arch/arc/kernel/entry.S

   1 /*
   2  * Common Low Level Interrupts/Traps/Exceptions(non-TLB) Handling for ARC
   3  * (included from entry-<isa>.S
   4  *
   5  * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
   6  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 /*------------------------------------------------------------------
  14  *    Function                            ABI
  15  *------------------------------------------------------------------
  16  *
  17  *  Arguments                           r0 - r7
  18  *  Caller Saved Registers              r0 - r12
  19  *  Callee Saved Registers              r13- r25
  20  *  Global Pointer (gp)                 r26
  21  *  Frame Pointer (fp)                  r27
  22  *  Stack Pointer (sp)                  r28
  23  *  Branch link register (blink)        r31
  24  *------------------------------------------------------------------
  25  */
  26
  27 ;################### Special Sys Call Wrappers ##########################
  28
  29 ENTRY(sys_clone_wrapper)
  30         SAVE_CALLEE_SAVED_USER
  31         bl  @sys_clone
  32         DISCARD_CALLEE_SAVED_USER
  33
  34         GET_CURR_THR_INFO_FLAGS   r10
  35         btst r10, TIF_SYSCALL_TRACE
  36         bnz  tracesys_exit
  37
  38         b .Lret_from_system_call
  39 END(sys_clone_wrapper)
  40
  41 ENTRY(ret_from_fork)
  42         ; when the forked child comes here from the __switch_to function
  43         ; r0 has the last task pointer.
  44         ; put last task in scheduler queue
  45         jl   @schedule_tail
  46
  47         ld   r9, [sp, PT_status32]
  48         brne r9, 0, 1f
  49
  50         jl.d [r14]              ; kernel thread entry point
  51         mov  r0, r13            ; (see PF_KTHREAD block in copy_thread)
  52
  53 1:
  54         ; Return to user space
  55         ; 1. Any forked task (Reach here via BRne above)
  56         ; 2. First ever init task (Reach here via return from JL above)
  57         ;    This is the historic "kernel_execve" use-case, to return to init
  58         ;    user mode, in a round about way since that is always done from
  59         ;    a kernel thread which is executed via JL above but always returns
  60         ;    out whenever kernel_execve (now inline do_fork()) is involved
  61         b    ret_from_exception
  62 END(ret_from_fork)
  63
  64 ;################### Non TLB Exception Handling #############################
  65
  66 ; ---------------------------------------------
  67 ; Instruction Error Exception Handler
  68 ; ---------------------------------------------
  69
  70 ENTRY(instr_service)
  71
  72         EXCEPTION_PROLOGUE
  73
  74         lr  r0, [efa]
  75         mov r1, sp
  76
  77         FAKE_RET_FROM_EXCPN
  78
  79         bl  do_insterror_or_kprobe
  80         b   ret_from_exception
  81 END(instr_service)
  82
  83 ; ---------------------------------------------
  84 ; Machine Check Exception Handler
  85 ; ---------------------------------------------
  86
  87 ENTRY(EV_MachineCheck)
  88
  89         EXCEPTION_PROLOGUE
  90
  91         lr  r2, [ecr]
  92         lr  r0, [efa]
  93         mov r1, sp
  94
  95         ; hardware auto-disables MMU, re-enable it to allow kernel vaddr
  96         ; access for say stack unwinding of modules for crash dumps
  97         lr      r3, [ARC_REG_PID]
  98         or      r3, r3, MMU_ENABLE
  99         sr      r3, [ARC_REG_PID]
 100
 101         lsr     r3, r2, 8
 102         bmsk    r3, r3, 7
 103         brne    r3, ECR_C_MCHK_DUP_TLB, 1f
 104
 105         bl      do_tlb_overlap_fault
 106         b       ret_from_exception
 107
 108 1:
 109         ; DEAD END: can't do much, display Regs and HALT
 110         SAVE_CALLEE_SAVED_USER
 111
 112         GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
 113         st  sp, [r10, THREAD_CALLEE_REG]
 114
 115         j  do_machine_check_fault
 116
 117 END(EV_MachineCheck)
 118
 119 ; ---------------------------------------------
 120 ; Privilege Violation Exception Handler
 121 ; ---------------------------------------------
 122 ENTRY(EV_PrivilegeV)
 123
 124         EXCEPTION_PROLOGUE
 125
 126         lr  r0, [efa]
 127         mov r1, sp
 128
 129         FAKE_RET_FROM_EXCPN
 130
 131         bl  do_privilege_fault
 132         b   ret_from_exception
 133 END(EV_PrivilegeV)
 134
 135 ; ---------------------------------------------
 136 ; Extension Instruction Exception Handler
 137 ; ---------------------------------------------
 138 ENTRY(EV_Extension)
 139
 140         EXCEPTION_PROLOGUE
 141
 142         lr  r0, [efa]
 143         mov r1, sp
 144
 145         FAKE_RET_FROM_EXCPN
 146
 147         bl  do_extension_fault
 148         b   ret_from_exception
 149 END(EV_Extension)
 150
 151 ;################ Trap Handling (Syscall, Breakpoint) ##################
 152
 153 ; ---------------------------------------------
 154 ; syscall Tracing
 155 ; ---------------------------------------------
 156 tracesys:
 157         ; save EFA in case tracer wants the PC of traced task
 158         ; using ERET won't work since next-PC has already committed
 159         lr  r12, [efa]
 160         GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r11
 161         st  r12, [r11, THREAD_FAULT_ADDR]       ; thread.fault_address
 162
 163         ; PRE Sys Call Ptrace hook
 164         mov r0, sp                      ; pt_regs needed
 165         bl  @syscall_trace_entry
 166
 167         ; Tracing code now returns the syscall num (orig or modif)
 168         mov r8, r0
 169
 170         ; Do the Sys Call as we normally would.
 171         ; Validate the Sys Call number
 172         cmp     r8,  NR_syscalls
 173         mov.hi  r0, -ENOSYS
 174         bhi     tracesys_exit
 175
 176         ; Restore the sys-call args. Mere invocation of the hook abv could have
 177         ; clobbered them (since they are in scratch regs). The tracer could also
 178         ; have deliberately changed the syscall args: r0-r7
 179         ld  r0, [sp, PT_r0]
 180         ld  r1, [sp, PT_r1]
 181         ld  r2, [sp, PT_r2]
 182         ld  r3, [sp, PT_r3]
 183         ld  r4, [sp, PT_r4]
 184         ld  r5, [sp, PT_r5]
 185         ld  r6, [sp, PT_r6]
 186         ld  r7, [sp, PT_r7]
 187         ld.as   r9, [sys_call_table, r8]
 188         jl      [r9]        ; Entry into Sys Call Handler
 189
 190 tracesys_exit:
 191         st  r0, [sp, PT_r0]     ; sys call return value in pt_regs
 192
 193         ;POST Sys Call Ptrace Hook
 194         bl  @syscall_trace_exit
 195         b   ret_from_exception ; NOT ret_from_system_call at is saves r0 which
 196         ; we'd done before calling post hook above
 197
 198 ; ---------------------------------------------
 199 ; Breakpoint TRAP
 200 ; ---------------------------------------------
 201 trap_with_param:
 202
 203         ; stop_pc info by gdb needs this info
 204         lr  r0, [efa]
 205         mov r1, sp
 206
 207         ; Now that we have read EFA, it is safe to do "fake" rtie
 208         ;   and get out of CPU exception mode
 209         FAKE_RET_FROM_EXCPN
 210
 211         ; Save callee regs in case gdb wants to have a look
 212         ; SP will grow up by size of CALLEE Reg-File
 213         ; NOTE: clobbers r12
 214         SAVE_CALLEE_SAVED_USER
 215
 216         ; save location of saved Callee Regs @ thread_struct->pc
 217         GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
 218         st  sp, [r10, THREAD_CALLEE_REG]
 219
 220         ; Call the trap handler
 221         bl  do_non_swi_trap
 222
 223         ; unwind stack to discard Callee saved Regs
 224         DISCARD_CALLEE_SAVED_USER
 225
 226         b   ret_from_exception
 227
 228 ; ---------------------------------------------
 229 ; syscall TRAP
 230 ; ABI: (r0-r7) upto 8 args, (r8) syscall number
 231 ; ---------------------------------------------
 232
 233 ENTRY(EV_Trap)
 234
 235         EXCEPTION_PROLOGUE
 236
 237         ;============ TRAP 1   :breakpoints
 238         ; Check ECR for trap with arg (PROLOGUE ensures r9 has ECR)
 239         bmsk.f 0, r9, 7
 240         bnz    trap_with_param
 241
 242         ;============ TRAP  (no param): syscall top level
 243
 244         ; First return from Exception to pure K mode (Exception/IRQs renabled)
 245         FAKE_RET_FROM_EXCPN
 246
 247         ; If syscall tracing ongoing, invoke pre-post-hooks
 248         GET_CURR_THR_INFO_FLAGS   r10
 249         btst r10, TIF_SYSCALL_TRACE
 250         bnz tracesys  ; this never comes back
 251
 252         ;============ Normal syscall case
 253
 254         ; syscall num shd not exceed the total system calls avail
 255         cmp     r8,  NR_syscalls
 256         mov.hi  r0, -ENOSYS
 257         bhi     .Lret_from_system_call
 258
 259         ; Offset into the syscall_table and call handler
 260         ld.as   r9,[sys_call_table, r8]
 261         jl      [r9]        ; Entry into Sys Call Handler
 262
 263 .Lret_from_system_call:
 264
 265         st  r0, [sp, PT_r0]     ; sys call return value in pt_regs
 266
 267         ; fall through to ret_from_exception
 268 END(EV_Trap)
 269
 270 ;############# Return from Intr/Excp/Trap (Linux Specifics) ##############
 271 ;
 272 ; If ret to user mode do we need to handle signals, schedule() et al.
 273
 274 ENTRY(ret_from_exception)
 275
 276         ; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32
 277         ld  r8, [sp, PT_status32]   ; returning to User/Kernel Mode
 278
 279         bbit0  r8, STATUS_U_BIT, resume_kernel_mode
 280
 281         ; Before returning to User mode check-for-and-complete any pending work
 282         ; such as rescheduling/signal-delivery etc.
 283 resume_user_mode_begin:
 284
 285         ; Disable IRQs to ensures that chk for pending work itself is atomic
 286         ; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an
 287         ; interim IRQ).
 288         IRQ_DISABLE     r10
 289
 290         ; Fast Path return to user mode if no pending work
 291         GET_CURR_THR_INFO_FLAGS   r9
 292         and.f  0,  r9, _TIF_WORK_MASK
 293         bz     .Lrestore_regs
 294
 295         ; --- (Slow Path #1) task preemption ---
 296         bbit0  r9, TIF_NEED_RESCHED, .Lchk_pend_signals
 297         mov    blink, resume_user_mode_begin  ; tail-call to U mode ret chks
 298         j      @schedule        ; BTST+Bnz causes relo error in link
 299
 300 .Lchk_pend_signals:
 301         IRQ_ENABLE      r10
 302
 303         ; --- (Slow Path #2) pending signal  ---
 304         mov r0, sp      ; pt_regs for arg to do_signal()/do_notify_resume()
 305
 306         GET_CURR_THR_INFO_FLAGS   r9
 307         bbit0  r9, TIF_SIGPENDING, .Lchk_notify_resume
 308
 309         ; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
 310         ; in pt_reg since the "C" ABI (kernel code) will automatically
 311         ; save/restore callee-saved regs.
 312         ;
 313         ; However, here we need to explicitly save callee regs because
 314         ; (i)  If this signal causes coredump - full regfile needed
 315         ; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus
 316         ;      tracer might call PEEKUSR(CALLEE reg)
 317         ;
 318         ; NOTE: SP will grow up by size of CALLEE Reg-File
 319         SAVE_CALLEE_SAVED_USER          ; clobbers r12
 320
 321         ; save location of saved Callee Regs @ thread_struct->callee
 322         GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
 323         st  sp, [r10, THREAD_CALLEE_REG]
 324
 325         bl  @do_signal
 326
 327         ; Ideally we want to discard the Callee reg above, however if this was
 328         ; a tracing signal, tracer could have done a POKEUSR(CALLEE reg)
 329         RESTORE_CALLEE_SAVED_USER
 330
 331         b      resume_user_mode_begin   ; loop back to start of U mode ret
 332
 333         ; --- (Slow Path #3) notify_resume ---
 334 .Lchk_notify_resume:
 335         btst   r9, TIF_NOTIFY_RESUME
 336         blnz   @do_notify_resume
 337         b      resume_user_mode_begin   ; unconditionally back to U mode ret chks
 338                                         ; for single exit point from this block
 339
 340 resume_kernel_mode:
 341
 342         ; Disable Interrupts from this point on
 343         ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq()
 344         ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe
 345         IRQ_DISABLE     r9
 346
 347 #ifdef CONFIG_PREEMPT
 348
 349         ; Can't preempt if preemption disabled
 350         GET_CURR_THR_INFO_FROM_SP   r10
 351         ld  r8, [r10, THREAD_INFO_PREEMPT_COUNT]
 352         brne  r8, 0, .Lrestore_regs
 353
 354         ; check if this task's NEED_RESCHED flag set
 355         ld  r9, [r10, THREAD_INFO_FLAGS]
 356         bbit0  r9, TIF_NEED_RESCHED, .Lrestore_regs
 357
 358         ; Invoke PREEMPTION
 359         jl      preempt_schedule_irq
 360
 361         ; preempt_schedule_irq() always returns with IRQ disabled
 362 #endif
 363
 364         b       .Lrestore_regs
 365
 366 ##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-<isa>.S
 367