arch/arc/kernel/entry.S

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Common Low Level Interrupts/Traps/Exceptions(non-TLB) Handling for ARC
   4  * (included from entry-<isa>.S
   5  *
   6  * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
   7  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   8  */
   9
  10 /*------------------------------------------------------------------
  11  *    Function                            ABI
  12  *------------------------------------------------------------------
  13  *
  14  *  Arguments                           r0 - r7
  15  *  Caller Saved Registers              r0 - r12
  16  *  Callee Saved Registers              r13- r25
  17  *  Global Pointer (gp)                 r26
  18  *  Frame Pointer (fp)                  r27
  19  *  Stack Pointer (sp)                  r28
  20  *  Branch link register (blink)        r31
  21  *------------------------------------------------------------------
  22  */
  23
  24 ;################### Special Sys Call Wrappers ##########################
  25
  26 ENTRY(sys_clone_wrapper)
  27         SAVE_CALLEE_SAVED_USER
  28         bl  @sys_clone
  29         DISCARD_CALLEE_SAVED_USER
  30
  31         GET_CURR_THR_INFO_FLAGS   r10
  32         btst r10, TIF_SYSCALL_TRACE
  33         bnz  tracesys_exit
  34
  35         b .Lret_from_system_call
  36 END(sys_clone_wrapper)
  37
  38 ENTRY(ret_from_fork)
  39         ; when the forked child comes here from the __switch_to function
  40         ; r0 has the last task pointer.
  41         ; put last task in scheduler queue
  42         jl   @schedule_tail
  43
  44         ld   r9, [sp, PT_status32]
  45         brne r9, 0, 1f
  46
  47         jl.d [r14]              ; kernel thread entry point
  48         mov  r0, r13            ; (see PF_KTHREAD block in copy_thread)
  49
  50 1:
  51         ; Return to user space
  52         ; 1. Any forked task (Reach here via BRne above)
  53         ; 2. First ever init task (Reach here via return from JL above)
  54         ;    This is the historic "kernel_execve" use-case, to return to init
  55         ;    user mode, in a round about way since that is always done from
  56         ;    a kernel thread which is executed via JL above but always returns
  57         ;    out whenever kernel_execve (now inline do_fork()) is involved
  58         b    ret_from_exception
  59 END(ret_from_fork)
  60
  61 ;################### Non TLB Exception Handling #############################
  62
  63 ; ---------------------------------------------
  64 ; Instruction Error Exception Handler
  65 ; ---------------------------------------------
  66
  67 ENTRY(instr_service)
  68
  69         EXCEPTION_PROLOGUE
  70
  71         lr  r0, [efa]
  72         mov r1, sp
  73
  74         FAKE_RET_FROM_EXCPN
  75
  76         bl  do_insterror_or_kprobe
  77         b   ret_from_exception
  78 END(instr_service)
  79
  80 ; ---------------------------------------------
  81 ; Machine Check Exception Handler
  82 ; ---------------------------------------------
  83
  84 ENTRY(EV_MachineCheck)
  85
  86         EXCEPTION_PROLOGUE
  87
  88         lr  r2, [ecr]
  89         lr  r0, [efa]
  90         mov r1, sp
  91
  92         ; hardware auto-disables MMU, re-enable it to allow kernel vaddr
  93         ; access for say stack unwinding of modules for crash dumps
  94         lr      r3, [ARC_REG_PID]
  95         or      r3, r3, MMU_ENABLE
  96         sr      r3, [ARC_REG_PID]
  97
  98         lsr     r3, r2, 8
  99         bmsk    r3, r3, 7
 100         brne    r3, ECR_C_MCHK_DUP_TLB, 1f
 101
 102         bl      do_tlb_overlap_fault
 103         b       ret_from_exception
 104
 105 1:
 106         ; DEAD END: can't do much, display Regs and HALT
 107         SAVE_CALLEE_SAVED_USER
 108
 109         GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
 110         st  sp, [r10, THREAD_CALLEE_REG]
 111
 112         j  do_machine_check_fault
 113
 114 END(EV_MachineCheck)
 115
 116 ; ---------------------------------------------
 117 ; Privilege Violation Exception Handler
 118 ; ---------------------------------------------
 119 ENTRY(EV_PrivilegeV)
 120
 121         EXCEPTION_PROLOGUE
 122
 123         lr  r0, [efa]
 124         mov r1, sp
 125
 126         FAKE_RET_FROM_EXCPN
 127
 128         bl  do_privilege_fault
 129         b   ret_from_exception
 130 END(EV_PrivilegeV)
 131
 132 ; ---------------------------------------------
 133 ; Extension Instruction Exception Handler
 134 ; ---------------------------------------------
 135 ENTRY(EV_Extension)
 136
 137         EXCEPTION_PROLOGUE
 138
 139         lr  r0, [efa]
 140         mov r1, sp
 141
 142         FAKE_RET_FROM_EXCPN
 143
 144         bl  do_extension_fault
 145         b   ret_from_exception
 146 END(EV_Extension)
 147
 148 ;################ Trap Handling (Syscall, Breakpoint) ##################
 149
 150 ; ---------------------------------------------
 151 ; syscall Tracing
 152 ; ---------------------------------------------
 153 tracesys:
 154         ; save EFA in case tracer wants the PC of traced task
 155         ; using ERET won't work since next-PC has already committed
 156         lr  r12, [efa]
 157         GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r11
 158         st  r12, [r11, THREAD_FAULT_ADDR]       ; thread.fault_address
 159
 160         ; PRE Sys Call Ptrace hook
 161         mov r0, sp                      ; pt_regs needed
 162         bl  @syscall_trace_entry
 163
 164         ; Tracing code now returns the syscall num (orig or modif)
 165         mov r8, r0
 166
 167         ; Do the Sys Call as we normally would.
 168         ; Validate the Sys Call number
 169         cmp     r8,  NR_syscalls
 170         mov.hi  r0, -ENOSYS
 171         bhi     tracesys_exit
 172
 173         ; Restore the sys-call args. Mere invocation of the hook abv could have
 174         ; clobbered them (since they are in scratch regs). The tracer could also
 175         ; have deliberately changed the syscall args: r0-r7
 176         ld  r0, [sp, PT_r0]
 177         ld  r1, [sp, PT_r1]
 178         ld  r2, [sp, PT_r2]
 179         ld  r3, [sp, PT_r3]
 180         ld  r4, [sp, PT_r4]
 181         ld  r5, [sp, PT_r5]
 182         ld  r6, [sp, PT_r6]
 183         ld  r7, [sp, PT_r7]
 184         ld.as   r9, [sys_call_table, r8]
 185         jl      [r9]        ; Entry into Sys Call Handler
 186
 187 tracesys_exit:
 188         st  r0, [sp, PT_r0]     ; sys call return value in pt_regs
 189
 190         ;POST Sys Call Ptrace Hook
 191         bl  @syscall_trace_exit
 192         b   ret_from_exception ; NOT ret_from_system_call at is saves r0 which
 193         ; we'd done before calling post hook above
 194
 195 ; ---------------------------------------------
 196 ; Breakpoint TRAP
 197 ; ---------------------------------------------
 198 trap_with_param:
 199
 200         ; stop_pc info by gdb needs this info
 201         lr  r0, [efa]
 202         mov r1, sp
 203
 204         ; Now that we have read EFA, it is safe to do "fake" rtie
 205         ;   and get out of CPU exception mode
 206         FAKE_RET_FROM_EXCPN
 207
 208         ; Save callee regs in case gdb wants to have a look
 209         ; SP will grow up by size of CALLEE Reg-File
 210         ; NOTE: clobbers r12
 211         SAVE_CALLEE_SAVED_USER
 212
 213         ; save location of saved Callee Regs @ thread_struct->pc
 214         GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
 215         st  sp, [r10, THREAD_CALLEE_REG]
 216
 217         ; Call the trap handler
 218         bl  do_non_swi_trap
 219
 220         ; unwind stack to discard Callee saved Regs
 221         DISCARD_CALLEE_SAVED_USER
 222
 223         b   ret_from_exception
 224
 225 ; ---------------------------------------------
 226 ; syscall TRAP
 227 ; ABI: (r0-r7) upto 8 args, (r8) syscall number
 228 ; ---------------------------------------------
 229
 230 ENTRY(EV_Trap)
 231
 232         EXCEPTION_PROLOGUE
 233
 234         ;============ TRAP 1   :breakpoints
 235         ; Check ECR for trap with arg (PROLOGUE ensures r9 has ECR)
 236         bmsk.f 0, r9, 7
 237         bnz    trap_with_param
 238
 239         ;============ TRAP  (no param): syscall top level
 240
 241         ; First return from Exception to pure K mode (Exception/IRQs renabled)
 242         FAKE_RET_FROM_EXCPN
 243
 244         ; If syscall tracing ongoing, invoke pre-post-hooks
 245         GET_CURR_THR_INFO_FLAGS   r10
 246         btst r10, TIF_SYSCALL_TRACE
 247         bnz tracesys  ; this never comes back
 248
 249         ;============ Normal syscall case
 250
 251         ; syscall num shd not exceed the total system calls avail
 252         cmp     r8,  NR_syscalls
 253         mov.hi  r0, -ENOSYS
 254         bhi     .Lret_from_system_call
 255
 256         ; Offset into the syscall_table and call handler
 257         ld.as   r9,[sys_call_table, r8]
 258         jl      [r9]        ; Entry into Sys Call Handler
 259
 260 .Lret_from_system_call:
 261
 262         st  r0, [sp, PT_r0]     ; sys call return value in pt_regs
 263
 264         ; fall through to ret_from_exception
 265 END(EV_Trap)
 266
 267 ;############# Return from Intr/Excp/Trap (Linux Specifics) ##############
 268 ;
 269 ; If ret to user mode do we need to handle signals, schedule() et al.
 270
 271 ENTRY(ret_from_exception)
 272
 273         ; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32
 274         ld  r8, [sp, PT_status32]   ; returning to User/Kernel Mode
 275
 276         bbit0  r8, STATUS_U_BIT, resume_kernel_mode
 277
 278         ; Before returning to User mode check-for-and-complete any pending work
 279         ; such as rescheduling/signal-delivery etc.
 280 resume_user_mode_begin:
 281
 282         ; Disable IRQs to ensures that chk for pending work itself is atomic
 283         ; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an
 284         ; interim IRQ).
 285         IRQ_DISABLE     r10
 286
 287         ; Fast Path return to user mode if no pending work
 288         GET_CURR_THR_INFO_FLAGS   r9
 289         and.f  0,  r9, _TIF_WORK_MASK
 290         bz     .Lrestore_regs
 291
 292         ; --- (Slow Path #1) task preemption ---
 293         bbit0  r9, TIF_NEED_RESCHED, .Lchk_pend_signals
 294         mov    blink, resume_user_mode_begin  ; tail-call to U mode ret chks
 295         j      @schedule        ; BTST+Bnz causes relo error in link
 296
 297 .Lchk_pend_signals:
 298         IRQ_ENABLE      r10
 299
 300         ; --- (Slow Path #2) pending signal  ---
 301         mov r0, sp      ; pt_regs for arg to do_signal()/do_notify_resume()
 302
 303         GET_CURR_THR_INFO_FLAGS   r9
 304         bbit0  r9, TIF_SIGPENDING, .Lchk_notify_resume
 305
 306         ; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
 307         ; in pt_reg since the "C" ABI (kernel code) will automatically
 308         ; save/restore callee-saved regs.
 309         ;
 310         ; However, here we need to explicitly save callee regs because
 311         ; (i)  If this signal causes coredump - full regfile needed
 312         ; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus
 313         ;      tracer might call PEEKUSR(CALLEE reg)
 314         ;
 315         ; NOTE: SP will grow up by size of CALLEE Reg-File
 316         SAVE_CALLEE_SAVED_USER          ; clobbers r12
 317
 318         ; save location of saved Callee Regs @ thread_struct->callee
 319         GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r10
 320         st  sp, [r10, THREAD_CALLEE_REG]
 321
 322         bl  @do_signal
 323
 324         ; Ideally we want to discard the Callee reg above, however if this was
 325         ; a tracing signal, tracer could have done a POKEUSR(CALLEE reg)
 326         RESTORE_CALLEE_SAVED_USER
 327
 328         b      resume_user_mode_begin   ; loop back to start of U mode ret
 329
 330         ; --- (Slow Path #3) notify_resume ---
 331 .Lchk_notify_resume:
 332         btst   r9, TIF_NOTIFY_RESUME
 333         blnz   @do_notify_resume
 334         b      resume_user_mode_begin   ; unconditionally back to U mode ret chks
 335                                         ; for single exit point from this block
 336
 337 resume_kernel_mode:
 338
 339         ; Disable Interrupts from this point on
 340         ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq()
 341         ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe
 342         IRQ_DISABLE     r9
 343
 344 #ifdef CONFIG_PREEMPT
 345
 346         ; Can't preempt if preemption disabled
 347         GET_CURR_THR_INFO_FROM_SP   r10
 348         ld  r8, [r10, THREAD_INFO_PREEMPT_COUNT]
 349         brne  r8, 0, .Lrestore_regs
 350
 351         ; check if this task's NEED_RESCHED flag set
 352         ld  r9, [r10, THREAD_INFO_FLAGS]
 353         bbit0  r9, TIF_NEED_RESCHED, .Lrestore_regs
 354
 355         ; Invoke PREEMPTION
 356         jl      preempt_schedule_irq
 357
 358         ; preempt_schedule_irq() always returns with IRQ disabled
 359 #endif
 360
 361         b       .Lrestore_regs
 362
 363 ##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-<isa>.S
 364