/* * linux/arch/x86_64/entry.S * * Copyright (C) 1991, 1992 Linus Torvalds * Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs * Copyright (C) 2000 Pavel Machek */ /* * entry.S contains the system-call and fault low-level handling routines. * * Some of this is documented in Documentation/x86/entry_64.txt * * NOTE: This code handles signal-recognition, which happens every time * after an interrupt and after each system call. * * Normal syscalls and interrupts don't save a full stack frame, this is * only done for syscall tracing, signals or fork/exec et.al. * * A note on terminology: * - top of stack: Architecture defined interrupt frame from SS to RIP * at the top of the kernel process stack. * - partial stack frame: partially saved registers up to R11. * - full stack frame: Like partial stack frame, but all register saved. * * Some macro usage: * - CFI macros are used to generate dwarf2 unwind information for better * backtraces. They don't change any code. * - SAVE_ALL/RESTORE_ALL - Save/restore all registers * - SAVE_ARGS/RESTORE_ARGS - Save/restore registers that C functions modify. * There are unfortunately lots of special cases where some registers * not touched. The macro is a big mess that should be cleaned up. * - SAVE_REST/RESTORE_REST - Handle the registers not saved by SAVE_ARGS. * Gives a full stack frame. * - ENTRY/END Define functions in the symbol table. * - FIXUP_TOP_OF_STACK/RESTORE_TOP_OF_STACK - Fix up the hardware stack * frame that is otherwise undefined after a SYSCALL * - TRACE_IRQ_* - Trace hard interrupt state for lock debugging. * - errorentry/paranoidentry/zeroentry - Define exception entry points. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* Avoid __ASSEMBLER__'ifying just for this. */ #include #define AUDIT_ARCH_X86_64 (EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE) #define __AUDIT_ARCH_64BIT 0x80000000 #define __AUDIT_ARCH_LE 0x40000000 .code64 .section .entry.text, "ax" #ifdef CONFIG_FUNCTION_TRACER #ifdef CONFIG_DYNAMIC_FTRACE ENTRY(mcount) retq END(mcount) ENTRY(ftrace_caller) cmpl $0, function_trace_stop jne ftrace_stub MCOUNT_SAVE_FRAME movq 0x38(%rsp), %rdi movq 8(%rbp), %rsi subq $MCOUNT_INSN_SIZE, %rdi GLOBAL(ftrace_call) call ftrace_stub MCOUNT_RESTORE_FRAME #ifdef CONFIG_FUNCTION_GRAPH_TRACER GLOBAL(ftrace_graph_call) jmp ftrace_stub #endif GLOBAL(ftrace_stub) retq END(ftrace_caller) #else /* ! CONFIG_DYNAMIC_FTRACE */ ENTRY(mcount) cmpl $0, function_trace_stop jne ftrace_stub cmpq $ftrace_stub, ftrace_trace_function jnz trace #ifdef CONFIG_FUNCTION_GRAPH_TRACER cmpq $ftrace_stub, ftrace_graph_return jnz ftrace_graph_caller cmpq $ftrace_graph_entry_stub, ftrace_graph_entry jnz ftrace_graph_caller #endif GLOBAL(ftrace_stub) retq trace: MCOUNT_SAVE_FRAME movq 0x38(%rsp), %rdi movq 8(%rbp), %rsi subq $MCOUNT_INSN_SIZE, %rdi call *ftrace_trace_function MCOUNT_RESTORE_FRAME jmp ftrace_stub END(mcount) #endif /* CONFIG_DYNAMIC_FTRACE */ #endif /* CONFIG_FUNCTION_TRACER */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER ENTRY(ftrace_graph_caller) cmpl $0, function_trace_stop jne ftrace_stub MCOUNT_SAVE_FRAME leaq 8(%rbp), %rdi movq 0x38(%rsp), %rsi movq (%rbp), %rdx subq $MCOUNT_INSN_SIZE, %rsi call prepare_ftrace_return MCOUNT_RESTORE_FRAME retq END(ftrace_graph_caller) GLOBAL(return_to_handler) subq $24, %rsp /* Save the return values */ movq %rax, (%rsp) movq %rdx, 8(%rsp) movq %rbp, %rdi call ftrace_return_to_handler movq %rax, %rdi movq 8(%rsp), %rdx movq (%rsp), %rax addq $24, %rsp jmp *%rdi #endif #ifndef CONFIG_PREEMPT #define retint_kernel retint_restore_args #endif #ifdef CONFIG_PARAVIRT ENTRY(native_usergs_sysret64) swapgs sysretq ENDPROC(native_usergs_sysret64) #endif /* CONFIG_PARAVIRT */ .macro TRACE_IRQS_IRETQ offset=ARGOFFSET #ifdef CONFIG_TRACE_IRQFLAGS bt $9,EFLAGS-\offset(%rsp) /* interrupts off? */ jnc 1f TRACE_IRQS_ON 1: #endif .endm /* * When dynamic function tracer is enabled it will add a breakpoint * to all locations that it is about to modify, sync CPUs, update * all the code, sync CPUs, then remove the breakpoints. In this time * if lockdep is enabled, it might jump back into the debug handler * outside the updating of the IST protection. (TRACE_IRQS_ON/OFF). * * We need to change the IDT table before calling TRACE_IRQS_ON/OFF to * make sure the stack pointer does not get reset back to the top * of the debug stack, and instead just reuses the current stack. */ #if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_TRACE_IRQFLAGS) .macro TRACE_IRQS_OFF_DEBUG call debug_stack_set_zero TRACE_IRQS_OFF call debug_stack_reset .endm .macro TRACE_IRQS_ON_DEBUG call debug_stack_set_zero TRACE_IRQS_ON call debug_stack_reset .endm .macro TRACE_IRQS_IRETQ_DEBUG offset=ARGOFFSET bt $9,EFLAGS-\offset(%rsp) /* interrupts off? */ jnc 1f TRACE_IRQS_ON_DEBUG 1: .endm #else # define TRACE_IRQS_OFF_DEBUG TRACE_IRQS_OFF # define TRACE_IRQS_ON_DEBUG TRACE_IRQS_ON # define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ #endif /* * C code is not supposed to know about undefined top of stack. Every time * a C function with an pt_regs argument is called from the SYSCALL based * fast path FIXUP_TOP_OF_STACK is needed. * RESTORE_TOP_OF_STACK syncs the syscall state after any possible ptregs * manipulation. */ /* %rsp:at FRAMEEND */ .macro FIXUP_TOP_OF_STACK tmp offset=0 movq PER_CPU_VAR(old_rsp),\tmp movq \tmp,RSP+\offset(%rsp) movq $__USER_DS,SS+\offset(%rsp) movq $__USER_CS,CS+\offset(%rsp) movq $-1,RCX+\offset(%rsp) movq R11+\offset(%rsp),\tmp /* get eflags */ movq \tmp,EFLAGS+\offset(%rsp) .endm .macro RESTORE_TOP_OF_STACK tmp offset=0 movq RSP+\offset(%rsp),\tmp movq \tmp,PER_CPU_VAR(old_rsp) movq EFLAGS+\offset(%rsp),\tmp movq \tmp,R11+\offset(%rsp) .endm .macro FAKE_STACK_FRAME child_rip /* push in order ss, rsp, eflags, cs, rip */ xorl %eax, %eax pushq_cfi $__KERNEL_DS /* ss */ /*CFI_REL_OFFSET ss,0*/ pushq_cfi %rax /* rsp */ CFI_REL_OFFSET rsp,0 pushq_cfi $(X86_EFLAGS_IF|X86_EFLAGS_BIT1) /* eflags - interrupts on */ /*CFI_REL_OFFSET rflags,0*/ pushq_cfi $__KERNEL_CS /* cs */ /*CFI_REL_OFFSET cs,0*/ pushq_cfi \child_rip /* rip */ CFI_REL_OFFSET rip,0 pushq_cfi %rax /* orig rax */ .endm .macro UNFAKE_STACK_FRAME addq $8*6, %rsp CFI_ADJUST_CFA_OFFSET -(6*8) .endm /* * initial frame state for interrupts (and exceptions without error code) */ .macro EMPTY_FRAME start=1 offset=0 .if \start CFI_STARTPROC simple CFI_SIGNAL_FRAME CFI_DEF_CFA rsp,8+\offset .else CFI_DEF_CFA_OFFSET 8+\offset .endif .endm /* * initial frame state for interrupts (and exceptions without error code) */ .macro INTR_FRAME start=1 offset=0 EMPTY_FRAME \start, SS+8+\offset-RIP /*CFI_REL_OFFSET ss, SS+\offset-RIP*/ CFI_REL_OFFSET rsp, RSP+\offset-RIP /*CFI_REL_OFFSET rflags, EFLAGS+\offset-RIP*/ /*CFI_REL_OFFSET cs, CS+\offset-RIP*/ CFI_REL_OFFSET rip, RIP+\offset-RIP .endm /* * initial frame state for exceptions with error code (and interrupts * with vector already pushed) */ .macro XCPT_FRAME start=1 offset=0 INTR_FRAME \start, RIP+\offset-ORIG_RAX /*CFI_REL_OFFSET orig_rax, ORIG_RAX-ORIG_RAX*/ .endm /* * frame that enables calling into C. */ .macro PARTIAL_FRAME start=1 offset=0 XCPT_FRAME \start, ORIG_RAX+\offset-ARGOFFSET CFI_REL_OFFSET rdi, RDI+\offset-ARGOFFSET CFI_REL_OFFSET rsi, RSI+\offset-ARGOFFSET CFI_REL_OFFSET rdx, RDX+\offset-ARGOFFSET CFI_REL_OFFSET rcx, RCX+\offset-ARGOFFSET CFI_REL_OFFSET rax, RAX+\offset-ARGOFFSET CFI_REL_OFFSET r8, R8+\offset-ARGOFFSET CFI_REL_OFFSET r9, R9+\offset-ARGOFFSET CFI_REL_OFFSET r10, R10+\offset-ARGOFFSET CFI_REL_OFFSET r11, R11+\offset-ARGOFFSET .endm /* * frame that enables passing a complete pt_regs to a C function. */ .macro DEFAULT_FRAME start=1 offset=0 PARTIAL_FRAME \start, R11+\offset-R15 CFI_REL_OFFSET rbx, RBX+\offset CFI_REL_OFFSET rbp, RBP+\offset CFI_REL_OFFSET r12, R12+\offset CFI_REL_OFFSET r13, R13+\offset CFI_REL_OFFSET r14, R14+\offset CFI_REL_OFFSET r15, R15+\offset .endm /* save partial stack frame */ .macro SAVE_ARGS_IRQ cld /* start from rbp in pt_regs and jump over */ movq_cfi rdi, RDI-RBP movq_cfi rsi, RSI-RBP movq_cfi rdx, RDX-RBP movq_cfi rcx, RCX-RBP movq_cfi rax, RAX-RBP movq_cfi r8, R8-RBP movq_cfi r9, R9-RBP movq_cfi r10, R10-RBP movq_cfi r11, R11-RBP /* Save rbp so that we can unwind from get_irq_regs() */ movq_cfi rbp, 0 /* Save previous stack value */ movq %rsp, %rsi leaq -RBP(%rsp),%rdi /* arg1 for handler */ testl $3, CS-RBP(%rsi) je 1f SWAPGS /* * irq_count is used to check if a CPU is already on an interrupt stack * or not. While this is essentially redundant with preempt_count it is * a little cheaper to use a separate counter in the PDA (short of * moving irq_enter into assembly, which would be too much work) */ 1: incl PER_CPU_VAR(irq_count) cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp CFI_DEF_CFA_REGISTER rsi /* Store previous stack value */ pushq %rsi CFI_ESCAPE 0x0f /* DW_CFA_def_cfa_expression */, 6, \ 0x77 /* DW_OP_breg7 */, 0, \ 0x06 /* DW_OP_deref */, \ 0x08 /* DW_OP_const1u */, SS+8-RBP, \ 0x22 /* DW_OP_plus */ /* We entered an interrupt context - irqs are off: */ TRACE_IRQS_OFF .endm ENTRY(save_rest) PARTIAL_FRAME 1 REST_SKIP+8 movq 5*8+16(%rsp), %r11 /* save return address */ movq_cfi rbx, RBX+16 movq_cfi rbp, RBP+16 movq_cfi r12, R12+16 movq_cfi r13, R13+16 movq_cfi r14, R14+16 movq_cfi r15, R15+16 movq %r11, 8(%rsp) /* return address */ FIXUP_TOP_OF_STACK %r11, 16 ret CFI_ENDPROC END(save_rest) /* save complete stack frame */ .pushsection .kprobes.text, "ax" ENTRY(save_paranoid) XCPT_FRAME 1 RDI+8 cld movq_cfi rdi, RDI+8 movq_cfi rsi, RSI+8 movq_cfi rdx, RDX+8 movq_cfi rcx, RCX+8 movq_cfi rax, RAX+8 movq_cfi r8, R8+8 movq_cfi r9, R9+8 movq_cfi r10, R10+8 movq_cfi r11, R11+8 movq_cfi rbx, RBX+8 movq_cfi rbp, RBP+8 movq_cfi r12, R12+8 movq_cfi r13, R13+8 movq_cfi r14, R14+8 movq_cfi r15, R15+8 movl $1,%ebx movl $MSR_GS_BASE,%ecx rdmsr testl %edx,%edx js 1f /* negative -> in kernel */ SWAPGS xorl %ebx,%ebx 1: ret CFI_ENDPROC END(save_paranoid) .popsection /* * A newly forked process directly context switches into this address. * * rdi: prev task we switched from */ ENTRY(ret_from_fork) DEFAULT_FRAME LOCK ; btr $TIF_FORK,TI_flags(%r8) pushq_cfi $0x0002 popfq_cfi # reset kernel eflags call schedule_tail # rdi: 'prev' task parameter GET_THREAD_INFO(%rcx) RESTORE_REST testl $3, CS-ARGOFFSET(%rsp) # from kernel_thread? jz retint_restore_args testl $_TIF_IA32, TI_flags(%rcx) # 32-bit compat task needs IRET jnz int_ret_from_sys_call RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET jmp ret_from_sys_call # go to the SYSRET fastpath CFI_ENDPROC END(ret_from_fork) /* * System call entry. Up to 6 arguments in registers are supported. * * SYSCALL does not save anything on the stack and does not change the * stack pointer. */ /* * Register setup: * rax system call number * rdi arg0 * rcx return address for syscall/sysret, C arg3 * rsi arg1 * rdx arg2 * r10 arg3 (--> moved to rcx for C) * r8 arg4 * r9 arg5 * r11 eflags for syscall/sysret, temporary for C * r12-r15,rbp,rbx saved by C code, not touched. * * Interrupts are off on entry. * Only called from user space. * * XXX if we had a free scratch register we could save the RSP into the stack frame * and report it properly in ps. Unfortunately we haven't. * * When user can change the frames always force IRET. That is because * it deals with uncanonical addresses better. SYSRET has trouble * with them due to bugs in both AMD and Intel CPUs. */ ENTRY(system_call) CFI_STARTPROC simple CFI_SIGNAL_FRAME CFI_DEF_CFA rsp,KERNEL_STACK_OFFSET CFI_REGISTER rip,rcx /*CFI_REGISTER rflags,r11*/ SWAPGS_UNSAFE_STACK /* * A hypervisor implementation might want to use a label * after the swapgs, so that it can do the swapgs * for the guest and jump here on syscall. */ GLOBAL(system_call_after_swapgs) movq %rsp,PER_CPU_VAR(old_rsp) movq PER_CPU_VAR(kernel_stack),%rsp /* * No need to follow this irqs off/on section - it's straight * and short: */ ENABLE_INTERRUPTS(CLBR_NONE) SAVE_ARGS 8,0 movq %rax,ORIG_RAX-ARGOFFSET(%rsp) movq %rcx,RIP-ARGOFFSET(%rsp) CFI_REL_OFFSET rip,RIP-ARGOFFSET testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jnz tracesys system_call_fastpath: #if __SYSCALL_MASK == ~0 cmpq $__NR_syscall_max,%rax #else andl $__SYSCALL_MASK,%eax cmpl $__NR_syscall_max,%eax #endif ja badsys movq %r10,%rcx call *sys_call_table(,%rax,8) # XXX: rip relative movq %rax,RAX-ARGOFFSET(%rsp) /* * Syscall return path ending with SYSRET (fast path) * Has incomplete stack frame and undefined top of stack. */ ret_from_sys_call: movl $_TIF_ALLWORK_MASK,%edi /* edi: flagmask */ sysret_check: LOCKDEP_SYS_EXIT DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF movl TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET),%edx andl %edi,%edx jnz sysret_careful CFI_REMEMBER_STATE /* * sysretq will re-enable interrupts: */ TRACE_IRQS_ON movq RIP-ARGOFFSET(%rsp),%rcx CFI_REGISTER rip,rcx RESTORE_ARGS 1,-ARG_SKIP,0 /*CFI_REGISTER rflags,r11*/ movq PER_CPU_VAR(old_rsp), %rsp USERGS_SYSRET64 CFI_RESTORE_STATE /* Handle reschedules */ /* edx: work, edi: workmask */ sysret_careful: bt $TIF_NEED_RESCHED,%edx jnc sysret_signal TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_NONE) pushq_cfi %rdi call schedule popq_cfi %rdi jmp sysret_check /* Handle a signal */ sysret_signal: TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_NONE) #ifdef CONFIG_AUDITSYSCALL bt $TIF_SYSCALL_AUDIT,%edx jc sysret_audit #endif /* * We have a signal, or exit tracing or single-step. * These all wind up with the iret return path anyway, * so just join that path right now. */ FIXUP_TOP_OF_STACK %r11, -ARGOFFSET jmp int_check_syscall_exit_work badsys: movq $-ENOSYS,RAX-ARGOFFSET(%rsp) jmp ret_from_sys_call #ifdef CONFIG_AUDITSYSCALL /* * Fast path for syscall audit without full syscall trace. * We just call __audit_syscall_entry() directly, and then * jump back to the normal fast path. */ auditsys: movq %r10,%r9 /* 6th arg: 4th syscall arg */ movq %rdx,%r8 /* 5th arg: 3rd syscall arg */ movq %rsi,%rcx /* 4th arg: 2nd syscall arg */ movq %rdi,%rdx /* 3rd arg: 1st syscall arg */ movq %rax,%rsi /* 2nd arg: syscall number */ movl $AUDIT_ARCH_X86_64,%edi /* 1st arg: audit arch */ call __audit_syscall_entry LOAD_ARGS 0 /* reload call-clobbered registers */ jmp system_call_fastpath /* * Return fast path for syscall audit. Call __audit_syscall_exit() * directly and then jump back to the fast path with TIF_SYSCALL_AUDIT * masked off. */ sysret_audit: movq RAX-ARGOFFSET(%rsp),%rsi /* second arg, syscall return value */ cmpq $-MAX_ERRNO,%rsi /* is it < -MAX_ERRNO? */ setbe %al /* 1 if so, 0 if not */ movzbl %al,%edi /* zero-extend that into %edi */ call __audit_syscall_exit movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi jmp sysret_check #endif /* CONFIG_AUDITSYSCALL */ /* Do syscall tracing */ tracesys: #ifdef CONFIG_AUDITSYSCALL testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) jz auditsys #endif SAVE_REST movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */ FIXUP_TOP_OF_STACK %rdi movq %rsp,%rdi call syscall_trace_enter /* * Reload arg registers from stack in case ptrace changed them. * We don't reload %rax because syscall_trace_enter() returned * the value it wants us to use in the table lookup. */ LOAD_ARGS ARGOFFSET, 1 RESTORE_REST #if __SYSCALL_MASK == ~0 cmpq $__NR_syscall_max,%rax #else andl $__SYSCALL_MASK,%eax cmpl $__NR_syscall_max,%eax #endif ja int_ret_from_sys_call /* RAX(%rsp) set to -ENOSYS above */ movq %r10,%rcx /* fixup for C */ call *sys_call_table(,%rax,8) movq %rax,RAX-ARGOFFSET(%rsp) /* Use IRET because user could have changed frame */ /* * Syscall return path ending with IRET. * Has correct top of stack, but partial stack frame. */ GLOBAL(int_ret_from_sys_call) DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF movl $_TIF_ALLWORK_MASK,%edi /* edi: mask to check */ GLOBAL(int_with_check) LOCKDEP_SYS_EXIT_IRQ GET_THREAD_INFO(%rcx) movl TI_flags(%rcx),%edx andl %edi,%edx jnz int_careful andl $~TS_COMPAT,TI_status(%rcx) jmp retint_swapgs /* Either reschedule or signal or syscall exit tracking needed. */ /* First do a reschedule test. */ /* edx: work, edi: workmask */ int_careful: bt $TIF_NEED_RESCHED,%edx jnc int_very_careful TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_NONE) pushq_cfi %rdi call schedule popq_cfi %rdi DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF jmp int_with_check /* handle signals and tracing -- both require a full stack frame */ int_very_careful: TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_NONE) int_check_syscall_exit_work: SAVE_REST /* Check for syscall exit trace */ testl $_TIF_WORK_SYSCALL_EXIT,%edx jz int_signal pushq_cfi %rdi leaq 8(%rsp),%rdi # &ptregs -> arg1 call syscall_trace_leave popq_cfi %rdi andl $~(_TIF_WORK_SYSCALL_EXIT|_TIF_SYSCALL_EMU),%edi jmp int_restore_rest int_signal: testl $_TIF_DO_NOTIFY_MASK,%edx jz 1f movq %rsp,%rdi # &ptregs -> arg1 xorl %esi,%esi # oldset -> arg2 call do_notify_resume 1: movl $_TIF_WORK_MASK,%edi int_restore_rest: RESTORE_REST DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF jmp int_with_check CFI_ENDPROC END(system_call) /* * Certain special system calls that need to save a complete full stack frame. */ .macro PTREGSCALL label,func,arg ENTRY(\label) PARTIAL_FRAME 1 8 /* offset 8: return address */ subq $REST_SKIP, %rsp CFI_ADJUST_CFA_OFFSET REST_SKIP call save_rest DEFAULT_FRAME 0 8 /* offset 8: return address */ leaq 8(%rsp), \arg /* pt_regs pointer */ call \func jmp ptregscall_common CFI_ENDPROC END(\label) .endm PTREGSCALL stub_clone, sys_clone, %r8 PTREGSCALL stub_fork, sys_fork, %rdi PTREGSCALL stub_vfork, sys_vfork, %rdi PTREGSCALL stub_sigaltstack, sys_sigaltstack, %rdx PTREGSCALL stub_iopl, sys_iopl, %rsi ENTRY(ptregscall_common) DEFAULT_FRAME 1 8 /* offset 8: return address */ RESTORE_TOP_OF_STACK %r11, 8 movq_cfi_restore R15+8, r15 movq_cfi_restore R14+8, r14 movq_cfi_restore R13+8, r13 movq_cfi_restore R12+8, r12 movq_cfi_restore RBP+8, rbp movq_cfi_restore RBX+8, rbx ret $REST_SKIP /* pop extended registers */ CFI_ENDPROC END(ptregscall_common) ENTRY(stub_execve) CFI_STARTPROC addq $8, %rsp PARTIAL_FRAME 0 SAVE_REST FIXUP_TOP_OF_STACK %r11 movq %rsp, %rcx call sys_execve RESTORE_TOP_OF_STACK %r11 movq %rax,RAX(%rsp) RESTORE_REST jmp int_ret_from_sys_call CFI_ENDPROC END(stub_execve) /* * sigreturn is special because it needs to restore all registers on return. * This cannot be done with SYSRET, so use the IRET return path instead. */ ENTRY(stub_rt_sigreturn) CFI_STARTPROC addq $8, %rsp PARTIAL_FRAME 0 SAVE_REST movq %rsp,%rdi FIXUP_TOP_OF_STACK %r11 call sys_rt_sigreturn movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer RESTORE_REST jmp int_ret_from_sys_call CFI_ENDPROC END(stub_rt_sigreturn) #ifdef CONFIG_X86_X32_ABI PTREGSCALL stub_x32_sigaltstack, sys32_sigaltstack, %rdx ENTRY(stub_x32_rt_sigreturn) CFI_STARTPROC addq $8, %rsp PARTIAL_FRAME 0 SAVE_REST movq %rsp,%rdi FIXUP_TOP_OF_STACK %r11 call sys32_x32_rt_sigreturn movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer RESTORE_REST jmp int_ret_from_sys_call CFI_ENDPROC END(stub_x32_rt_sigreturn) ENTRY(stub_x32_execve) CFI_STARTPROC addq $8, %rsp PARTIAL_FRAME 0 SAVE_REST FIXUP_TOP_OF_STACK %r11 movq %rsp, %rcx call sys32_execve RESTORE_TOP_OF_STACK %r11 movq %rax,RAX(%rsp) RESTORE_REST jmp int_ret_from_sys_call CFI_ENDPROC END(stub_x32_execve) #endif /* * Build the entry stubs and pointer table with some assembler magic. * We pack 7 stubs into a single 32-byte chunk, which will fit in a * single cache line on all modern x86 implementations. */ .section .init.rodata,"a" ENTRY(interrupt) .section .entry.text .p2align 5 .p2align CONFIG_X86_L1_CACHE_SHIFT ENTRY(irq_entries_start) INTR_FRAME vector=FIRST_EXTERNAL_VECTOR .rept (NR_VECTORS-FIRST_EXTERNAL_VECTOR+6)/7 .balign 32 .rept 7 .if vector < NR_VECTORS .if vector <> FIRST_EXTERNAL_VECTOR CFI_ADJUST_CFA_OFFSET -8 .endif 1: pushq_cfi $(~vector+0x80) /* Note: always in signed byte range */ .if ((vector-FIRST_EXTERNAL_VECTOR)%7) <> 6 jmp 2f .endif .previous .quad 1b .section .entry.text vector=vector+1 .endif .endr 2: jmp common_interrupt .endr CFI_ENDPROC END(irq_entries_start) .previous END(interrupt) .previous /* * Interrupt entry/exit. * * Interrupt entry points save only callee clobbered registers in fast path. * * Entry runs with interrupts off. */ /* 0(%rsp): ~(interrupt number) */ .macro interrupt func /* reserve pt_regs for scratch regs and rbp */ subq $ORIG_RAX-RBP, %rsp CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP SAVE_ARGS_IRQ call \func .endm /* * Interrupt entry/exit should be protected against kprobes */ .pushsection .kprobes.text, "ax" /* * The interrupt stubs push (~vector+0x80) onto the stack and * then jump to common_interrupt. */ .p2align CONFIG_X86_L1_CACHE_SHIFT common_interrupt: XCPT_FRAME addq $-0x80,(%rsp) /* Adjust vector to [-256,-1] range */ interrupt do_IRQ /* 0(%rsp): old_rsp-ARGOFFSET */ ret_from_intr: DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF decl PER_CPU_VAR(irq_count) /* Restore saved previous stack */ popq %rsi CFI_DEF_CFA rsi,SS+8-RBP /* reg/off reset after def_cfa_expr */ leaq ARGOFFSET-RBP(%rsi), %rsp CFI_DEF_CFA_REGISTER rsp CFI_ADJUST_CFA_OFFSET RBP-ARGOFFSET exit_intr: GET_THREAD_INFO(%rcx) testl $3,CS-ARGOFFSET(%rsp) je retint_kernel /* Interrupt came from user space */ /* * Has a correct top of stack, but a partial stack frame * %rcx: thread info. Interrupts off. */ retint_with_reschedule: movl $_TIF_WORK_MASK,%edi retint_check: LOCKDEP_SYS_EXIT_IRQ movl TI_flags(%rcx),%edx andl %edi,%edx CFI_REMEMBER_STATE jnz retint_careful retint_swapgs: /* return to user-space */ /* * The iretq could re-enable interrupts: */ DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_IRETQ SWAPGS jmp restore_args retint_restore_args: /* return to kernel space */ DISABLE_INTERRUPTS(CLBR_ANY) /* * The iretq could re-enable interrupts: */ TRACE_IRQS_IRETQ restore_args: RESTORE_ARGS 1,8,1 irq_return: INTERRUPT_RETURN _ASM_EXTABLE(irq_return, bad_iret) #ifdef CONFIG_PARAVIRT ENTRY(native_iret) iretq _ASM_EXTABLE(native_iret, bad_iret) #endif .section .fixup,"ax" bad_iret: /* * The iret traps when the %cs or %ss being restored is bogus. * We've lost the original trap vector and error code. * #GPF is the most likely one to get for an invalid selector. * So pretend we completed the iret and took the #GPF in user mode. * * We are now running with the kernel GS after exception recovery. * But error_entry expects us to have user GS to match the user %cs, * so swap back. */ pushq $0 SWAPGS jmp general_protection .previous /* edi: workmask, edx: work */ retint_careful: CFI_RESTORE_STATE bt $TIF_NEED_RESCHED,%edx jnc retint_signal TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_NONE) pushq_cfi %rdi call schedule popq_cfi %rdi GET_THREAD_INFO(%rcx) DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF jmp retint_check retint_signal: testl $_TIF_DO_NOTIFY_MASK,%edx jz retint_swapgs TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_NONE) SAVE_REST movq $-1,ORIG_RAX(%rsp) xorl %esi,%esi # oldset movq %rsp,%rdi # &pt_regs call do_notify_resume RESTORE_REST DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF GET_THREAD_INFO(%rcx) jmp retint_with_reschedule #ifdef CONFIG_PREEMPT /* Returning to kernel space. Check if we need preemption */ /* rcx: threadinfo. interrupts off. */ ENTRY(retint_kernel) cmpl $0,TI_preempt_count(%rcx) jnz retint_restore_args bt $TIF_NEED_RESCHED,TI_flags(%rcx) jnc retint_restore_args bt $9,EFLAGS-ARGOFFSET(%rsp) /* interrupts off? */ jnc retint_restore_args call preempt_schedule_irq jmp exit_intr #endif CFI_ENDPROC END(common_interrupt) /* * End of kprobes section */ .popsection /* * APIC interrupts. */ .macro apicinterrupt num sym do_sym ENTRY(\sym) INTR_FRAME pushq_cfi $~(\num) .Lcommon_\sym: interrupt \do_sym jmp ret_from_intr CFI_ENDPROC END(\sym) .endm #ifdef CONFIG_SMP apicinterrupt IRQ_MOVE_CLEANUP_VECTOR \ irq_move_cleanup_interrupt smp_irq_move_cleanup_interrupt apicinterrupt REBOOT_VECTOR \ reboot_interrupt smp_reboot_interrupt #endif #ifdef CONFIG_X86_UV apicinterrupt UV_BAU_MESSAGE \ uv_bau_message_intr1 uv_bau_message_interrupt #endif apicinterrupt LOCAL_TIMER_VECTOR \ apic_timer_interrupt smp_apic_timer_interrupt apicinterrupt X86_PLATFORM_IPI_VECTOR \ x86_platform_ipi smp_x86_platform_ipi apicinterrupt THRESHOLD_APIC_VECTOR \ threshold_interrupt smp_threshold_interrupt apicinterrupt THERMAL_APIC_VECTOR \ thermal_interrupt smp_thermal_interrupt #ifdef CONFIG_SMP apicinterrupt CALL_FUNCTION_SINGLE_VECTOR \ call_function_single_interrupt smp_call_function_single_interrupt apicinterrupt CALL_FUNCTION_VECTOR \ call_function_interrupt smp_call_function_interrupt apicinterrupt RESCHEDULE_VECTOR \ reschedule_interrupt smp_reschedule_interrupt #endif apicinterrupt ERROR_APIC_VECTOR \ error_interrupt smp_error_interrupt apicinterrupt SPURIOUS_APIC_VECTOR \ spurious_interrupt smp_spurious_interrupt #ifdef CONFIG_IRQ_WORK apicinterrupt IRQ_WORK_VECTOR \ irq_work_interrupt smp_irq_work_interrupt #endif /* * Exception entry points. */ .macro zeroentry sym do_sym ENTRY(\sym) INTR_FRAME PARAVIRT_ADJUST_EXCEPTION_FRAME pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */ subq $ORIG_RAX-R15, %rsp CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15 call error_entry DEFAULT_FRAME 0 movq %rsp,%rdi /* pt_regs pointer */ xorl %esi,%esi /* no error code */ call \do_sym jmp error_exit /* %ebx: no swapgs flag */ CFI_ENDPROC END(\sym) .endm .macro paranoidzeroentry sym do_sym ENTRY(\sym) INTR_FRAME PARAVIRT_ADJUST_EXCEPTION_FRAME pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */ subq $ORIG_RAX-R15, %rsp CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15 call save_paranoid TRACE_IRQS_OFF movq %rsp,%rdi /* pt_regs pointer */ xorl %esi,%esi /* no error code */ call \do_sym jmp paranoid_exit /* %ebx: no swapgs flag */ CFI_ENDPROC END(\sym) .endm #define INIT_TSS_IST(x) PER_CPU_VAR(init_tss) + (TSS_ist + ((x) - 1) * 8) .macro paranoidzeroentry_ist sym do_sym ist ENTRY(\sym) INTR_FRAME PARAVIRT_ADJUST_EXCEPTION_FRAME pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */ subq $ORIG_RAX-R15, %rsp CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15 call save_paranoid TRACE_IRQS_OFF_DEBUG movq %rsp,%rdi /* pt_regs pointer */ xorl %esi,%esi /* no error code */ subq $EXCEPTION_STKSZ, INIT_TSS_IST(\ist) call \do_sym addq $EXCEPTION_STKSZ, INIT_TSS_IST(\ist) jmp paranoid_exit /* %ebx: no swapgs flag */ CFI_ENDPROC END(\sym) .endm .macro errorentry sym do_sym ENTRY(\sym) XCPT_FRAME PARAVIRT_ADJUST_EXCEPTION_FRAME subq $ORIG_RAX-R15, %rsp CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15 call error_entry DEFAULT_FRAME 0 movq %rsp,%rdi /* pt_regs pointer */ movq ORIG_RAX(%rsp),%rsi /* get error code */ movq $-1,ORIG_RAX(%rsp) /* no syscall to restart */ call \do_sym jmp error_exit /* %ebx: no swapgs flag */ CFI_ENDPROC END(\sym) .endm /* error code is on the stack already */ .macro paranoiderrorentry sym do_sym ENTRY(\sym) XCPT_FRAME PARAVIRT_ADJUST_EXCEPTION_FRAME subq $ORIG_RAX-R15, %rsp CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15 call save_paranoid DEFAULT_FRAME 0 TRACE_IRQS_OFF movq %rsp,%rdi /* pt_regs pointer */ movq ORIG_RAX(%rsp),%rsi /* get error code */ movq $-1,ORIG_RAX(%rsp) /* no syscall to restart */ call \do_sym jmp paranoid_exit /* %ebx: no swapgs flag */ CFI_ENDPROC END(\sym) .endm zeroentry divide_error do_divide_error zeroentry overflow do_overflow zeroentry bounds do_bounds zeroentry invalid_op do_invalid_op zeroentry device_not_available do_device_not_available paranoiderrorentry double_fault do_double_fault zeroentry coprocessor_segment_overrun do_coprocessor_segment_overrun errorentry invalid_TSS do_invalid_TSS errorentry segment_not_present do_segment_not_present zeroentry spurious_interrupt_bug do_spurious_interrupt_bug zeroentry coprocessor_error do_coprocessor_error errorentry alignment_check do_alignment_check zeroentry simd_coprocessor_error do_simd_coprocessor_error /* Reload gs selector with exception handling */ /* edi: new selector */ ENTRY(native_load_gs_index) CFI_STARTPROC pushfq_cfi DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI) SWAPGS gs_change: movl %edi,%gs 2: mfence /* workaround */ SWAPGS popfq_cfi ret CFI_ENDPROC END(native_load_gs_index) _ASM_EXTABLE(gs_change,bad_gs) .section .fixup,"ax" /* running with kernelgs */ bad_gs: SWAPGS /* switch back to user gs */ xorl %eax,%eax movl %eax,%gs jmp 2b .previous ENTRY(kernel_thread_helper) pushq $0 # fake return address CFI_STARTPROC /* * Here we are in the child and the registers are set as they were * at kernel_thread() invocation in the parent. */ call *%rsi # exit mov %eax, %edi call do_exit ud2 # padding for call trace CFI_ENDPROC END(kernel_thread_helper) /* * execve(). This function needs to use IRET, not SYSRET, to set up all state properly. * * C extern interface: * extern long execve(const char *name, char **argv, char **envp) * * asm input arguments: * rdi: name, rsi: argv, rdx: envp * * We want to fallback into: * extern long sys_execve(const char *name, char **argv,char **envp, struct pt_regs *regs) * * do_sys_execve asm fallback arguments: * rdi: name, rsi: argv, rdx: envp, rcx: fake frame on the stack */ ENTRY(kernel_execve) CFI_STARTPROC FAKE_STACK_FRAME $0 SAVE_ALL movq %rsp,%rcx call sys_execve movq %rax, RAX(%rsp) RESTORE_REST testq %rax,%rax je int_ret_from_sys_call RESTORE_ARGS UNFAKE_STACK_FRAME ret CFI_ENDPROC END(kernel_execve) /* Call softirq on interrupt stack. Interrupts are off. */ ENTRY(call_softirq) CFI_STARTPROC pushq_cfi %rbp CFI_REL_OFFSET rbp,0 mov %rsp,%rbp CFI_DEF_CFA_REGISTER rbp incl PER_CPU_VAR(irq_count) cmove PER_CPU_VAR(irq_stack_ptr),%rsp push %rbp # backlink for old unwinder call __do_softirq leaveq CFI_RESTORE rbp CFI_DEF_CFA_REGISTER rsp CFI_ADJUST_CFA_OFFSET -8 decl PER_CPU_VAR(irq_count) ret CFI_ENDPROC END(call_softirq) #ifdef CONFIG_XEN zeroentry xen_hypervisor_callback xen_do_hypervisor_callback /* * A note on the "critical region" in our callback handler. * We want to avoid stacking callback handlers due to events occurring * during handling of the last event. To do this, we keep events disabled * until we've done all processing. HOWEVER, we must enable events before * popping the stack frame (can't be done atomically) and so it would still * be possible to get enough handler activations to overflow the stack. * Although unlikely, bugs of that kind are hard to track down, so we'd * like to avoid the possibility. * So, on entry to the handler we detect whether we interrupted an * existing activation in its critical region -- if so, we pop the current * activation and restart the handler using the previous one. */ ENTRY(xen_do_hypervisor_callback) # do_hypervisor_callback(struct *pt_regs) CFI_STARTPROC /* * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will * see the correct pointer to the pt_regs */ movq %rdi, %rsp # we don't return, adjust the stack frame CFI_ENDPROC DEFAULT_FRAME 11: incl PER_CPU_VAR(irq_count) movq %rsp,%rbp CFI_DEF_CFA_REGISTER rbp cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp pushq %rbp # backlink for old unwinder call xen_evtchn_do_upcall popq %rsp CFI_DEF_CFA_REGISTER rsp decl PER_CPU_VAR(irq_count) jmp error_exit CFI_ENDPROC END(xen_do_hypervisor_callback) /* * Hypervisor uses this for application faults while it executes. * We get here for two reasons: * 1. Fault while reloading DS, ES, FS or GS * 2. Fault while executing IRET * Category 1 we do not need to fix up as Xen has already reloaded all segment * registers that could be reloaded and zeroed the others. * Category 2 we fix up by killing the current process. We cannot use the * normal Linux return path in this case because if we use the IRET hypercall * to pop the stack frame we end up in an infinite loop of failsafe callbacks. * We distinguish between categories by comparing each saved segment register * with its current contents: any discrepancy means we in category 1. */ ENTRY(xen_failsafe_callback) INTR_FRAME 1 (6*8) /*CFI_REL_OFFSET gs,GS*/ /*CFI_REL_OFFSET fs,FS*/ /*CFI_REL_OFFSET es,ES*/ /*CFI_REL_OFFSET ds,DS*/ CFI_REL_OFFSET r11,8 CFI_REL_OFFSET rcx,0 movw %ds,%cx cmpw %cx,0x10(%rsp) CFI_REMEMBER_STATE jne 1f movw %es,%cx cmpw %cx,0x18(%rsp) jne 1f movw %fs,%cx cmpw %cx,0x20(%rsp) jne 1f movw %gs,%cx cmpw %cx,0x28(%rsp) jne 1f /* All segments match their saved values => Category 2 (Bad IRET). */ movq (%rsp),%rcx CFI_RESTORE rcx movq 8(%rsp),%r11 CFI_RESTORE r11 addq $0x30,%rsp CFI_ADJUST_CFA_OFFSET -0x30 pushq_cfi $0 /* RIP */ pushq_cfi %r11 pushq_cfi %rcx jmp general_protection CFI_RESTORE_STATE 1: /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */ movq (%rsp),%rcx CFI_RESTORE rcx movq 8(%rsp),%r11 CFI_RESTORE r11 addq $0x30,%rsp CFI_ADJUST_CFA_OFFSET -0x30 pushq_cfi $0 SAVE_ALL jmp error_exit CFI_ENDPROC END(xen_failsafe_callback) apicinterrupt XEN_HVM_EVTCHN_CALLBACK \ xen_hvm_callback_vector xen_evtchn_do_upcall #endif /* CONFIG_XEN */ /* * Some functions should be protected against kprobes */ .pushsection .kprobes.text, "ax" paranoidzeroentry_ist debug do_debug DEBUG_STACK paranoidzeroentry_ist int3 do_int3 DEBUG_STACK paranoiderrorentry stack_segment do_stack_segment #ifdef CONFIG_XEN zeroentry xen_debug do_debug zeroentry xen_int3 do_int3 errorentry xen_stack_segment do_stack_segment #endif errorentry general_protection do_general_protection errorentry page_fault do_page_fault #ifdef CONFIG_KVM_GUEST errorentry async_page_fault do_async_page_fault #endif #ifdef CONFIG_X86_MCE paranoidzeroentry machine_check *machine_check_vector(%rip) #endif /* * "Paranoid" exit path from exception stack. * Paranoid because this is used by NMIs and cannot take * any kernel state for granted. * We don't do kernel preemption checks here, because only * NMI should be common and it does not enable IRQs and * cannot get reschedule ticks. * * "trace" is 0 for the NMI handler only, because irq-tracing * is fundamentally NMI-unsafe. (we cannot change the soft and * hard flags at once, atomically) */ /* ebx: no swapgs flag */ ENTRY(paranoid_exit) DEFAULT_FRAME DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF_DEBUG testl %ebx,%ebx /* swapgs needed? */ jnz paranoid_restore testl $3,CS(%rsp) jnz paranoid_userspace paranoid_swapgs: TRACE_IRQS_IRETQ 0 SWAPGS_UNSAFE_STACK RESTORE_ALL 8 jmp irq_return paranoid_restore: TRACE_IRQS_IRETQ_DEBUG 0 RESTORE_ALL 8 jmp irq_return paranoid_userspace: GET_THREAD_INFO(%rcx) movl TI_flags(%rcx),%ebx andl $_TIF_WORK_MASK,%ebx jz paranoid_swapgs movq %rsp,%rdi /* &pt_regs */ call sync_regs movq %rax,%rsp /* switch stack for scheduling */ testl $_TIF_NEED_RESCHED,%ebx jnz paranoid_schedule movl %ebx,%edx /* arg3: thread flags */ TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_NONE) xorl %esi,%esi /* arg2: oldset */ movq %rsp,%rdi /* arg1: &pt_regs */ call do_notify_resume DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF jmp paranoid_userspace paranoid_schedule: TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_ANY) call schedule DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_OFF jmp paranoid_userspace CFI_ENDPROC END(paranoid_exit) /* * Exception entry point. This expects an error code/orig_rax on the stack. * returns in "no swapgs flag" in %ebx. */ ENTRY(error_entry) XCPT_FRAME CFI_ADJUST_CFA_OFFSET 15*8 /* oldrax contains error code */ cld movq_cfi rdi, RDI+8 movq_cfi rsi, RSI+8 movq_cfi rdx, RDX+8 movq_cfi rcx, RCX+8 movq_cfi rax, RAX+8 movq_cfi r8, R8+8 movq_cfi r9, R9+8 movq_cfi r10, R10+8 movq_cfi r11, R11+8 movq_cfi rbx, RBX+8 movq_cfi rbp, RBP+8 movq_cfi r12, R12+8 movq_cfi r13, R13+8 movq_cfi r14, R14+8 movq_cfi r15, R15+8 xorl %ebx,%ebx testl $3,CS+8(%rsp) je error_kernelspace error_swapgs: SWAPGS error_sti: TRACE_IRQS_OFF ret /* * There are two places in the kernel that can potentially fault with * usergs. Handle them here. The exception handlers after iret run with * kernel gs again, so don't set the user space flag. B stepping K8s * sometimes report an truncated RIP for IRET exceptions returning to * compat mode. Check for these here too. */ error_kernelspace: incl %ebx leaq irq_return(%rip),%rcx cmpq %rcx,RIP+8(%rsp) je error_swapgs movl %ecx,%eax /* zero extend */ cmpq %rax,RIP+8(%rsp) je bstep_iret cmpq $gs_change,RIP+8(%rsp) je error_swapgs jmp error_sti bstep_iret: /* Fix truncated RIP */ movq %rcx,RIP+8(%rsp) jmp error_swapgs CFI_ENDPROC END(error_entry) /* ebx: no swapgs flag (1: don't need swapgs, 0: need it) */ ENTRY(error_exit) DEFAULT_FRAME movl %ebx,%eax RESTORE_REST DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF GET_THREAD_INFO(%rcx) testl %eax,%eax jne retint_kernel LOCKDEP_SYS_EXIT_IRQ movl TI_flags(%rcx),%edx movl $_TIF_WORK_MASK,%edi andl %edi,%edx jnz retint_careful jmp retint_swapgs CFI_ENDPROC END(error_exit) /* * Test if a given stack is an NMI stack or not. */ .macro test_in_nmi reg stack nmi_ret normal_ret cmpq %\reg, \stack ja \normal_ret subq $EXCEPTION_STKSZ, %\reg cmpq %\reg, \stack jb \normal_ret jmp \nmi_ret .endm /* runs on exception stack */ ENTRY(nmi) INTR_FRAME PARAVIRT_ADJUST_EXCEPTION_FRAME /* * We allow breakpoints in NMIs. If a breakpoint occurs, then * the iretq it performs will take us out of NMI context. * This means that we can have nested NMIs where the next * NMI is using the top of the stack of the previous NMI. We * can't let it execute because the nested NMI will corrupt the * stack of the previous NMI. NMI handlers are not re-entrant * anyway. * * To handle this case we do the following: * Check the a special location on the stack that contains * a variable that is set when NMIs are executing. * The interrupted task's stack is also checked to see if it * is an NMI stack. * If the variable is not set and the stack is not the NMI * stack then: * o Set the special variable on the stack * o Copy the interrupt frame into a "saved" location on the stack * o Copy the interrupt frame into a "copy" location on the stack * o Continue processing the NMI * If the variable is set or the previous stack is the NMI stack: * o Modify the "copy" location to jump to the repeate_nmi * o return back to the first NMI * * Now on exit of the first NMI, we first clear the stack variable * The NMI stack will tell any nested NMIs at that point that it is * nested. Then we pop the stack normally with iret, and if there was * a nested NMI that updated the copy interrupt stack frame, a * jump will be made to the repeat_nmi code that will handle the second * NMI. */ /* Use %rdx as out temp variable throughout */ pushq_cfi %rdx CFI_REL_OFFSET rdx, 0 /* * If %cs was not the kernel segment, then the NMI triggered in user * space, which means it is definitely not nested. */ cmpl $__KERNEL_CS, 16(%rsp) jne first_nmi /* * Check the special variable on the stack to see if NMIs are * executing. */ cmpl $1, -8(%rsp) je nested_nmi /* * Now test if the previous stack was an NMI stack. * We need the double check. We check the NMI stack to satisfy the * race when the first NMI clears the variable before returning. * We check the variable because the first NMI could be in a * breakpoint routine using a breakpoint stack. */ lea 6*8(%rsp), %rdx test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi CFI_REMEMBER_STATE nested_nmi: /* * Do nothing if we interrupted the fixup in repeat_nmi. * It's about to repeat the NMI handler, so we are fine * with ignoring this one. */ movq $repeat_nmi, %rdx cmpq 8(%rsp), %rdx ja 1f movq $end_repeat_nmi, %rdx cmpq 8(%rsp), %rdx ja nested_nmi_out 1: /* Set up the interrupted NMIs stack to jump to repeat_nmi */ leaq -6*8(%rsp), %rdx movq %rdx, %rsp CFI_ADJUST_CFA_OFFSET 6*8 pushq_cfi $__KERNEL_DS pushq_cfi %rdx pushfq_cfi pushq_cfi $__KERNEL_CS pushq_cfi $repeat_nmi /* Put stack back */ addq $(11*8), %rsp CFI_ADJUST_CFA_OFFSET -11*8 nested_nmi_out: popq_cfi %rdx CFI_RESTORE rdx /* No need to check faults here */ INTERRUPT_RETURN CFI_RESTORE_STATE first_nmi: /* * Because nested NMIs will use the pushed location that we * stored in rdx, we must keep that space available. * Here's what our stack frame will look like: * +-------------------------+ * | original SS | * | original Return RSP | * | original RFLAGS | * | original CS | * | original RIP | * +-------------------------+ * | temp storage for rdx | * +-------------------------+ * | NMI executing variable | * +-------------------------+ * | Saved SS | * | Saved Return RSP | * | Saved RFLAGS | * | Saved CS | * | Saved RIP | * +-------------------------+ * | copied SS | * | copied Return RSP | * | copied RFLAGS | * | copied CS | * | copied RIP | * +-------------------------+ * | pt_regs | * +-------------------------+ * * The saved stack frame is used to fix up the copied stack frame * that a nested NMI may change to make the interrupted NMI iret jump * to the repeat_nmi. The original stack frame and the temp storage * is also used by nested NMIs and can not be trusted on exit. */ /* Do not pop rdx, nested NMIs will corrupt that part of the stack */ movq (%rsp), %rdx CFI_RESTORE rdx /* Set the NMI executing variable on the stack. */ pushq_cfi $1 /* Copy the stack frame to the Saved frame */ .rept 5 pushq_cfi 6*8(%rsp) .endr CFI_DEF_CFA_OFFSET SS+8-RIP /* Everything up to here is safe from nested NMIs */ /* * If there was a nested NMI, the first NMI's iret will return * here. But NMIs are still enabled and we can take another * nested NMI. The nested NMI checks the interrupted RIP to see * if it is between repeat_nmi and end_repeat_nmi, and if so * it will just return, as we are about to repeat an NMI anyway. * This makes it safe to copy to the stack frame that a nested * NMI will update. */ repeat_nmi: /* * Update the stack variable to say we are still in NMI (the update * is benign for the non-repeat case, where 1 was pushed just above * to this very stack slot). */ movq $1, 5*8(%rsp) /* Make another copy, this one may be modified by nested NMIs */ .rept 5 pushq_cfi 4*8(%rsp) .endr CFI_DEF_CFA_OFFSET SS+8-RIP end_repeat_nmi: /* * Everything below this point can be preempted by a nested * NMI if the first NMI took an exception and reset our iret stack * so that we repeat another NMI. */ pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */ subq $ORIG_RAX-R15, %rsp CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15 /* * Use save_paranoid to handle SWAPGS, but no need to use paranoid_exit * as we should not be calling schedule in NMI context. * Even with normal interrupts enabled. An NMI should not be * setting NEED_RESCHED or anything that normal interrupts and * exceptions might do. */ call save_paranoid DEFAULT_FRAME 0 /* * Save off the CR2 register. If we take a page fault in the NMI then * it could corrupt the CR2 value. If the NMI preempts a page fault * handler before it was able to read the CR2 register, and then the * NMI itself takes a page fault, the page fault that was preempted * will read the information from the NMI page fault and not the * origin fault. Save it off and restore it if it changes. * Use the r12 callee-saved register. */ movq %cr2, %r12 /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */ movq %rsp,%rdi movq $-1,%rsi call do_nmi /* Did the NMI take a page fault? Restore cr2 if it did */ movq %cr2, %rcx cmpq %rcx, %r12 je 1f movq %r12, %cr2 1: testl %ebx,%ebx /* swapgs needed? */ jnz nmi_restore nmi_swapgs: SWAPGS_UNSAFE_STACK nmi_restore: RESTORE_ALL 8 /* Clear the NMI executing stack variable */ movq $0, 10*8(%rsp) jmp irq_return CFI_ENDPROC END(nmi) ENTRY(ignore_sysret) CFI_STARTPROC mov $-ENOSYS,%eax sysret CFI_ENDPROC END(ignore_sysret) /* * End of kprobes section */ .popsection