/*
 *  linux/arch/arm/kernel/entry-common.S
 *
 *  Copyright (C) 2000 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <asm/unistd.h>
#include <asm/ftrace.h>
#include <asm/unwind.h>

#ifdef CONFIG_NEED_RET_TO_USER
#include <mach/entry-macro.S>
#else
        .macro  arch_ret_to_user, tmp1, tmp2
        .endm
#endif

#include "entry-header.S"


        .align  5
/*
 * This is the fast syscall return path.  We do as little as
 * possible here, and this includes saving r0 back into the SVC
 * stack.
 */
ret_fast_syscall:
 UNWIND(.fnstart        )
 UNWIND(.cantunwind     )
        disable_irq                             @ disable interrupts
        ldr     r1, [tsk, #TI_FLAGS]
        tst     r1, #_TIF_WORK_MASK
        bne     fast_work_pending
        asm_trace_hardirqs_on

        /* perform architecture specific actions before user return */
        arch_ret_to_user r1, lr
        ct_user_enter

        restore_user_regs fast = 1, offset = S_OFF
 UNWIND(.fnend          )

/*
 * Ok, we need to do extra processing, enter the slow path.
 */
fast_work_pending:
        str     r0, [sp, #S_R0+S_OFF]!          @ returned r0
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

/*
 * "slow" syscall return path.  "why" tells us if this was a real syscall.
 */
ENTRY(ret_to_user)
ret_slow_syscall:
        disable_irq                             @ disable interrupts
ENTRY(ret_to_user_from_irq)
        ldr     r1, [tsk, #TI_FLAGS]
        tst     r1, #_TIF_WORK_MASK
        bne     work_pending
no_work_pending:
        asm_trace_hardirqs_on

        /* 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
        adrne   lr, BSYM(1f)
        movne   pc, r5
1:      get_thread_info tsk
        b       ret_slow_syscall
ENDPROC(ret_from_fork)

        .equ NR_syscalls,0
#define CALL(x) .equ NR_syscalls,NR_syscalls+1
#include "calls.S"

/*
 * Ensure that the system call table is equal to __NR_syscalls,
 * which is the value the rest of the system sees
 */
.ifne NR_syscalls - __NR_syscalls
.error "__NR_syscalls is not equal to the size of the syscall table"
.endif

#undef CALL
#define CALL(x) .long x

#ifdef CONFIG_FUNCTION_TRACER
/*
 * When compiling with -pg, gcc inserts a call to the mcount routine at the
 * start of every function.  In mcount, apart from the function's address (in
 * lr), we need to get hold of the function's caller's address.
 *
 * Older GCCs (pre-4.4) inserted a call to a routine called mcount like this:
 *
 *      bl      mcount
 *
 * These versions have the limitation that in order for the mcount routine to
 * be able to determine the function's caller's address, an APCS-style frame
 * pointer (which is set up with something like the code below) is required.
 *
 *      mov     ip, sp
 *      push    {fp, ip, lr, pc}
 *      sub     fp, ip, #4
 *
 * With EABI, these frame pointers are not available unless -mapcs-frame is
 * specified, and if building as Thumb-2, not even then.
 *
 * Newer GCCs (4.4+) solve this problem by introducing a new version of mcount,
 * with call sites like:
 *
 *      push    {lr}
 *      bl      __gnu_mcount_nc
 *
 * With these compilers, frame pointers are not necessary.
 *
 * mcount can be thought of as a function called in the middle of a subroutine
 * call.  As such, it needs to be transparent for both the caller and the
 * callee: the original lr needs to be restored when leaving mcount, and no
 * registers should be clobbered.  (In the __gnu_mcount_nc implementation, we
 * clobber the ip register.  This is OK because the ARM calling convention
 * allows it to be clobbered in subroutines and doesn't use it to hold
 * parameters.)
 *
 * When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0"
 * for the mcount case, and a "pop {lr}" for the __gnu_mcount_nc case (see
 * arch/arm/kernel/ftrace.c).
 */

#ifndef CONFIG_OLD_MCOUNT
#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4))
#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0.
#endif
#endif

.macro mcount_adjust_addr rd, rn
        bic     \rd, \rn, #1            @ clear the Thumb bit if present
        sub     \rd, \rd, #MCOUNT_INSN_SIZE
.endm

.macro __mcount suffix
        mcount_enter
        ldr     r0, =ftrace_trace_function
        ldr     r2, [r0]
        adr     r0, .Lftrace_stub
        cmp     r0, r2
        bne     1f

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        ldr     r1, =ftrace_graph_return
        ldr     r2, [r1]
        cmp     r0, r2
        bne     ftrace_graph_caller\suffix

        ldr     r1, =ftrace_graph_entry
        ldr     r2, [r1]
        ldr     r0, =ftrace_graph_entry_stub
        cmp     r0, r2
        bne     ftrace_graph_caller\suffix
#endif

        mcount_exit

1:      mcount_get_lr   r1                      @ lr of instrumented func
        mcount_adjust_addr      r0, lr          @ instrumented function
        adr     lr, BSYM(2f)
        mov     pc, r2
2:      mcount_exit
.endm

.macro __ftrace_caller suffix
        mcount_enter

        mcount_get_lr   r1                      @ lr of instrumented func
        mcount_adjust_addr      r0, lr          @ instrumented function

        .globl ftrace_call\suffix
ftrace_call\suffix:
        bl      ftrace_stub

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        .globl ftrace_graph_call\suffix
ftrace_graph_call\suffix:
        mov     r0, r0
#endif

        mcount_exit
.endm

.macro __ftrace_graph_caller
        sub     r0, fp, #4              @ &lr of instrumented routine (&parent)
#ifdef CONFIG_DYNAMIC_FTRACE
        @ called from __ftrace_caller, saved in mcount_enter
        ldr     r1, [sp, #16]           @ instrumented routine (func)
        mcount_adjust_addr      r1, r1
#else
        @ called from __mcount, untouched in lr
        mcount_adjust_addr      r1, lr  @ instrumented routine (func)
#endif
        mov     r2, fp                  @ frame pointer
        bl      prepare_ftrace_return
        mcount_exit
.endm

#ifdef CONFIG_OLD_MCOUNT
/*
 * mcount
 */

.macro mcount_enter
        stmdb   sp!, {r0-r3, lr}
.endm

.macro mcount_get_lr reg
        ldr     \reg, [fp, #-4]
.endm

.macro mcount_exit
        ldr     lr, [fp, #-4]
        ldmia   sp!, {r0-r3, pc}
.endm

ENTRY(mcount)
#ifdef CONFIG_DYNAMIC_FTRACE
        stmdb   sp!, {lr}
        ldr     lr, [fp, #-4]
        ldmia   sp!, {pc}
#else
        __mcount _old
#endif
ENDPROC(mcount)

#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(ftrace_caller_old)
        __ftrace_caller _old
ENDPROC(ftrace_caller_old)
#endif

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(ftrace_graph_caller_old)
        __ftrace_graph_caller
ENDPROC(ftrace_graph_caller_old)
#endif

.purgem mcount_enter
.purgem mcount_get_lr
.purgem mcount_exit
#endif

/*
 * __gnu_mcount_nc
 */

.macro mcount_enter
/*
 * This pad compensates for the push {lr} at the call site.  Note that we are
 * unable to unwind through a function which does not otherwise save its lr.
 */
 UNWIND(.pad    #4)
        stmdb   sp!, {r0-r3, lr}
 UNWIND(.save   {r0-r3, lr})
.endm

.macro mcount_get_lr reg
        ldr     \reg, [sp, #20]
.endm

.macro mcount_exit
        ldmia   sp!, {r0-r3, ip, lr}
        mov     pc, ip
.endm

ENTRY(__gnu_mcount_nc)
UNWIND(.fnstart)
#ifdef CONFIG_DYNAMIC_FTRACE
        mov     ip, lr
        ldmia   sp!, {lr}
        mov     pc, ip
#else
        __mcount
#endif
UNWIND(.fnend)
ENDPROC(__gnu_mcount_nc)

#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(ftrace_caller)
UNWIND(.fnstart)
        __ftrace_caller
UNWIND(.fnend)
ENDPROC(ftrace_caller)
#endif

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(ftrace_graph_caller)
UNWIND(.fnstart)
        __ftrace_graph_caller
UNWIND(.fnend)
ENDPROC(ftrace_graph_caller)
#endif

.purgem mcount_enter
.purgem mcount_get_lr
.purgem mcount_exit

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        .globl return_to_handler
return_to_handler:
        stmdb   sp!, {r0-r3}
        mov     r0, fp                  @ frame pointer
        bl      ftrace_return_to_handler
        mov     lr, r0                  @ r0 has real ret addr
        ldmia   sp!, {r0-r3}
        mov     pc, lr
#endif

ENTRY(ftrace_stub)
.Lftrace_stub:
        mov     pc, lr
ENDPROC(ftrace_stub)

#endif /* CONFIG_FUNCTION_TRACER */

/*=============================================================================
 * SWI handler
 *-----------------------------------------------------------------------------
 */

        .align  5
ENTRY(vector_swi)
#ifdef CONFIG_CPU_V7M
        v7m_exception_entry
#else
        sub     sp, sp, #S_FRAME_SIZE
        stmia   sp, {r0 - r12}                  @ Calling r0 - r12
 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     r8, spsr                        @ called from non-FIQ mode, so ok.
        str     lr, [sp, #S_PC]                 @ Save calling PC
        str     r8, [sp, #S_PSR]                @ Save CPSR
        str     r0, [sp, #S_OLD_R0]             @ Save OLD_R0
#endif
        zero_fp

#ifdef CONFIG_ALIGNMENT_TRAP
        ldr     ip, __cr_alignment
        ldr     ip, [ip]
        mcr     p15, 0, ip, c1, c0              @ update control register
#endif

        enable_irq
        ct_user_exit
        get_thread_info tsk

        /*
         * 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     r8, #PSR_T_BIT
        movne   r10, #0                         @ no thumb OABI emulation
 USER(  ldreq   r10, [lr, #-4]          )       @ get SWI instruction
#else
 USER(  ldr     r10, [lr, #-4]          )       @ get SWI instruction
#endif
#ifdef CONFIG_CPU_ENDIAN_BE8
        rev     r10, r10                        @ little endian instruction
#endif

#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     r8, #PSR_T_BIT                  @ this is SPSR from save_user_regs
        addne   scno, r7, #__NR_SYSCALL_BASE    @ put OS number in
 USER(  ldreq   scno, [lr, #-4]         )

#else
        /* Legacy ABI only. */
 USER(  ldr     scno, [lr, #-4]         )       @ get SWI instruction
#endif

        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
        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
        eor     scno, scno, #__NR_SYSCALL_BASE  @ check OS number
#endif

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

        cmp     scno, #NR_syscalls              @ check upper syscall limit
        adr     lr, BSYM(ret_fast_syscall)      @ return address
        ldrcc   pc, [tbl, scno, lsl #2]         @ call sys_* routine

        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, lr, #4
        str     lr, [sp, #S_PC]
        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:
        mov     r1, scno
        add     r0, sp, #S_OFF
        bl      syscall_trace_enter

        adr     lr, BSYM(__sys_trace_return)    @ return address
        mov     scno, r0                        @ syscall number (possibly new)
        add     r1, sp, #S_R0 + S_OFF           @ pointer to regs
        cmp     scno, #NR_syscalls              @ check upper syscall limit
        ldmccia r1, {r0 - r6}                   @ have to reload r0 - r6
        stmccia sp, {r4, r5}                    @ and update the stack args
        ldrcc   pc, [tbl, scno, lsl #2]         @ call sys_* routine
        cmp     scno, #-1                       @ skip the syscall?
        bne     2b
        add     sp, sp, #S_OFF                  @ restore stack
        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

/*
 * This is the syscall table declaration for native ABI syscalls.
 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
 */
#define ABI(native, compat) native
#ifdef CONFIG_AEABI
#define OBSOLETE(syscall) sys_ni_syscall
#else
#define OBSOLETE(syscall) syscall
#endif

        .type   sys_call_table, #object
ENTRY(sys_call_table)
#include "calls.S"
#undef ABI
#undef OBSOLETE

/*============================================================================
 * 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
                stmloia 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:
#if PAGE_SHIFT > 12
                tst     r5, #PGOFF_MASK
                moveq   r5, r5, lsr #PAGE_SHIFT - 12
                streq   r5, [sp, #4]
                beq     sys_mmap_pgoff
                mov     r0, #-EINVAL
                mov     pc, lr
#else
                str     r5, [sp, #4]
                b       sys_mmap_pgoff
#endif
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.
 */
#define ABI(native, compat) compat
#define OBSOLETE(syscall) syscall

        .type   sys_oabi_call_table, #object
ENTRY(sys_oabi_call_table)
#include "calls.S"
#undef ABI
#undef OBSOLETE

#endif