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 29ENTRY(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 39END(sys_clone_wrapper) 40 41ENTRY(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) 52 531: 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 62END(ret_from_fork) 63 64;################### Non TLB Exception Handling ############################# 65 66; --------------------------------------------- 67; Instruction Error Exception Handler 68; --------------------------------------------- 69 70ENTRY(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 81END(instr_service) 82 83; --------------------------------------------- 84; Machine Check Exception Handler 85; --------------------------------------------- 86 87ENTRY(EV_MachineCheck) 88 89 EXCEPTION_PROLOGUE 90 91 lr r2, [ecr] 92 lr r0, [efa] 93 mov r1, sp 94 95 lsr r3, r2, 8 96 bmsk r3, r3, 7 97 brne r3, ECR_C_MCHK_DUP_TLB, 1f 98 99 bl do_tlb_overlap_fault 100 b ret_from_exception 101 1021: 103 ; DEAD END: can't do much, display Regs and HALT 104 SAVE_CALLEE_SAVED_USER 105 106 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 107 st sp, [r10, THREAD_CALLEE_REG] 108 109 j do_machine_check_fault 110 111END(EV_MachineCheck) 112 113; --------------------------------------------- 114; Privilege Violation Exception Handler 115; --------------------------------------------- 116ENTRY(EV_PrivilegeV) 117 118 EXCEPTION_PROLOGUE 119 120 lr r0, [efa] 121 mov r1, sp 122 123 FAKE_RET_FROM_EXCPN 124 125 bl do_privilege_fault 126 b ret_from_exception 127END(EV_PrivilegeV) 128 129; --------------------------------------------- 130; Extension Instruction Exception Handler 131; --------------------------------------------- 132ENTRY(EV_Extension) 133 134 EXCEPTION_PROLOGUE 135 136 lr r0, [efa] 137 mov r1, sp 138 139 FAKE_RET_FROM_EXCPN 140 141 bl do_extension_fault 142 b ret_from_exception 143END(EV_Extension) 144 145;################ Trap Handling (Syscall, Breakpoint) ################## 146 147; --------------------------------------------- 148; syscall Tracing 149; --------------------------------------------- 150tracesys: 151 ; save EFA in case tracer wants the PC of traced task 152 ; using ERET won't work since next-PC has already committed 153 lr r12, [efa] 154 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r11 155 st r12, [r11, THREAD_FAULT_ADDR] ; thread.fault_address 156 157 ; PRE Sys Call Ptrace hook 158 mov r0, sp ; pt_regs needed 159 bl @syscall_trace_entry 160 161 ; Tracing code now returns the syscall num (orig or modif) 162 mov r8, r0 163 164 ; Do the Sys Call as we normally would. 165 ; Validate the Sys Call number 166 cmp r8, NR_syscalls 167 mov.hi r0, -ENOSYS 168 bhi tracesys_exit 169 170 ; Restore the sys-call args. Mere invocation of the hook abv could have 171 ; clobbered them (since they are in scratch regs). The tracer could also 172 ; have deliberately changed the syscall args: r0-r7 173 ld r0, [sp, PT_r0] 174 ld r1, [sp, PT_r1] 175 ld r2, [sp, PT_r2] 176 ld r3, [sp, PT_r3] 177 ld r4, [sp, PT_r4] 178 ld r5, [sp, PT_r5] 179 ld r6, [sp, PT_r6] 180 ld r7, [sp, PT_r7] 181 ld.as r9, [sys_call_table, r8] 182 jl [r9] ; Entry into Sys Call Handler 183 184tracesys_exit: 185 st r0, [sp, PT_r0] ; sys call return value in pt_regs 186 187 ;POST Sys Call Ptrace Hook 188 bl @syscall_trace_exit 189 b ret_from_exception ; NOT ret_from_system_call at is saves r0 which 190 ; we'd done before calling post hook above 191 192; --------------------------------------------- 193; Breakpoint TRAP 194; --------------------------------------------- 195trap_with_param: 196 197 ; stop_pc info by gdb needs this info 198 lr r0, [efa] 199 mov r1, sp 200 201 ; Now that we have read EFA, it is safe to do "fake" rtie 202 ; and get out of CPU exception mode 203 FAKE_RET_FROM_EXCPN 204 205 ; Save callee regs in case gdb wants to have a look 206 ; SP will grow up by size of CALLEE Reg-File 207 ; NOTE: clobbers r12 208 SAVE_CALLEE_SAVED_USER 209 210 ; save location of saved Callee Regs @ thread_struct->pc 211 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 212 st sp, [r10, THREAD_CALLEE_REG] 213 214 ; Call the trap handler 215 bl do_non_swi_trap 216 217 ; unwind stack to discard Callee saved Regs 218 DISCARD_CALLEE_SAVED_USER 219 220 b ret_from_exception 221 222; --------------------------------------------- 223; syscall TRAP 224; ABI: (r0-r7) upto 8 args, (r8) syscall number 225; --------------------------------------------- 226 227ENTRY(EV_Trap) 228 229 EXCEPTION_PROLOGUE 230 231 ;============ TRAP 1 :breakpoints 232 ; Check ECR for trap with arg (PROLOGUE ensures r9 has ECR) 233 bmsk.f 0, r9, 7 234 bnz trap_with_param 235 236 ;============ TRAP (no param): syscall top level 237 238 ; First return from Exception to pure K mode (Exception/IRQs renabled) 239 FAKE_RET_FROM_EXCPN 240 241 ; If syscall tracing ongoing, invoke pre-post-hooks 242 GET_CURR_THR_INFO_FLAGS r10 243 btst r10, TIF_SYSCALL_TRACE 244 bnz tracesys ; this never comes back 245 246 ;============ Normal syscall case 247 248 ; syscall num shd not exceed the total system calls avail 249 cmp r8, NR_syscalls 250 mov.hi r0, -ENOSYS 251 bhi .Lret_from_system_call 252 253 ; Offset into the syscall_table and call handler 254 ld.as r9,[sys_call_table, r8] 255 jl [r9] ; Entry into Sys Call Handler 256 257.Lret_from_system_call: 258 259 st r0, [sp, PT_r0] ; sys call return value in pt_regs 260 261 ; fall through to ret_from_exception 262END(EV_Trap) 263 264;############# Return from Intr/Excp/Trap (Linux Specifics) ############## 265; 266; If ret to user mode do we need to handle signals, schedule() et al. 267 268ENTRY(ret_from_exception) 269 270 ; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32 271 ld r8, [sp, PT_status32] ; returning to User/Kernel Mode 272 273 bbit0 r8, STATUS_U_BIT, resume_kernel_mode 274 275 ; Before returning to User mode check-for-and-complete any pending work 276 ; such as rescheduling/signal-delivery etc. 277resume_user_mode_begin: 278 279 ; Disable IRQs to ensures that chk for pending work itself is atomic 280 ; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an 281 ; interim IRQ). 282 IRQ_DISABLE r10 283 284 ; Fast Path return to user mode if no pending work 285 GET_CURR_THR_INFO_FLAGS r9 286 and.f 0, r9, _TIF_WORK_MASK 287 bz .Lrestore_regs 288 289 ; --- (Slow Path #1) task preemption --- 290 bbit0 r9, TIF_NEED_RESCHED, .Lchk_pend_signals 291 mov blink, resume_user_mode_begin ; tail-call to U mode ret chks 292 j @schedule ; BTST+Bnz causes relo error in link 293 294.Lchk_pend_signals: 295 IRQ_ENABLE r10 296 297 ; --- (Slow Path #2) pending signal --- 298 mov r0, sp ; pt_regs for arg to do_signal()/do_notify_resume() 299 300 GET_CURR_THR_INFO_FLAGS r9 301 bbit0 r9, TIF_SIGPENDING, .Lchk_notify_resume 302 303 ; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs 304 ; in pt_reg since the "C" ABI (kernel code) will automatically 305 ; save/restore callee-saved regs. 306 ; 307 ; However, here we need to explicitly save callee regs because 308 ; (i) If this signal causes coredump - full regfile needed 309 ; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus 310 ; tracer might call PEEKUSR(CALLEE reg) 311 ; 312 ; NOTE: SP will grow up by size of CALLEE Reg-File 313 SAVE_CALLEE_SAVED_USER ; clobbers r12 314 315 ; save location of saved Callee Regs @ thread_struct->callee 316 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 317 st sp, [r10, THREAD_CALLEE_REG] 318 319 bl @do_signal 320 321 ; Ideally we want to discard the Callee reg above, however if this was 322 ; a tracing signal, tracer could have done a POKEUSR(CALLEE reg) 323 RESTORE_CALLEE_SAVED_USER 324 325 b resume_user_mode_begin ; loop back to start of U mode ret 326 327 ; --- (Slow Path #3) notify_resume --- 328.Lchk_notify_resume: 329 btst r9, TIF_NOTIFY_RESUME 330 blnz @do_notify_resume 331 b resume_user_mode_begin ; unconditionally back to U mode ret chks 332 ; for single exit point from this block 333 334resume_kernel_mode: 335 336 ; Disable Interrupts from this point on 337 ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq() 338 ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe 339 IRQ_DISABLE r9 340 341#ifdef CONFIG_PREEMPT 342 343 ; Can't preempt if preemption disabled 344 GET_CURR_THR_INFO_FROM_SP r10 345 ld r8, [r10, THREAD_INFO_PREEMPT_COUNT] 346 brne r8, 0, .Lrestore_regs 347 348 ; check if this task's NEED_RESCHED flag set 349 ld r9, [r10, THREAD_INFO_FLAGS] 350 bbit0 r9, TIF_NEED_RESCHED, .Lrestore_regs 351 352 ; Invoke PREEMPTION 353 jl preempt_schedule_irq 354 355 ; preempt_schedule_irq() always returns with IRQ disabled 356#endif 357 358 b .Lrestore_regs 359 360##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-<isa>.S 361 362