/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *  linux/arch/arm/kernel/head-common.S
 *
 *  Copyright (C) 1994-2002 Russell King
 *  Copyright (c) 2003 ARM Limited
 *  All Rights Reserved
 */
#include <asm/assembler.h>

#define ATAG_CORE 0x54410001
#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
#define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)

#ifdef CONFIG_CPU_BIG_ENDIAN
#define OF_DT_MAGIC 0xd00dfeed
#else
#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
#endif

/*
 * Exception handling.  Something went wrong and we can't proceed.  We
 * ought to tell the user, but since we don't have any guarantee that
 * we're even running on the right architecture, we do virtually nothing.
 *
 * If CONFIG_DEBUG_LL is set we try to print out something about the error
 * and hope for the best (useful if bootloader fails to pass a proper
 * machine ID for example).
 */
        __HEAD

/* Determine validity of the r2 atags pointer.  The heuristic requires
 * that the pointer be aligned, in the first 16k of physical RAM and
 * that the ATAG_CORE marker is first and present.  If CONFIG_OF_FLATTREE
 * is selected, then it will also accept a dtb pointer.  Future revisions
 * of this function may be more lenient with the physical address and
 * may also be able to move the ATAGS block if necessary.
 *
 * Returns:
 *  r2 either valid atags pointer, valid dtb pointer, or zero
 *  r5, r6 corrupted
 */
__vet_atags:
        tst     r2, #0x3                        @ aligned?
        bne     1f

        ldr     r5, [r2, #0]
#ifdef CONFIG_OF_FLATTREE
        ldr     r6, =OF_DT_MAGIC                @ is it a DTB?
        cmp     r5, r6
        beq     2f
#endif
        cmp     r5, #ATAG_CORE_SIZE             @ is first tag ATAG_CORE?
        cmpne   r5, #ATAG_CORE_SIZE_EMPTY
        bne     1f
        ldr     r5, [r2, #4]
        ldr     r6, =ATAG_CORE
        cmp     r5, r6
        bne     1f

2:      ret     lr                              @ atag/dtb pointer is ok

1:      mov     r2, #0
        ret     lr
ENDPROC(__vet_atags)

/*
 * The following fragment of code is executed with the MMU on in MMU mode,
 * and uses absolute addresses; this is not position independent.
 *
 *  r0  = cp#15 control register (exc_ret for M-class)
 *  r1  = machine ID
 *  r2  = atags/dtb pointer
 *  r9  = processor ID
 */
        __INIT
__mmap_switched:

        mov     r7, r1
        mov     r8, r2
        mov     r10, r0

        adr     r4, __mmap_switched_data
        mov     fp, #0

#if defined(CONFIG_XIP_DEFLATED_DATA)
   ARM( ldr     sp, [r4], #4 )
 THUMB( ldr     sp, [r4] )
 THUMB( add     r4, #4 )
        bl      __inflate_kernel_data           @ decompress .data to RAM
        teq     r0, #0
        bne     __error
#elif defined(CONFIG_XIP_KERNEL)
   ARM( ldmia   r4!, {r0, r1, r2, sp} )
 THUMB( ldmia   r4!, {r0, r1, r2, r3} )
 THUMB( mov     sp, r3 )
        sub     r2, r2, r1
        bl      __memcpy                        @ copy .data to RAM
#endif

   ARM( ldmia   r4!, {r0, r1, sp} )
 THUMB( ldmia   r4!, {r0, r1, r3} )
 THUMB( mov     sp, r3 )
        sub     r2, r1, r0
        mov     r1, #0
        bl      __memset                        @ clear .bss

        adr_l   r0, init_task                   @ get swapper task_struct
        set_current r0, r1

        ldmia   r4, {r0, r1, r2, r3}
        str     r9, [r0]                        @ Save processor ID
        str     r7, [r1]                        @ Save machine type
        str     r8, [r2]                        @ Save atags pointer
        cmp     r3, #0
        strne   r10, [r3]                       @ Save control register values
#ifdef CONFIG_KASAN
        bl      kasan_early_init
#endif
        mov     lr, #0
        b       start_kernel
ENDPROC(__mmap_switched)

        .align  2
        .type   __mmap_switched_data, %object
__mmap_switched_data:
#ifdef CONFIG_XIP_KERNEL
#ifndef CONFIG_XIP_DEFLATED_DATA
        .long   _sdata                          @ r0
        .long   __data_loc                      @ r1
        .long   _edata_loc                      @ r2
#endif
        .long   __bss_stop                      @ sp (temporary stack in .bss)
#endif

        .long   __bss_start                     @ r0
        .long   __bss_stop                      @ r1
        .long   init_thread_union + THREAD_START_SP @ sp

        .long   processor_id                    @ r0
        .long   __machine_arch_type             @ r1
        .long   __atags_pointer                 @ r2
#ifdef CONFIG_CPU_CP15
        .long   cr_alignment                    @ r3
#else
M_CLASS(.long   exc_ret)                        @ r3
AR_CLASS(.long  0)                              @ r3
#endif
        .size   __mmap_switched_data, . - __mmap_switched_data

        __FINIT
        .text

/*
 * This provides a C-API version of __lookup_processor_type
 */
ENTRY(lookup_processor_type)
        stmfd   sp!, {r4 - r6, r9, lr}
        mov     r9, r0
        bl      __lookup_processor_type
        mov     r0, r5
        ldmfd   sp!, {r4 - r6, r9, pc}
ENDPROC(lookup_processor_type)

/*
 * Read processor ID register (CP#15, CR0), and look up in the linker-built
 * supported processor list.  Note that we can't use the absolute addresses
 * for the __proc_info lists since we aren't running with the MMU on
 * (and therefore, we are not in the correct address space).  We have to
 * calculate the offset.
 *
 *      r9 = cpuid
 * Returns:
 *      r3, r4, r6 corrupted
 *      r5 = proc_info pointer in physical address space
 *      r9 = cpuid (preserved)
 */
__lookup_processor_type:
        /*
         * Look in <asm/procinfo.h> for information about the __proc_info
         * structure.
         */
        adr_l   r5, __proc_info_begin
        adr_l   r6, __proc_info_end
1:      ldmia   r5, {r3, r4}                    @ value, mask
        and     r4, r4, r9                      @ mask wanted bits
        teq     r3, r4
        beq     2f
        add     r5, r5, #PROC_INFO_SZ           @ sizeof(proc_info_list)
        cmp     r5, r6
        blo     1b
        mov     r5, #0                          @ unknown processor
2:      ret     lr
ENDPROC(__lookup_processor_type)

__error_lpae:
#ifdef CONFIG_DEBUG_LL
        adr     r0, str_lpae
        bl      printascii
        b       __error
str_lpae: .asciz "\nError: Kernel with LPAE support, but CPU does not support LPAE.\n"
#else
        b       __error
#endif
        .align
ENDPROC(__error_lpae)

__error_p:
#ifdef CONFIG_DEBUG_LL
        adr     r0, str_p1
        bl      printascii
        mov     r0, r9
        bl      printhex8
        adr     r0, str_p2
        bl      printascii
        b       __error
str_p1: .asciz  "\nError: unrecognized/unsupported processor variant (0x"
str_p2: .asciz  ").\n"
        .align
#endif
ENDPROC(__error_p)

__error:
#ifdef CONFIG_ARCH_RPC
/*
 * Turn the screen red on a error - RiscPC only.
 */
        mov     r0, #0x02000000
        mov     r3, #0x11
        orr     r3, r3, r3, lsl #8
        orr     r3, r3, r3, lsl #16
        str     r3, [r0], #4
        str     r3, [r0], #4
        str     r3, [r0], #4
        str     r3, [r0], #4
#endif
1:      mov     r0, r0
        b       1b
ENDPROC(__error)