/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *  linux/arch/arm/kernel/entry-common.S
 *
 *  Copyright (C) 2000 Russell King
 */

#include <asm/assembler.h>
#include <asm/unistd.h>
#include <asm/ftrace.h>
#include <asm/unwind.h>
#include <asm/page.h>
#ifdef CONFIG_AEABI
#include <asm/unistd-oabi.h>
#endif

        .equ    NR_syscalls, __NR_syscalls

#include "entry-header.S"

saved_psr       .req    r8
#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING_USER)
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_USER) || \
        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

        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)
        str     scno, [tsk, #TI_ABI_SYSCALL]    @ make sure tracers see update
        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

        ct_user_enter save = 0

#ifdef CONFIG_KSTACK_ERASE
        bl      stackleak_erase_on_task_stack
#endif
        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     nsh
        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
        reload_current r10, ip
        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)
        .ltorg

        /*
         * 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

        .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 <calls-eabi.S>
#else
#include <calls-oabi.S>
#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 <calls-oabi.S>
        syscall_table_end sys_oabi_call_table

#endif