/* * linux/arch/i386/entry.S * * Copyright (C) 1991, 1992 Linus Torvalds */ /* * entry.S contains the system-call and fault low-level handling routines. * This also contains the timer-interrupt handler, as well as all interrupts * and faults that can result in a task-switch. * * NOTE: This code handles signal-recognition, which happens every time * after a timer-interrupt and after each system call. * * I changed all the .align's to 4 (16 byte alignment), as that's faster * on a 486. * * Stack layout in 'ret_from_system_call': * ptrace needs to have all regs on the stack. * if the order here is changed, it needs to be * updated in fork.c:copy_process, signal.c:do_signal, * ptrace.c and ptrace.h * * 0(%esp) - %ebx * 4(%esp) - %ecx * 8(%esp) - %edx * C(%esp) - %esi * 10(%esp) - %edi * 14(%esp) - %ebp * 18(%esp) - %eax * 1C(%esp) - %ds * 20(%esp) - %es * 24(%esp) - orig_eax * 28(%esp) - %eip * 2C(%esp) - %cs * 30(%esp) - %eflags * 34(%esp) - %oldesp * 38(%esp) - %oldss * * "current" is in register %ebx during any slow entries. */ #include #include #include #include #include #include #include #include #include "irq_vectors.h" #define nr_syscalls ((syscall_table_size)/4) EBX = 0x00 ECX = 0x04 EDX = 0x08 ESI = 0x0C EDI = 0x10 EBP = 0x14 EAX = 0x18 DS = 0x1C ES = 0x20 ORIG_EAX = 0x24 EIP = 0x28 CS = 0x2C EFLAGS = 0x30 OLDESP = 0x34 OLDSS = 0x38 CF_MASK = 0x00000001 TF_MASK = 0x00000100 IF_MASK = 0x00000200 DF_MASK = 0x00000400 NT_MASK = 0x00004000 VM_MASK = 0x00020000 #ifdef CONFIG_PREEMPT #define preempt_stop cli #else #define preempt_stop #define resume_kernel restore_nocheck #endif #define SAVE_ALL \ cld; \ pushl %es; \ pushl %ds; \ pushl %eax; \ pushl %ebp; \ pushl %edi; \ pushl %esi; \ pushl %edx; \ pushl %ecx; \ pushl %ebx; \ movl $(__USER_DS), %edx; \ movl %edx, %ds; \ movl %edx, %es; #define RESTORE_INT_REGS \ popl %ebx; \ popl %ecx; \ popl %edx; \ popl %esi; \ popl %edi; \ popl %ebp; \ popl %eax #define RESTORE_REGS \ RESTORE_INT_REGS; \ 1: popl %ds; \ 2: popl %es; \ .section .fixup,"ax"; \ 3: movl $0,(%esp); \ jmp 1b; \ 4: movl $0,(%esp); \ jmp 2b; \ .previous; \ .section __ex_table,"a";\ .align 4; \ .long 1b,3b; \ .long 2b,4b; \ .previous ENTRY(ret_from_fork) pushl %eax call schedule_tail GET_THREAD_INFO(%ebp) popl %eax jmp syscall_exit /* * Return to user mode is not as complex as all this looks, * but we want the default path for a system call return to * go as quickly as possible which is why some of this is * less clear than it otherwise should be. */ # userspace resumption stub bypassing syscall exit tracing ALIGN ret_from_exception: preempt_stop ret_from_intr: GET_THREAD_INFO(%ebp) movl EFLAGS(%esp), %eax # mix EFLAGS and CS movb CS(%esp), %al testl $(VM_MASK | 3), %eax jz resume_kernel ENTRY(resume_userspace) cli # make sure we don't miss an interrupt # setting need_resched or sigpending # between sampling and the iret movl TI_flags(%ebp), %ecx andl $_TIF_WORK_MASK, %ecx # is there any work to be done on # int/exception return? jne work_pending jmp restore_all #ifdef CONFIG_PREEMPT ENTRY(resume_kernel) cli cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ? jnz restore_nocheck need_resched: movl TI_flags(%ebp), %ecx # need_resched set ? testb $_TIF_NEED_RESCHED, %cl jz restore_all testl $IF_MASK,EFLAGS(%esp) # interrupts off (exception path) ? jz restore_all call preempt_schedule_irq jmp need_resched #endif /* SYSENTER_RETURN points to after the "sysenter" instruction in the vsyscall page. See vsyscall-sysentry.S, which defines the symbol. */ # sysenter call handler stub ENTRY(sysenter_entry) movl TSS_sysenter_esp0(%esp),%esp sysenter_past_esp: sti pushl $(__USER_DS) pushl %ebp pushfl pushl $(__USER_CS) pushl $SYSENTER_RETURN /* * Load the potential sixth argument from user stack. * Careful about security. */ cmpl $__PAGE_OFFSET-3,%ebp jae syscall_fault 1: movl (%ebp),%ebp .section __ex_table,"a" .align 4 .long 1b,syscall_fault .previous pushl %eax SAVE_ALL GET_THREAD_INFO(%ebp) /* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */ testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp) jnz syscall_trace_entry cmpl $(nr_syscalls), %eax jae syscall_badsys call *sys_call_table(,%eax,4) movl %eax,EAX(%esp) cli movl TI_flags(%ebp), %ecx testw $_TIF_ALLWORK_MASK, %cx jne syscall_exit_work /* if something modifies registers it must also disable sysexit */ movl EIP(%esp), %edx movl OLDESP(%esp), %ecx xorl %ebp,%ebp sti sysexit # system call handler stub ENTRY(system_call) pushl %eax # save orig_eax SAVE_ALL GET_THREAD_INFO(%ebp) # system call tracing in operation / emulation /* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */ testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp) jnz syscall_trace_entry cmpl $(nr_syscalls), %eax jae syscall_badsys syscall_call: call *sys_call_table(,%eax,4) movl %eax,EAX(%esp) # store the return value syscall_exit: cli # make sure we don't miss an interrupt # setting need_resched or sigpending # between sampling and the iret movl TI_flags(%ebp), %ecx testw $_TIF_ALLWORK_MASK, %cx # current->work jne syscall_exit_work restore_all: movl EFLAGS(%esp), %eax # mix EFLAGS, SS and CS # Warning: OLDSS(%esp) contains the wrong/random values if we # are returning to the kernel. # See comments in process.c:copy_thread() for details. movb OLDSS(%esp), %ah movb CS(%esp), %al andl $(VM_MASK | (4 << 8) | 3), %eax cmpl $((4 << 8) | 3), %eax je ldt_ss # returning to user-space with LDT SS restore_nocheck: RESTORE_REGS addl $4, %esp 1: iret .section .fixup,"ax" iret_exc: sti pushl $0 # no error code pushl $do_iret_error jmp error_code .previous .section __ex_table,"a" .align 4 .long 1b,iret_exc .previous ldt_ss: larl OLDSS(%esp), %eax jnz restore_nocheck testl $0x00400000, %eax # returning to 32bit stack? jnz restore_nocheck # allright, normal return /* If returning to userspace with 16bit stack, * try to fix the higher word of ESP, as the CPU * won't restore it. * This is an "official" bug of all the x86-compatible * CPUs, which we can try to work around to make * dosemu and wine happy. */ subl $8, %esp # reserve space for switch16 pointer cli movl %esp, %eax /* Set up the 16bit stack frame with switch32 pointer on top, * and a switch16 pointer on top of the current frame. */ call setup_x86_bogus_stack RESTORE_REGS lss 20+4(%esp), %esp # switch to 16bit stack 1: iret .section __ex_table,"a" .align 4 .long 1b,iret_exc .previous # perform work that needs to be done immediately before resumption ALIGN work_pending: testb $_TIF_NEED_RESCHED, %cl jz work_notifysig work_resched: call schedule cli # make sure we don't miss an interrupt # setting need_resched or sigpending # between sampling and the iret movl TI_flags(%ebp), %ecx andl $_TIF_WORK_MASK, %ecx # is there any work to be done other # than syscall tracing? jz restore_all testb $_TIF_NEED_RESCHED, %cl jnz work_resched work_notifysig: # deal with pending signals and # notify-resume requests testl $VM_MASK, EFLAGS(%esp) movl %esp, %eax jne work_notifysig_v86 # returning to kernel-space or # vm86-space xorl %edx, %edx call do_notify_resume jmp restore_all ALIGN work_notifysig_v86: pushl %ecx # save ti_flags for do_notify_resume call save_v86_state # %eax contains pt_regs pointer popl %ecx movl %eax, %esp xorl %edx, %edx call do_notify_resume jmp restore_all # perform syscall exit tracing ALIGN syscall_trace_entry: movl $-ENOSYS,EAX(%esp) movl %esp, %eax xorl %edx,%edx call do_syscall_trace cmpl $0, %eax jne resume_userspace # ret != 0 -> running under PTRACE_SYSEMU, # so must skip actual syscall movl ORIG_EAX(%esp), %eax cmpl $(nr_syscalls), %eax jnae syscall_call jmp syscall_exit # perform syscall exit tracing ALIGN syscall_exit_work: testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP), %cl jz work_pending sti # could let do_syscall_trace() call # schedule() instead movl %esp, %eax movl $1, %edx call do_syscall_trace jmp resume_userspace ALIGN syscall_fault: pushl %eax # save orig_eax SAVE_ALL GET_THREAD_INFO(%ebp) movl $-EFAULT,EAX(%esp) jmp resume_userspace ALIGN syscall_badsys: movl $-ENOSYS,EAX(%esp) jmp resume_userspace #define FIXUP_ESPFIX_STACK \ movl %esp, %eax; \ /* switch to 32bit stack using the pointer on top of 16bit stack */ \ lss %ss:CPU_16BIT_STACK_SIZE-8, %esp; \ /* copy data from 16bit stack to 32bit stack */ \ call fixup_x86_bogus_stack; \ /* put ESP to the proper location */ \ movl %eax, %esp; #define UNWIND_ESPFIX_STACK \ pushl %eax; \ movl %ss, %eax; \ /* see if on 16bit stack */ \ cmpw $__ESPFIX_SS, %ax; \ jne 28f; \ movl $__KERNEL_DS, %edx; \ movl %edx, %ds; \ movl %edx, %es; \ /* switch to 32bit stack */ \ FIXUP_ESPFIX_STACK \ 28: popl %eax; /* * Build the entry stubs and pointer table with * some assembler magic. */ .data ENTRY(interrupt) .text vector=0 ENTRY(irq_entries_start) .rept NR_IRQS ALIGN 1: pushl $vector-256 jmp common_interrupt .data .long 1b .text vector=vector+1 .endr ALIGN common_interrupt: SAVE_ALL movl %esp,%eax call do_IRQ jmp ret_from_intr #define BUILD_INTERRUPT(name, nr) \ ENTRY(name) \ pushl $nr-256; \ SAVE_ALL \ movl %esp,%eax; \ call smp_/**/name; \ jmp ret_from_intr; /* The include is where all of the SMP etc. interrupts come from */ #include "entry_arch.h" ENTRY(divide_error) pushl $0 # no error code pushl $do_divide_error ALIGN error_code: pushl %ds pushl %eax xorl %eax, %eax pushl %ebp pushl %edi pushl %esi pushl %edx decl %eax # eax = -1 pushl %ecx pushl %ebx cld pushl %es UNWIND_ESPFIX_STACK popl %ecx movl ES(%esp), %edi # get the function address movl ORIG_EAX(%esp), %edx # get the error code movl %eax, ORIG_EAX(%esp) movl %ecx, ES(%esp) movl $(__USER_DS), %ecx movl %ecx, %ds movl %ecx, %es movl %esp,%eax # pt_regs pointer call *%edi jmp ret_from_exception ENTRY(coprocessor_error) pushl $0 pushl $do_coprocessor_error jmp error_code ENTRY(simd_coprocessor_error) pushl $0 pushl $do_simd_coprocessor_error jmp error_code ENTRY(device_not_available) pushl $-1 # mark this as an int SAVE_ALL movl %cr0, %eax testl $0x4, %eax # EM (math emulation bit) jne device_not_available_emulate preempt_stop call math_state_restore jmp ret_from_exception device_not_available_emulate: pushl $0 # temporary storage for ORIG_EIP call math_emulate addl $4, %esp jmp ret_from_exception /* * Debug traps and NMI can happen at the one SYSENTER instruction * that sets up the real kernel stack. Check here, since we can't * allow the wrong stack to be used. * * "TSS_sysenter_esp0+12" is because the NMI/debug handler will have * already pushed 3 words if it hits on the sysenter instruction: * eflags, cs and eip. * * We just load the right stack, and push the three (known) values * by hand onto the new stack - while updating the return eip past * the instruction that would have done it for sysenter. */ #define FIX_STACK(offset, ok, label) \ cmpw $__KERNEL_CS,4(%esp); \ jne ok; \ label: \ movl TSS_sysenter_esp0+offset(%esp),%esp; \ pushfl; \ pushl $__KERNEL_CS; \ pushl $sysenter_past_esp KPROBE_ENTRY(debug) cmpl $sysenter_entry,(%esp) jne debug_stack_correct FIX_STACK(12, debug_stack_correct, debug_esp_fix_insn) debug_stack_correct: pushl $-1 # mark this as an int SAVE_ALL xorl %edx,%edx # error code 0 movl %esp,%eax # pt_regs pointer call do_debug jmp ret_from_exception .previous .text /* * NMI is doubly nasty. It can happen _while_ we're handling * a debug fault, and the debug fault hasn't yet been able to * clear up the stack. So we first check whether we got an * NMI on the sysenter entry path, but after that we need to * check whether we got an NMI on the debug path where the debug * fault happened on the sysenter path. */ ENTRY(nmi) pushl %eax movl %ss, %eax cmpw $__ESPFIX_SS, %ax popl %eax je nmi_16bit_stack cmpl $sysenter_entry,(%esp) je nmi_stack_fixup pushl %eax movl %esp,%eax /* Do not access memory above the end of our stack page, * it might not exist. */ andl $(THREAD_SIZE-1),%eax cmpl $(THREAD_SIZE-20),%eax popl %eax jae nmi_stack_correct cmpl $sysenter_entry,12(%esp) je nmi_debug_stack_check nmi_stack_correct: pushl %eax SAVE_ALL xorl %edx,%edx # zero error code movl %esp,%eax # pt_regs pointer call do_nmi jmp restore_all nmi_stack_fixup: FIX_STACK(12,nmi_stack_correct, 1) jmp nmi_stack_correct nmi_debug_stack_check: cmpw $__KERNEL_CS,16(%esp) jne nmi_stack_correct cmpl $debug - 1,(%esp) jle nmi_stack_correct cmpl $debug_esp_fix_insn,(%esp) jle nmi_debug_stack_fixup nmi_debug_stack_fixup: FIX_STACK(24,nmi_stack_correct, 1) jmp nmi_stack_correct nmi_16bit_stack: /* create the pointer to lss back */ pushl %ss pushl %esp movzwl %sp, %esp addw $4, (%esp) /* copy the iret frame of 12 bytes */ .rept 3 pushl 16(%esp) .endr pushl %eax SAVE_ALL FIXUP_ESPFIX_STACK # %eax == %esp xorl %edx,%edx # zero error code call do_nmi RESTORE_REGS lss 12+4(%esp), %esp # back to 16bit stack 1: iret .section __ex_table,"a" .align 4 .long 1b,iret_exc .previous KPROBE_ENTRY(int3) pushl $-1 # mark this as an int SAVE_ALL xorl %edx,%edx # zero error code movl %esp,%eax # pt_regs pointer call do_int3 jmp ret_from_exception .previous .text ENTRY(overflow) pushl $0 pushl $do_overflow jmp error_code ENTRY(bounds) pushl $0 pushl $do_bounds jmp error_code ENTRY(invalid_op) pushl $0 pushl $do_invalid_op jmp error_code ENTRY(coprocessor_segment_overrun) pushl $0 pushl $do_coprocessor_segment_overrun jmp error_code ENTRY(invalid_TSS) pushl $do_invalid_TSS jmp error_code ENTRY(segment_not_present) pushl $do_segment_not_present jmp error_code ENTRY(stack_segment) pushl $do_stack_segment jmp error_code KPROBE_ENTRY(general_protection) pushl $do_general_protection jmp error_code .previous .text ENTRY(alignment_check) pushl $do_alignment_check jmp error_code KPROBE_ENTRY(page_fault) pushl $do_page_fault jmp error_code .previous .text #ifdef CONFIG_X86_MCE ENTRY(machine_check) pushl $0 pushl machine_check_vector jmp error_code #endif ENTRY(spurious_interrupt_bug) pushl $0 pushl $do_spurious_interrupt_bug jmp error_code #include "syscall_table.S" syscall_table_size=(.-sys_call_table)