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 ret_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#ifdef CONFIG_ARC_DW2_UNWIND 65; Workaround for bug 94179 (STAR ): 66; Despite -fasynchronous-unwind-tables, linker is not making dwarf2 unwinder 67; section (.debug_frame) as loadable. So we force it here. 68; This also fixes STAR 9000487933 where the prev-workaround (objcopy --setflag) 69; would not work after a clean build due to kernel build system dependencies. 70.section .debug_frame, "wa",@progbits 71 72; Reset to .text as this file is included in entry-<isa>.S 73.section .text, "ax",@progbits 74#endif 75 76;################### Non TLB Exception Handling ############################# 77 78; --------------------------------------------- 79; Instruction Error Exception Handler 80; --------------------------------------------- 81 82ENTRY(instr_service) 83 84 EXCEPTION_PROLOGUE 85 86 lr r0, [efa] 87 mov r1, sp 88 89 FAKE_RET_FROM_EXCPN 90 91 bl do_insterror_or_kprobe 92 b ret_from_exception 93END(instr_service) 94 95; --------------------------------------------- 96; Machine Check Exception Handler 97; --------------------------------------------- 98 99ENTRY(EV_MachineCheck) 100 101 EXCEPTION_PROLOGUE 102 103 lr r2, [ecr] 104 lr r0, [efa] 105 mov r1, sp 106 107 lsr r3, r2, 8 108 bmsk r3, r3, 7 109 brne r3, ECR_C_MCHK_DUP_TLB, 1f 110 111 bl do_tlb_overlap_fault 112 b ret_from_exception 113 1141: 115 ; DEAD END: can't do much, display Regs and HALT 116 SAVE_CALLEE_SAVED_USER 117 118 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 119 st sp, [r10, THREAD_CALLEE_REG] 120 121 j do_machine_check_fault 122 123END(EV_MachineCheck) 124 125; --------------------------------------------- 126; Privilege Violation Exception Handler 127; --------------------------------------------- 128ENTRY(EV_PrivilegeV) 129 130 EXCEPTION_PROLOGUE 131 132 lr r0, [efa] 133 mov r1, sp 134 135 FAKE_RET_FROM_EXCPN 136 137 bl do_privilege_fault 138 b ret_from_exception 139END(EV_PrivilegeV) 140 141; --------------------------------------------- 142; Extension Instruction Exception Handler 143; --------------------------------------------- 144ENTRY(EV_Extension) 145 146 EXCEPTION_PROLOGUE 147 148 lr r0, [efa] 149 mov r1, sp 150 151 FAKE_RET_FROM_EXCPN 152 153 bl do_extension_fault 154 b ret_from_exception 155END(EV_Extension) 156 157;################ Trap Handling (Syscall, Breakpoint) ################## 158 159; --------------------------------------------- 160; syscall Tracing 161; --------------------------------------------- 162tracesys: 163 ; save EFA in case tracer wants the PC of traced task 164 ; using ERET won't work since next-PC has already committed 165 lr r12, [efa] 166 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r11 167 st r12, [r11, THREAD_FAULT_ADDR] ; thread.fault_address 168 169 ; PRE Sys Call Ptrace hook 170 mov r0, sp ; pt_regs needed 171 bl @syscall_trace_entry 172 173 ; Tracing code now returns the syscall num (orig or modif) 174 mov r8, r0 175 176 ; Do the Sys Call as we normally would. 177 ; Validate the Sys Call number 178 cmp r8, NR_syscalls 179 mov.hi r0, -ENOSYS 180 bhi tracesys_exit 181 182 ; Restore the sys-call args. Mere invocation of the hook abv could have 183 ; clobbered them (since they are in scratch regs). The tracer could also 184 ; have deliberately changed the syscall args: r0-r7 185 ld r0, [sp, PT_r0] 186 ld r1, [sp, PT_r1] 187 ld r2, [sp, PT_r2] 188 ld r3, [sp, PT_r3] 189 ld r4, [sp, PT_r4] 190 ld r5, [sp, PT_r5] 191 ld r6, [sp, PT_r6] 192 ld r7, [sp, PT_r7] 193 ld.as r9, [sys_call_table, r8] 194 jl [r9] ; Entry into Sys Call Handler 195 196tracesys_exit: 197 st r0, [sp, PT_r0] ; sys call return value in pt_regs 198 199 ;POST Sys Call Ptrace Hook 200 bl @syscall_trace_exit 201 b ret_from_exception ; NOT ret_from_system_call at is saves r0 which 202 ; we'd done before calling post hook above 203 204; --------------------------------------------- 205; Breakpoint TRAP 206; --------------------------------------------- 207trap_with_param: 208 209 ; stop_pc info by gdb needs this info 210 lr r0, [efa] 211 mov r1, sp 212 213 ; Now that we have read EFA, it is safe to do "fake" rtie 214 ; and get out of CPU exception mode 215 FAKE_RET_FROM_EXCPN 216 217 ; Save callee regs in case gdb wants to have a look 218 ; SP will grow up by size of CALLEE Reg-File 219 ; NOTE: clobbers r12 220 SAVE_CALLEE_SAVED_USER 221 222 ; save location of saved Callee Regs @ thread_struct->pc 223 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 224 st sp, [r10, THREAD_CALLEE_REG] 225 226 ; Call the trap handler 227 bl do_non_swi_trap 228 229 ; unwind stack to discard Callee saved Regs 230 DISCARD_CALLEE_SAVED_USER 231 232 b ret_from_exception 233 234; --------------------------------------------- 235; syscall TRAP 236; ABI: (r0-r7) upto 8 args, (r8) syscall number 237; --------------------------------------------- 238 239ENTRY(EV_Trap) 240 241 EXCEPTION_PROLOGUE 242 243 ;============ TRAP 1 :breakpoints 244 ; Check ECR for trap with arg (PROLOGUE ensures r9 has ECR) 245 bmsk.f 0, r9, 7 246 bnz trap_with_param 247 248 ;============ TRAP (no param): syscall top level 249 250 ; First return from Exception to pure K mode (Exception/IRQs renabled) 251 FAKE_RET_FROM_EXCPN 252 253 ; If syscall tracing ongoing, invoke pre-post-hooks 254 GET_CURR_THR_INFO_FLAGS r10 255 btst r10, TIF_SYSCALL_TRACE 256 bnz tracesys ; this never comes back 257 258 ;============ Normal syscall case 259 260 ; syscall num shd not exceed the total system calls avail 261 cmp r8, NR_syscalls 262 mov.hi r0, -ENOSYS 263 bhi ret_from_system_call 264 265 ; Offset into the syscall_table and call handler 266 ld.as r9,[sys_call_table, r8] 267 jl [r9] ; Entry into Sys Call Handler 268 269 ; fall through to ret_from_system_call 270END(EV_Trap) 271 272ENTRY(ret_from_system_call) 273 274 st r0, [sp, PT_r0] ; sys call return value in pt_regs 275 276 ; fall through yet again to ret_from_exception 277 278;############# Return from Intr/Excp/Trap (Linux Specifics) ############## 279; 280; If ret to user mode do we need to handle signals, schedule() et al. 281 282ENTRY(ret_from_exception) 283 284 ; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32 285 ld r8, [sp, PT_status32] ; returning to User/Kernel Mode 286 287 bbit0 r8, STATUS_U_BIT, resume_kernel_mode 288 289 ; Before returning to User mode check-for-and-complete any pending work 290 ; such as rescheduling/signal-delivery etc. 291resume_user_mode_begin: 292 293 ; Disable IRQs to ensures that chk for pending work itself is atomic 294 ; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an 295 ; interim IRQ). 296 IRQ_DISABLE r10 297 298 ; Fast Path return to user mode if no pending work 299 GET_CURR_THR_INFO_FLAGS r9 300 and.f 0, r9, _TIF_WORK_MASK 301 bz .Lrestore_regs 302 303 ; --- (Slow Path #1) task preemption --- 304 bbit0 r9, TIF_NEED_RESCHED, .Lchk_pend_signals 305 mov blink, resume_user_mode_begin ; tail-call to U mode ret chks 306 j @schedule ; BTST+Bnz causes relo error in link 307 308.Lchk_pend_signals: 309 IRQ_ENABLE r10 310 311 ; --- (Slow Path #2) pending signal --- 312 mov r0, sp ; pt_regs for arg to do_signal()/do_notify_resume() 313 314 GET_CURR_THR_INFO_FLAGS r9 315 bbit0 r9, TIF_SIGPENDING, .Lchk_notify_resume 316 317 ; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs 318 ; in pt_reg since the "C" ABI (kernel code) will automatically 319 ; save/restore callee-saved regs. 320 ; 321 ; However, here we need to explicitly save callee regs because 322 ; (i) If this signal causes coredump - full regfile needed 323 ; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus 324 ; tracer might call PEEKUSR(CALLEE reg) 325 ; 326 ; NOTE: SP will grow up by size of CALLEE Reg-File 327 SAVE_CALLEE_SAVED_USER ; clobbers r12 328 329 ; save location of saved Callee Regs @ thread_struct->callee 330 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 331 st sp, [r10, THREAD_CALLEE_REG] 332 333 bl @do_signal 334 335 ; Ideally we want to discard the Callee reg above, however if this was 336 ; a tracing signal, tracer could have done a POKEUSR(CALLEE reg) 337 RESTORE_CALLEE_SAVED_USER 338 339 b resume_user_mode_begin ; loop back to start of U mode ret 340 341 ; --- (Slow Path #3) notify_resume --- 342.Lchk_notify_resume: 343 btst r9, TIF_NOTIFY_RESUME 344 blnz @do_notify_resume 345 b resume_user_mode_begin ; unconditionally back to U mode ret chks 346 ; for single exit point from this block 347 348resume_kernel_mode: 349 350 ; Disable Interrupts from this point on 351 ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq() 352 ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe 353 IRQ_DISABLE r9 354 355#ifdef CONFIG_PREEMPT 356 357 ; Can't preempt if preemption disabled 358 GET_CURR_THR_INFO_FROM_SP r10 359 ld r8, [r10, THREAD_INFO_PREEMPT_COUNT] 360 brne r8, 0, .Lrestore_regs 361 362 ; check if this task's NEED_RESCHED flag set 363 ld r9, [r10, THREAD_INFO_FLAGS] 364 bbit0 r9, TIF_NEED_RESCHED, .Lrestore_regs 365 366 ; Invoke PREEMPTION 367 jl preempt_schedule_irq 368 369 ; preempt_schedule_irq() always returns with IRQ disabled 370#endif 371 372 b .Lrestore_regs 373 374##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-<isa>.S 375 376