Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * arch/v850/kernel/head.S -- Lowest-level startup code |
| 3 | * |
| 4 | * Copyright (C) 2001,02,03 NEC Electronics Corporation |
| 5 | * Copyright (C) 2001,02,03 Miles Bader <miles@gnu.org> |
| 6 | * |
| 7 | * This file is subject to the terms and conditions of the GNU General |
| 8 | * Public License. See the file COPYING in the main directory of this |
| 9 | * archive for more details. |
| 10 | * |
| 11 | * Written by Miles Bader <miles@gnu.org> |
| 12 | */ |
| 13 | |
| 14 | #include <asm/clinkage.h> |
| 15 | #include <asm/current.h> |
| 16 | #include <asm/entry.h> |
| 17 | #include <asm/thread_info.h> |
| 18 | #include <asm/irq.h> |
| 19 | |
| 20 | |
| 21 | /* Make a slightly more convenient alias for C_SYMBOL_NAME. */ |
| 22 | #define CSYM C_SYMBOL_NAME |
| 23 | |
| 24 | |
| 25 | .text |
| 26 | |
| 27 | // Define `mach_early_init' as a weak symbol |
| 28 | .global CSYM(mach_early_init) |
| 29 | .weak CSYM(mach_early_init) |
| 30 | |
| 31 | C_ENTRY(start): |
| 32 | // Make sure interrupts are turned off, just in case |
| 33 | di |
| 34 | |
| 35 | #ifdef CONFIG_RESET_GUARD |
| 36 | // See if we got here via an unexpected reset |
| 37 | ld.w RESET_GUARD, r19 // Check current value of reset guard |
| 38 | mov RESET_GUARD_ACTIVE, r20 |
| 39 | cmp r19, r20 |
| 40 | bne 1f // Guard was not active |
| 41 | |
| 42 | // If we get here, the reset guard was active. Load up some |
| 43 | // interesting values as arguments, and jump to the handler. |
| 44 | st.w r0, RESET_GUARD // Allow further resets to succeed |
| 45 | mov lp, r6 // Arg 0: return address |
| 46 | ld.b KM, r7 // Arg 1: kernel mode |
| 47 | mov sp, r9 // Arg 3: stack pointer |
| 48 | ld.w KSP, r19 // maybe switch to kernel stack |
| 49 | cmp r7, r0 // see if already in kernel mode |
| 50 | cmov z, r19, sp, sp // and switch to kernel stack if not |
| 51 | GET_CURRENT_TASK(r8) // Arg 2: task pointer |
| 52 | jr CSYM(unexpected_reset) |
| 53 | |
| 54 | 1: st.w r20, RESET_GUARD // Turn on reset guard |
| 55 | #endif /* CONFIG_RESET_GUARD */ |
| 56 | |
| 57 | // Setup a temporary stack for doing pre-initialization function calls. |
| 58 | // |
| 59 | // We can't use the initial kernel stack, because (1) it may be |
| 60 | // located in memory we're not allowed to touch, and (2) since |
| 61 | // it's in the data segment, calling memcpy to initialize that |
| 62 | // area from ROM will overwrite memcpy's return address. |
| 63 | mov hilo(CSYM(_init_stack_end) - 4), sp |
| 64 | |
| 65 | // See if there's a platform-specific early-initialization routine |
| 66 | // defined; it's a weak symbol, so it will have an address of zero if |
| 67 | // there's not. |
| 68 | mov hilo(CSYM(mach_early_init)), r6 |
| 69 | cmp r6, r0 |
| 70 | bz 3f |
| 71 | |
| 72 | // There is one, so call it. If this function is written in C, it |
| 73 | // should be very careful -- the stack pointer is valid, but very |
| 74 | // little else is (e.g., bss is not zeroed yet, and initialized data |
| 75 | // hasn't been). |
| 76 | jarl 2f, lp // first figure out return address |
| 77 | 2: add 3f - ., lp |
| 78 | jmp [r6] // do call |
| 79 | 3: |
| 80 | |
| 81 | #ifdef CONFIG_ROM_KERNEL |
| 82 | // Copy the data area from ROM to RAM |
| 83 | mov hilo(CSYM(_rom_copy_dst_start)), r6 |
| 84 | mov hilo(CSYM(_rom_copy_src_start)), r7 |
| 85 | mov hilo(CSYM(_rom_copy_dst_end)), r8 |
| 86 | sub r6, r8 |
| 87 | jarl CSYM(memcpy), lp |
| 88 | #endif |
| 89 | |
| 90 | // Load the initial thread's stack, and current task pointer (in r16) |
| 91 | mov hilo(CSYM(init_thread_union)), r19 |
| 92 | movea THREAD_SIZE, r19, sp |
| 93 | ld.w TI_TASK[r19], CURRENT_TASK |
| 94 | |
| 95 | #ifdef CONFIG_TIME_BOOTUP |
| 96 | /* This stuff must come after mach_early_init, because interrupts may |
| 97 | not work until after its been called. */ |
| 98 | jarl CSYM(highres_timer_reset), lp |
| 99 | jarl CSYM(highres_timer_start), lp |
| 100 | #endif |
| 101 | |
| 102 | // Kernel stack pointer save location |
| 103 | st.w sp, KSP |
| 104 | |
| 105 | // Assert that we're in `kernel mode' |
| 106 | mov 1, r19 |
| 107 | st.w r19, KM |
| 108 | |
| 109 | #ifdef CONFIG_ZERO_BSS |
| 110 | // Zero bss area, since we can't rely upon any loader to do so |
| 111 | mov hilo(CSYM(_sbss)), r6 |
| 112 | mov r0, r7 |
| 113 | mov hilo(CSYM(_ebss)), r8 |
| 114 | sub r6, r8 |
| 115 | jarl CSYM(memset), lp |
| 116 | #endif |
| 117 | |
| 118 | // What happens if the main kernel function returns (it shouldn't) |
| 119 | mov hilo(CSYM(machine_halt)), lp |
| 120 | |
| 121 | // Start the linux kernel. We use an indirect jump to get extra |
| 122 | // range, because on some platforms this initial startup code |
| 123 | // (and the associated platform-specific code in mach_early_init) |
| 124 | // are located far away from the main kernel, e.g. so that they |
| 125 | // can initialize RAM first and copy the kernel or something. |
| 126 | mov hilo(CSYM(start_kernel)), r12 |
| 127 | jmp [r12] |
| 128 | C_END(start) |