Russell King | 8211237 | 2014-10-28 13:26:48 +0000 | [diff] [blame] | 1 | /* |
| 2 | * This program is free software; you can redistribute it and/or modify |
| 3 | * it under the terms of the GNU General Public License version 2 as |
| 4 | * published by the Free Software Foundation. |
| 5 | */ |
| 6 | |
| 7 | #include <asm/assembler.h> |
| 8 | #include <asm/ftrace.h> |
| 9 | #include <asm/unwind.h> |
| 10 | |
| 11 | #include "entry-header.S" |
| 12 | |
| 13 | /* |
| 14 | * When compiling with -pg, gcc inserts a call to the mcount routine at the |
| 15 | * start of every function. In mcount, apart from the function's address (in |
| 16 | * lr), we need to get hold of the function's caller's address. |
| 17 | * |
| 18 | * Older GCCs (pre-4.4) inserted a call to a routine called mcount like this: |
| 19 | * |
| 20 | * bl mcount |
| 21 | * |
| 22 | * These versions have the limitation that in order for the mcount routine to |
| 23 | * be able to determine the function's caller's address, an APCS-style frame |
| 24 | * pointer (which is set up with something like the code below) is required. |
| 25 | * |
| 26 | * mov ip, sp |
| 27 | * push {fp, ip, lr, pc} |
| 28 | * sub fp, ip, #4 |
| 29 | * |
| 30 | * With EABI, these frame pointers are not available unless -mapcs-frame is |
| 31 | * specified, and if building as Thumb-2, not even then. |
| 32 | * |
| 33 | * Newer GCCs (4.4+) solve this problem by introducing a new version of mcount, |
| 34 | * with call sites like: |
| 35 | * |
| 36 | * push {lr} |
| 37 | * bl __gnu_mcount_nc |
| 38 | * |
| 39 | * With these compilers, frame pointers are not necessary. |
| 40 | * |
| 41 | * mcount can be thought of as a function called in the middle of a subroutine |
| 42 | * call. As such, it needs to be transparent for both the caller and the |
| 43 | * callee: the original lr needs to be restored when leaving mcount, and no |
| 44 | * registers should be clobbered. (In the __gnu_mcount_nc implementation, we |
| 45 | * clobber the ip register. This is OK because the ARM calling convention |
| 46 | * allows it to be clobbered in subroutines and doesn't use it to hold |
| 47 | * parameters.) |
| 48 | * |
| 49 | * When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0" |
| 50 | * for the mcount case, and a "pop {lr}" for the __gnu_mcount_nc case (see |
| 51 | * arch/arm/kernel/ftrace.c). |
| 52 | */ |
| 53 | |
| 54 | #ifndef CONFIG_OLD_MCOUNT |
| 55 | #if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4)) |
| 56 | #error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0. |
| 57 | #endif |
| 58 | #endif |
| 59 | |
| 60 | .macro mcount_adjust_addr rd, rn |
| 61 | bic \rd, \rn, #1 @ clear the Thumb bit if present |
| 62 | sub \rd, \rd, #MCOUNT_INSN_SIZE |
| 63 | .endm |
| 64 | |
| 65 | .macro __mcount suffix |
| 66 | mcount_enter |
| 67 | ldr r0, =ftrace_trace_function |
| 68 | ldr r2, [r0] |
| 69 | adr r0, .Lftrace_stub |
| 70 | cmp r0, r2 |
| 71 | bne 1f |
| 72 | |
| 73 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| 74 | ldr r1, =ftrace_graph_return |
| 75 | ldr r2, [r1] |
| 76 | cmp r0, r2 |
| 77 | bne ftrace_graph_caller\suffix |
| 78 | |
| 79 | ldr r1, =ftrace_graph_entry |
| 80 | ldr r2, [r1] |
| 81 | ldr r0, =ftrace_graph_entry_stub |
| 82 | cmp r0, r2 |
| 83 | bne ftrace_graph_caller\suffix |
| 84 | #endif |
| 85 | |
| 86 | mcount_exit |
| 87 | |
| 88 | 1: mcount_get_lr r1 @ lr of instrumented func |
| 89 | mcount_adjust_addr r0, lr @ instrumented function |
Russell King | 14327c6 | 2015-04-21 14:17:25 +0100 | [diff] [blame] | 90 | badr lr, 2f |
Russell King | 8211237 | 2014-10-28 13:26:48 +0000 | [diff] [blame] | 91 | mov pc, r2 |
| 92 | 2: mcount_exit |
| 93 | .endm |
| 94 | |
| 95 | .macro __ftrace_caller suffix |
| 96 | mcount_enter |
| 97 | |
| 98 | mcount_get_lr r1 @ lr of instrumented func |
| 99 | mcount_adjust_addr r0, lr @ instrumented function |
| 100 | |
| 101 | .globl ftrace_call\suffix |
| 102 | ftrace_call\suffix: |
| 103 | bl ftrace_stub |
| 104 | |
| 105 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| 106 | .globl ftrace_graph_call\suffix |
| 107 | ftrace_graph_call\suffix: |
| 108 | mov r0, r0 |
| 109 | #endif |
| 110 | |
| 111 | mcount_exit |
| 112 | .endm |
| 113 | |
| 114 | .macro __ftrace_graph_caller |
| 115 | sub r0, fp, #4 @ &lr of instrumented routine (&parent) |
| 116 | #ifdef CONFIG_DYNAMIC_FTRACE |
| 117 | @ called from __ftrace_caller, saved in mcount_enter |
| 118 | ldr r1, [sp, #16] @ instrumented routine (func) |
| 119 | mcount_adjust_addr r1, r1 |
| 120 | #else |
| 121 | @ called from __mcount, untouched in lr |
| 122 | mcount_adjust_addr r1, lr @ instrumented routine (func) |
| 123 | #endif |
| 124 | mov r2, fp @ frame pointer |
| 125 | bl prepare_ftrace_return |
| 126 | mcount_exit |
| 127 | .endm |
| 128 | |
| 129 | #ifdef CONFIG_OLD_MCOUNT |
| 130 | /* |
| 131 | * mcount |
| 132 | */ |
| 133 | |
| 134 | .macro mcount_enter |
| 135 | stmdb sp!, {r0-r3, lr} |
| 136 | .endm |
| 137 | |
| 138 | .macro mcount_get_lr reg |
| 139 | ldr \reg, [fp, #-4] |
| 140 | .endm |
| 141 | |
| 142 | .macro mcount_exit |
| 143 | ldr lr, [fp, #-4] |
| 144 | ldmia sp!, {r0-r3, pc} |
| 145 | .endm |
| 146 | |
| 147 | ENTRY(mcount) |
| 148 | #ifdef CONFIG_DYNAMIC_FTRACE |
| 149 | stmdb sp!, {lr} |
| 150 | ldr lr, [fp, #-4] |
| 151 | ldmia sp!, {pc} |
| 152 | #else |
| 153 | __mcount _old |
| 154 | #endif |
| 155 | ENDPROC(mcount) |
| 156 | |
| 157 | #ifdef CONFIG_DYNAMIC_FTRACE |
| 158 | ENTRY(ftrace_caller_old) |
| 159 | __ftrace_caller _old |
| 160 | ENDPROC(ftrace_caller_old) |
| 161 | #endif |
| 162 | |
| 163 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| 164 | ENTRY(ftrace_graph_caller_old) |
| 165 | __ftrace_graph_caller |
| 166 | ENDPROC(ftrace_graph_caller_old) |
| 167 | #endif |
| 168 | |
| 169 | .purgem mcount_enter |
| 170 | .purgem mcount_get_lr |
| 171 | .purgem mcount_exit |
| 172 | #endif |
| 173 | |
| 174 | /* |
| 175 | * __gnu_mcount_nc |
| 176 | */ |
| 177 | |
| 178 | .macro mcount_enter |
| 179 | /* |
| 180 | * This pad compensates for the push {lr} at the call site. Note that we are |
| 181 | * unable to unwind through a function which does not otherwise save its lr. |
| 182 | */ |
| 183 | UNWIND(.pad #4) |
| 184 | stmdb sp!, {r0-r3, lr} |
| 185 | UNWIND(.save {r0-r3, lr}) |
| 186 | .endm |
| 187 | |
| 188 | .macro mcount_get_lr reg |
| 189 | ldr \reg, [sp, #20] |
| 190 | .endm |
| 191 | |
| 192 | .macro mcount_exit |
| 193 | ldmia sp!, {r0-r3, ip, lr} |
| 194 | ret ip |
| 195 | .endm |
| 196 | |
| 197 | ENTRY(__gnu_mcount_nc) |
| 198 | UNWIND(.fnstart) |
| 199 | #ifdef CONFIG_DYNAMIC_FTRACE |
| 200 | mov ip, lr |
| 201 | ldmia sp!, {lr} |
| 202 | ret ip |
| 203 | #else |
| 204 | __mcount |
| 205 | #endif |
| 206 | UNWIND(.fnend) |
| 207 | ENDPROC(__gnu_mcount_nc) |
Russell King | 8211237 | 2014-10-28 13:26:48 +0000 | [diff] [blame] | 208 | |
| 209 | #ifdef CONFIG_DYNAMIC_FTRACE |
| 210 | ENTRY(ftrace_caller) |
| 211 | UNWIND(.fnstart) |
| 212 | __ftrace_caller |
| 213 | UNWIND(.fnend) |
| 214 | ENDPROC(ftrace_caller) |
| 215 | #endif |
| 216 | |
| 217 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| 218 | ENTRY(ftrace_graph_caller) |
| 219 | UNWIND(.fnstart) |
| 220 | __ftrace_graph_caller |
| 221 | UNWIND(.fnend) |
| 222 | ENDPROC(ftrace_graph_caller) |
| 223 | #endif |
| 224 | |
| 225 | .purgem mcount_enter |
| 226 | .purgem mcount_get_lr |
| 227 | .purgem mcount_exit |
| 228 | |
| 229 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| 230 | .globl return_to_handler |
| 231 | return_to_handler: |
| 232 | stmdb sp!, {r0-r3} |
| 233 | mov r0, fp @ frame pointer |
| 234 | bl ftrace_return_to_handler |
| 235 | mov lr, r0 @ r0 has real ret addr |
| 236 | ldmia sp!, {r0-r3} |
| 237 | ret lr |
| 238 | #endif |
| 239 | |
| 240 | ENTRY(ftrace_stub) |
| 241 | .Lftrace_stub: |
| 242 | ret lr |
| 243 | ENDPROC(ftrace_stub) |