diff options
Diffstat (limited to 'arch/v850/kernel/head.S')
| -rw-r--r-- | arch/v850/kernel/head.S | 128 |
1 files changed, 128 insertions, 0 deletions
diff --git a/arch/v850/kernel/head.S b/arch/v850/kernel/head.S new file mode 100644 index 000000000000..c490b937ef14 --- /dev/null +++ b/arch/v850/kernel/head.S @@ -0,0 +1,128 @@ +/* + * arch/v850/kernel/head.S -- Lowest-level startup code + * + * Copyright (C) 2001,02,03 NEC Electronics Corporation + * Copyright (C) 2001,02,03 Miles Bader <miles@gnu.org> + * + * This file is subject to the terms and conditions of the GNU General + * Public License. See the file COPYING in the main directory of this + * archive for more details. + * + * Written by Miles Bader <miles@gnu.org> + */ + +#include <asm/clinkage.h> +#include <asm/current.h> +#include <asm/entry.h> +#include <asm/thread_info.h> +#include <asm/irq.h> + + +/* Make a slightly more convenient alias for C_SYMBOL_NAME. */ +#define CSYM C_SYMBOL_NAME + + + .text + + // Define `mach_early_init' as a weak symbol + .global CSYM(mach_early_init) + .weak CSYM(mach_early_init) + +C_ENTRY(start): + // Make sure interrupts are turned off, just in case + di + +#ifdef CONFIG_RESET_GUARD + // See if we got here via an unexpected reset + ld.w RESET_GUARD, r19 // Check current value of reset guard + mov RESET_GUARD_ACTIVE, r20 + cmp r19, r20 + bne 1f // Guard was not active + + // If we get here, the reset guard was active. Load up some + // interesting values as arguments, and jump to the handler. + st.w r0, RESET_GUARD // Allow further resets to succeed + mov lp, r6 // Arg 0: return address + ld.b KM, r7 // Arg 1: kernel mode + mov sp, r9 // Arg 3: stack pointer + ld.w KSP, r19 // maybe switch to kernel stack + cmp r7, r0 // see if already in kernel mode + cmov z, r19, sp, sp // and switch to kernel stack if not + GET_CURRENT_TASK(r8) // Arg 2: task pointer + jr CSYM(unexpected_reset) + +1: st.w r20, RESET_GUARD // Turn on reset guard +#endif /* CONFIG_RESET_GUARD */ + + // Setup a temporary stack for doing pre-initialization function calls. + // + // We can't use the initial kernel stack, because (1) it may be + // located in memory we're not allowed to touch, and (2) since + // it's in the data segment, calling memcpy to initialize that + // area from ROM will overwrite memcpy's return address. + mov hilo(CSYM(_init_stack_end) - 4), sp + + // See if there's a platform-specific early-initialization routine + // defined; it's a weak symbol, so it will have an address of zero if + // there's not. + mov hilo(CSYM(mach_early_init)), r6 + cmp r6, r0 + bz 3f + + // There is one, so call it. If this function is written in C, it + // should be very careful -- the stack pointer is valid, but very + // little else is (e.g., bss is not zeroed yet, and initialized data + // hasn't been). + jarl 2f, lp // first figure out return address +2: add 3f - ., lp + jmp [r6] // do call +3: + +#ifdef CONFIG_ROM_KERNEL + // Copy the data area from ROM to RAM + mov hilo(CSYM(_rom_copy_dst_start)), r6 + mov hilo(CSYM(_rom_copy_src_start)), r7 + mov hilo(CSYM(_rom_copy_dst_end)), r8 + sub r6, r8 + jarl CSYM(memcpy), lp +#endif + + // Load the initial thread's stack, and current task pointer (in r16) + mov hilo(CSYM(init_thread_union)), r19 + movea THREAD_SIZE, r19, sp + ld.w TI_TASK[r19], CURRENT_TASK + +#ifdef CONFIG_TIME_BOOTUP + /* This stuff must come after mach_early_init, because interrupts may + not work until after its been called. */ + jarl CSYM(highres_timer_reset), lp + jarl CSYM(highres_timer_start), lp +#endif + + // Kernel stack pointer save location + st.w sp, KSP + + // Assert that we're in `kernel mode' + mov 1, r19 + st.w r19, KM + +#ifdef CONFIG_ZERO_BSS + // Zero bss area, since we can't rely upon any loader to do so + mov hilo(CSYM(_sbss)), r6 + mov r0, r7 + mov hilo(CSYM(_ebss)), r8 + sub r6, r8 + jarl CSYM(memset), lp +#endif + + // What happens if the main kernel function returns (it shouldn't) + mov hilo(CSYM(machine_halt)), lp + + // Start the linux kernel. We use an indirect jump to get extra + // range, because on some platforms this initial startup code + // (and the associated platform-specific code in mach_early_init) + // are located far away from the main kernel, e.g. so that they + // can initialize RAM first and copy the kernel or something. + mov hilo(CSYM(start_kernel)), r12 + jmp [r12] +C_END(start) |