/* SPDX-License-Identifier: GPL-2.0-only */ /* * linux/arch/arm/kernel/entry-common.S * * Copyright (C) 2000 Russell King */ #include #include #include #include #include #ifdef CONFIG_AEABI #include #endif .equ NR_syscalls, __NR_syscalls #ifdef CONFIG_NEED_RET_TO_USER #include #else .macro arch_ret_to_user, tmp1, tmp2 .endm #endif #include "entry-header.S" saved_psr .req r8 #if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING) saved_pc .req r9 #define TRACE(x...) x #else saved_pc .req lr #define TRACE(x...) #endif .section .entry.text,"ax",%progbits .align 5 #if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING) || \ IS_ENABLED(CONFIG_DEBUG_RSEQ)) /* * This is the fast syscall return path. We do as little as possible here, * such as avoiding writing r0 to the stack. We only use this path if we * have tracing, context tracking and rseq debug disabled - the overheads * from those features make this path too inefficient. */ ret_fast_syscall: __ret_fast_syscall: UNWIND(.fnstart ) UNWIND(.cantunwind ) disable_irq_notrace @ disable interrupts ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing movs r1, r1, lsl #16 bne fast_work_pending /* perform architecture specific actions before user return */ arch_ret_to_user r1, lr restore_user_regs fast = 1, offset = S_OFF UNWIND(.fnend ) ENDPROC(ret_fast_syscall) /* Ok, we need to do extra processing, enter the slow path. */ fast_work_pending: str r0, [sp, #S_R0+S_OFF]! @ returned r0 /* fall through to work_pending */ #else /* * The "replacement" ret_fast_syscall for when tracing, context tracking, * or rseq debug is enabled. As we will need to call out to some C functions, * we save r0 first to avoid needing to save registers around each C function * call. */ ret_fast_syscall: __ret_fast_syscall: UNWIND(.fnstart ) UNWIND(.cantunwind ) str r0, [sp, #S_R0 + S_OFF]! @ save returned r0 #if IS_ENABLED(CONFIG_DEBUG_RSEQ) /* do_rseq_syscall needs interrupts enabled. */ mov r0, sp @ 'regs' bl do_rseq_syscall #endif disable_irq_notrace @ disable interrupts ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing movs r1, r1, lsl #16 beq no_work_pending UNWIND(.fnend ) ENDPROC(ret_fast_syscall) /* Slower path - fall through to work_pending */ #endif tst r1, #_TIF_SYSCALL_WORK bne __sys_trace_return_nosave slow_work_pending: mov r0, sp @ 'regs' mov r2, why @ 'syscall' bl do_work_pending cmp r0, #0 beq no_work_pending movlt scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE) ldmia sp, {r0 - r6} @ have to reload r0 - r6 b local_restart @ ... and off we go ENDPROC(ret_fast_syscall) /* * "slow" syscall return path. "why" tells us if this was a real syscall. * IRQs may be enabled here, so always disable them. Note that we use the * "notrace" version to avoid calling into the tracing code unnecessarily. * do_work_pending() will update this state if necessary. */ ENTRY(ret_to_user) ret_slow_syscall: #if IS_ENABLED(CONFIG_DEBUG_RSEQ) /* do_rseq_syscall needs interrupts enabled. */ enable_irq_notrace @ enable interrupts mov r0, sp @ 'regs' bl do_rseq_syscall #endif disable_irq_notrace @ disable interrupts ENTRY(ret_to_user_from_irq) ldr r1, [tsk, #TI_FLAGS] movs r1, r1, lsl #16 bne slow_work_pending no_work_pending: asm_trace_hardirqs_on save = 0 /* perform architecture specific actions before user return */ arch_ret_to_user r1, lr ct_user_enter save = 0 restore_user_regs fast = 0, offset = 0 ENDPROC(ret_to_user_from_irq) ENDPROC(ret_to_user) /* * This is how we return from a fork. */ ENTRY(ret_from_fork) bl schedule_tail cmp r5, #0 movne r0, r4 badrne lr, 1f retne r5 1: get_thread_info tsk b ret_slow_syscall ENDPROC(ret_from_fork) /*============================================================================= * SWI handler *----------------------------------------------------------------------------- */ .align 5 #ifdef CONFIG_HARDEN_BRANCH_HISTORY ENTRY(vector_bhb_loop8_swi) sub sp, sp, #PT_REGS_SIZE stmia sp, {r0 - r12} mov r8, #8 1: b 2f 2: subs r8, r8, #1 bne 1b dsb isb b 3f ENDPROC(vector_bhb_loop8_swi) .align 5 ENTRY(vector_bhb_bpiall_swi) sub sp, sp, #PT_REGS_SIZE stmia sp, {r0 - r12} mcr p15, 0, r8, c7, c5, 6 @ BPIALL isb b 3f ENDPROC(vector_bhb_bpiall_swi) #endif .align 5 ENTRY(vector_swi) #ifdef CONFIG_CPU_V7M v7m_exception_entry #else sub sp, sp, #PT_REGS_SIZE stmia sp, {r0 - r12} @ Calling r0 - r12 3: ARM( add r8, sp, #S_PC ) ARM( stmdb r8, {sp, lr}^ ) @ Calling sp, lr THUMB( mov r8, sp ) THUMB( store_user_sp_lr r8, r10, S_SP ) @ calling sp, lr mrs saved_psr, spsr @ called from non-FIQ mode, so ok. TRACE( mov saved_pc, lr ) str saved_pc, [sp, #S_PC] @ Save calling PC str saved_psr, [sp, #S_PSR] @ Save CPSR str r0, [sp, #S_OLD_R0] @ Save OLD_R0 #endif zero_fp alignment_trap r10, ip, __cr_alignment asm_trace_hardirqs_on save=0 enable_irq_notrace ct_user_exit save=0 /* * Get the system call number. */ #if defined(CONFIG_OABI_COMPAT) /* * If we have CONFIG_OABI_COMPAT then we need to look at the swi * value to determine if it is an EABI or an old ABI call. */ #ifdef CONFIG_ARM_THUMB tst saved_psr, #PSR_T_BIT movne r10, #0 @ no thumb OABI emulation USER( ldreq r10, [saved_pc, #-4] ) @ get SWI instruction #else USER( ldr r10, [saved_pc, #-4] ) @ get SWI instruction #endif ARM_BE8(rev r10, r10) @ little endian instruction #elif defined(CONFIG_AEABI) /* * Pure EABI user space always put syscall number into scno (r7). */ #elif defined(CONFIG_ARM_THUMB) /* Legacy ABI only, possibly thumb mode. */ tst saved_psr, #PSR_T_BIT @ this is SPSR from save_user_regs addne scno, r7, #__NR_SYSCALL_BASE @ put OS number in USER( ldreq scno, [saved_pc, #-4] ) #else /* Legacy ABI only. */ USER( ldr scno, [saved_pc, #-4] ) @ get SWI instruction #endif /* saved_psr and saved_pc are now dead */ uaccess_disable tbl get_thread_info tsk adr tbl, sys_call_table @ load syscall table pointer #if defined(CONFIG_OABI_COMPAT) /* * If the swi argument is zero, this is an EABI call and we do nothing. * * If this is an old ABI call, get the syscall number into scno and * get the old ABI syscall table address. */ bics r10, r10, #0xff000000 strne r10, [tsk, #TI_ABI_SYSCALL] streq scno, [tsk, #TI_ABI_SYSCALL] eorne scno, r10, #__NR_OABI_SYSCALL_BASE ldrne tbl, =sys_oabi_call_table #elif !defined(CONFIG_AEABI) bic scno, scno, #0xff000000 @ mask off SWI op-code str scno, [tsk, #TI_ABI_SYSCALL] eor scno, scno, #__NR_SYSCALL_BASE @ check OS number #else str scno, [tsk, #TI_ABI_SYSCALL] #endif /* * Reload the registers that may have been corrupted on entry to * the syscall assembly (by tracing or context tracking.) */ TRACE( ldmia sp, {r0 - r3} ) local_restart: ldr r10, [tsk, #TI_FLAGS] @ check for syscall tracing stmdb sp!, {r4, r5} @ push fifth and sixth args tst r10, #_TIF_SYSCALL_WORK @ are we tracing syscalls? bne __sys_trace invoke_syscall tbl, scno, r10, __ret_fast_syscall add r1, sp, #S_OFF 2: cmp scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE) eor r0, scno, #__NR_SYSCALL_BASE @ put OS number back bcs arm_syscall mov why, #0 @ no longer a real syscall b sys_ni_syscall @ not private func #if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI) /* * We failed to handle a fault trying to access the page * containing the swi instruction, but we're not really in a * position to return -EFAULT. Instead, return back to the * instruction and re-enter the user fault handling path trying * to page it in. This will likely result in sending SEGV to the * current task. */ 9001: sub lr, saved_pc, #4 str lr, [sp, #S_PC] get_thread_info tsk b ret_fast_syscall #endif ENDPROC(vector_swi) /* * This is the really slow path. We're going to be doing * context switches, and waiting for our parent to respond. */ __sys_trace: add r0, sp, #S_OFF bl syscall_trace_enter mov scno, r0 invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1 cmp scno, #-1 @ skip the syscall? bne 2b add sp, sp, #S_OFF @ restore stack __sys_trace_return_nosave: enable_irq_notrace mov r0, sp bl syscall_trace_exit b ret_slow_syscall __sys_trace_return: str r0, [sp, #S_R0 + S_OFF]! @ save returned r0 mov r0, sp bl syscall_trace_exit b ret_slow_syscall .align 5 #ifdef CONFIG_ALIGNMENT_TRAP .type __cr_alignment, #object __cr_alignment: .word cr_alignment #endif .ltorg .macro syscall_table_start, sym .equ __sys_nr, 0 .type \sym, #object ENTRY(\sym) .endm .macro syscall, nr, func .ifgt __sys_nr - \nr .error "Duplicated/unorded system call entry" .endif .rept \nr - __sys_nr .long sys_ni_syscall .endr .long \func .equ __sys_nr, \nr + 1 .endm .macro syscall_table_end, sym .ifgt __sys_nr - __NR_syscalls .error "System call table too big" .endif .rept __NR_syscalls - __sys_nr .long sys_ni_syscall .endr .size \sym, . - \sym .endm #define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native) #define __SYSCALL(nr, func) syscall nr, func /* * This is the syscall table declaration for native ABI syscalls. * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall. */ syscall_table_start sys_call_table #ifdef CONFIG_AEABI #include #else #include #endif syscall_table_end sys_call_table /*============================================================================ * Special system call wrappers */ @ r0 = syscall number @ r8 = syscall table sys_syscall: bic scno, r0, #__NR_OABI_SYSCALL_BASE cmp scno, #__NR_syscall - __NR_SYSCALL_BASE cmpne scno, #NR_syscalls @ check range #ifdef CONFIG_CPU_SPECTRE movhs scno, #0 csdb #endif stmialo sp, {r5, r6} @ shuffle args movlo r0, r1 movlo r1, r2 movlo r2, r3 movlo r3, r4 ldrlo pc, [tbl, scno, lsl #2] b sys_ni_syscall ENDPROC(sys_syscall) sys_sigreturn_wrapper: add r0, sp, #S_OFF mov why, #0 @ prevent syscall restart handling b sys_sigreturn ENDPROC(sys_sigreturn_wrapper) sys_rt_sigreturn_wrapper: add r0, sp, #S_OFF mov why, #0 @ prevent syscall restart handling b sys_rt_sigreturn ENDPROC(sys_rt_sigreturn_wrapper) sys_statfs64_wrapper: teq r1, #88 moveq r1, #84 b sys_statfs64 ENDPROC(sys_statfs64_wrapper) sys_fstatfs64_wrapper: teq r1, #88 moveq r1, #84 b sys_fstatfs64 ENDPROC(sys_fstatfs64_wrapper) /* * Note: off_4k (r5) is always units of 4K. If we can't do the requested * offset, we return EINVAL. */ sys_mmap2: str r5, [sp, #4] b sys_mmap_pgoff ENDPROC(sys_mmap2) #ifdef CONFIG_OABI_COMPAT /* * These are syscalls with argument register differences */ sys_oabi_pread64: stmia sp, {r3, r4} b sys_pread64 ENDPROC(sys_oabi_pread64) sys_oabi_pwrite64: stmia sp, {r3, r4} b sys_pwrite64 ENDPROC(sys_oabi_pwrite64) sys_oabi_truncate64: mov r3, r2 mov r2, r1 b sys_truncate64 ENDPROC(sys_oabi_truncate64) sys_oabi_ftruncate64: mov r3, r2 mov r2, r1 b sys_ftruncate64 ENDPROC(sys_oabi_ftruncate64) sys_oabi_readahead: str r3, [sp] mov r3, r2 mov r2, r1 b sys_readahead ENDPROC(sys_oabi_readahead) /* * Let's declare a second syscall table for old ABI binaries * using the compatibility syscall entries. */ syscall_table_start sys_oabi_call_table #undef __SYSCALL_WITH_COMPAT #define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, compat) #include syscall_table_end sys_oabi_call_table #endif