root/arch/arm/kernel/entry-common.S

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  *  linux/arch/arm/kernel/entry-common.S
   4  *
   5  *  Copyright (C) 2000 Russell King
   6  */
   7 
   8 #include <asm/assembler.h>
   9 #include <asm/unistd.h>
  10 #include <asm/ftrace.h>
  11 #include <asm/unwind.h>
  12 #include <asm/memory.h>
  13 #ifdef CONFIG_AEABI
  14 #include <asm/unistd-oabi.h>
  15 #endif
  16 
  17         .equ    NR_syscalls, __NR_syscalls
  18 
  19 #ifdef CONFIG_NEED_RET_TO_USER
  20 #include <mach/entry-macro.S>
  21 #else
  22         .macro  arch_ret_to_user, tmp1, tmp2
  23         .endm
  24 #endif
  25 
  26 #include "entry-header.S"
  27 
  28 saved_psr       .req    r8
  29 #if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING)
  30 saved_pc        .req    r9
  31 #define TRACE(x...) x
  32 #else
  33 saved_pc        .req    lr
  34 #define TRACE(x...)
  35 #endif
  36 
  37         .section .entry.text,"ax",%progbits
  38         .align  5
  39 #if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING) || \
  40         IS_ENABLED(CONFIG_DEBUG_RSEQ))
  41 /*
  42  * This is the fast syscall return path.  We do as little as possible here,
  43  * such as avoiding writing r0 to the stack.  We only use this path if we
  44  * have tracing, context tracking and rseq debug disabled - the overheads
  45  * from those features make this path too inefficient.
  46  */
  47 ret_fast_syscall:
  48 __ret_fast_syscall:
  49  UNWIND(.fnstart        )
  50  UNWIND(.cantunwind     )
  51         disable_irq_notrace                     @ disable interrupts
  52         ldr     r2, [tsk, #TI_ADDR_LIMIT]
  53         cmp     r2, #TASK_SIZE
  54         blne    addr_limit_check_failed
  55         ldr     r1, [tsk, #TI_FLAGS]            @ re-check for syscall tracing
  56         tst     r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
  57         bne     fast_work_pending
  58 
  59 
  60         /* perform architecture specific actions before user return */
  61         arch_ret_to_user r1, lr
  62 
  63         restore_user_regs fast = 1, offset = S_OFF
  64  UNWIND(.fnend          )
  65 ENDPROC(ret_fast_syscall)
  66 
  67         /* Ok, we need to do extra processing, enter the slow path. */
  68 fast_work_pending:
  69         str     r0, [sp, #S_R0+S_OFF]!          @ returned r0
  70         /* fall through to work_pending */
  71 #else
  72 /*
  73  * The "replacement" ret_fast_syscall for when tracing, context tracking,
  74  * or rseq debug is enabled.  As we will need to call out to some C functions,
  75  * we save r0 first to avoid needing to save registers around each C function
  76  * call.
  77  */
  78 ret_fast_syscall:
  79 __ret_fast_syscall:
  80  UNWIND(.fnstart        )
  81  UNWIND(.cantunwind     )
  82         str     r0, [sp, #S_R0 + S_OFF]!        @ save returned r0
  83 #if IS_ENABLED(CONFIG_DEBUG_RSEQ)
  84         /* do_rseq_syscall needs interrupts enabled. */
  85         mov     r0, sp                          @ 'regs'
  86         bl      do_rseq_syscall
  87 #endif
  88         disable_irq_notrace                     @ disable interrupts
  89         ldr     r2, [tsk, #TI_ADDR_LIMIT]
  90         cmp     r2, #TASK_SIZE
  91         blne    addr_limit_check_failed
  92         ldr     r1, [tsk, #TI_FLAGS]            @ re-check for syscall tracing
  93         tst     r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
  94         beq     no_work_pending
  95  UNWIND(.fnend          )
  96 ENDPROC(ret_fast_syscall)
  97 
  98         /* Slower path - fall through to work_pending */
  99 #endif
 100 
 101         tst     r1, #_TIF_SYSCALL_WORK
 102         bne     __sys_trace_return_nosave
 103 slow_work_pending:
 104         mov     r0, sp                          @ 'regs'
 105         mov     r2, why                         @ 'syscall'
 106         bl      do_work_pending
 107         cmp     r0, #0
 108         beq     no_work_pending
 109         movlt   scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
 110         ldmia   sp, {r0 - r6}                   @ have to reload r0 - r6
 111         b       local_restart                   @ ... and off we go
 112 ENDPROC(ret_fast_syscall)
 113 
 114 /*
 115  * "slow" syscall return path.  "why" tells us if this was a real syscall.
 116  * IRQs may be enabled here, so always disable them.  Note that we use the
 117  * "notrace" version to avoid calling into the tracing code unnecessarily.
 118  * do_work_pending() will update this state if necessary.
 119  */
 120 ENTRY(ret_to_user)
 121 ret_slow_syscall:
 122 #if IS_ENABLED(CONFIG_DEBUG_RSEQ)
 123         /* do_rseq_syscall needs interrupts enabled. */
 124         enable_irq_notrace                      @ enable interrupts
 125         mov     r0, sp                          @ 'regs'
 126         bl      do_rseq_syscall
 127 #endif
 128         disable_irq_notrace                     @ disable interrupts
 129 ENTRY(ret_to_user_from_irq)
 130         ldr     r2, [tsk, #TI_ADDR_LIMIT]
 131         cmp     r2, #TASK_SIZE
 132         blne    addr_limit_check_failed
 133         ldr     r1, [tsk, #TI_FLAGS]
 134         tst     r1, #_TIF_WORK_MASK
 135         bne     slow_work_pending
 136 no_work_pending:
 137         asm_trace_hardirqs_on save = 0
 138 
 139         /* perform architecture specific actions before user return */
 140         arch_ret_to_user r1, lr
 141         ct_user_enter save = 0
 142 
 143         restore_user_regs fast = 0, offset = 0
 144 ENDPROC(ret_to_user_from_irq)
 145 ENDPROC(ret_to_user)
 146 
 147 /*
 148  * This is how we return from a fork.
 149  */
 150 ENTRY(ret_from_fork)
 151         bl      schedule_tail
 152         cmp     r5, #0
 153         movne   r0, r4
 154         badrne  lr, 1f
 155         retne   r5
 156 1:      get_thread_info tsk
 157         b       ret_slow_syscall
 158 ENDPROC(ret_from_fork)
 159 
 160 /*=============================================================================
 161  * SWI handler
 162  *-----------------------------------------------------------------------------
 163  */
 164 
 165         .align  5
 166 ENTRY(vector_swi)
 167 #ifdef CONFIG_CPU_V7M
 168         v7m_exception_entry
 169 #else
 170         sub     sp, sp, #PT_REGS_SIZE
 171         stmia   sp, {r0 - r12}                  @ Calling r0 - r12
 172  ARM(   add     r8, sp, #S_PC           )
 173  ARM(   stmdb   r8, {sp, lr}^           )       @ Calling sp, lr
 174  THUMB( mov     r8, sp                  )
 175  THUMB( store_user_sp_lr r8, r10, S_SP  )       @ calling sp, lr
 176         mrs     saved_psr, spsr                 @ called from non-FIQ mode, so ok.
 177  TRACE( mov     saved_pc, lr            )
 178         str     saved_pc, [sp, #S_PC]           @ Save calling PC
 179         str     saved_psr, [sp, #S_PSR]         @ Save CPSR
 180         str     r0, [sp, #S_OLD_R0]             @ Save OLD_R0
 181 #endif
 182         zero_fp
 183         alignment_trap r10, ip, __cr_alignment
 184         asm_trace_hardirqs_on save=0
 185         enable_irq_notrace
 186         ct_user_exit save=0
 187 
 188         /*
 189          * Get the system call number.
 190          */
 191 
 192 #if defined(CONFIG_OABI_COMPAT)
 193 
 194         /*
 195          * If we have CONFIG_OABI_COMPAT then we need to look at the swi
 196          * value to determine if it is an EABI or an old ABI call.
 197          */
 198 #ifdef CONFIG_ARM_THUMB
 199         tst     saved_psr, #PSR_T_BIT
 200         movne   r10, #0                         @ no thumb OABI emulation
 201  USER(  ldreq   r10, [saved_pc, #-4]    )       @ get SWI instruction
 202 #else
 203  USER(  ldr     r10, [saved_pc, #-4]    )       @ get SWI instruction
 204 #endif
 205  ARM_BE8(rev    r10, r10)                       @ little endian instruction
 206 
 207 #elif defined(CONFIG_AEABI)
 208 
 209         /*
 210          * Pure EABI user space always put syscall number into scno (r7).
 211          */
 212 #elif defined(CONFIG_ARM_THUMB)
 213         /* Legacy ABI only, possibly thumb mode. */
 214         tst     saved_psr, #PSR_T_BIT           @ this is SPSR from save_user_regs
 215         addne   scno, r7, #__NR_SYSCALL_BASE    @ put OS number in
 216  USER(  ldreq   scno, [saved_pc, #-4]   )
 217 
 218 #else
 219         /* Legacy ABI only. */
 220  USER(  ldr     scno, [saved_pc, #-4]   )       @ get SWI instruction
 221 #endif
 222 
 223         /* saved_psr and saved_pc are now dead */
 224 
 225         uaccess_disable tbl
 226 
 227         adr     tbl, sys_call_table             @ load syscall table pointer
 228 
 229 #if defined(CONFIG_OABI_COMPAT)
 230         /*
 231          * If the swi argument is zero, this is an EABI call and we do nothing.
 232          *
 233          * If this is an old ABI call, get the syscall number into scno and
 234          * get the old ABI syscall table address.
 235          */
 236         bics    r10, r10, #0xff000000
 237         eorne   scno, r10, #__NR_OABI_SYSCALL_BASE
 238         ldrne   tbl, =sys_oabi_call_table
 239 #elif !defined(CONFIG_AEABI)
 240         bic     scno, scno, #0xff000000         @ mask off SWI op-code
 241         eor     scno, scno, #__NR_SYSCALL_BASE  @ check OS number
 242 #endif
 243         get_thread_info tsk
 244         /*
 245          * Reload the registers that may have been corrupted on entry to
 246          * the syscall assembly (by tracing or context tracking.)
 247          */
 248  TRACE( ldmia   sp, {r0 - r3}           )
 249 
 250 local_restart:
 251         ldr     r10, [tsk, #TI_FLAGS]           @ check for syscall tracing
 252         stmdb   sp!, {r4, r5}                   @ push fifth and sixth args
 253 
 254         tst     r10, #_TIF_SYSCALL_WORK         @ are we tracing syscalls?
 255         bne     __sys_trace
 256 
 257         invoke_syscall tbl, scno, r10, __ret_fast_syscall
 258 
 259         add     r1, sp, #S_OFF
 260 2:      cmp     scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
 261         eor     r0, scno, #__NR_SYSCALL_BASE    @ put OS number back
 262         bcs     arm_syscall
 263         mov     why, #0                         @ no longer a real syscall
 264         b       sys_ni_syscall                  @ not private func
 265 
 266 #if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
 267         /*
 268          * We failed to handle a fault trying to access the page
 269          * containing the swi instruction, but we're not really in a
 270          * position to return -EFAULT. Instead, return back to the
 271          * instruction and re-enter the user fault handling path trying
 272          * to page it in. This will likely result in sending SEGV to the
 273          * current task.
 274          */
 275 9001:
 276         sub     lr, saved_pc, #4
 277         str     lr, [sp, #S_PC]
 278         get_thread_info tsk
 279         b       ret_fast_syscall
 280 #endif
 281 ENDPROC(vector_swi)
 282 
 283         /*
 284          * This is the really slow path.  We're going to be doing
 285          * context switches, and waiting for our parent to respond.
 286          */
 287 __sys_trace:
 288         mov     r1, scno
 289         add     r0, sp, #S_OFF
 290         bl      syscall_trace_enter
 291         mov     scno, r0
 292         invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1
 293         cmp     scno, #-1                       @ skip the syscall?
 294         bne     2b
 295         add     sp, sp, #S_OFF                  @ restore stack
 296 
 297 __sys_trace_return_nosave:
 298         enable_irq_notrace
 299         mov     r0, sp
 300         bl      syscall_trace_exit
 301         b       ret_slow_syscall
 302 
 303 __sys_trace_return:
 304         str     r0, [sp, #S_R0 + S_OFF]!        @ save returned r0
 305         mov     r0, sp
 306         bl      syscall_trace_exit
 307         b       ret_slow_syscall
 308 
 309         .align  5
 310 #ifdef CONFIG_ALIGNMENT_TRAP
 311         .type   __cr_alignment, #object
 312 __cr_alignment:
 313         .word   cr_alignment
 314 #endif
 315         .ltorg
 316 
 317         .macro  syscall_table_start, sym
 318         .equ    __sys_nr, 0
 319         .type   \sym, #object
 320 ENTRY(\sym)
 321         .endm
 322 
 323         .macro  syscall, nr, func
 324         .ifgt   __sys_nr - \nr
 325         .error  "Duplicated/unorded system call entry"
 326         .endif
 327         .rept   \nr - __sys_nr
 328         .long   sys_ni_syscall
 329         .endr
 330         .long   \func
 331         .equ    __sys_nr, \nr + 1
 332         .endm
 333 
 334         .macro  syscall_table_end, sym
 335         .ifgt   __sys_nr - __NR_syscalls
 336         .error  "System call table too big"
 337         .endif
 338         .rept   __NR_syscalls - __sys_nr
 339         .long   sys_ni_syscall
 340         .endr
 341         .size   \sym, . - \sym
 342         .endm
 343 
 344 #define NATIVE(nr, func) syscall nr, func
 345 
 346 /*
 347  * This is the syscall table declaration for native ABI syscalls.
 348  * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
 349  */
 350         syscall_table_start sys_call_table
 351 #define COMPAT(nr, native, compat) syscall nr, native
 352 #ifdef CONFIG_AEABI
 353 #include <calls-eabi.S>
 354 #else
 355 #include <calls-oabi.S>
 356 #endif
 357 #undef COMPAT
 358         syscall_table_end sys_call_table
 359 
 360 /*============================================================================
 361  * Special system call wrappers
 362  */
 363 @ r0 = syscall number
 364 @ r8 = syscall table
 365 sys_syscall:
 366                 bic     scno, r0, #__NR_OABI_SYSCALL_BASE
 367                 cmp     scno, #__NR_syscall - __NR_SYSCALL_BASE
 368                 cmpne   scno, #NR_syscalls      @ check range
 369 #ifdef CONFIG_CPU_SPECTRE
 370                 movhs   scno, #0
 371                 csdb
 372 #endif
 373                 stmialo sp, {r5, r6}            @ shuffle args
 374                 movlo   r0, r1
 375                 movlo   r1, r2
 376                 movlo   r2, r3
 377                 movlo   r3, r4
 378                 ldrlo   pc, [tbl, scno, lsl #2]
 379                 b       sys_ni_syscall
 380 ENDPROC(sys_syscall)
 381 
 382 sys_sigreturn_wrapper:
 383                 add     r0, sp, #S_OFF
 384                 mov     why, #0         @ prevent syscall restart handling
 385                 b       sys_sigreturn
 386 ENDPROC(sys_sigreturn_wrapper)
 387 
 388 sys_rt_sigreturn_wrapper:
 389                 add     r0, sp, #S_OFF
 390                 mov     why, #0         @ prevent syscall restart handling
 391                 b       sys_rt_sigreturn
 392 ENDPROC(sys_rt_sigreturn_wrapper)
 393 
 394 sys_statfs64_wrapper:
 395                 teq     r1, #88
 396                 moveq   r1, #84
 397                 b       sys_statfs64
 398 ENDPROC(sys_statfs64_wrapper)
 399 
 400 sys_fstatfs64_wrapper:
 401                 teq     r1, #88
 402                 moveq   r1, #84
 403                 b       sys_fstatfs64
 404 ENDPROC(sys_fstatfs64_wrapper)
 405 
 406 /*
 407  * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
 408  * offset, we return EINVAL.
 409  */
 410 sys_mmap2:
 411                 str     r5, [sp, #4]
 412                 b       sys_mmap_pgoff
 413 ENDPROC(sys_mmap2)
 414 
 415 #ifdef CONFIG_OABI_COMPAT
 416 
 417 /*
 418  * These are syscalls with argument register differences
 419  */
 420 
 421 sys_oabi_pread64:
 422                 stmia   sp, {r3, r4}
 423                 b       sys_pread64
 424 ENDPROC(sys_oabi_pread64)
 425 
 426 sys_oabi_pwrite64:
 427                 stmia   sp, {r3, r4}
 428                 b       sys_pwrite64
 429 ENDPROC(sys_oabi_pwrite64)
 430 
 431 sys_oabi_truncate64:
 432                 mov     r3, r2
 433                 mov     r2, r1
 434                 b       sys_truncate64
 435 ENDPROC(sys_oabi_truncate64)
 436 
 437 sys_oabi_ftruncate64:
 438                 mov     r3, r2
 439                 mov     r2, r1
 440                 b       sys_ftruncate64
 441 ENDPROC(sys_oabi_ftruncate64)
 442 
 443 sys_oabi_readahead:
 444                 str     r3, [sp]
 445                 mov     r3, r2
 446                 mov     r2, r1
 447                 b       sys_readahead
 448 ENDPROC(sys_oabi_readahead)
 449 
 450 /*
 451  * Let's declare a second syscall table for old ABI binaries
 452  * using the compatibility syscall entries.
 453  */
 454         syscall_table_start sys_oabi_call_table
 455 #define COMPAT(nr, native, compat) syscall nr, compat
 456 #include <calls-oabi.S>
 457         syscall_table_end sys_oabi_call_table
 458 
 459 #endif
 460