TF results in a 298 * trap from userspace immediately after SYSRET. This would cause an 299 * infinite loop whenever #DB happens with register state that satisfies 300 * the opportunistic SYSRET conditions. For example, single-stepping 301 * this user code: 302 * 303 * movq $stuck_here, %rcx 304 * pushfq 305 * popq %r11 306 * stuck_here: 307 * 308 * would never get past 'stuck_here'. 309 */ 310 testq $(X86_EFLAGS_RF|X86_EFLAGS_TF), %r11 311 jnz opportunistic_sysret_failed 312 313 /* nothing to check for RSP */ 314 315 cmpq $__USER_DS, SS(%rsp) /* SS must match SYSRET */ 316 jne opportunistic_sysret_failed 317 318 /* 319 * We win! This label is here just for ease of understanding 320 * perf profiles. Nothing jumps here. 321 */ 322syscall_return_via_sysret: 323 /* rcx and r11 are already restored (see code above) */ 324 RESTORE_C_REGS_EXCEPT_RCX_R11 325 movq RSP(%rsp), %rsp 326 USERGS_SYSRET64 327 328opportunistic_sysret_failed: 329 SWAPGS 330 jmp restore_c_regs_and_iret 331END(entry_SYSCALL_64) 332 333ENTRY(stub_ptregs_64) 334 /* 335 * Syscalls marked as needing ptregs land here. 336 * If we are on the fast path, we need to save the extra regs, 337 * which we achieve by trying again on the slow path. If we are on 338 * the slow path, the extra regs are already saved. 339 * 340 * RAX stores a pointer to the C function implementing the syscall. 341 * IRQs are on. 342 */ 343 cmpq $.Lentry_SYSCALL_64_after_fastpath_call, (%rsp) 344 jne 1f 345 346 /* 347 * Called from fast path -- disable IRQs again, pop return address 348 * and jump to slow path 349 */ 350 DISABLE_INTERRUPTS(CLBR_NONE) 351 TRACE_IRQS_OFF 352 popq %rax 353 jmp entry_SYSCALL64_slow_path 354 3551: 356 jmp *%rax /* Called from C */ 357END(stub_ptregs_64) 358 359.macro ptregs_stub func 360ENTRY(ptregs_\func) 361 leaq \func(%rip), %rax 362 jmp stub_ptregs_64 363END(ptregs_\func) 364.endm 365 366/* Instantiate ptregs_stub for each ptregs-using syscall */ 367#define __SYSCALL_64_QUAL_(sym) 368#define __SYSCALL_64_QUAL_ptregs(sym) ptregs_stub sym 369#define __SYSCALL_64(nr, sym, qual) __SYSCALL_64_QUAL_##qual(sym) 370#include <asm/syscalls_64.h> 371 372/* 373 * %rdi: prev task 374 * %rsi: next task 375 */ 376ENTRY(__switch_to_asm) 377 /* 378 * Save callee-saved registers 379 * This must match the order in inactive_task_frame 380 */ 381 pushq %rbp 382 pushq %rbx 383 pushq %r12 384 pushq %r13 385 pushq %r14 386 pushq %r15 387 388 /* switch stack */ 389 movq %rsp, TASK_threadsp(%rdi) 390 movq TASK_threadsp(%rsi), %rsp 391 392#ifdef CONFIG_CC_STACKPROTECTOR 393 movq TASK_stack_canary(%rsi), %rbx 394 movq %rbx, PER_CPU_VAR(irq_stack_union)+stack_canary_offset 395#endif 396 397 /* restore callee-saved registers */ 398 popq %r15 399 popq %r14 400 popq %r13 401 popq %r12 402 popq %rbx 403 popq %rbp 404 405 jmp __switch_to 406END(__switch_to_asm) 407 408/* 409 * A newly forked process directly context switches into this address. 410 * 411 * rax: prev task we switched from 412 * rbx: kernel thread func (NULL for user thread) 413 * r12: kernel thread arg 414 */ 415ENTRY(ret_from_fork) 416 movq %rax, %rdi 417 call schedule_tail /* rdi: 'prev' task parameter */ 418 419 testq %rbx, %rbx /* from kernel_thread? */ 420 jnz 1f /* kernel threads are uncommon */ 421 4222: 423 movq %rsp, %rdi 424 call syscall_return_slowpath /* returns with IRQs disabled */ 425 TRACE_IRQS_ON /* user mode is traced as IRQS on */ 426 SWAPGS 427 jmp restore_regs_and_iret 428 4291: 430 /* kernel thread */ 431 movq %r12, %rdi 432 call *%rbx 433 /* 434 * A kernel thread is allowed to return here after successfully 435 * calling do_execve(). Exit to userspace to complete the execve() 436 * syscall. 437 */ 438 movq $0, RAX(%rsp) 439 jmp 2b 440END(ret_from_fork) 441 442/* 443 * Build the entry stubs with some assembler magic. 444 * We pack 1 stub into every 8-byte block. 445 */ 446 .align 8 447ENTRY(irq_entries_start) 448 vector=FIRST_EXTERNAL_VECTOR 449 .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR) 450 pushq $(~vector+0x80) /* Note: always in signed byte range */ 451 vector=vector+1 452 jmp common_interrupt 453 .align 8 454 .endr 455END(irq_entries_start) 456 457/* 458 * Interrupt entry/exit. 459 * 460 * Interrupt entry points save only callee clobbered registers in fast path. 461 * 462 * Entry runs with interrupts off. 463 */ 464 465/* 0(%rsp): ~(interrupt number) */ 466 .macro interrupt func 467 cld 468 ALLOC_PT_GPREGS_ON_STACK 469 SAVE_C_REGS 470 SAVE_EXTRA_REGS 471 472 testb $3, CS(%rsp) 473 jz 1f 474 475 /* 476 * IRQ from user mode. Switch to kernel gsbase and inform context 477 * tracking that we're in kernel mode. 478 */ 479 SWAPGS 480 481 /* 482 * We need to tell lockdep that IRQs are off. We can't do this until 483 * we fix gsbase, and we should do it before enter_from_user_mode 484 * (which can take locks). Since TRACE_IRQS_OFF idempotent, 485 * the simplest way to handle it is to just call it twice if 486 * we enter from user mode. There's no reason to optimize this since 487 * TRACE_IRQS_OFF is a no-op if lockdep is off. 488 */ 489 TRACE_IRQS_OFF 490 491 CALL_enter_from_user_mode 492 4931: 494 /* 495 * Save previous stack pointer, optionally switch to interrupt stack. 496 * irq_count is used to check if a CPU is already on an interrupt stack 497 * or not. While this is essentially redundant with preempt_count it is 498 * a little cheaper to use a separate counter in the PDA (short of 499 * moving irq_enter into assembly, which would be too much work) 500 */ 501 movq %rsp, %rdi 502 incl PER_CPU_VAR(irq_count) 503 cmovzq PER_CPU_VAR(irq_stack_ptr), %rsp 504 pushq %rdi 505 /* We entered an interrupt context - irqs are off: */ 506 TRACE_IRQS_OFF 507 508 call \func /* rdi points to pt_regs */ 509 .endm 510 511 /* 512 * The interrupt stubs push (~vector+0x80) onto the stack and 513 * then jump to common_interrupt. 514 */ 515 .p2align CONFIG_X86_L1_CACHE_SHIFT 516common_interrupt: 517 ASM_CLAC 518 addq $-0x80, (%rsp) /* Adjust vector to [-256, -1] range */ 519 interrupt do_IRQ 520 /* 0(%rsp): old RSP */ 521ret_from_intr: 522 DISABLE_INTERRUPTS(CLBR_NONE) 523 TRACE_IRQS_OFF 524 decl PER_CPU_VAR(irq_count) 525 526 /* Restore saved previous stack */ 527 popq %rsp 528 529 testb $3, CS(%rsp) 530 jz retint_kernel 531 532 /* Interrupt came from user space */ 533GLOBAL(retint_user) 534 mov %rsp,%rdi 535 call prepare_exit_to_usermode 536 TRACE_IRQS_IRETQ 537 SWAPGS 538 jmp restore_regs_and_iret 539 540/* Returning to kernel space */ 541retint_kernel: 542#ifdef CONFIG_PREEMPT 543 /* Interrupts are off */ 544 /* Check if we need preemption */ 545 bt $9, EFLAGS(%rsp) /* were interrupts off? */ 546 jnc 1f 5470: cmpl $0, PER_CPU_VAR(__preempt_count) 548 jnz 1f 549 call preempt_schedule_irq 550 jmp 0b 5511: 552#endif 553 /* 554 * The iretq could re-enable interrupts: 555 */ 556 TRACE_IRQS_IRETQ 557 558/* 559 * At this label, code paths which return to kernel and to user, 560 * which come from interrupts/exception and from syscalls, merge. 561 */ 562GLOBAL(restore_regs_and_iret) 563 RESTORE_EXTRA_REGS 564restore_c_regs_and_iret: 565 RESTORE_C_REGS 566 REMOVE_PT_GPREGS_FROM_STACK 8 567 INTERRUPT_RETURN 568 569ENTRY(native_iret) 570 /* 571 * Are we returning to a stack segment from the LDT? Note: in 572 * 64-bit mode SS:RSP on the exception stack is always valid. 573 */ 574#ifdef CONFIG_X86_ESPFIX64 575 testb $4, (SS-RIP)(%rsp) 576 jnz native_irq_return_ldt 577#endif 578 579.global native_irq_return_iret 580native_irq_return_iret: 581 /* 582 * This may fault. Non-paranoid faults on return to userspace are 583 * handled by fixup_bad_iret. These include #SS, #GP, and #NP. 584 * Double-faults due to espfix64 are handled in do_double_fault. 585 * Other faults here are fatal. 586 */ 587 iretq 588 589#ifdef CONFIG_X86_ESPFIX64 590native_irq_return_ldt: 591 /* 592 * We are running with user GSBASE. All GPRs contain their user 593 * values. We have a percpu ESPFIX stack that is eight slots 594 * long (see ESPFIX_STACK_SIZE). espfix_waddr points to the bottom 595 * of the ESPFIX stack. 596 * 597 * We clobber RAX and RDI in this code. We stash RDI on the 598 * normal stack and RAX on the ESPFIX stack. 599 * 600 * The ESPFIX stack layout we set up looks like this: 601 * 602 * --- top of ESPFIX stack --- 603 * SS 604 * RSP 605 * RFLAGS 606 * CS 607 * RIP <-- RSP points here when we're done 608 * RAX <-- espfix_waddr points here 609 * --- bottom of ESPFIX stack --- 610 */ 611 612 pushq %rdi /* Stash user RDI */ 613 SWAPGS 614 movq PER_CPU_VAR(espfix_waddr), %rdi 615 movq %rax, (0*8)(%rdi) /* user RAX */ 616 movq (1*8)(%rsp), %rax /* user RIP */ 617 movq %rax, (1*8)(%rdi) 618 movq (2*8)(%rsp), %rax /* user CS */ 619 movq %rax, (2*8)(%rdi) 620 movq (3*8)(%rsp), %rax /* user RFLAGS */ 621 movq %rax, (3*8)(%rdi) 622 movq (5*8)(%rsp), %rax /* user SS */ 623 movq %rax, (5*8)(%rdi) 624 movq (4*8)(%rsp), %rax /* user RSP */ 625 movq %rax, (4*8)(%rdi) 626 /* Now RAX == RSP. */ 627 628 andl $0xffff0000, %eax /* RAX = (RSP & 0xffff0000) */ 629 popq %rdi /* Restore user RDI */ 630 631 /* 632 * espfix_stack[31:16] == 0. The page tables are set up such that 633 * (espfix_stack | (X & 0xffff0000)) points to a read-only alias of 634 * espfix_waddr for any X. That is, there are 65536 RO aliases of 635 * the same page. Set up RSP so that RSP[31:16] contains the 636 * respective 16 bits of the /userspace/ RSP and RSP nonetheless 637 * still points to an RO alias of the ESPFIX stack. 638 */ 639 orq PER_CPU_VAR(espfix_stack), %rax 640 SWAPGS 641 movq %rax, %rsp 642 643 /* 644 * At this point, we cannot write to the stack any more, but we can 645 * still read. 646 */ 647 popq %rax /* Restore user RAX */ 648 649 /* 650 * RSP now points to an ordinary IRET frame, except that the page 651 * is read-only and RSP[31:16] are preloaded with the userspace 652 * values. We can now IRET back to userspace. 653 */ 654 jmp native_irq_return_iret 655#endif 656END(common_interrupt) 657 658/* 659 * APIC interrupts. 660 */ 661.macro apicinterrupt3 num sym do_sym 662ENTRY(\sym) 663 ASM_CLAC 664 pushq $~(\num) 665.Lcommon_\sym: 666 interrupt \do_sym 667 jmp ret_from_intr 668END(\sym) 669.endm 670 671#ifdef CONFIG_TRACING 672#define trace(sym) trace_##sym 673#define smp_trace(sym) smp_trace_##sym 674 675.macro trace_apicinterrupt num sym 676apicinterrupt3 \num trace(\sym) smp_trace(\sym) 677.endm 678#else 679.macro trace_apicinterrupt num sym do_sym 680.endm 681#endif 682 683/* Make sure APIC interrupt handlers end up in the irqentry section: */ 684#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) 685# define PUSH_SECTION_IRQENTRY .pushsection .irqentry.text, "ax" 686# define POP_SECTION_IRQENTRY .popsection 687#else 688# define PUSH_SECTION_IRQENTRY 689# define POP_SECTION_IRQENTRY 690#endif 691 692.macro apicinterrupt num sym do_sym 693PUSH_SECTION_IRQENTRY 694apicinterrupt3 \num \sym \do_sym 695trace_apicinterrupt \num \sym 696POP_SECTION_IRQENTRY 697.endm 698 699#ifdef CONFIG_SMP 700apicinterrupt3 IRQ_MOVE_CLEANUP_VECTOR irq_move_cleanup_interrupt smp_irq_move_cleanup_interrupt 701apicinterrupt3 REBOOT_VECTOR reboot_interrupt smp_reboot_interrupt 702#endif 703 704#ifdef CONFIG_X86_UV 705apicinterrupt3 UV_BAU_MESSAGE uv_bau_message_intr1 uv_bau_message_interrupt 706#endif 707 708apicinterrupt LOCAL_TIMER_VECTOR apic_timer_interrupt smp_apic_timer_interrupt 709apicinterrupt X86_PLATFORM_IPI_VECTOR x86_platform_ipi smp_x86_platform_ipi 710 711#ifdef CONFIG_HAVE_KVM 712apicinterrupt3 POSTED_INTR_VECTOR kvm_posted_intr_ipi smp_kvm_posted_intr_ipi 713apicinterrupt3 POSTED_INTR_WAKEUP_VECTOR kvm_posted_intr_wakeup_ipi smp_kvm_posted_intr_wakeup_ipi 714#endif 715 716#ifdef CONFIG_X86_MCE_THRESHOLD 717apicinterrupt THRESHOLD_APIC_VECTOR threshold_interrupt smp_threshold_interrupt 718#endif 719 720#ifdef CONFIG_X86_MCE_AMD 721apicinterrupt DEFERRED_ERROR_VECTOR deferred_error_interrupt smp_deferred_error_interrupt 722#endif 723 724#ifdef CONFIG_X86_THERMAL_VECTOR 725apicinterrupt THERMAL_APIC_VECTOR thermal_interrupt smp_thermal_interrupt 726#endif 727 728#ifdef CONFIG_SMP 729apicinterrupt CALL_FUNCTION_SINGLE_VECTOR call_function_single_interrupt smp_call_function_single_interrupt 730apicinterrupt CALL_FUNCTION_VECTOR call_function_interrupt smp_call_function_interrupt 731apicinterrupt RESCHEDULE_VECTOR reschedule_interrupt smp_reschedule_interrupt 732#endif 733 734apicinterrupt ERROR_APIC_VECTOR error_interrupt smp_error_interrupt 735apicinterrupt SPURIOUS_APIC_VECTOR spurious_interrupt smp_spurious_interrupt 736 737#ifdef CONFIG_IRQ_WORK 738apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt 739#endif 740 741/* 742 * Exception entry points. 743 */ 744#define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss) + (TSS_ist + ((x) - 1) * 8) 745 746.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 747ENTRY(\sym) 748 /* Sanity check */ 749 .if \shift_ist != -1 && \paranoid == 0 750 .error "using shift_ist requires paranoid=1" 751 .endif 752 753 ASM_CLAC 754 PARAVIRT_ADJUST_EXCEPTION_FRAME 755 756 .ifeq \has_error_code 757 pushq $-1 /* ORIG_RAX: no syscall to restart */ 758 .endif 759 760 ALLOC_PT_GPREGS_ON_STACK 761 762 .if \paranoid 763 .if \paranoid == 1 764 testb $3, CS(%rsp) /* If coming from userspace, switch stacks */ 765 jnz 1f 766 .endif 767 call paranoid_entry 768 .else 769 call error_entry 770 .endif 771 /* returned flag: ebx=0: need swapgs on exit, ebx=1: don't need it */ 772 773 .if \paranoid 774 .if \shift_ist != -1 775 TRACE_IRQS_OFF_DEBUG /* reload IDT in case of recursion */ 776 .else 777 TRACE_IRQS_OFF 778 .endif 779 .endif 780 781 movq %rsp, %rdi /* pt_regs pointer */ 782 783 .if \has_error_code 784 movq ORIG_RAX(%rsp), %rsi /* get error code */ 785 movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */ 786 .else 787 xorl %esi, %esi /* no error code */ 788 .endif 789 790 .if \shift_ist != -1 791 subq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist) 792 .endif 793 794 call \do_sym 795 796 .if \shift_ist != -1 797 addq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist) 798 .endif 799 800 /* these procedures expect "no swapgs" flag in ebx */ 801 .if \paranoid 802 jmp paranoid_exit 803 .else 804 jmp error_exit 805 .endif 806 807 .if \paranoid == 1 808 /* 809 * Paranoid entry from userspace. Switch stacks and treat it 810 * as a normal entry. This means that paranoid handlers 811 * run in real process context if user_mode(regs). 812 */ 8131: 814 call error_entry 815 816 817 movq %rsp, %rdi /* pt_regs pointer */ 818 call sync_regs 819 movq %rax, %rsp /* switch stack */ 820 821 movq %rsp, %rdi /* pt_regs pointer */ 822 823 .if \has_error_code 824 movq ORIG_RAX(%rsp), %rsi /* get error code */ 825 movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */ 826 .else 827 xorl %esi, %esi /* no error code */ 828 .endif 829 830 call \do_sym 831 832 jmp error_exit /* %ebx: no swapgs flag */ 833 .endif 834END(\sym) 835.endm 836 837#ifdef CONFIG_TRACING 838.macro trace_idtentry sym do_sym has_error_code:req 839idtentry trace(\sym) trace(\do_sym) has_error_code=\has_error_code 840idtentry \sym \do_sym has_error_code=\has_error_code 841.endm 842#else 843.macro trace_idtentry sym do_sym has_error_code:req 844idtentry \sym \do_sym has_error_code=\has_error_code 845.endm 846#endif 847 848idtentry divide_error do_divide_error has_error_code=0 849idtentry overflow do_overflow has_error_code=0 850idtentry bounds do_bounds has_error_code=0 851idtentry invalid_op do_invalid_op has_error_code=0 852idtentry device_not_available do_device_not_available has_error_code=0 853idtentry double_fault do_double_fault has_error_code=1 paranoid=2 854idtentry coprocessor_segment_overrun do_coprocessor_segment_overrun has_error_code=0 855idtentry invalid_TSS do_invalid_TSS has_error_code=1 856idtentry segment_not_present do_segment_not_present has_error_code=1 857idtentry spurious_interrupt_bug do_spurious_interrupt_bug has_error_code=0 858idtentry coprocessor_error do_coprocessor_error has_error_code=0 859idtentry alignment_check do_alignment_check has_error_code=1 860idtentry simd_coprocessor_error do_simd_coprocessor_error has_error_code=0 861 862 863 /* 864 * Reload gs selector with exception handling 865 * edi: new selector 866 */ 867ENTRY(native_load_gs_index) 868 pushfq 869 DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI) 870 SWAPGS 871.Lgs_change: 872 movl %edi, %gs 8732: ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE 874 SWAPGS 875 popfq 876 ret 877END(native_load_gs_index) 878 879 _ASM_EXTABLE(.Lgs_change, bad_gs) 880 .section .fixup, "ax" 881 /* running with kernelgs */ 882bad_gs: 883 SWAPGS /* switch back to user gs */ 884.macro ZAP_GS 885 /* This can't be a string because the preprocessor needs to see it. */ 886 movl $__USER_DS, %eax 887 movl %eax, %gs 888.endm 889 ALTERNATIVE "", "ZAP_GS", X86_BUG_NULL_SEG 890 xorl %eax, %eax 891 movl %eax, %gs 892 jmp 2b 893 .previous 894 895/* Call softirq on interrupt stack. Interrupts are off. */ 896ENTRY(do_softirq_own_stack) 897 pushq %rbp 898 mov %rsp, %rbp 899 incl PER_CPU_VAR(irq_count) 900 cmove PER_CPU_VAR(irq_stack_ptr), %rsp 901 push %rbp /* frame pointer backlink */ 902 call __do_softirq 903 leaveq 904 decl PER_CPU_VAR(irq_count) 905 ret 906END(do_softirq_own_stack) 907 908#ifdef CONFIG_XEN 909idtentry xen_hypervisor_callback xen_do_hypervisor_callback has_error_code=0 910 911/* 912 * A note on the "critical region" in our callback handler. 913 * We want to avoid stacking callback handlers due to events occurring 914 * during handling of the last event. To do this, we keep events disabled 915 * until we've done all processing. HOWEVER, we must enable events before 916 * popping the stack frame (can't be done atomically) and so it would still 917 * be possible to get enough handler activations to overflow the stack. 918 * Although unlikely, bugs of that kind are hard to track down, so we'd 919 * like to avoid the possibility. 920 * So, on entry to the handler we detect whether we interrupted an 921 * existing activation in its critical region -- if so, we pop the current 922 * activation and restart the handler using the previous one. 923 */ 924ENTRY(xen_do_hypervisor_callback) /* do_hypervisor_callback(struct *pt_regs) */ 925 926/* 927 * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will 928 * see the correct pointer to the pt_regs 929 */ 930 movq %rdi, %rsp /* we don't return, adjust the stack frame */ 93111: incl PER_CPU_VAR(irq_count) 932 movq %rsp, %rbp 933 cmovzq PER_CPU_VAR(irq_stack_ptr), %rsp 934 pushq %rbp /* frame pointer backlink */ 935 call xen_evtchn_do_upcall 936 popq %rsp 937 decl PER_CPU_VAR(irq_count) 938#ifndef CONFIG_PREEMPT 939 call xen_maybe_preempt_hcall 940#endif 941 jmp error_exit 942END(xen_do_hypervisor_callback) 943 944/* 945 * Hypervisor uses this for application faults while it executes. 946 * We get here for two reasons: 947 * 1. Fault while reloading DS, ES, FS or GS 948 * 2. Fault while executing IRET 949 * Category 1 we do not need to fix up as Xen has already reloaded all segment 950 * registers that could be reloaded and zeroed the others. 951 * Category 2 we fix up by killing the current process. We cannot use the 952 * normal Linux return path in this case because if we use the IRET hypercall 953 * to pop the stack frame we end up in an infinite loop of failsafe callbacks. 954 * We distinguish between categories by comparing each saved segment register 955 * with its current contents: any discrepancy means we in category 1. 956 */ 957ENTRY(xen_failsafe_callback) 958 movl %ds, %ecx 959 cmpw %cx, 0x10(%rsp) 960 jne 1f 961 movl %es, %ecx 962 cmpw %cx, 0x18(%rsp) 963 jne 1f 964 movl %fs, %ecx 965 cmpw %cx, 0x20(%rsp) 966 jne 1f 967 movl %gs, %ecx 968 cmpw %cx, 0x28(%rsp) 969 jne 1f 970 /* All segments match their saved values => Category 2 (Bad IRET). */ 971 movq (%rsp), %rcx 972 movq 8(%rsp), %r11 973 addq $0x30, %rsp 974 pushq $0 /* RIP */ 975 pushq %r11 976 pushq %rcx 977 jmp general_protection 9781: /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */ 979 movq (%rsp), %rcx 980 movq 8(%rsp), %r11 981 addq $0x30, %rsp 982 pushq $-1 /* orig_ax = -1 => not a system call */ 983 ALLOC_PT_GPREGS_ON_STACK 984 SAVE_C_REGS 985 SAVE_EXTRA_REGS 986 jmp error_exit 987END(xen_failsafe_callback) 988 989apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ 990 xen_hvm_callback_vector xen_evtchn_do_upcall 991 992#endif /* CONFIG_XEN */ 993 994#if IS_ENABLED(CONFIG_HYPERV) 995apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ 996 hyperv_callback_vector hyperv_vector_handler 997#endif /* CONFIG_HYPERV */ 998 999idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK 1000idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK 1001idtentry stack_segment do_stack_segment has_error_code=1 1002 1003#ifdef CONFIG_XEN 1004idtentry xen_debug do_debug has_error_code=0 1005idtentry xen_int3 do_int3 has_error_code=0 1006idtentry xen_stack_segment do_stack_segment has_error_code=1 1007#endif 1008 1009idtentry general_protection do_general_protection has_error_code=1 1010trace_idtentry page_fault do_page_fault has_error_code=1 1011 1012#ifdef CONFIG_KVM_GUEST 1013idtentry async_page_fault do_async_page_fault has_error_code=1 1014#endif 1015 1016#ifdef CONFIG_X86_MCE 1017idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip) 1018#endif 1019 1020/* 1021 * Save all registers in pt_regs, and switch gs if needed. 1022 * Use slow, but surefire "are we in kernel?" check. 1023 * Return: ebx=0: need swapgs on exit, ebx=1: otherwise 1024 */ 1025ENTRY(paranoid_entry) 1026 cld 1027 SAVE_C_REGS 8 1028 SAVE_EXTRA_REGS 8 1029 movl $1, %ebx 1030 movl $MSR_GS_BASE, %ecx 1031 rdmsr 1032 testl %edx, %edx 1033 js 1f /* negative -> in kernel */ 1034 SWAPGS 1035 xorl %ebx, %ebx 10361: ret 1037END(paranoid_entry) 1038 1039/* 1040 * "Paranoid" exit path from exception stack. This is invoked 1041 * only on return from non-NMI IST interrupts that came 1042 * from kernel space. 1043 * 1044 * We may be returning to very strange contexts (e.g. very early 1045 * in syscall entry), so checking for preemption here would 1046 * be complicated. Fortunately, we there's no good reason 1047 * to try to handle preemption here. 1048 * 1049 * On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) 1050 */ 1051ENTRY(paranoid_exit) 1052 DISABLE_INTERRUPTS(CLBR_NONE) 1053 TRACE_IRQS_OFF_DEBUG 1054 testl %ebx, %ebx /* swapgs needed? */ 1055 jnz paranoid_exit_no_swapgs 1056 TRACE_IRQS_IRETQ 1057 SWAPGS_UNSAFE_STACK 1058 jmp paranoid_exit_restore 1059paranoid_exit_no_swapgs: 1060 TRACE_IRQS_IRETQ_DEBUG 1061paranoid_exit_restore: 1062 RESTORE_EXTRA_REGS 1063 RESTORE_C_REGS 1064 REMOVE_PT_GPREGS_FROM_STACK 8 1065 INTERRUPT_RETURN 1066END(paranoid_exit) 1067 1068/* 1069 * Save all registers in pt_regs, and switch gs if needed. 1070 * Return: EBX=0: came from user mode; EBX=1: otherwise 1071 */ 1072ENTRY(error_entry) 1073 cld 1074 SAVE_C_REGS 8 1075 SAVE_EXTRA_REGS 8 1076 xorl %ebx, %ebx 1077 testb $3, CS+8(%rsp) 1078 jz .Lerror_kernelspace 1079 1080 /* 1081 * We entered from user mode or we're pretending to have entered 1082 * from user mode due to an IRET fault. 1083 */ 1084 SWAPGS 1085 1086.Lerror_entry_from_usermode_after_swapgs: 1087 /* 1088 * We need to tell lockdep that IRQs are off. We can't do this until 1089 * we fix gsbase, and we should do it before enter_from_user_mode 1090 * (which can take locks). 1091 */ 1092 TRACE_IRQS_OFF 1093 CALL_enter_from_user_mode 1094 ret 1095 1096.Lerror_entry_done: 1097 TRACE_IRQS_OFF 1098 ret 1099 1100 /* 1101 * There are two places in the kernel that can potentially fault with 1102 * usergs. Handle them here. B stepping K8s sometimes report a 1103 * truncated RIP for IRET exceptions returning to compat mode. Check 1104 * for these here too. 1105 */ 1106.Lerror_kernelspace: 1107 incl %ebx 1108 leaq native_irq_return_iret(%rip), %rcx 1109 cmpq %rcx, RIP+8(%rsp) 1110 je .Lerror_bad_iret 1111 movl %ecx, %eax /* zero extend */ 1112 cmpq %rax, RIP+8(%rsp) 1113 je .Lbstep_iret 1114 cmpq $.Lgs_change, RIP+8(%rsp) 1115 jne .Lerror_entry_done 1116 1117 /* 1118 * hack: .Lgs_change can fail with user gsbase. If this happens, fix up 1119 * gsbase and proceed. We'll fix up the exception and land in 1120 * .Lgs_change's error handler with kernel gsbase. 1121 */ 1122 SWAPGS 1123 jmp .Lerror_entry_done 1124 1125.Lbstep_iret: 1126 /* Fix truncated RIP */ 1127 movq %rcx, RIP+8(%rsp) 1128 /* fall through */ 1129 1130.Lerror_bad_iret: 1131 /* 1132 * We came from an IRET to user mode, so we have user gsbase. 1133 * Switch to kernel gsbase: 1134 */ 1135 SWAPGS 1136 1137 /* 1138 * Pretend that the exception came from user mode: set up pt_regs 1139 * as if we faulted immediately after IRET and clear EBX so that 1140 * error_exit knows that we will be returning to user mode. 1141 */ 1142 mov %rsp, %rdi 1143 call fixup_bad_iret 1144 mov %rax, %rsp 1145 decl %ebx 1146 jmp .Lerror_entry_from_usermode_after_swapgs 1147END(error_entry) 1148 1149 1150/* 1151 * On entry, EBX is a "return to kernel mode" flag: 1152 * 1: already in kernel mode, don't need SWAPGS 1153 * 0: user gsbase is loaded, we need SWAPGS and standard preparation for return to usermode 1154 */ 1155ENTRY(error_exit) 1156 movl %ebx, %eax 1157 DISABLE_INTERRUPTS(CLBR_NONE) 1158 TRACE_IRQS_OFF 1159 testl %eax, %eax 1160 jnz retint_kernel 1161 jmp retint_user 1162END(error_exit) 1163 1164/* Runs on exception stack */ 1165ENTRY(nmi) 1166 /* 1167 * Fix up the exception frame if we're on Xen. 1168 * PARAVIRT_ADJUST_EXCEPTION_FRAME is guaranteed to push at most 1169 * one value to the stack on native, so it may clobber the rdx 1170 * scratch slot, but it won't clobber any of the important 1171 * slots past it. 1172 * 1173 * Xen is a different story, because the Xen frame itself overlaps 1174 * the "NMI executing" variable. 1175 */ 1176 PARAVIRT_ADJUST_EXCEPTION_FRAME 1177 1178 /* 1179 * We allow breakpoints in NMIs. If a breakpoint occurs, then 1180 * the iretq it performs will take us out of NMI context. 1181 * This means that we can have nested NMIs where the next 1182 * NMI is using the top of the stack of the previous NMI. We 1183 * can't let it execute because the nested NMI will corrupt the 1184 * stack of the previous NMI. NMI handlers are not re-entrant 1185 * anyway. 1186 * 1187 * To handle this case we do the following: 1188 * Check the a special location on the stack that contains 1189 * a variable that is set when NMIs are executing. 1190 * The interrupted task's stack is also checked to see if it 1191 * is an NMI stack. 1192 * If the variable is not set and the stack is not the NMI 1193 * stack then: 1194 * o Set the special variable on the stack 1195 * o Copy the interrupt frame into an "outermost" location on the 1196 * stack 1197 * o Copy the interrupt frame into an "iret" location on the stack 1198 * o Continue processing the NMI 1199 * If the variable is set or the previous stack is the NMI stack: 1200 * o Modify the "iret" location to jump to the repeat_nmi 1201 * o return back to the first NMI 1202 * 1203 * Now on exit of the first NMI, we first clear the stack variable 1204 * The NMI stack will tell any nested NMIs at that point that it is 1205 * nested. Then we pop the stack normally with iret, and if there was 1206 * a nested NMI that updated the copy interrupt stack frame, a 1207 * jump will be made to the repeat_nmi code that will handle the second 1208 * NMI. 1209 * 1210 * However, espfix prevents us from directly returning to userspace 1211 * with a single IRET instruction. Similarly, IRET to user mode 1212 * can fault. We therefore handle NMIs from user space like 1213 * other IST entries. 1214 */ 1215 1216 /* Use %rdx as our temp variable throughout */ 1217 pushq %rdx 1218 1219 testb $3, CS-RIP+8(%rsp) 1220 jz .Lnmi_from_kernel 1221 1222 /* 1223 * NMI from user mode. We need to run on the thread stack, but we 1224 * can't go through the normal entry paths: NMIs are masked, and 1225 * we don't want to enable interrupts, because then we'll end 1226 * up in an awkward situation in which IRQs are on but NMIs 1227 * are off. 1228 * 1229 * We also must not push anything to the stack before switching 1230 * stacks lest we corrupt the "NMI executing" variable. 1231 */ 1232 1233 SWAPGS_UNSAFE_STACK 1234 cld 1235 movq %rsp, %rdx 1236 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp 1237 pushq 5*8(%rdx) /* pt_regs->ss */ 1238 pushq 4*8(%rdx) /* pt_regs->rsp */ 1239 pushq 3*8(%rdx) /* pt_regs->flags */ 1240 pushq 2*8(%rdx) /* pt_regs->cs */ 1241 pushq 1*8(%rdx) /* pt_regs->rip */ 1242 pushq $-1 /* pt_regs->orig_ax */ 1243 pushq %rdi /* pt_regs->di */ 1244 pushq %rsi /* pt_regs->si */ 1245 pushq (%rdx) /* pt_regs->dx */ 1246 pushq %rcx /* pt_regs->cx */ 1247 pushq %rax /* pt_regs->ax */ 1248 pushq %r8 /* pt_regs->r8 */ 1249 pushq %r9 /* pt_regs->r9 */ 1250 pushq %r10 /* pt_regs->r10 */ 1251 pushq %r11 /* pt_regs->r11 */ 1252 pushq %rbx /* pt_regs->rbx */ 1253 pushq %rbp /* pt_regs->rbp */ 1254 pushq %r12 /* pt_regs->r12 */ 1255 pushq %r13 /* pt_regs->r13 */ 1256 pushq %r14 /* pt_regs->r14 */ 1257 pushq %r15 /* pt_regs->r15 */ 1258 1259 /* 1260 * At this point we no longer need to worry about stack damage 1261 * due to nesting -- we're on the normal thread stack and we're 1262 * done with the NMI stack. 1263 */ 1264 1265 movq %rsp, %rdi 1266 movq $-1, %rsi 1267 call do_nmi 1268 1269 /* 1270 * Return back to user mode. We must *not* do the normal exit 1271 * work, because we don't want to enable interrupts. Fortunately, 1272 * do_nmi doesn't modify pt_regs. 1273 */ 1274 SWAPGS 1275 jmp restore_c_regs_and_iret 1276 1277.Lnmi_from_kernel: 1278 /* 1279 * Here's what our stack frame will look like: 1280 * +---------------------------------------------------------+ 1281 * | original SS | 1282 * | original Return RSP | 1283 * | original RFLAGS | 1284 * | original CS | 1285 * | original RIP | 1286 * +---------------------------------------------------------+ 1287 * | temp storage for rdx | 1288 * +---------------------------------------------------------+ 1289 * | "NMI executing" variable | 1290 * +---------------------------------------------------------+ 1291 * | iret SS } Copied from "outermost" frame | 1292 * | iret Return RSP } on each loop iteration; overwritten | 1293 * | iret RFLAGS } by a nested NMI to force another | 1294 * | iret CS } iteration if needed. | 1295 * | iret RIP } | 1296 * +---------------------------------------------------------+ 1297 * | outermost SS } initialized in first_nmi; | 1298 * | outermost Return RSP } will not be changed before | 1299 * | outermost RFLAGS } NMI processing is done. | 1300 * | outermost CS } Copied to "iret" frame on each | 1301 * | outermost RIP } iteration. | 1302 * +---------------------------------------------------------+ 1303 * | pt_regs | 1304 * +---------------------------------------------------------+ 1305 * 1306 * The "original" frame is used by hardware. Before re-enabling 1307 * NMIs, we need to be done with it, and we need to leave enough 1308 * space for the asm code here. 1309 * 1310 * We return by executing IRET while RSP points to the "iret" frame. 1311 * That will either return for real or it will loop back into NMI 1312 * processing. 1313 * 1314 * The "outermost" frame is copied to the "iret" frame on each 1315 * iteration of the loop, so each iteration starts with the "iret" 1316 * frame pointing to the final return target. 1317 */ 1318 1319 /* 1320 * Determine whether we're a nested NMI. 1321 * 1322 * If we interrupted kernel code between repeat_nmi and 1323 * end_repeat_nmi, then we are a nested NMI. We must not 1324 * modify the "iret" frame because it's being written by 1325 * the outer NMI. That's okay; the outer NMI handler is 1326 * about to about to call do_nmi anyway, so we can just 1327 * resume the outer NMI. 1328 */ 1329 1330 movq $repeat_nmi, %rdx 1331 cmpq 8(%rsp), %rdx 1332 ja 1f 1333 movq $end_repeat_nmi, %rdx 1334 cmpq 8(%rsp), %rdx 1335 ja nested_nmi_out 13361: 1337 1338 /* 1339 * Now check "NMI executing". If it's set, then we're nested. 1340 * This will not detect if we interrupted an outer NMI just 1341 * before IRET. 1342 */ 1343 cmpl $1, -8(%rsp) 1344 je nested_nmi 1345 1346 /* 1347 * Now test if the previous stack was an NMI stack. This covers 1348 * the case where we interrupt an outer NMI after it clears 1349 * "NMI executing" but before IRET. We need to be careful, though: 1350 * there is one case in which RSP could point to the NMI stack 1351 * despite there being no NMI active: naughty userspace controls 1352 * RSP at the very beginning of the SYSCALL targets. We can 1353 * pull a fast one on naughty userspace, though: we program 1354 * SYSCALL to mask DF, so userspace cannot cause DF to be set 1355 * if it controls the kernel's RSP. We set DF before we clear 1356 * "NMI executing". 1357 */ 1358 lea 6*8(%rsp), %rdx 1359 /* Compare the NMI stack (rdx) with the stack we came from (4*8(%rsp)) */ 1360 cmpq %rdx, 4*8(%rsp) 1361 /* If the stack pointer is above the NMI stack, this is a normal NMI */ 1362 ja first_nmi 1363 1364 subq $EXCEPTION_STKSZ, %rdx 1365 cmpq %rdx, 4*8(%rsp) 1366 /* If it is below the NMI stack, it is a normal NMI */ 1367 jb first_nmi 1368 1369 /* Ah, it is within the NMI stack. */ 1370 1371 testb $(X86_EFLAGS_DF >> 8), (3*8 + 1)(%rsp) 1372 jz first_nmi /* RSP was user controlled. */ 1373 1374 /* This is a nested NMI. */ 1375 1376nested_nmi: 1377 /* 1378 * Modify the "iret" frame to point to repeat_nmi, forcing another 1379 * iteration of NMI handling. 1380 */ 1381 subq $8, %rsp 1382 leaq -10*8(%rsp), %rdx 1383 pushq $__KERNEL_DS 1384 pushq %rdx 1385 pushfq 1386 pushq $__KERNEL_CS 1387 pushq $repeat_nmi 1388 1389 /* Put stack back */ 1390 addq $(6*8), %rsp 1391 1392nested_nmi_out: 1393 popq %rdx 1394 1395 /* We are returning to kernel mode, so this cannot result in a fault. */ 1396 INTERRUPT_RETURN 1397 1398first_nmi: 1399 /* Restore rdx. */ 1400 movq (%rsp), %rdx 1401 1402 /* Make room for "NMI executing". */ 1403 pushq $0 1404 1405 /* Leave room for the "iret" frame */ 1406 subq $(5*8), %rsp 1407 1408 /* Copy the "original" frame to the "outermost" frame */ 1409 .rept 5 1410 pushq 11*8(%rsp) 1411 .endr 1412 1413 /* Everything up to here is safe from nested NMIs */ 1414 1415#ifdef CONFIG_DEBUG_ENTRY 1416 /* 1417 * For ease of testing, unmask NMIs right away. Disabled by 1418 * default because IRET is very expensive. 1419 */ 1420 pushq $0 /* SS */ 1421 pushq %rsp /* RSP (minus 8 because of the previous push) */ 1422 addq $8, (%rsp) /* Fix up RSP */ 1423 pushfq /* RFLAGS */ 1424 pushq $__KERNEL_CS /* CS */ 1425 pushq $1f /* RIP */ 1426 INTERRUPT_RETURN /* continues at repeat_nmi below */ 14271: 1428#endif 1429 1430repeat_nmi: 1431 /* 1432 * If there was a nested NMI, the first NMI's iret will return 1433 * here. But NMIs are still enabled and we can take another 1434 * nested NMI. The nested NMI checks the interrupted RIP to see 1435 * if it is between repeat_nmi and end_repeat_nmi, and if so 1436 * it will just return, as we are about to repeat an NMI anyway. 1437 * This makes it safe to copy to the stack frame that a nested 1438 * NMI will update. 1439 * 1440 * RSP is pointing to "outermost RIP". gsbase is unknown, but, if 1441 * we're repeating an NMI, gsbase has the same value that it had on 1442 * the first iteration. paranoid_entry will load the kernel 1443 * gsbase if needed before we call do_nmi. "NMI executing" 1444 * is zero. 1445 */ 1446 movq $1, 10*8(%rsp) /* Set "NMI executing". */ 1447 1448 /* 1449 * Copy the "outermost" frame to the "iret" frame. NMIs that nest 1450 * here must not modify the "iret" frame while we're writing to 1451 * it or it will end up containing garbage. 1452 */ 1453 addq $(10*8), %rsp 1454 .rept 5 1455 pushq -6*8(%rsp) 1456 .endr 1457 subq $(5*8), %rsp 1458end_repeat_nmi: 1459 1460 /* 1461 * Everything below this point can be preempted by a nested NMI. 1462 * If this happens, then the inner NMI will change the "iret" 1463 * frame to point back to repeat_nmi. 1464 */ 1465 pushq $-1 /* ORIG_RAX: no syscall to restart */ 1466 ALLOC_PT_GPREGS_ON_STACK 1467 1468 /* 1469 * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit 1470 * as we should not be calling schedule in NMI context. 1471 * Even with normal interrupts enabled. An NMI should not be 1472 * setting NEED_RESCHED or anything that normal interrupts and 1473 * exceptions might do. 1474 */ 1475 call paranoid_entry 1476 1477 /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */ 1478 movq %rsp, %rdi 1479 movq $-1, %rsi 1480 call do_nmi 1481 1482 testl %ebx, %ebx /* swapgs needed? */ 1483 jnz nmi_restore 1484nmi_swapgs: 1485 SWAPGS_UNSAFE_STACK 1486nmi_restore: 1487 RESTORE_EXTRA_REGS 1488 RESTORE_C_REGS 1489 1490 /* Point RSP at the "iret" frame. */ 1491 REMOVE_PT_GPREGS_FROM_STACK 6*8 1492 1493 /* 1494 * Clear "NMI executing". Set DF first so that we can easily 1495 * distinguish the remaining code between here and IRET from 1496 * the SYSCALL entry and exit paths. On a native kernel, we 1497 * could just inspect RIP, but, on paravirt kernels, 1498 * INTERRUPT_RETURN can translate into a jump into a 1499 * hypercall page. 1500 */ 1501 std 1502 movq $0, 5*8(%rsp) /* clear "NMI executing" */ 1503 1504 /* 1505 * INTERRUPT_RETURN reads the "iret" frame and exits the NMI 1506 * stack in a single instruction. We are returning to kernel 1507 * mode, so this cannot result in a fault. 1508 */ 1509 INTERRUPT_RETURN 1510END(nmi) 1511 1512ENTRY(ignore_sysret) 1513 mov $-ENOSYS, %eax 1514 sysret 1515END(ignore_sysret) 1516 1517ENTRY(rewind_stack_do_exit) 1518 /* Prevent any naive code from trying to unwind to our caller. */ 1519 xorl %ebp, %ebp 1520 1521 movq PER_CPU_VAR(cpu_current_top_of_stack), %rax 1522 leaq -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%rax), %rsp 1523 1524 call do_exit 15251: jmp 1b 1526END(rewind_stack_do_exit) 1527