1/* 2 * Copyright (C) 1999, 2000, 2002 Niibe Yutaka 3 * Copyright (C) 2003 - 2008 Paul Mundt 4 * 5 * This file is subject to the terms and conditions of the GNU General Public 6 * License. See the file "COPYING" in the main directory of this archive 7 * for more details. 8 * 9 */ 10 11! NOTE: 12! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address 13! to be jumped is too far, but it causes illegal slot exception. 14 15/* 16 * entry.S contains the system-call and fault low-level handling routines. 17 * This also contains the timer-interrupt handler, as well as all interrupts 18 * and faults that can result in a task-switch. 19 * 20 * NOTE: This code handles signal-recognition, which happens every time 21 * after a timer-interrupt and after each system call. 22 * 23 * NOTE: This code uses a convention that instructions in the delay slot 24 * of a transfer-control instruction are indented by an extra space, thus: 25 * 26 * jmp @k0 ! control-transfer instruction 27 * ldc k1, ssr ! delay slot 28 * 29 * Stack layout in 'ret_from_syscall': 30 * ptrace needs to have all regs on the stack. 31 * if the order here is changed, it needs to be 32 * updated in ptrace.c and ptrace.h 33 * 34 * r0 35 * ... 36 * r15 = stack pointer 37 * spc 38 * pr 39 * ssr 40 * gbr 41 * mach 42 * macl 43 * syscall # 44 * 45 */ 46#include <asm/dwarf.h> 47 48#if defined(CONFIG_PREEMPT) 49# define preempt_stop() cli ; TRACE_IRQS_OFF 50#else 51# define preempt_stop() 52# define resume_kernel __restore_all 53#endif 54 55 56 .align 2 57ENTRY(exception_error) 58 ! 59 TRACE_IRQS_ON 60 sti 61 mov.l 1f, r0 62 jmp @r0 63 nop 64 65 .align 2 661: .long do_exception_error 67 68 .align 2 69ret_from_exception: 70 CFI_STARTPROC simple 71 CFI_DEF_CFA r14, 0 72 CFI_REL_OFFSET 17, 64 73 CFI_REL_OFFSET 15, 60 74 CFI_REL_OFFSET 14, 56 75 CFI_REL_OFFSET 13, 52 76 CFI_REL_OFFSET 12, 48 77 CFI_REL_OFFSET 11, 44 78 CFI_REL_OFFSET 10, 40 79 CFI_REL_OFFSET 9, 36 80 CFI_REL_OFFSET 8, 32 81 preempt_stop() 82ENTRY(ret_from_irq) 83 ! 84 mov #OFF_SR, r0 85 mov.l @(r0,r15), r0 ! get status register 86 shll r0 87 shll r0 ! kernel space? 88 get_current_thread_info r8, r0 89 bt resume_kernel ! Yes, it's from kernel, go back soon 90 91#ifdef CONFIG_PREEMPT 92 bra resume_userspace 93 nop 94ENTRY(resume_kernel) 95 cli 96 TRACE_IRQS_OFF 97 mov.l @(TI_PRE_COUNT,r8), r0 ! current_thread_info->preempt_count 98 tst r0, r0 99 bf noresched 100need_resched: 101 mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags 102 tst #_TIF_NEED_RESCHED, r0 ! need_resched set? 103 bt noresched 104 105 mov #OFF_SR, r0 106 mov.l @(r0,r15), r0 ! get status register 107 shlr r0 108 and #(0xf0>>1), r0 ! interrupts off (exception path)? 109 cmp/eq #(0xf0>>1), r0 110 bt noresched 111 mov.l 1f, r0 112 jsr @r0 ! call preempt_schedule_irq 113 nop 114 bra need_resched 115 nop 116 117noresched: 118 bra __restore_all 119 nop 120 121 .align 2 1221: .long preempt_schedule_irq 123#endif 124 125ENTRY(resume_userspace) 126 ! r8: current_thread_info 127 cli 128 TRACE_IRQS_OFF 129 mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags 130 tst #(_TIF_WORK_MASK & 0xff), r0 131 bt/s __restore_all 132 tst #_TIF_NEED_RESCHED, r0 133 134 .align 2 135work_pending: 136 ! r0: current_thread_info->flags 137 ! r8: current_thread_info 138 ! t: result of "tst #_TIF_NEED_RESCHED, r0" 139 bf/s work_resched 140 tst #(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME), r0 141work_notifysig: 142 bt/s __restore_all 143 mov r15, r4 144 mov r12, r5 ! set arg1(save_r0) 145 mov r0, r6 146 sti 147 mov.l 2f, r1 148 mov.l 3f, r0 149 jmp @r1 150 lds r0, pr 151work_resched: 152 mov.l 1f, r1 153 jsr @r1 ! schedule 154 nop 155 cli 156 TRACE_IRQS_OFF 157 ! 158 mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags 159 tst #(_TIF_WORK_MASK & 0xff), r0 160 bt __restore_all 161 bra work_pending 162 tst #_TIF_NEED_RESCHED, r0 163 164 .align 2 1651: .long schedule 1662: .long do_notify_resume 1673: .long resume_userspace 168 169 .align 2 170syscall_exit_work: 171 ! r0: current_thread_info->flags 172 ! r8: current_thread_info 173 tst #(_TIF_WORK_SYSCALL_MASK & 0xff), r0 174 bt/s work_pending 175 tst #_TIF_NEED_RESCHED, r0 176 TRACE_IRQS_ON 177 sti 178 mov r15, r4 179 mov.l 8f, r0 ! do_syscall_trace_leave 180 jsr @r0 181 nop 182 bra resume_userspace 183 nop 184 185 .align 2 186syscall_trace_entry: 187 ! Yes it is traced. 188 mov r15, r4 189 mov.l 7f, r11 ! Call do_syscall_trace_enter which notifies 190 jsr @r11 ! superior (will chomp R[0-7]) 191 nop 192 mov.l r0, @(OFF_R0,r15) ! Save return value 193 ! Reload R0-R4 from kernel stack, where the 194 ! parent may have modified them using 195 ! ptrace(POKEUSR). (Note that R0-R2 are 196 ! reloaded from the kernel stack by syscall_call 197 ! below, so don't need to be reloaded here.) 198 ! This allows the parent to rewrite system calls 199 ! and args on the fly. 200 mov.l @(OFF_R4,r15), r4 ! arg0 201 mov.l @(OFF_R5,r15), r5 202 mov.l @(OFF_R6,r15), r6 203 mov.l @(OFF_R7,r15), r7 ! arg3 204 mov.l @(OFF_R3,r15), r3 ! syscall_nr 205 ! 206 mov.l 2f, r10 ! Number of syscalls 207 cmp/hs r10, r3 208 bf syscall_call 209 mov #-ENOSYS, r0 210 bra syscall_exit 211 mov.l r0, @(OFF_R0,r15) ! Return value 212 213__restore_all: 214 mov #OFF_SR, r0 215 mov.l @(r0,r15), r0 ! get status register 216 217 shlr2 r0 218 and #0x3c, r0 219 cmp/eq #0x3c, r0 220 bt 1f 221 TRACE_IRQS_ON 222 bra 2f 223 nop 2241: 225 TRACE_IRQS_OFF 2262: 227 mov.l 3f, r0 228 jmp @r0 229 nop 230 231 .align 2 2323: .long restore_all 233 234 .align 2 235syscall_badsys: ! Bad syscall number 236 get_current_thread_info r8, r0 237 mov #-ENOSYS, r0 238 bra resume_userspace 239 mov.l r0, @(OFF_R0,r15) ! Return value 240 241/* 242 * The main debug trap handler. 243 * 244 * r8=TRA (not the trap number!) 245 * 246 * Note: This assumes that the trapa value is left in its original 247 * form (without the shlr2 shift) so the calculation for the jump 248 * call table offset remains a simple in place mask. 249 */ 250debug_trap: 251 mov r8, r0 252 and #(0xf << 2), r0 253 mov.l 1f, r8 254 add r0, r8 255 mov.l @r8, r8 256 jsr @r8 257 nop 258 bra ret_from_exception 259 nop 260 CFI_ENDPROC 261 262 .align 2 2631: .long debug_trap_table 264 265/* 266 * Syscall interface: 267 * 268 * Syscall #: R3 269 * Arguments #0 to #3: R4--R7 270 * Arguments #4 to #6: R0, R1, R2 271 * TRA: See following table. 272 * 273 * (TRA>>2) Purpose 274 * -------- ------- 275 * 0x00-0x0f original SH-3/4 syscall ABI (not in general use). 276 * 0x10-0x1f general SH-3/4 syscall ABI. 277 * 0x1f unified SH-2/3/4 syscall ABI (preferred). 278 * 0x20-0x2f original SH-2 syscall ABI. 279 * 0x30-0x3f debug traps used by the kernel. 280 * 0x40-0xff Not supported by all parts, so left unhandled. 281 * 282 * For making system calls, any trap number in the range for the 283 * given cpu model may be used, but the unified trap number 0x1f is 284 * preferred for compatibility with all models. 285 * 286 * The low bits of the trap number were once documented as matching 287 * the number of arguments, but they were never actually used as such 288 * by the kernel. SH-2 originally used its own separate trap range 289 * because several hardware exceptions fell in the range used for the 290 * SH-3/4 syscall ABI. 291 * 292 * This code also handles delegating other traps to the BIOS/gdb stub. 293 * 294 * Note: When we're first called, the TRA value must be shifted 295 * right 2 bits in order to get the value that was used as the "trapa" 296 * argument. 297 */ 298 299 .align 2 300 .globl ret_from_fork 301ret_from_fork: 302 mov.l 1f, r8 303 jsr @r8 304 mov r0, r4 305 bra syscall_exit 306 nop 307 308 .align 2 309 .globl ret_from_kernel_thread 310ret_from_kernel_thread: 311 mov.l 1f, r8 312 jsr @r8 313 mov r0, r4 314 mov.l @(OFF_R5,r15), r5 ! fn 315 jsr @r5 316 mov.l @(OFF_R4,r15), r4 ! arg 317 bra syscall_exit 318 nop 319 320 .align 2 3211: .long schedule_tail 322 323/* 324 * The poorly named main trapa decode and dispatch routine, for 325 * system calls and debug traps through their respective jump tables. 326 */ 327ENTRY(system_call) 328 setup_frame_reg 329#if !defined(CONFIG_CPU_SH2) 330 mov.l 1f, r9 331 mov.l @r9, r8 ! Read from TRA (Trap Address) Register 332#endif 333 334 mov #OFF_TRA, r10 335 add r15, r10 336 mov.l r8, @r10 ! set TRA value to tra 337 338 /* 339 * Check the trap type 340 */ 341 mov #((0x20 << 2) - 1), r9 342 cmp/hi r9, r8 343 bt/s debug_trap ! it's a debug trap.. 344 nop 345 346 TRACE_IRQS_ON 347 sti 348 349 ! 350 get_current_thread_info r8, r10 351 mov.l @(TI_FLAGS,r8), r8 352 mov #(_TIF_WORK_SYSCALL_MASK & 0xff), r10 353 mov #(_TIF_WORK_SYSCALL_MASK >> 8), r9 354 tst r10, r8 355 shll8 r9 356 bf syscall_trace_entry 357 tst r9, r8 358 bf syscall_trace_entry 359 ! 360 mov.l 2f, r8 ! Number of syscalls 361 cmp/hs r8, r3 362 bt syscall_badsys 363 ! 364syscall_call: 365 shll2 r3 ! x4 366 mov.l 3f, r8 ! Load the address of sys_call_table 367 add r8, r3 368 mov.l @r3, r8 369 mov.l @(OFF_R2,r15), r2 370 mov.l @(OFF_R1,r15), r1 371 mov.l @(OFF_R0,r15), r0 372 mov.l r2, @-r15 373 mov.l r1, @-r15 374 mov.l r0, @-r15 375 jsr @r8 ! jump to specific syscall handler 376 nop 377 add #12, r15 378 mov.l @(OFF_R0,r15), r12 ! save r0 379 mov.l r0, @(OFF_R0,r15) ! save the return value 380 ! 381syscall_exit: 382 cli 383 TRACE_IRQS_OFF 384 ! 385 get_current_thread_info r8, r0 386 mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags 387 tst #(_TIF_ALLWORK_MASK & 0xff), r0 388 mov #(_TIF_ALLWORK_MASK >> 8), r1 389 bf syscall_exit_work 390 shlr8 r0 391 tst r0, r1 392 bf syscall_exit_work 393 bra __restore_all 394 nop 395 .align 2 396#if !defined(CONFIG_CPU_SH2) 3971: .long TRA 398#endif 3992: .long NR_syscalls 4003: .long sys_call_table 4017: .long do_syscall_trace_enter 4028: .long do_syscall_trace_leave 403