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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) |