2 * Common Low Level Interrupts/Traps/Exceptions(non-TLB) Handling for ARC
3 * (included from entry-<isa>.S
5 * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
6 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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.
13 /*------------------------------------------------------------------
15 *------------------------------------------------------------------
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 *------------------------------------------------------------------
27 ;################### Non TLB Exception Handling #############################
29 ; ---------------------------------------------
30 ; Instruction Error Exception Handler
31 ; ---------------------------------------------
42 bl do_insterror_or_kprobe
46 ; ---------------------------------------------
47 ; Memory Error Exception Handler
48 ; ---------------------------------------------
63 ; ---------------------------------------------
64 ; Machine Check Exception Handler
65 ; ---------------------------------------------
67 ENTRY(EV_MachineCheck)
77 brne r3, ECR_C_MCHK_DUP_TLB, 1f
79 bl do_tlb_overlap_fault
83 ; DEAD END: can't do much, display Regs and HALT
84 SAVE_CALLEE_SAVED_USER
86 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10
87 st sp, [r10, THREAD_CALLEE_REG]
89 j do_machine_check_fault
93 ; ---------------------------------------------
94 ; Privilege Violation Exception Handler
95 ; ---------------------------------------------
105 bl do_privilege_fault
109 ; ---------------------------------------------
110 ; Extension Instruction Exception Handler
111 ; ---------------------------------------------
121 bl do_extension_fault
125 ;################ Trap Handling (Syscall, Breakpoint) ##################
127 ; ---------------------------------------------
129 ; ---------------------------------------------
131 ; save EFA in case tracer wants the PC of traced task
132 ; using ERET won't work since next-PC has already committed
134 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r11
135 st r12, [r11, THREAD_FAULT_ADDR] ; thread.fault_address
137 ; PRE Sys Call Ptrace hook
138 mov r0, sp ; pt_regs needed
139 bl @syscall_trace_entry
141 ; Tracing code now returns the syscall num (orig or modif)
144 ; Do the Sys Call as we normally would.
145 ; Validate the Sys Call number
150 ; Restore the sys-call args. Mere invocation of the hook abv could have
151 ; clobbered them (since they are in scratch regs). The tracer could also
152 ; have deliberately changed the syscall args: r0-r7
161 ld.as r9, [sys_call_table, r8]
162 jl [r9] ; Entry into Sys Call Handler
165 st r0, [sp, PT_r0] ; sys call return value in pt_regs
167 ;POST Sys Call Ptrace Hook
168 bl @syscall_trace_exit
169 b ret_from_exception ; NOT ret_from_system_call at is saves r0 which
170 ; we'd done before calling post hook above
172 ; ---------------------------------------------
174 ; ---------------------------------------------
177 ; stop_pc info by gdb needs this info
181 ; Now that we have read EFA, it is safe to do "fake" rtie
182 ; and get out of CPU exception mode
185 ; Save callee regs in case gdb wants to have a look
186 ; SP will grow up by size of CALLEE Reg-File
188 SAVE_CALLEE_SAVED_USER
190 ; save location of saved Callee Regs @ thread_struct->pc
191 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10
192 st sp, [r10, THREAD_CALLEE_REG]
194 ; Call the trap handler
197 ; unwind stack to discard Callee saved Regs
198 DISCARD_CALLEE_SAVED_USER
202 ; ---------------------------------------------
204 ; ABI: (r0-r7) upto 8 args, (r8) syscall number
205 ; ---------------------------------------------
211 ;============ TRAP 1 :breakpoints
216 ;============ TRAP (no param): syscall top level
218 ; First return from Exception to pure K mode (Exception/IRQs renabled)
221 ; If syscall tracing ongoing, invoke pre-post-hooks
222 GET_CURR_THR_INFO_FLAGS r10
223 btst r10, TIF_SYSCALL_TRACE
224 bnz tracesys ; this never comes back
226 ;============ Normal syscall case
228 ; syscall num shd not exceed the total system calls avail
231 bhi ret_from_system_call
233 ; Offset into the syscall_table and call handler
234 ld.as r9,[sys_call_table, r8]
235 jl [r9] ; Entry into Sys Call Handler
237 ; fall through to ret_from_system_call
240 ENTRY(ret_from_system_call)
242 st r0, [sp, PT_r0] ; sys call return value in pt_regs
244 ; fall through yet again to ret_from_exception
246 ;############# Return from Intr/Excp/Trap (Linux Specifics) ##############
248 ; If ret to user mode do we need to handle signals, schedule() et al.
250 ENTRY(ret_from_exception)
252 ; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32
253 ld r8, [sp, PT_status32] ; returning to User/Kernel Mode
255 bbit0 r8, STATUS_U_BIT, resume_kernel_mode
257 ; Before returning to User mode check-for-and-complete any pending work
258 ; such as rescheduling/signal-delivery etc.
259 resume_user_mode_begin:
261 ; Disable IRQs to ensures that chk for pending work itself is atomic
262 ; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an
266 ; Fast Path return to user mode if no pending work
267 GET_CURR_THR_INFO_FLAGS r9
268 and.f 0, r9, _TIF_WORK_MASK
271 ; --- (Slow Path #1) task preemption ---
272 bbit0 r9, TIF_NEED_RESCHED, .Lchk_pend_signals
273 mov blink, resume_user_mode_begin ; tail-call to U mode ret chks
274 b @schedule ; BTST+Bnz causes relo error in link
279 ; --- (Slow Path #2) pending signal ---
280 mov r0, sp ; pt_regs for arg to do_signal()/do_notify_resume()
282 GET_CURR_THR_INFO_FLAGS r9
283 bbit0 r9, TIF_SIGPENDING, .Lchk_notify_resume
285 ; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
286 ; in pt_reg since the "C" ABI (kernel code) will automatically
287 ; save/restore callee-saved regs.
289 ; However, here we need to explicitly save callee regs because
290 ; (i) If this signal causes coredump - full regfile needed
291 ; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus
292 ; tracer might call PEEKUSR(CALLEE reg)
294 ; NOTE: SP will grow up by size of CALLEE Reg-File
295 SAVE_CALLEE_SAVED_USER ; clobbers r12
297 ; save location of saved Callee Regs @ thread_struct->callee
298 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10
299 st sp, [r10, THREAD_CALLEE_REG]
303 ; Ideally we want to discard the Callee reg above, however if this was
304 ; a tracing signal, tracer could have done a POKEUSR(CALLEE reg)
305 RESTORE_CALLEE_SAVED_USER
307 b resume_user_mode_begin ; loop back to start of U mode ret
309 ; --- (Slow Path #3) notify_resume ---
311 btst r9, TIF_NOTIFY_RESUME
312 blnz @do_notify_resume
313 b resume_user_mode_begin ; unconditionally back to U mode ret chks
314 ; for single exit point from this block
318 ; Disable Interrupts from this point on
319 ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq()
320 ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe
323 #ifdef CONFIG_PREEMPT
325 ; Can't preempt if preemption disabled
326 GET_CURR_THR_INFO_FROM_SP r10
327 ld r8, [r10, THREAD_INFO_PREEMPT_COUNT]
328 brne r8, 0, .Lrestore_regs
330 ; check if this task's NEED_RESCHED flag set
331 ld r9, [r10, THREAD_INFO_FLAGS]
332 bbit0 r9, TIF_NEED_RESCHED, .Lrestore_regs
335 bl preempt_schedule_irq
337 ; preempt_schedule_irq() always returns with IRQ disabled
341 END(ret_from_exception)
344 ; when the forked child comes here from the __switch_to function
345 ; r0 has the last task pointer.
346 ; put last task in scheduler queue
349 ld r9, [sp, PT_status32]
352 jl.d [r14] ; kernel thread entry point
353 mov r0, r13 ; (see PF_KTHREAD block in copy_thread)
356 ; Return to user space
357 ; 1. Any forked task (Reach here via BRne above)
358 ; 2. First ever init task (Reach here via return from JL above)
359 ; This is the historic "kernel_execve" use-case, to return to init
360 ; user mode, in a round about way since that is always done from
361 ; a kernel thread which is executed via JL above but always returns
362 ; out whenever kernel_execve (now inline do_fork()) is involved
366 ;################### Special Sys Call Wrappers ##########################
368 ENTRY(sys_clone_wrapper)
369 SAVE_CALLEE_SAVED_USER
371 DISCARD_CALLEE_SAVED_USER
373 GET_CURR_THR_INFO_FLAGS r10
374 btst r10, TIF_SYSCALL_TRACE
377 b ret_from_system_call
378 END(sys_clone_wrapper)
380 #ifdef CONFIG_ARC_DW2_UNWIND
381 ; Workaround for bug 94179 (STAR ):
382 ; Despite -fasynchronous-unwind-tables, linker is not making dwarf2 unwinder
383 ; section (.debug_frame) as loadable. So we force it here.
384 ; This also fixes STAR 9000487933 where the prev-workaround (objcopy --setflag)
385 ; would not work after a clean build due to kernel build system dependencies.
386 .section .debug_frame, "wa",@progbits
388 ; Reset to .text as this file is included in entry-<isa>.S
389 .section .text, "ax",@progbits