129 lines
3.9 KiB
ArmAsm
129 lines
3.9 KiB
ArmAsm
/*
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* arch/v850/kernel/head.S -- Lowest-level startup code
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*
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* Copyright (C) 2001,02,03 NEC Electronics Corporation
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* Copyright (C) 2001,02,03 Miles Bader <miles@gnu.org>
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*
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* This file is subject to the terms and conditions of the GNU General
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* Public License. See the file COPYING in the main directory of this
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* archive for more details.
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*
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* Written by Miles Bader <miles@gnu.org>
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*/
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#include <asm/clinkage.h>
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#include <asm/current.h>
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#include <asm/entry.h>
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#include <asm/thread_info.h>
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#include <asm/irq.h>
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/* Make a slightly more convenient alias for C_SYMBOL_NAME. */
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#define CSYM C_SYMBOL_NAME
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.text
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// Define `mach_early_init' as a weak symbol
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.global CSYM(mach_early_init)
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.weak CSYM(mach_early_init)
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C_ENTRY(start):
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// Make sure interrupts are turned off, just in case
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di
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#ifdef CONFIG_RESET_GUARD
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// See if we got here via an unexpected reset
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ld.w RESET_GUARD, r19 // Check current value of reset guard
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mov RESET_GUARD_ACTIVE, r20
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cmp r19, r20
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bne 1f // Guard was not active
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// If we get here, the reset guard was active. Load up some
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// interesting values as arguments, and jump to the handler.
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st.w r0, RESET_GUARD // Allow further resets to succeed
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mov lp, r6 // Arg 0: return address
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ld.b KM, r7 // Arg 1: kernel mode
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mov sp, r9 // Arg 3: stack pointer
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ld.w KSP, r19 // maybe switch to kernel stack
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cmp r7, r0 // see if already in kernel mode
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cmov z, r19, sp, sp // and switch to kernel stack if not
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GET_CURRENT_TASK(r8) // Arg 2: task pointer
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jr CSYM(unexpected_reset)
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1: st.w r20, RESET_GUARD // Turn on reset guard
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#endif /* CONFIG_RESET_GUARD */
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// Setup a temporary stack for doing pre-initialization function calls.
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//
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// We can't use the initial kernel stack, because (1) it may be
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// located in memory we're not allowed to touch, and (2) since
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// it's in the data segment, calling memcpy to initialize that
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// area from ROM will overwrite memcpy's return address.
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mov hilo(CSYM(_init_stack_end) - 4), sp
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// See if there's a platform-specific early-initialization routine
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// defined; it's a weak symbol, so it will have an address of zero if
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// there's not.
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mov hilo(CSYM(mach_early_init)), r6
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cmp r6, r0
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bz 3f
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// There is one, so call it. If this function is written in C, it
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// should be very careful -- the stack pointer is valid, but very
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// little else is (e.g., bss is not zeroed yet, and initialized data
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// hasn't been).
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jarl 2f, lp // first figure out return address
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2: add 3f - ., lp
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jmp [r6] // do call
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3:
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#ifdef CONFIG_ROM_KERNEL
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// Copy the data area from ROM to RAM
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mov hilo(CSYM(_rom_copy_dst_start)), r6
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mov hilo(CSYM(_rom_copy_src_start)), r7
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mov hilo(CSYM(_rom_copy_dst_end)), r8
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sub r6, r8
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jarl CSYM(memcpy), lp
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#endif
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// Load the initial thread's stack, and current task pointer (in r16)
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mov hilo(CSYM(init_thread_union)), r19
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movea THREAD_SIZE, r19, sp
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ld.w TI_TASK[r19], CURRENT_TASK
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#ifdef CONFIG_TIME_BOOTUP
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/* This stuff must come after mach_early_init, because interrupts may
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not work until after its been called. */
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jarl CSYM(highres_timer_reset), lp
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jarl CSYM(highres_timer_start), lp
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#endif
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// Kernel stack pointer save location
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st.w sp, KSP
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// Assert that we're in `kernel mode'
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mov 1, r19
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st.w r19, KM
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#ifdef CONFIG_ZERO_BSS
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// Zero bss area, since we can't rely upon any loader to do so
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mov hilo(CSYM(_sbss)), r6
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mov r0, r7
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mov hilo(CSYM(_ebss)), r8
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sub r6, r8
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jarl CSYM(memset), lp
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#endif
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// What happens if the main kernel function returns (it shouldn't)
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mov hilo(CSYM(machine_halt)), lp
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// Start the linux kernel. We use an indirect jump to get extra
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// range, because on some platforms this initial startup code
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// (and the associated platform-specific code in mach_early_init)
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// are located far away from the main kernel, e.g. so that they
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// can initialize RAM first and copy the kernel or something.
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mov hilo(CSYM(start_kernel)), r12
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jmp [r12]
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C_END(start)
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