| Heiko Carstens | dfd9f7a | 2009-06-12 10:26:44 +0200 | [diff] [blame^] | 1 | /* |
| 2 | * Dynamic function tracer architecture backend. |
| 3 | * |
| 4 | * Copyright IBM Corp. 2009 |
| 5 | * |
| 6 | * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>, |
| 7 | * |
| 8 | */ |
| 9 | |
| 10 | #include <linux/uaccess.h> |
| 11 | #include <linux/ftrace.h> |
| 12 | #include <linux/kernel.h> |
| 13 | #include <linux/types.h> |
| 14 | #include <asm/lowcore.h> |
| 15 | |
| 16 | void ftrace_disable_code(void); |
| 17 | void ftrace_call_code(void); |
| 18 | void ftrace_nop_code(void); |
| 19 | |
| 20 | #define FTRACE_INSN_SIZE 4 |
| 21 | |
| 22 | #ifdef CONFIG_64BIT |
| 23 | |
| 24 | asm( |
| 25 | " .align 4\n" |
| 26 | "ftrace_disable_code:\n" |
| 27 | " j 0f\n" |
| 28 | " .word 0x0024\n" |
| 29 | " lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n" |
| 30 | " basr %r14,%r1\n" |
| 31 | " lg %r14,8(15)\n" |
| 32 | " lgr %r0,%r0\n" |
| 33 | "0:\n"); |
| 34 | |
| 35 | asm( |
| 36 | " .align 4\n" |
| 37 | "ftrace_nop_code:\n" |
| 38 | " j .+"__stringify(MCOUNT_INSN_SIZE)"\n"); |
| 39 | |
| 40 | asm( |
| 41 | " .align 4\n" |
| 42 | "ftrace_call_code:\n" |
| 43 | " stg %r14,8(%r15)\n"); |
| 44 | |
| 45 | #else /* CONFIG_64BIT */ |
| 46 | |
| 47 | asm( |
| 48 | " .align 4\n" |
| 49 | "ftrace_disable_code:\n" |
| 50 | " j 0f\n" |
| 51 | " l %r1,"__stringify(__LC_FTRACE_FUNC)"\n" |
| 52 | " basr %r14,%r1\n" |
| 53 | " l %r14,4(%r15)\n" |
| 54 | " j 0f\n" |
| 55 | " bcr 0,%r7\n" |
| 56 | " bcr 0,%r7\n" |
| 57 | " bcr 0,%r7\n" |
| 58 | " bcr 0,%r7\n" |
| 59 | " bcr 0,%r7\n" |
| 60 | " bcr 0,%r7\n" |
| 61 | "0:\n"); |
| 62 | |
| 63 | asm( |
| 64 | " .align 4\n" |
| 65 | "ftrace_nop_code:\n" |
| 66 | " j .+"__stringify(MCOUNT_INSN_SIZE)"\n"); |
| 67 | |
| 68 | asm( |
| 69 | " .align 4\n" |
| 70 | "ftrace_call_code:\n" |
| 71 | " st %r14,4(%r15)\n"); |
| 72 | |
| 73 | #endif /* CONFIG_64BIT */ |
| 74 | |
| 75 | static int ftrace_modify_code(unsigned long ip, |
| 76 | void *old_code, int old_size, |
| 77 | void *new_code, int new_size) |
| 78 | { |
| 79 | unsigned char replaced[MCOUNT_INSN_SIZE]; |
| 80 | |
| 81 | /* |
| 82 | * Note: Due to modules code can disappear and change. |
| 83 | * We need to protect against faulting as well as code |
| 84 | * changing. We do this by using the probe_kernel_* |
| 85 | * functions. |
| 86 | * This however is just a simple sanity check. |
| 87 | */ |
| 88 | if (probe_kernel_read(replaced, (void *)ip, old_size)) |
| 89 | return -EFAULT; |
| 90 | if (memcmp(replaced, old_code, old_size) != 0) |
| 91 | return -EINVAL; |
| 92 | if (probe_kernel_write((void *)ip, new_code, new_size)) |
| 93 | return -EPERM; |
| 94 | return 0; |
| 95 | } |
| 96 | |
| 97 | static int ftrace_make_initial_nop(struct module *mod, struct dyn_ftrace *rec, |
| 98 | unsigned long addr) |
| 99 | { |
| 100 | return ftrace_modify_code(rec->ip, |
| 101 | ftrace_call_code, FTRACE_INSN_SIZE, |
| 102 | ftrace_disable_code, MCOUNT_INSN_SIZE); |
| 103 | } |
| 104 | |
| 105 | int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, |
| 106 | unsigned long addr) |
| 107 | { |
| 108 | if (addr == MCOUNT_ADDR) |
| 109 | return ftrace_make_initial_nop(mod, rec, addr); |
| 110 | return ftrace_modify_code(rec->ip, |
| 111 | ftrace_call_code, FTRACE_INSN_SIZE, |
| 112 | ftrace_nop_code, FTRACE_INSN_SIZE); |
| 113 | } |
| 114 | |
| 115 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) |
| 116 | { |
| 117 | return ftrace_modify_code(rec->ip, |
| 118 | ftrace_nop_code, FTRACE_INSN_SIZE, |
| 119 | ftrace_call_code, FTRACE_INSN_SIZE); |
| 120 | } |
| 121 | |
| 122 | int ftrace_update_ftrace_func(ftrace_func_t func) |
| 123 | { |
| 124 | ftrace_dyn_func = (unsigned long)func; |
| 125 | return 0; |
| 126 | } |
| 127 | |
| 128 | int __init ftrace_dyn_arch_init(void *data) |
| 129 | { |
| 130 | *(unsigned long *)data = 0; |
| 131 | return 0; |
| 132 | } |