]> git.saurik.com Git - apple/xnu.git/blobdiff - osfmk/i386/idt.s
xnu-1699.26.8.tar.gz
[apple/xnu.git] / osfmk / i386 / idt.s
index bc45d5d4a5ad06881779ef88297deb95627e8767..362b783a463621d8a23b5397088d4dc1cee7e5ac 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2006 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2000-2010 Apple Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
 #include <mach_kdb.h>
 #include <i386/eflags.h>
 #include <i386/trap.h>
+#include <i386/rtclock_asm.h>
+#define _ARCH_I386_ASM_HELP_H_  /* Prevent inclusion of user header */
+#include <mach/i386/syscall_sw.h>
+#include <i386/postcode.h>
+#include <i386/proc_reg.h>
+#include <mach/exception_types.h>
+
+/*
+ * Low-memory handlers.
+ */
+#define        LO_ALLINTRS             EXT(lo_allintrs32)
+#define        LO_ALLTRAPS             EXT(lo_alltraps32)
+#define        LO_SYSENTER             EXT(lo_sysenter32)
+#define        LO_UNIX_SCALL           EXT(lo_unix_scall32)
+#define        LO_MACH_SCALL           EXT(lo_mach_scall32)
+#define        LO_MDEP_SCALL           EXT(lo_mdep_scall32)
+#define        LO_DIAG_SCALL           EXT(lo_diag_scall32)
+
 
 #define HI_DATA(lo_addr)       ( (EXT(lo_addr) - EXT(hi_remap_data)) + HIGH_IDT_BASE )
 #define HI_TEXT(lo_text)       ( (EXT(lo_text) - EXT(hi_remap_text)) + HIGH_MEM_BASE )
        .byte   type            ;\
        .text
 
-#define        IDT_ENTRY(vec,type)     IDT_BASE_ENTRY(vec,KERNEL_CS,type)
-#define        IDT_ENTRY_INT(vec,type) IDT_BASE_ENTRY_INT(vec,KERNEL_CS,type)
+#define        IDT_ENTRY(vec,type)     IDT_BASE_ENTRY(vec,KERNEL32_CS,type)
+#define        IDT_ENTRY_INT(vec,type) IDT_BASE_ENTRY_INT(vec,KERNEL32_CS,type)
 
 /*
  * No error code.  Clear error code and push trap number.
@@ -103,7 +121,7 @@ Entry(name)                         ;\
        pushl   $0                      ;\
        pushl   $(n)                    ;\
        pusha                           ;\
-       movl    $ EXT(lo_alltraps),%ebx ;\
+       movl    $(LO_ALLTRAPS),%ebx     ;\
        jmp     enter_lohandler
 
        
@@ -116,7 +134,7 @@ Entry(name)                         ;\
        pushl   $0                      ;\
        pushl   $(n)                    ;\
        pusha                           ;\
-       movl    $ EXT(lo_alltraps),%ebx ;\
+       movl    $(LO_ALLTRAPS),%ebx     ;\
        jmp     enter_lohandler
        
 
@@ -152,11 +170,11 @@ Entry(name)                               ;\
  * Error code has been pushed.  Push trap number.
  */
 #define        EXCEP_ERR(n,name) \
-       IDT_ENTRY(name,K_INTR_GATE);\
-Entry(name)                            ;\
-       pushl   $(n)                    ;\
-       pusha                           ;\
-       movl    $ EXT(lo_alltraps),%ebx ;\
+       IDT_ENTRY(name,K_INTR_GATE)             ;\
+Entry(name)                                    ;\
+       pushl   $(n)                            ;\
+       pusha                                   ;\
+       movl    $(LO_ALLTRAPS),%ebx             ;\
        jmp     enter_lohandler
 
        
@@ -170,7 +188,7 @@ L_ ## n:                                    ;\
        pushl   $0                              ;\
        pushl   $(n)                            ;\
        pusha                                   ;\
-       movl    $ EXT(lo_allintrs),%ebx         ;\
+       movl    $(LO_ALLINTRS),%ebx             ;\
        jmp     enter_lohandler
 
 
@@ -179,6 +197,7 @@ L_ ## n:                                    ;\
 Entry(master_idt)
 Entry(hi_remap_data)
        .text
+       .align 12
 Entry(hi_remap_text)
 
 EXCEPTION(0x00,t_zero_div)
@@ -470,8 +489,7 @@ Entry(lo_kernel_cr3)
         .text
 
        
-/*******************************************************************************************************
- *
+/*
  * Trap/interrupt entry points.
  *
  * All traps must create the following save area on the PCB "stack":
@@ -497,14 +515,21 @@ Entry(lo_kernel_cr3)
  *     user ss  - if from user
  */
 
-       
+ret_to_kernel:
+       jmp *1f
+1:     .long HI_TEXT(hi_ret_to_kernel)
+
+ret_to_user:
+       jmp *1f
+1:     .long HI_TEXT(hi_ret_to_user) 
+
 Entry(hi_ret_to_user)
        movl    %esp,%ebx
        movl    %gs:CPU_ACTIVE_THREAD,%ecx
-       subl    ACT_PCB_ISS(%ecx),%ebx
-       movl    $(WINDOWS_CLEAN),ACT_COPYIO_STATE(%ecx)
+       subl    TH_PCB_ISS(%ecx),%ebx
+       movl    $(WINDOWS_CLEAN),TH_COPYIO_STATE(%ecx)
 
-       movl    ACT_PCB_IDS(%ecx),%eax  /* get debug state struct */
+       movl    TH_PCB_IDS(%ecx),%eax   /* get debug state struct */
        cmpl    $0,%eax                 /* is there a debug state */
        je      1f                      /* branch if not */
        movl    DS_DR0(%eax), %ecx      /* Load the 32 bit debug registers */
@@ -561,7 +586,7 @@ Entry(hi_unix_scall)
        pushl   %eax                    /* save system call number */
         pushl   $0                      /* clear trap number slot */
         pusha                           /* save the general registers */
-       movl    $ EXT(lo_unix_scall),%ebx
+       movl    $(LO_UNIX_SCALL),%ebx
        jmp     enter_lohandler
 
        
@@ -569,7 +594,7 @@ Entry(hi_mach_scall)
        pushl   %eax                    /* save system call number */
         pushl   $0                      /* clear trap number slot */
         pusha                           /* save the general registers */
-       movl    $ EXT(lo_mach_scall),%ebx
+       movl    $(LO_MACH_SCALL),%ebx
        jmp     enter_lohandler
 
        
@@ -577,7 +602,7 @@ Entry(hi_mdep_scall)
        pushl   %eax                    /* save system call number */
         pushl   $0                      /* clear trap number slot */
         pusha                           /* save the general registers */
-       movl    $ EXT(lo_mdep_scall),%ebx
+       movl    $(LO_MDEP_SCALL),%ebx
        jmp     enter_lohandler
 
        
@@ -585,7 +610,7 @@ Entry(hi_diag_scall)
        pushl   %eax                    // Save sselector
         pushl   $0                      // Clear trap number slot
         pusha                           // save the general registers
-       movl    $EXT(lo_diag_scall),%ebx        // Get the function down low to transfer to
+       movl    $(LO_DIAG_SCALL),%ebx   // Get the function down low to transfer to
        jmp     enter_lohandler                 // Leap to it...
 
        
@@ -620,8 +645,8 @@ hi_sysenter_2:
        pushl   %eax                    /* err/eax - syscall code */
        pushl   $0                      /* clear trap number slot */
        pusha                           /* save the general registers */
-       orl     $(EFL_IF),R_EFLAGS-R_EDI(%esp)  /* (edi was last reg pushed) */
-       movl    $ EXT(lo_sysenter),%ebx
+       orl     $(EFL_IF),R32_EFLAGS-R32_EDI(%esp)      /* (edi was last reg pushed) */
+       movl    $(LO_SYSENTER),%ebx
 enter_lohandler:
        pushl   %ds
        pushl   %es
@@ -646,19 +671,20 @@ enter_lohandler1:
        movl    %ecx,%cr3
        movl    %ecx,%gs:CPU_ACTIVE_CR3
 1:
-       testb   $3,R_CS(%esp)
+       testb   $3,R32_CS(%esp)
        jz      2f
        movl    %esp,%edx                       /* came from user mode */
+       xor     %ebp, %ebp
        subl    %gs:CPU_HI_ISS,%edx
        movl    %gs:CPU_ACTIVE_THREAD,%ecx
-       addl    ACT_PCB_ISS(%ecx),%edx          /* rebase the high stack to a low address */
+       addl    TH_PCB_ISS(%ecx),%edx           /* rebase the high stack to a low address */
        movl    %edx,%esp
-       cmpl    $0, ACT_PCB_IDS(%ecx)   /* Is there a debug register state? */
+       cmpl    $0, TH_PCB_IDS(%ecx)    /* Is there a debug register state? */
        je      2f
        movl    $0, %ecx                /* If so, reset DR7 (the control) */
        movl    %ecx, %dr7
 2:
-       movl    R_TRAPNO(%esp),%ecx                     // Get the interrupt vector
+       movl    R32_TRAPNO(%esp),%ecx                   // Get the interrupt vector
        addl    $1,%gs:hwIntCnt(,%ecx,4)        // Bump the count
        jmp             *%ebx
 
@@ -670,9 +696,9 @@ Entry(hi_page_fault)
        pushl   $(T_PAGE_FAULT)         /* mark a page fault trap */
        pusha                           /* save the general registers */
        movl    %cr2,%eax               /* get the faulting address */
-       movl    %eax,R_CR2-R_EDI(%esp)  /* save in esp save slot */
+       movl    %eax,R32_CR2-R32_EDI(%esp)/* save in esp save slot */
 
-       movl    $ EXT(lo_alltraps),%ebx
+       movl    $(LO_ALLTRAPS),%ebx
        jmp     enter_lohandler
 
 
@@ -727,7 +753,7 @@ hi_debug_trap:
        pushl   $0
        pushl   $(T_DEBUG)              /* handle as user trap */
        pusha                           /* save the general registers */
-       movl    $ EXT(lo_alltraps),%ebx
+       movl    $(LO_ALLTRAPS),%ebx
        jmp     enter_lohandler 
 
 
@@ -768,7 +794,7 @@ trap_check_kernel_exit:
        je      fault_popl_gs
 hi_take_trap:
        pusha                           /* save the general registers */
-       movl    $ EXT(lo_alltraps),%ebx
+       movl    $(LO_ALLTRAPS),%ebx
        jmp     enter_lohandler
 
                
@@ -797,7 +823,7 @@ fault_iret:
        popl    %eax                    /* restore eax */
                                        /* now treat as fault from user */
        pusha                           /* save the general registers */
-       movl    $ EXT(lo_alltraps),%ebx
+       movl    $(LO_ALLTRAPS),%ebx
        jmp     enter_lohandler
 
 /*
@@ -834,24 +860,476 @@ push_gs:
        pushl   %gs                     /* restore gs. */
 push_none:
        pushl   $(SS_32)                /* 32-bit state flavor */
-       movl    %eax,R_TRAPNO(%esp)     /* set trap number */
-       movl    %edx,R_ERR(%esp)        /* set error code */
+       movl    %eax,R32_TRAPNO(%esp)   /* set trap number */
+       movl    %edx,R32_ERR(%esp)      /* set error code */
                                        /* now treat as fault from user */
                                        /* except that segment registers are */
                                        /* already pushed */
-       movl    $ EXT(lo_alltraps),%ebx
+       movl    $(LO_ALLTRAPS),%ebx
        jmp     enter_lohandler1
 
        
         .text
 
 
-Entry(lo_ret_to_user)
-       jmp *1f
-1:     .long HI_TEXT(hi_ret_to_user) 
+Entry(hi_remap_etext)
 
-Entry(lo_ret_to_kernel)
-       jmp *1f
-1:     .long HI_TEXT(hi_ret_to_kernel)
 
-Entry(hi_remap_etext)
+/*
+ * All 32 bit task 'exceptions' enter lo_alltraps:
+ *     esp     -> x86_saved_state_t
+ * 
+ * The rest of the state is set up as: 
+ *     cr3      -> kernel directory
+ *     esp      -> low based stack
+ *     gs       -> CPU_DATA_GS
+ *     cs       -> KERNEL32_CS
+ *     ss/ds/es -> KERNEL_DS
+ *
+ *     interrupts disabled
+ *     direction flag cleared
+ */
+Entry(lo_alltraps32)
+       movl    R32_CS(%esp),%eax       /* assume 32-bit state */
+       cmpl    $(SS_64),SS_FLAVOR(%esp)/* 64-bit? */   
+       jne     1f
+       movl    R64_CS(%esp),%eax       /* 64-bit user mode */
+1:
+       testb   $3,%al
+       jz      trap_from_kernel
+                                               /* user mode trap */
+       TIME_TRAP_UENTRY
+
+       movl    %gs:CPU_ACTIVE_THREAD,%ecx
+       movl    TH_TASK(%ecx),%ebx
+
+       /* Check for active vtimers in the current task */
+       TASK_VTIMER_CHECK(%ebx, %ecx)
+
+       movl    %gs:CPU_KERNEL_STACK,%ebx
+       xchgl   %ebx,%esp               /* switch to kernel stack */
+
+       CCALL1(user_trap, %ebx)         /* call user trap routine */
+       /* user_trap() unmasks interrupts */
+       cli                             /* hold off intrs - critical section */
+       xorl    %ecx,%ecx               /* don't check if we're in the PFZ */
+       
+/*
+ * Return from trap or system call, checking for ASTs.
+ * On lowbase PCB stack with intrs disabled
+ */    
+Entry(return_from_trap32)
+       movl    %gs:CPU_ACTIVE_THREAD, %esp
+       movl    TH_PCB_ISS(%esp), %esp  /* switch back to PCB stack */
+       movl    %gs:CPU_PENDING_AST, %eax
+       testl   %eax, %eax
+       je      EXT(return_to_user)     /* branch if no AST */
+LEXT(return_from_trap_with_ast)
+       movl    %gs:CPU_KERNEL_STACK, %ebx
+       xchgl   %ebx, %esp              /* switch to kernel stack */
+
+       testl   %ecx, %ecx              /* see if we need to check for an EIP in the PFZ */
+       je      2f                      /* no, go handle the AST */
+       cmpl    $(SS_64), SS_FLAVOR(%ebx)       /* are we a 64-bit task? */
+       je      1f
+                                       /* no... 32-bit user mode */
+       movl    R32_EIP(%ebx), %eax
+       pushl   %ebx                    /* save PCB stack */
+       xorl    %ebp, %ebp              /* clear frame pointer */
+       CCALL1(commpage_is_in_pfz32, %eax)
+       popl    %ebx                    /* retrieve pointer to PCB stack */
+       testl   %eax, %eax
+       je      2f                      /* not in the PFZ... go service AST */
+       movl    %eax, R32_EBX(%ebx)     /* let the PFZ know we've pended an AST */
+       xchgl   %ebx, %esp              /* switch back to PCB stack */
+       jmp     EXT(return_to_user)
+1:                                     /* 64-bit user mode */
+       movl    R64_RIP(%ebx), %ecx
+       movl    R64_RIP+4(%ebx), %eax
+       pushl   %ebx                    /* save PCB stack */
+       xorl    %ebp, %ebp              /* clear frame pointer */
+       CCALL2(commpage_is_in_pfz64, %ecx, %eax)
+       popl    %ebx                    /* retrieve pointer to PCB stack */
+       testl   %eax, %eax              
+       je      2f                      /* not in the PFZ... go service AST */
+       movl    %eax, R64_RBX(%ebx)     /* let the PFZ know we've pended an AST */
+       xchgl   %ebx, %esp              /* switch back to PCB stack */
+       jmp     EXT(return_to_user)
+2:     
+       sti                             /* interrupts always enabled on return to user mode */
+       xorl    %ebp, %ebp              /* Clear framepointer */
+       CCALL1(i386_astintr, $0)        /* take the AST */
+       cli
+       xorl    %ecx, %ecx              /* don't check if we're in the PFZ */
+       jmp     EXT(return_from_trap32) /* and check again (rare) */
+
+
+/*
+ * Trap from kernel mode.  No need to switch stacks.
+ * Interrupts must be off here - we will set them to state at time of trap
+ * as soon as it's safe for us to do so and not recurse doing preemption
+ */
+trap_from_kernel:
+       movl    %esp, %eax              /* saved state addr */
+       pushl   R32_EIP(%esp)           /* Simulate a CALL from fault point */
+       pushl   %ebp                    /* Extend framepointer chain */
+       movl    %esp, %ebp
+       CCALL1WITHSP(kernel_trap, %eax) /* Call kernel trap handler */
+       popl    %ebp
+       addl    $4, %esp
+       cli
+
+       movl    %gs:CPU_PENDING_AST,%eax                /* get pending asts */
+       testl   $ AST_URGENT,%eax       /* any urgent preemption? */
+       je      ret_to_kernel                   /* no, nothing to do */
+       cmpl    $ T_PREEMPT,R32_TRAPNO(%esp)
+       je      ret_to_kernel                     /* T_PREEMPT handled in kernel_trap() */
+       testl   $ EFL_IF,R32_EFLAGS(%esp)               /* interrupts disabled? */
+       je      ret_to_kernel
+       cmpl    $0,%gs:CPU_PREEMPTION_LEVEL             /* preemption disabled? */
+       jne     ret_to_kernel
+       movl    %gs:CPU_KERNEL_STACK,%eax
+       movl    %esp,%ecx
+       xorl    %eax,%ecx
+       and     EXT(kernel_stack_mask),%ecx
+       testl   %ecx,%ecx               /* are we on the kernel stack? */
+       jne     ret_to_kernel           /* no, skip it */
+
+       CCALL1(i386_astintr, $1)        /* take the AST */
+
+       jmp     ret_to_kernel
+
+
+/*
+ * All interrupts on all tasks enter here with:
+ *     esp->    -> x86_saved_state_t
+ *
+ *     cr3      -> kernel directory
+ *     esp      -> low based stack
+ *     gs       -> CPU_DATA_GS
+ *     cs       -> KERNEL32_CS
+ *     ss/ds/es -> KERNEL_DS
+ *
+ *     interrupts disabled
+ *     direction flag cleared
+ */
+Entry(lo_allintrs32)
+       /*
+        * test whether already on interrupt stack
+        */
+       movl    %gs:CPU_INT_STACK_TOP,%ecx
+       cmpl    %esp,%ecx
+       jb      1f
+       leal    -INTSTACK_SIZE(%ecx),%edx
+       cmpl    %esp,%edx
+       jb      int_from_intstack
+1:     
+       xchgl   %ecx,%esp               /* switch to interrupt stack */
+
+       movl    %cr0,%eax               /* get cr0 */
+       orl     $(CR0_TS),%eax          /* or in TS bit */
+       movl    %eax,%cr0               /* set cr0 */
+
+       subl    $8, %esp                /* for 16-byte stack alignment */
+       pushl   %ecx                    /* save pointer to old stack */
+       movl    %ecx,%gs:CPU_INT_STATE  /* save intr state */
+       
+       TIME_INT_ENTRY                  /* do timing */
+
+       movl    %gs:CPU_ACTIVE_THREAD,%ecx
+       movl    TH_TASK(%ecx),%ebx
+
+       /* Check for active vtimers in the current task */
+       TASK_VTIMER_CHECK(%ebx, %ecx)
+
+       incl    %gs:CPU_PREEMPTION_LEVEL
+       incl    %gs:CPU_INTERRUPT_LEVEL
+
+       movl    %gs:CPU_INT_STATE, %eax
+       CCALL1(interrupt, %eax)         /* call generic interrupt routine */
+
+       cli                             /* just in case we returned with intrs enabled */
+       xorl    %eax,%eax
+       movl    %eax,%gs:CPU_INT_STATE  /* clear intr state pointer */
+
+       decl    %gs:CPU_INTERRUPT_LEVEL
+       decl    %gs:CPU_PREEMPTION_LEVEL
+
+       TIME_INT_EXIT                   /* do timing */
+
+       movl    %gs:CPU_ACTIVE_THREAD,%eax
+       movl    TH_PCB_FPS(%eax),%eax   /* get pcb's ifps */
+       testl   %eax, %eax              /* Is there a context */
+       je      1f                      /* Branch if not */
+       cmpl    $0, FP_VALID(%eax)      /* Check fp_valid */
+       jne     1f                      /* Branch if valid */
+       clts                            /* Clear TS */
+       jmp     2f
+1:
+       movl    %cr0,%eax               /* get cr0 */
+       orl     $(CR0_TS),%eax          /* or in TS bit */
+       movl    %eax,%cr0               /* set cr0 */
+2:
+       popl    %esp                    /* switch back to old stack */
+
+       /* Load interrupted code segment into %eax */
+       movl    R32_CS(%esp),%eax       /* assume 32-bit state */
+       cmpl    $(SS_64),SS_FLAVOR(%esp)/* 64-bit? */   
+       jne     3f
+       movl    R64_CS(%esp),%eax       /* 64-bit user mode */
+3:
+       testb   $3,%al                  /* user mode, */
+       jnz     ast_from_interrupt_user /* go handle potential ASTs */
+       /*
+        * we only want to handle preemption requests if
+        * the interrupt fell in the kernel context
+        * and preemption isn't disabled
+        */
+       movl    %gs:CPU_PENDING_AST,%eax        
+       testl   $ AST_URGENT,%eax               /* any urgent requests? */
+       je      ret_to_kernel                   /* no, nothing to do */
+
+       cmpl    $0,%gs:CPU_PREEMPTION_LEVEL     /* preemption disabled? */
+       jne     ret_to_kernel                   /* yes, skip it */
+
+       movl    %gs:CPU_KERNEL_STACK,%eax
+       movl    %esp,%ecx
+       xorl    %eax,%ecx
+       and     EXT(kernel_stack_mask),%ecx
+       testl   %ecx,%ecx                       /* are we on the kernel stack? */
+       jne     ret_to_kernel                   /* no, skip it */
+
+       /*
+        * Take an AST from kernel space.  We don't need (and don't want)
+        * to do as much as the case where the interrupt came from user
+        * space.
+        */
+       CCALL1(i386_astintr, $1)
+
+       jmp     ret_to_kernel
+
+
+/*
+ * nested int - simple path, can't preempt etc on way out
+ */
+int_from_intstack:
+       incl    %gs:CPU_PREEMPTION_LEVEL
+       incl    %gs:CPU_INTERRUPT_LEVEL
+
+       movl    %esp, %edx              /* x86_saved_state */
+       CCALL1(interrupt, %edx)
+
+       decl    %gs:CPU_INTERRUPT_LEVEL
+       decl    %gs:CPU_PREEMPTION_LEVEL
+
+       jmp     ret_to_kernel
+
+/*
+ *     Take an AST from an interrupted user
+ */
+ast_from_interrupt_user:
+       movl    %gs:CPU_PENDING_AST,%eax
+       testl   %eax,%eax               /* pending ASTs? */
+       je      ret_to_user             /* no, nothing to do */
+
+       TIME_TRAP_UENTRY
+
+       movl    $1, %ecx                /* check if we're in the PFZ */
+       jmp     EXT(return_from_trap_with_ast)  /* return */
+
+
+/*
+ * 32bit Tasks
+ * System call entries via INTR_GATE or sysenter:
+ *
+ *     esp      -> x86_saved_state32_t
+ *     cr3      -> kernel directory
+ *     esp      -> low based stack
+ *     gs       -> CPU_DATA_GS
+ *     cs       -> KERNEL32_CS
+ *     ss/ds/es -> KERNEL_DS
+ *
+ *     interrupts disabled
+ *     direction flag cleared
+ */
+
+Entry(lo_sysenter32)
+       /*
+        * We can be here either for a mach syscall or a unix syscall,
+        * as indicated by the sign of the code:
+        */
+       movl    R32_EAX(%esp),%eax
+       testl   %eax,%eax
+       js      EXT(lo_mach_scall32)            /* < 0 => mach */
+                                               /* > 0 => unix */
+       
+Entry(lo_unix_scall32)
+       TIME_TRAP_UENTRY
+
+       movl    %gs:CPU_KERNEL_STACK,%edi
+       xchgl   %edi,%esp                       /* switch to kernel stack */
+       movl    %gs:CPU_ACTIVE_THREAD,%ecx      /* get current thread     */
+       movl    TH_TASK(%ecx),%ebx              /* point to current task  */
+       incl    TH_SYSCALLS_UNIX(%ecx)          /* increment call count   */
+
+       /* Check for active vtimers in the current task */
+       TASK_VTIMER_CHECK(%ebx, %ecx)
+
+       sti
+
+       CCALL1(unix_syscall, %edi)
+       /*
+        * always returns through thread_exception_return
+        */
+
+
+Entry(lo_mach_scall32)
+       TIME_TRAP_UENTRY
+
+       movl    %gs:CPU_KERNEL_STACK,%edi
+       xchgl   %edi,%esp                       /* switch to kernel stack */
+       movl    %gs:CPU_ACTIVE_THREAD,%ecx      /* get current thread     */
+       movl    TH_TASK(%ecx),%ebx              /* point to current task  */
+       incl    TH_SYSCALLS_MACH(%ecx)          /* increment call count   */
+
+       /* Check for active vtimers in the current task */
+       TASK_VTIMER_CHECK(%ebx, %ecx)
+
+       sti
+
+       CCALL1(mach_call_munger, %edi)
+       /*
+        * always returns through thread_exception_return
+        */
+
+
+Entry(lo_mdep_scall32)
+       TIME_TRAP_UENTRY
+
+       movl    %gs:CPU_KERNEL_STACK,%edi
+       xchgl   %edi,%esp                       /* switch to kernel stack */
+       movl    %gs:CPU_ACTIVE_THREAD,%ecx      /* get current thread     */
+       movl    TH_TASK(%ecx),%ebx              /* point to current task  */
+
+       /* Check for active vtimers in the current task */
+       TASK_VTIMER_CHECK(%ebx, %ecx)
+       
+       sti
+
+       CCALL1(machdep_syscall, %edi)
+       /*
+        * always returns through thread_exception_return
+        */
+
+
+Entry(lo_diag_scall32)
+       TIME_TRAP_UENTRY
+
+       movl    %gs:CPU_KERNEL_STACK,%edi
+       xchgl   %edi,%esp                       /* switch to kernel stack */
+       movl    %gs:CPU_ACTIVE_THREAD,%ecx      /* get current thread     */
+       movl    TH_TASK(%ecx),%ebx              /* point to current task  */
+
+       /* Check for active vtimers in the current task */
+       TASK_VTIMER_CHECK(%ebx, %ecx)
+
+       pushl   %edi                    /* push pbc stack for later */
+
+       CCALL1(diagCall, %edi)          // Call diagnostics
+       
+       cli                             // Disable interruptions just in case
+       popl    %esp                    // Get back the original stack
+       cmpl    $0,%eax                 // What kind of return is this?
+       jne     EXT(return_to_user)     // Normal return, do not check asts...
+
+       CCALL5(i386_exception, $EXC_SYSCALL, $0x6000, $0, $1, $0)
+               // pass what would be the diag syscall
+               // error return - cause an exception
+       /* no return */
+       
+
+LEXT(return_to_user)
+       TIME_TRAP_UEXIT
+       jmp     ret_to_user
+
+
+/*
+ * Double-fault exception handler task. The last gasp...
+ */
+Entry(df_task_start)
+       CCALL1(panic_double_fault32, $(T_DOUBLE_FAULT))
+       hlt
+
+
+/*
+ * machine-check handler task. The last gasp...
+ */
+Entry(mc_task_start)
+       CCALL1(panic_machine_check32, $(T_MACHINE_CHECK))
+       hlt
+
+#if MACH_KDB
+#include <i386/lapic.h>
+#define CX(addr,reg)   addr(,reg,4)
+#if    0
+/*
+ * Note that the per-fault entry points are not currently
+ * functional.  The only way to make them work would be to
+ * set up separate TSS's for each fault type, which doesn't
+ * currently seem worthwhile.  (The offset part of a task
+ * gate is always ignored.)  So all faults that task switch
+ * currently resume at db_task_start.
+ */
+/*
+ * Double fault (Murphy's point) - error code (0) on stack
+ */
+Entry(db_task_dbl_fault)
+       popl    %eax
+       movl    $(T_DOUBLE_FAULT),%ebx
+       jmp     db_task_start
+/*
+ * Segment not present - error code on stack
+ */
+Entry(db_task_seg_np)
+       popl    %eax
+       movl    $(T_SEGMENT_NOT_PRESENT),%ebx
+       jmp     db_task_start
+/*
+ * Stack fault - error code on (current) stack
+ */
+Entry(db_task_stk_fault)
+       popl    %eax
+       movl    $(T_STACK_FAULT),%ebx
+       jmp     db_task_start
+/*
+ * General protection fault - error code on stack
+ */
+Entry(db_task_gen_prot)
+       popl    %eax
+       movl    $(T_GENERAL_PROTECTION),%ebx
+       jmp     db_task_start
+#endif /* 0 */
+/*
+ * The entry point where execution resumes after last-ditch debugger task
+ * switch.
+ */
+Entry(db_task_start)
+       movl    %esp,%edx
+       subl    $(ISS32_SIZE),%edx
+       movl    %edx,%esp               /* allocate x86_saved_state on stack */
+       movl    %eax,R32_ERR(%esp)
+       movl    %ebx,R32_TRAPNO(%esp)
+       pushl   %edx
+       CPU_NUMBER(%edx)
+       movl    CX(EXT(master_dbtss),%edx),%edx
+       movl    TSS_LINK(%edx),%eax
+       pushl   %eax                    /* pass along selector of previous TSS */
+       call    EXT(db_tss_to_frame)
+       popl    %eax                    /* get rid of TSS selector */
+       call    EXT(db_trap_from_asm)
+       addl    $0x4,%esp
+       /*
+        * And now...?
+        */
+       iret                            /* ha, ha, ha... */
+#endif /* MACH_KDB */