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Diffstat (limited to 'arch/arm/kernel/entry-ftrace.S')
| -rw-r--r-- | arch/arm/kernel/entry-ftrace.S | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S new file mode 100644 index 00000000000..fe57c73e70a --- /dev/null +++ b/arch/arm/kernel/entry-ftrace.S @@ -0,0 +1,243 @@ +/* + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <asm/assembler.h> +#include <asm/ftrace.h> +#include <asm/unwind.h> + +#include "entry-header.S" + +/* + * When compiling with -pg, gcc inserts a call to the mcount routine at the + * start of every function. In mcount, apart from the function's address (in + * lr), we need to get hold of the function's caller's address. + * + * Older GCCs (pre-4.4) inserted a call to a routine called mcount like this: + * + * bl mcount + * + * These versions have the limitation that in order for the mcount routine to + * be able to determine the function's caller's address, an APCS-style frame + * pointer (which is set up with something like the code below) is required. + * + * mov ip, sp + * push {fp, ip, lr, pc} + * sub fp, ip, #4 + * + * With EABI, these frame pointers are not available unless -mapcs-frame is + * specified, and if building as Thumb-2, not even then. + * + * Newer GCCs (4.4+) solve this problem by introducing a new version of mcount, + * with call sites like: + * + * push {lr} + * bl __gnu_mcount_nc + * + * With these compilers, frame pointers are not necessary. + * + * mcount can be thought of as a function called in the middle of a subroutine + * call. As such, it needs to be transparent for both the caller and the + * callee: the original lr needs to be restored when leaving mcount, and no + * registers should be clobbered. (In the __gnu_mcount_nc implementation, we + * clobber the ip register. This is OK because the ARM calling convention + * allows it to be clobbered in subroutines and doesn't use it to hold + * parameters.) + * + * When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0" + * for the mcount case, and a "pop {lr}" for the __gnu_mcount_nc case (see + * arch/arm/kernel/ftrace.c). + */ + +#ifndef CONFIG_OLD_MCOUNT +#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4)) +#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0. +#endif +#endif + +.macro mcount_adjust_addr rd, rn + bic \rd, \rn, #1 @ clear the Thumb bit if present + sub \rd, \rd, #MCOUNT_INSN_SIZE +.endm + +.macro __mcount suffix + mcount_enter + ldr r0, =ftrace_trace_function + ldr r2, [r0] + adr r0, .Lftrace_stub + cmp r0, r2 + bne 1f + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + ldr r1, =ftrace_graph_return + ldr r2, [r1] + cmp r0, r2 + bne ftrace_graph_caller\suffix + + ldr r1, =ftrace_graph_entry + ldr r2, [r1] + ldr r0, =ftrace_graph_entry_stub + cmp r0, r2 + bne ftrace_graph_caller\suffix +#endif + + mcount_exit + +1: mcount_get_lr r1 @ lr of instrumented func + mcount_adjust_addr r0, lr @ instrumented function + adr lr, BSYM(2f) + mov pc, r2 +2: mcount_exit +.endm + +.macro __ftrace_caller suffix + mcount_enter + + mcount_get_lr r1 @ lr of instrumented func + mcount_adjust_addr r0, lr @ instrumented function + + .globl ftrace_call\suffix +ftrace_call\suffix: + bl ftrace_stub + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + .globl ftrace_graph_call\suffix +ftrace_graph_call\suffix: + mov r0, r0 +#endif + + mcount_exit +.endm + +.macro __ftrace_graph_caller + sub r0, fp, #4 @ &lr of instrumented routine (&parent) +#ifdef CONFIG_DYNAMIC_FTRACE + @ called from __ftrace_caller, saved in mcount_enter + ldr r1, [sp, #16] @ instrumented routine (func) + mcount_adjust_addr r1, r1 +#else + @ called from __mcount, untouched in lr + mcount_adjust_addr r1, lr @ instrumented routine (func) +#endif + mov r2, fp @ frame pointer + bl prepare_ftrace_return + mcount_exit +.endm + +#ifdef CONFIG_OLD_MCOUNT +/* + * mcount + */ + +.macro mcount_enter + stmdb sp!, {r0-r3, lr} +.endm + +.macro mcount_get_lr reg + ldr \reg, [fp, #-4] +.endm + +.macro mcount_exit + ldr lr, [fp, #-4] + ldmia sp!, {r0-r3, pc} +.endm + +ENTRY(mcount) +#ifdef CONFIG_DYNAMIC_FTRACE + stmdb sp!, {lr} + ldr lr, [fp, #-4] + ldmia sp!, {pc} +#else + __mcount _old +#endif +ENDPROC(mcount) + +#ifdef CONFIG_DYNAMIC_FTRACE +ENTRY(ftrace_caller_old) + __ftrace_caller _old +ENDPROC(ftrace_caller_old) +#endif + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +ENTRY(ftrace_graph_caller_old) + __ftrace_graph_caller +ENDPROC(ftrace_graph_caller_old) +#endif + +.purgem mcount_enter +.purgem mcount_get_lr +.purgem mcount_exit +#endif + +/* + * __gnu_mcount_nc + */ + +.macro mcount_enter +/* + * This pad compensates for the push {lr} at the call site. Note that we are + * unable to unwind through a function which does not otherwise save its lr. + */ + UNWIND(.pad #4) + stmdb sp!, {r0-r3, lr} + UNWIND(.save {r0-r3, lr}) +.endm + +.macro mcount_get_lr reg + ldr \reg, [sp, #20] +.endm + +.macro mcount_exit + ldmia sp!, {r0-r3, ip, lr} + ret ip +.endm + +ENTRY(__gnu_mcount_nc) +UNWIND(.fnstart) +#ifdef CONFIG_DYNAMIC_FTRACE + mov ip, lr + ldmia sp!, {lr} + ret ip +#else + __mcount +#endif +UNWIND(.fnend) +ENDPROC(__gnu_mcount_nc) + +#ifdef CONFIG_DYNAMIC_FTRACE +ENTRY(ftrace_caller) +UNWIND(.fnstart) + __ftrace_caller +UNWIND(.fnend) +ENDPROC(ftrace_caller) +#endif + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +ENTRY(ftrace_graph_caller) +UNWIND(.fnstart) + __ftrace_graph_caller +UNWIND(.fnend) +ENDPROC(ftrace_graph_caller) +#endif + +.purgem mcount_enter +.purgem mcount_get_lr +.purgem mcount_exit + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + .globl return_to_handler +return_to_handler: + stmdb sp!, {r0-r3} + mov r0, fp @ frame pointer + bl ftrace_return_to_handler + mov lr, r0 @ r0 has real ret addr + ldmia sp!, {r0-r3} + ret lr +#endif + +ENTRY(ftrace_stub) +.Lftrace_stub: + ret lr +ENDPROC(ftrace_stub) |