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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 r10 has ECR)
236 bmsk.f 0, r10, 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