arm/kernel/entry-common.S

0001 /* SPDX-License-Identifier: GPL-2.0-only */
0002 /*
0003  *  linux/arch/arm/kernel/entry-common.S
0004  *
0005  *  Copyright (C) 2000 Russell King
0006  */
0007
0008 #include <asm/assembler.h>
0009 #include <asm/unistd.h>
0010 #include <asm/ftrace.h>
0011 #include <asm/unwind.h>
0012 #include <asm/memory.h>
0013 #ifdef CONFIG_AEABI
0014 #include <asm/unistd-oabi.h>
0015 #endif
0016
0017     .equ    NR_syscalls, __NR_syscalls
0018
0019     .macro  arch_ret_to_user, tmp
0020 #ifdef CONFIG_ARCH_IOP32X
0021     mrc p15, 0, \tmp, c15, c1, 0
0022     tst \tmp, #(1 << 6)
0023     bicne   \tmp, \tmp, #(1 << 6)
0024     mcrne   p15, 0, \tmp, c15, c1, 0    @ Disable cp6 access
0025 #endif
0026     .endm
0027
0028 #include "entry-header.S"
0029
0030 saved_psr   .req    r8
0031 #if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING_USER)
0032 saved_pc    .req    r9
0033 #define TRACE(x...) x
0034 #else
0035 saved_pc    .req    lr
0036 #define TRACE(x...)
0037 #endif
0038
0039     .section .entry.text,"ax",%progbits
0040     .align  5
0041 #if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING_USER) || \
0042     IS_ENABLED(CONFIG_DEBUG_RSEQ))
0043 /*
0044  * This is the fast syscall return path.  We do as little as possible here,
0045  * such as avoiding writing r0 to the stack.  We only use this path if we
0046  * have tracing, context tracking and rseq debug disabled - the overheads
0047  * from those features make this path too inefficient.
0048  */
0049 ret_fast_syscall:
0050 __ret_fast_syscall:
0051  UNWIND(.fnstart    )
0052  UNWIND(.cantunwind )
0053     disable_irq_notrace         @ disable interrupts
0054     ldr r1, [tsk, #TI_FLAGS]        @ re-check for syscall tracing
0055     movs    r1, r1, lsl #16
0056     bne fast_work_pending
0057
0058
0059     /* perform architecture specific actions before user return */
0060     arch_ret_to_user r1
0061
0062     restore_user_regs fast = 1, offset = S_OFF
0063  UNWIND(.fnend      )
0064 ENDPROC(ret_fast_syscall)
0065
0066     /* Ok, we need to do extra processing, enter the slow path. */
0067 fast_work_pending:
0068     str r0, [sp, #S_R0+S_OFF]!      @ returned r0
0069     /* fall through to work_pending */
0070 #else
0071 /*
0072  * The "replacement" ret_fast_syscall for when tracing, context tracking,
0073  * or rseq debug is enabled.  As we will need to call out to some C functions,
0074  * we save r0 first to avoid needing to save registers around each C function
0075  * call.
0076  */
0077 ret_fast_syscall:
0078 __ret_fast_syscall:
0079  UNWIND(.fnstart    )
0080  UNWIND(.cantunwind )
0081     str r0, [sp, #S_R0 + S_OFF]!    @ save returned r0
0082 #if IS_ENABLED(CONFIG_DEBUG_RSEQ)
0083     /* do_rseq_syscall needs interrupts enabled. */
0084     mov r0, sp              @ 'regs'
0085     bl  do_rseq_syscall
0086 #endif
0087     disable_irq_notrace         @ disable interrupts
0088     ldr r1, [tsk, #TI_FLAGS]        @ re-check for syscall tracing
0089     movs    r1, r1, lsl #16
0090     beq no_work_pending
0091  UNWIND(.fnend      )
0092 ENDPROC(ret_fast_syscall)
0093
0094     /* Slower path - fall through to work_pending */
0095 #endif
0096
0097     tst r1, #_TIF_SYSCALL_WORK
0098     bne __sys_trace_return_nosave
0099 slow_work_pending:
0100     mov r0, sp              @ 'regs'
0101     mov r2, why             @ 'syscall'
0102     bl  do_work_pending
0103     cmp r0, #0
0104     beq no_work_pending
0105     movlt   scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
0106     ldmia   sp, {r0 - r6}           @ have to reload r0 - r6
0107     b   local_restart           @ ... and off we go
0108 ENDPROC(ret_fast_syscall)
0109
0110 /*
0111  * "slow" syscall return path.  "why" tells us if this was a real syscall.
0112  * IRQs may be enabled here, so always disable them.  Note that we use the
0113  * "notrace" version to avoid calling into the tracing code unnecessarily.
0114  * do_work_pending() will update this state if necessary.
0115  */
0116 ENTRY(ret_to_user)
0117 ret_slow_syscall:
0118 #if IS_ENABLED(CONFIG_DEBUG_RSEQ)
0119     /* do_rseq_syscall needs interrupts enabled. */
0120     enable_irq_notrace          @ enable interrupts
0121     mov r0, sp              @ 'regs'
0122     bl  do_rseq_syscall
0123 #endif
0124     disable_irq_notrace         @ disable interrupts
0125 ENTRY(ret_to_user_from_irq)
0126     ldr r1, [tsk, #TI_FLAGS]
0127     movs    r1, r1, lsl #16
0128     bne slow_work_pending
0129 no_work_pending:
0130     asm_trace_hardirqs_on save = 0
0131
0132     /* perform architecture specific actions before user return */
0133     arch_ret_to_user r1
0134     ct_user_enter save = 0
0135
0136     restore_user_regs fast = 0, offset = 0
0137 ENDPROC(ret_to_user_from_irq)
0138 ENDPROC(ret_to_user)
0139
0140 /*
0141  * This is how we return from a fork.
0142  */
0143 ENTRY(ret_from_fork)
0144     bl  schedule_tail
0145     cmp r5, #0
0146     movne   r0, r4
0147     badrne  lr, 1f
0148     retne   r5
0149 1:  get_thread_info tsk
0150     b   ret_slow_syscall
0151 ENDPROC(ret_from_fork)
0152
0153 /*=============================================================================
0154  * SWI handler
0155  *-----------------------------------------------------------------------------
0156  */
0157
0158     .align  5
0159 #ifdef CONFIG_HARDEN_BRANCH_HISTORY
0160 ENTRY(vector_bhb_loop8_swi)
0161     sub sp, sp, #PT_REGS_SIZE
0162     stmia   sp, {r0 - r12}
0163     mov r8, #8
0164 1:  b   2f
0165 2:  subs    r8, r8, #1
0166     bne 1b
0167     dsb nsh
0168     isb
0169     b   3f
0170 ENDPROC(vector_bhb_loop8_swi)
0171
0172     .align  5
0173 ENTRY(vector_bhb_bpiall_swi)
0174     sub sp, sp, #PT_REGS_SIZE
0175     stmia   sp, {r0 - r12}
0176     mcr p15, 0, r8, c7, c5, 6   @ BPIALL
0177     isb
0178     b   3f
0179 ENDPROC(vector_bhb_bpiall_swi)
0180 #endif
0181     .align  5
0182 ENTRY(vector_swi)
0183 #ifdef CONFIG_CPU_V7M
0184     v7m_exception_entry
0185 #else
0186     sub sp, sp, #PT_REGS_SIZE
0187     stmia   sp, {r0 - r12}          @ Calling r0 - r12
0188 3:
0189  ARM(   add r8, sp, #S_PC       )
0190  ARM(   stmdb   r8, {sp, lr}^       )   @ Calling sp, lr
0191  THUMB( mov r8, sp          )
0192  THUMB( store_user_sp_lr r8, r10, S_SP  )   @ calling sp, lr
0193     mrs saved_psr, spsr         @ called from non-FIQ mode, so ok.
0194  TRACE( mov saved_pc, lr        )
0195     str saved_pc, [sp, #S_PC]       @ Save calling PC
0196     str saved_psr, [sp, #S_PSR]     @ Save CPSR
0197     str r0, [sp, #S_OLD_R0]     @ Save OLD_R0
0198 #endif
0199     reload_current r10, ip
0200     zero_fp
0201     alignment_trap r10, ip, cr_alignment
0202     asm_trace_hardirqs_on save=0
0203     enable_irq_notrace
0204     ct_user_exit save=0
0205
0206     /*
0207      * Get the system call number.
0208      */
0209
0210 #if defined(CONFIG_OABI_COMPAT)
0211
0212     /*
0213      * If we have CONFIG_OABI_COMPAT then we need to look at the swi
0214      * value to determine if it is an EABI or an old ABI call.
0215      */
0216 #ifdef CONFIG_ARM_THUMB
0217     tst saved_psr, #PSR_T_BIT
0218     movne   r10, #0             @ no thumb OABI emulation
0219  USER(  ldreq   r10, [saved_pc, #-4]    )   @ get SWI instruction
0220 #else
0221  USER(  ldr r10, [saved_pc, #-4]    )   @ get SWI instruction
0222 #endif
0223  ARM_BE8(rev    r10, r10)           @ little endian instruction
0224
0225 #elif defined(CONFIG_AEABI)
0226
0227     /*
0228      * Pure EABI user space always put syscall number into scno (r7).
0229      */
0230 #elif defined(CONFIG_ARM_THUMB)
0231     /* Legacy ABI only, possibly thumb mode. */
0232     tst saved_psr, #PSR_T_BIT       @ this is SPSR from save_user_regs
0233     addne   scno, r7, #__NR_SYSCALL_BASE    @ put OS number in
0234  USER(  ldreq   scno, [saved_pc, #-4]   )
0235
0236 #else
0237     /* Legacy ABI only. */
0238  USER(  ldr scno, [saved_pc, #-4]   )   @ get SWI instruction
0239 #endif
0240
0241     /* saved_psr and saved_pc are now dead */
0242
0243     uaccess_disable tbl
0244     get_thread_info tsk
0245
0246     adr tbl, sys_call_table     @ load syscall table pointer
0247
0248 #if defined(CONFIG_OABI_COMPAT)
0249     /*
0250      * If the swi argument is zero, this is an EABI call and we do nothing.
0251      *
0252      * If this is an old ABI call, get the syscall number into scno and
0253      * get the old ABI syscall table address.
0254      */
0255     bics    r10, r10, #0xff000000
0256     strne   r10, [tsk, #TI_ABI_SYSCALL]
0257     streq   scno, [tsk, #TI_ABI_SYSCALL]
0258     eorne   scno, r10, #__NR_OABI_SYSCALL_BASE
0259     ldrne   tbl, =sys_oabi_call_table
0260 #elif !defined(CONFIG_AEABI)
0261     bic scno, scno, #0xff000000     @ mask off SWI op-code
0262     str scno, [tsk, #TI_ABI_SYSCALL]
0263     eor scno, scno, #__NR_SYSCALL_BASE  @ check OS number
0264 #else
0265     str scno, [tsk, #TI_ABI_SYSCALL]
0266 #endif
0267     /*
0268      * Reload the registers that may have been corrupted on entry to
0269      * the syscall assembly (by tracing or context tracking.)
0270      */
0271  TRACE( ldmia   sp, {r0 - r3}       )
0272
0273 local_restart:
0274     ldr r10, [tsk, #TI_FLAGS]       @ check for syscall tracing
0275     stmdb   sp!, {r4, r5}           @ push fifth and sixth args
0276
0277     tst r10, #_TIF_SYSCALL_WORK     @ are we tracing syscalls?
0278     bne __sys_trace
0279
0280     invoke_syscall tbl, scno, r10, __ret_fast_syscall
0281
0282     add r1, sp, #S_OFF
0283 2:  cmp scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
0284     eor r0, scno, #__NR_SYSCALL_BASE    @ put OS number back
0285     bcs arm_syscall
0286     mov why, #0             @ no longer a real syscall
0287     b   sys_ni_syscall          @ not private func
0288
0289 #if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
0290     /*
0291      * We failed to handle a fault trying to access the page
0292      * containing the swi instruction, but we're not really in a
0293      * position to return -EFAULT. Instead, return back to the
0294      * instruction and re-enter the user fault handling path trying
0295      * to page it in. This will likely result in sending SEGV to the
0296      * current task.
0297      */
0298 9001:
0299     sub lr, saved_pc, #4
0300     str lr, [sp, #S_PC]
0301     get_thread_info tsk
0302     b   ret_fast_syscall
0303 #endif
0304 ENDPROC(vector_swi)
0305     .ltorg
0306
0307     /*
0308      * This is the really slow path.  We're going to be doing
0309      * context switches, and waiting for our parent to respond.
0310      */
0311 __sys_trace:
0312     add r0, sp, #S_OFF
0313     bl  syscall_trace_enter
0314     mov scno, r0
0315     invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1
0316     cmp scno, #-1           @ skip the syscall?
0317     bne 2b
0318     add sp, sp, #S_OFF          @ restore stack
0319
0320 __sys_trace_return_nosave:
0321     enable_irq_notrace
0322     mov r0, sp
0323     bl  syscall_trace_exit
0324     b   ret_slow_syscall
0325
0326 __sys_trace_return:
0327     str r0, [sp, #S_R0 + S_OFF]!    @ save returned r0
0328     mov r0, sp
0329     bl  syscall_trace_exit
0330     b   ret_slow_syscall
0331
0332     .macro  syscall_table_start, sym
0333     .equ    __sys_nr, 0
0334     .type   \sym, #object
0335 ENTRY(\sym)
0336     .endm
0337
0338     .macro  syscall, nr, func
0339     .ifgt   __sys_nr - \nr
0340     .error  "Duplicated/unorded system call entry"
0341     .endif
0342     .rept   \nr - __sys_nr
0343     .long   sys_ni_syscall
0344     .endr
0345     .long   \func
0346     .equ    __sys_nr, \nr + 1
0347     .endm
0348
0349     .macro  syscall_table_end, sym
0350     .ifgt   __sys_nr - __NR_syscalls
0351     .error  "System call table too big"
0352     .endif
0353     .rept   __NR_syscalls - __sys_nr
0354     .long   sys_ni_syscall
0355     .endr
0356     .size   \sym, . - \sym
0357     .endm
0358
0359 #define __SYSCALL_WITH_COMPAT(nr, native, compat)   __SYSCALL(nr, native)
0360 #define __SYSCALL(nr, func) syscall nr, func
0361
0362 /*
0363  * This is the syscall table declaration for native ABI syscalls.
0364  * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
0365  */
0366     syscall_table_start sys_call_table
0367 #ifdef CONFIG_AEABI
0368 #include <calls-eabi.S>
0369 #else
0370 #include <calls-oabi.S>
0371 #endif
0372     syscall_table_end sys_call_table
0373
0374 /*============================================================================
0375  * Special system call wrappers
0376  */
0377 @ r0 = syscall number
0378 @ r8 = syscall table
0379 sys_syscall:
0380         bic scno, r0, #__NR_OABI_SYSCALL_BASE
0381         cmp scno, #__NR_syscall - __NR_SYSCALL_BASE
0382         cmpne   scno, #NR_syscalls  @ check range
0383 #ifdef CONFIG_CPU_SPECTRE
0384         movhs   scno, #0
0385         csdb
0386 #endif
0387         stmialo sp, {r5, r6}        @ shuffle args
0388         movlo   r0, r1
0389         movlo   r1, r2
0390         movlo   r2, r3
0391         movlo   r3, r4
0392         ldrlo   pc, [tbl, scno, lsl #2]
0393         b   sys_ni_syscall
0394 ENDPROC(sys_syscall)
0395
0396 sys_sigreturn_wrapper:
0397         add r0, sp, #S_OFF
0398         mov why, #0     @ prevent syscall restart handling
0399         b   sys_sigreturn
0400 ENDPROC(sys_sigreturn_wrapper)
0401
0402 sys_rt_sigreturn_wrapper:
0403         add r0, sp, #S_OFF
0404         mov why, #0     @ prevent syscall restart handling
0405         b   sys_rt_sigreturn
0406 ENDPROC(sys_rt_sigreturn_wrapper)
0407
0408 sys_statfs64_wrapper:
0409         teq r1, #88
0410         moveq   r1, #84
0411         b   sys_statfs64
0412 ENDPROC(sys_statfs64_wrapper)
0413
0414 sys_fstatfs64_wrapper:
0415         teq r1, #88
0416         moveq   r1, #84
0417         b   sys_fstatfs64
0418 ENDPROC(sys_fstatfs64_wrapper)
0419
0420 /*
0421  * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
0422  * offset, we return EINVAL.
0423  */
0424 sys_mmap2:
0425         str r5, [sp, #4]
0426         b   sys_mmap_pgoff
0427 ENDPROC(sys_mmap2)
0428
0429 #ifdef CONFIG_OABI_COMPAT
0430
0431 /*
0432  * These are syscalls with argument register differences
0433  */
0434
0435 sys_oabi_pread64:
0436         stmia   sp, {r3, r4}
0437         b   sys_pread64
0438 ENDPROC(sys_oabi_pread64)
0439
0440 sys_oabi_pwrite64:
0441         stmia   sp, {r3, r4}
0442         b   sys_pwrite64
0443 ENDPROC(sys_oabi_pwrite64)
0444
0445 sys_oabi_truncate64:
0446         mov r3, r2
0447         mov r2, r1
0448         b   sys_truncate64
0449 ENDPROC(sys_oabi_truncate64)
0450
0451 sys_oabi_ftruncate64:
0452         mov r3, r2
0453         mov r2, r1
0454         b   sys_ftruncate64
0455 ENDPROC(sys_oabi_ftruncate64)
0456
0457 sys_oabi_readahead:
0458         str r3, [sp]
0459         mov r3, r2
0460         mov r2, r1
0461         b   sys_readahead
0462 ENDPROC(sys_oabi_readahead)
0463
0464 /*
0465  * Let's declare a second syscall table for old ABI binaries
0466  * using the compatibility syscall entries.
0467  */
0468     syscall_table_start sys_oabi_call_table
0469 #undef __SYSCALL_WITH_COMPAT
0470 #define __SYSCALL_WITH_COMPAT(nr, native, compat)   __SYSCALL(nr, compat)
0471 #include <calls-oabi.S>
0472     syscall_table_end sys_oabi_call_table
0473
0474 #endif
0475