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 26ENTRY(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 36END(sys_clone_wrapper) 37 38ENTRY(sys_clone3_wrapper) 39 SAVE_CALLEE_SAVED_USER 40 bl @sys_clone3 41 DISCARD_CALLEE_SAVED_USER 42 43 GET_CURR_THR_INFO_FLAGS r10 44 btst r10, TIF_SYSCALL_TRACE 45 bnz tracesys_exit 46 47 b .Lret_from_system_call 48END(sys_clone3_wrapper) 49 50ENTRY(ret_from_fork) 51 ; when the forked child comes here from the __switch_to function 52 ; r0 has the last task pointer. 53 ; put last task in scheduler queue 54 jl @schedule_tail 55 56 ld r9, [sp, PT_status32] 57 brne r9, 0, 1f 58 59 jl.d [r14] ; kernel thread entry point 60 mov r0, r13 ; (see PF_KTHREAD block in copy_thread) 61 621: 63 ; Return to user space 64 ; 1. Any forked task (Reach here via BRne above) 65 ; 2. First ever init task (Reach here via return from JL above) 66 ; This is the historic "kernel_execve" use-case, to return to init 67 ; user mode, in a round about way since that is always done from 68 ; a kernel thread which is executed via JL above but always returns 69 ; out whenever kernel_execve (now inline do_fork()) is involved 70 b ret_from_exception 71END(ret_from_fork) 72 73;################### Non TLB Exception Handling ############################# 74 75; --------------------------------------------- 76; Instruction Error Exception Handler 77; --------------------------------------------- 78 79ENTRY(instr_service) 80 81 EXCEPTION_PROLOGUE 82 83 lr r0, [efa] 84 mov r1, sp 85 86 FAKE_RET_FROM_EXCPN 87 88 bl do_insterror_or_kprobe 89 b ret_from_exception 90END(instr_service) 91 92; --------------------------------------------- 93; Machine Check Exception Handler 94; --------------------------------------------- 95 96ENTRY(EV_MachineCheck) 97 98 EXCEPTION_PROLOGUE 99 100 lr r2, [ecr] 101 lr r0, [efa] 102 mov r1, sp 103 104 ; hardware auto-disables MMU, re-enable it to allow kernel vaddr 105 ; access for say stack unwinding of modules for crash dumps 106 lr r3, [ARC_REG_PID] 107 or r3, r3, MMU_ENABLE 108 sr r3, [ARC_REG_PID] 109 110 lsr r3, r2, 8 111 bmsk r3, r3, 7 112 brne r3, ECR_C_MCHK_DUP_TLB, 1f 113 114 bl do_tlb_overlap_fault 115 b ret_from_exception 116 1171: 118 ; DEAD END: can't do much, display Regs and HALT 119 SAVE_CALLEE_SAVED_USER 120 121 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 122 st sp, [r10, THREAD_CALLEE_REG] 123 124 j do_machine_check_fault 125 126END(EV_MachineCheck) 127 128; --------------------------------------------- 129; Privilege Violation Exception Handler 130; --------------------------------------------- 131ENTRY(EV_PrivilegeV) 132 133 EXCEPTION_PROLOGUE 134 135 lr r0, [efa] 136 mov r1, sp 137 138 FAKE_RET_FROM_EXCPN 139 140 bl do_privilege_fault 141 b ret_from_exception 142END(EV_PrivilegeV) 143 144; --------------------------------------------- 145; Extension Instruction Exception Handler 146; --------------------------------------------- 147ENTRY(EV_Extension) 148 149 EXCEPTION_PROLOGUE 150 151 lr r0, [efa] 152 mov r1, sp 153 154 FAKE_RET_FROM_EXCPN 155 156 bl do_extension_fault 157 b ret_from_exception 158END(EV_Extension) 159 160;################ Trap Handling (Syscall, Breakpoint) ################## 161 162; --------------------------------------------- 163; syscall Tracing 164; --------------------------------------------- 165tracesys: 166 ; save EFA in case tracer wants the PC of traced task 167 ; using ERET won't work since next-PC has already committed 168 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r11 169 st r12, [r11, THREAD_FAULT_ADDR] ; thread.fault_address 170 171 ; PRE Sys Call Ptrace hook 172 mov r0, sp ; pt_regs needed 173 bl @syscall_trace_entry 174 175 ; Tracing code now returns the syscall num (orig or modif) 176 mov r8, r0 177 178 ; Do the Sys Call as we normally would. 179 ; Validate the Sys Call number 180 cmp r8, NR_syscalls - 1 181 mov.hi r0, -ENOSYS 182 bhi tracesys_exit 183 184 ; Restore the sys-call args. Mere invocation of the hook abv could have 185 ; clobbered them (since they are in scratch regs). The tracer could also 186 ; have deliberately changed the syscall args: r0-r7 187 ld r0, [sp, PT_r0] 188 ld r1, [sp, PT_r1] 189 ld r2, [sp, PT_r2] 190 ld r3, [sp, PT_r3] 191 ld r4, [sp, PT_r4] 192 ld r5, [sp, PT_r5] 193 ld r6, [sp, PT_r6] 194 ld r7, [sp, PT_r7] 195 ld.as r9, [sys_call_table, r8] 196 jl [r9] ; Entry into Sys Call Handler 197 198tracesys_exit: 199 st r0, [sp, PT_r0] ; sys call return value in pt_regs 200 201 ;POST Sys Call Ptrace Hook 202 bl @syscall_trace_exit 203 b ret_from_exception ; NOT ret_from_system_call at is saves r0 which 204 ; we'd done before calling post hook above 205 206; --------------------------------------------- 207; Breakpoint TRAP 208; --------------------------------------------- 209trap_with_param: 210 mov r0, r12 ; EFA in case ptracer/gdb wants stop_pc 211 mov r1, sp 212 213 ; Save callee regs in case gdb wants to have a look 214 ; SP will grow up by size of CALLEE Reg-File 215 ; NOTE: clobbers r12 216 SAVE_CALLEE_SAVED_USER 217 218 ; save location of saved Callee Regs @ thread_struct->pc 219 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 220 st sp, [r10, THREAD_CALLEE_REG] 221 222 ; Call the trap handler 223 bl do_non_swi_trap 224 225 ; unwind stack to discard Callee saved Regs 226 DISCARD_CALLEE_SAVED_USER 227 228 b ret_from_exception 229 230; --------------------------------------------- 231; syscall TRAP 232; ABI: (r0-r7) upto 8 args, (r8) syscall number 233; --------------------------------------------- 234 235ENTRY(EV_Trap) 236 237 EXCEPTION_PROLOGUE 238 239 lr r12, [efa] 240 241 FAKE_RET_FROM_EXCPN 242 243 ;============ TRAP 1 :breakpoints 244 ; Check ECR for trap with arg (PROLOGUE ensures r10 has ECR) 245 bmsk.f 0, r10, 7 246 bnz trap_with_param 247 248 ;============ TRAP (no param): syscall top level 249 250 ; If syscall tracing ongoing, invoke pre-post-hooks 251 GET_CURR_THR_INFO_FLAGS r10 252 btst r10, TIF_SYSCALL_TRACE 253 bnz tracesys ; this never comes back 254 255 ;============ Normal syscall case 256 257 ; syscall num shd not exceed the total system calls avail 258 cmp r8, NR_syscalls - 1 259 mov.hi r0, -ENOSYS 260 bhi .Lret_from_system_call 261 262 ; Offset into the syscall_table and call handler 263 ld.as r9,[sys_call_table, r8] 264 jl [r9] ; Entry into Sys Call Handler 265 266.Lret_from_system_call: 267 268 st r0, [sp, PT_r0] ; sys call return value in pt_regs 269 270 ; fall through to ret_from_exception 271END(EV_Trap) 272 273;############# Return from Intr/Excp/Trap (Linux Specifics) ############## 274; 275; If ret to user mode do we need to handle signals, schedule() et al. 276 277ENTRY(ret_from_exception) 278 279 ; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32 280 ld r8, [sp, PT_status32] ; returning to User/Kernel Mode 281 282 bbit0 r8, STATUS_U_BIT, resume_kernel_mode 283 284 ; Before returning to User mode check-for-and-complete any pending work 285 ; such as rescheduling/signal-delivery etc. 286resume_user_mode_begin: 287 288 ; Disable IRQs to ensures that chk for pending work itself is atomic 289 ; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an 290 ; interim IRQ). 291 IRQ_DISABLE r10 292 293 ; Fast Path return to user mode if no pending work 294 GET_CURR_THR_INFO_FLAGS r9 295 and.f 0, r9, _TIF_WORK_MASK 296 bz .Lrestore_regs 297 298 ; --- (Slow Path #1) task preemption --- 299 bbit0 r9, TIF_NEED_RESCHED, .Lchk_pend_signals 300 mov blink, resume_user_mode_begin ; tail-call to U mode ret chks 301 j @schedule ; BTST+Bnz causes relo error in link 302 303.Lchk_pend_signals: 304 IRQ_ENABLE r10 305 306 ; --- (Slow Path #2) pending signal --- 307 mov r0, sp ; pt_regs for arg to do_signal()/do_notify_resume() 308 309 GET_CURR_THR_INFO_FLAGS r9 310 and.f 0, r9, _TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL 311 bz .Lchk_notify_resume 312 313 ; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs 314 ; in pt_reg since the "C" ABI (kernel code) will automatically 315 ; save/restore callee-saved regs. 316 ; 317 ; However, here we need to explicitly save callee regs because 318 ; (i) If this signal causes coredump - full regfile needed 319 ; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus 320 ; tracer might call PEEKUSR(CALLEE reg) 321 ; 322 ; NOTE: SP will grow up by size of CALLEE Reg-File 323 SAVE_CALLEE_SAVED_USER ; clobbers r12 324 325 ; save location of saved Callee Regs @ thread_struct->callee 326 GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10 327 st sp, [r10, THREAD_CALLEE_REG] 328 329 bl @do_signal 330 331 ; Ideally we want to discard the Callee reg above, however if this was 332 ; a tracing signal, tracer could have done a POKEUSR(CALLEE reg) 333 RESTORE_CALLEE_SAVED_USER 334 335 b resume_user_mode_begin ; loop back to start of U mode ret 336 337 ; --- (Slow Path #3) notify_resume --- 338.Lchk_notify_resume: 339 btst r9, TIF_NOTIFY_RESUME 340 blnz @do_notify_resume 341 b resume_user_mode_begin ; unconditionally back to U mode ret chks 342 ; for single exit point from this block 343 344resume_kernel_mode: 345 346 ; Disable Interrupts from this point on 347 ; CONFIG_PREEMPTION: This is a must for preempt_schedule_irq() 348 ; !CONFIG_PREEMPTION: To ensure restore_regs is intr safe 349 IRQ_DISABLE r9 350 351#ifdef CONFIG_PREEMPTION 352 353 ; Can't preempt if preemption disabled 354 GET_CURR_THR_INFO_FROM_SP r10 355 ld r8, [r10, THREAD_INFO_PREEMPT_COUNT] 356 brne r8, 0, .Lrestore_regs 357 358 ; check if this task's NEED_RESCHED flag set 359 ld r9, [r10, THREAD_INFO_FLAGS] 360 bbit0 r9, TIF_NEED_RESCHED, .Lrestore_regs 361 362 ; Invoke PREEMPTION 363 jl preempt_schedule_irq 364 365 ; preempt_schedule_irq() always returns with IRQ disabled 366#endif 367 368 b .Lrestore_regs 369 370##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-<isa>.S 371 372