| Mike Frysinger | 1c873be | 2009-06-09 07:25:09 -0400 | [diff] [blame^] | 1 | /* |
| 2 | * mcount and friends -- ftrace stuff |
| 3 | * |
| 4 | * Copyright (C) 2009 Analog Devices Inc. |
| 5 | * Licensed under the GPL-2 or later. |
| 6 | */ |
| 7 | |
| 8 | #include <linux/linkage.h> |
| 9 | #include <asm/ftrace.h> |
| 10 | |
| 11 | .text |
| 12 | |
| 13 | /* GCC will have called us before setting up the function prologue, so we |
| 14 | * can clobber the normal scratch registers, but we need to make sure to |
| 15 | * save/restore the registers used for argument passing (R0-R2) in case |
| 16 | * the profiled function is using them. With data registers, R3 is the |
| 17 | * only one we can blow away. With pointer registers, we have P0-P2. |
| 18 | * |
| 19 | * Upon entry, the RETS will point to the top of the current profiled |
| 20 | * function. And since GCC setup the frame for us, the previous function |
| 21 | * will be waiting there. mmmm pie. |
| 22 | */ |
| 23 | ENTRY(__mcount) |
| 24 | /* save third function arg early so we can do testing below */ |
| 25 | [--sp] = r2; |
| 26 | |
| 27 | /* load the function pointer to the tracer */ |
| 28 | p0.l = _ftrace_trace_function; |
| 29 | p0.h = _ftrace_trace_function; |
| 30 | r3 = [p0]; |
| 31 | |
| 32 | /* optional micro optimization: don't call the stub tracer */ |
| 33 | r2.l = _ftrace_stub; |
| 34 | r2.h = _ftrace_stub; |
| 35 | cc = r2 == r3; |
| 36 | if ! cc jump .Ldo_trace; |
| 37 | |
| 38 | r2 = [sp++]; |
| 39 | rts; |
| 40 | |
| 41 | .Ldo_trace: |
| 42 | |
| 43 | /* save first/second function arg and the return register */ |
| 44 | [--sp] = r0; |
| 45 | [--sp] = r1; |
| 46 | [--sp] = rets; |
| 47 | |
| 48 | /* setup the tracer function */ |
| 49 | p0 = r3; |
| 50 | |
| 51 | /* tracer(ulong frompc, ulong selfpc): |
| 52 | * frompc: the pc that did the call to ... |
| 53 | * selfpc: ... this location |
| 54 | * the selfpc itself will need adjusting for the mcount call |
| 55 | */ |
| 56 | r1 = rets; |
| 57 | r0 = [fp + 4]; |
| 58 | r1 += -MCOUNT_INSN_SIZE; |
| 59 | |
| 60 | /* call the tracer */ |
| 61 | call (p0); |
| 62 | |
| 63 | /* restore state and get out of dodge */ |
| 64 | rets = [sp++]; |
| 65 | r1 = [sp++]; |
| 66 | r0 = [sp++]; |
| 67 | r2 = [sp++]; |
| 68 | |
| 69 | .globl _ftrace_stub |
| 70 | _ftrace_stub: |
| 71 | rts; |
| 72 | ENDPROC(__mcount) |