This enables FUNCTION_TRACER and FUNCTION_GRAPH_TRACER, and also provides the base for other tracers which depend on FUNCTION_TRACER.
_mcount() is the entry point which is inserted at the very beginning of every function by gcc with -pg option. function graph tracer intercepts instrumented function's return path by faking the return address (lr) stored in stack in order to trace a call graph.
See Documentation/trace/ftrace-design.txt
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org --- arch/arm64/Kconfig | 2 + arch/arm64/include/asm/ftrace.h | 23 +++++ arch/arm64/kernel/Makefile | 6 ++ arch/arm64/kernel/arm64ksyms.c | 4 + arch/arm64/kernel/entry-ftrace.S | 172 ++++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/ftrace.c | 83 ++++++++++++++++++ 6 files changed, 290 insertions(+) create mode 100644 arch/arm64/include/asm/ftrace.h create mode 100644 arch/arm64/kernel/entry-ftrace.S create mode 100644 arch/arm64/kernel/ftrace.c
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index da388e4..3776319 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -23,6 +23,8 @@ config ARM64 select HAVE_DEBUG_KMEMLEAK select HAVE_DMA_API_DEBUG select HAVE_DMA_ATTRS + select HAVE_FUNCTION_TRACER + select HAVE_FUNCTION_GRAPH_TRACER select HAVE_GENERIC_DMA_COHERENT select HAVE_HW_BREAKPOINT if PERF_EVENTS select HAVE_MEMBLOCK diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h new file mode 100644 index 0000000..0d5dfdb --- /dev/null +++ b/arch/arm64/include/asm/ftrace.h @@ -0,0 +1,23 @@ +/* + * arch/arm64/include/asm/ftrace.h + * + * Copyright (C) 2013 Linaro Limited + * Author: AKASHI Takahiro takahiro.akashi@linaro.org + * + * 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. + */ +#ifndef __ASM_FTRACE_H +#define __ASM_FTRACE_H + +#ifdef CONFIG_FUNCTION_TRACER +#define MCOUNT_ADDR ((unsigned long)_mcount) +#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ + +#ifndef __ASSEMBLY__ +extern void _mcount(unsigned long); +#endif /* __ASSEMBLY__ */ +#endif /* CONFIG_FUNCTION_TRACER */ + +#endif /* __ASM_FTRACE_H */ diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index b7db65e..92429e4 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -5,6 +5,11 @@ CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET) AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
+ifdef CONFIG_FUNCTION_TRACER +CFLAGS_REMOVE_ftrace.o = -pg +CFLAGS_REMOVE_insn.o = -pg +endif + # Object file lists. arm64-obj-y := cputable.o debug-monitors.o entry.o irq.o fpsimd.o \ entry-fpsimd.o process.o ptrace.o setup.o signal.o \ @@ -13,6 +18,7 @@ arm64-obj-y := cputable.o debug-monitors.o entry.o irq.o fpsimd.o \
arm64-obj-$(CONFIG_COMPAT) += sys32.o kuser32.o signal32.o \ sys_compat.o +arm64-obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o entry-ftrace.o arm64-obj-$(CONFIG_MODULES) += arm64ksyms.o module.o arm64-obj-$(CONFIG_SMP) += smp.o smp_spin_table.o smp_psci.o arm64-obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o diff --git a/arch/arm64/kernel/arm64ksyms.c b/arch/arm64/kernel/arm64ksyms.c index 41b4f62..ef9b63d 100644 --- a/arch/arm64/kernel/arm64ksyms.c +++ b/arch/arm64/kernel/arm64ksyms.c @@ -58,3 +58,7 @@ EXPORT_SYMBOL(clear_bit); EXPORT_SYMBOL(test_and_clear_bit); EXPORT_SYMBOL(change_bit); EXPORT_SYMBOL(test_and_change_bit); + +#ifdef CONFIG_FUNCTION_TRACER +EXPORT_SYMBOL(_mcount); +#endif diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S new file mode 100644 index 0000000..ae14ece --- /dev/null +++ b/arch/arm64/kernel/entry-ftrace.S @@ -0,0 +1,172 @@ +/* + * arch/arm64/kernel/entry-ftrace.S + * + * Copyright (C) 2013 Linaro Limited + * Author: AKASHI Takahiro takahiro.akashi@linaro.org + * + * 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 <linux/linkage.h> +#include <asm/ftrace.h> + +/* + * Gcc with -pg will put the following code in the beginning of each function: + * mov x0, x30 + * bl _mcount + * On contrary to tricky arm(32) implementation, this is a normal function + * call and so x0 & x30 will be safely saved and restored around tracer + * call (_mcount/ftrace_caller) in an instrumented function (callsite). + * + * stack layout: + * 0 ---------------------------------------- sp in tracer function + * x29: fp in instrumented function fp is not winded + * -------------------- + * x30: lr in tracer function + * +16 -------------------- + * x0: arg 0 (lr in instrumented function) + * -------------------- + * x1 (temporary) + * +32 -------------------- + * x2 (temporary) + * -------------------- + * (don't care) + * +48 ---------------------------------------- sp in instrumented function + * + * .... + * + * +xx ---------------------------------------- fp in instrumented function + * x29: fp in parent function + * -------------------- + * x30: lr in insturmented function + * -------------------- + * xxx + */ + + .macro mcount_enter + stp x29, x30, [sp, #-48]! + stp x0, x1, [sp, #16] + str x2, [sp, #32] + .endm + + .macro mcount_exit + ldr x2, [sp, #32] + ldp x0, x1, [sp, #16] + ldp x29, x30, [sp], #48 + ret + .endm + + .macro mcount_adjust_addr rd, rn + sub \rd, \rn, #MCOUNT_INSN_SIZE + .endm + + /* for instrumented function's parent */ + .macro mcount_get_parent_fp reg + ldr \reg, [sp] + ldr \reg, [\reg] + .endm + + /* for instrumented function */ + .macro mcount_get_pc0 reg + mcount_adjust_addr \reg, x30 + .endm + + .macro mcount_get_pc reg + ldr \reg, [sp, #8] + mcount_adjust_addr \reg, \reg + .endm + + .macro mcount_get_lr reg + ldr \reg, [sp, #16] + mcount_adjust_addr \reg, \reg + .endm + + .macro mcount_get_saved_lr_addr reg + ldr \reg, [sp] + add \reg, \reg, #8 + .endm + +/* + * void _mcount(unsigned long return_address) + * @return_address: return address to instrumented function (callsite) + */ +ENTRY(_mcount) +#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST + ldr x0, =ftrace_trace_stop + ldr x0, [x0] // if ftrace_trace_stop + ret // return; +#endif + mcount_enter + + ldr x0, =ftrace_trace_function + ldr x2, [x0] + adr x0, ftrace_stub + cmp x0, x2 // if (ftrace_trace_function + b.eq skip_ftrace_call // != ftrace_stub) { + + mcount_get_pc x0 // pc in callsite + mcount_get_lr x1 // callsite's lr (adjusted) + blr x2 // (*ftrace_trace_function)(pc, lr); + +#ifndef CONFIG_FUNCTION_GRAPH_TRACER +skip_ftrace_call: // return; + mcount_exit // } +#else + mcount_exit // return; + // } +skip_ftrace_call: + ldr x1, =ftrace_graph_return + ldr x2, [x1] // if ((ftrace_graph_return + cmp x0, x2 // != ftrace_stub) + b.ne ftrace_graph_caller + + ldr x1, =ftrace_graph_entry // || (ftrace_graph_entry + ldr x2, [x1] // != ftrace_graph_entry_stub)) + ldr x0, =ftrace_graph_entry_stub + cmp x0, x2 + b.ne ftrace_graph_caller // ftrace_graph_caller(); + + mcount_exit +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ +ENDPROC(_mcount) + +ENTRY(ftrace_stub) + ret +ENDPROC(ftrace_stub) + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +/* + * void ftrace_graph_caller(void) + * + * This function fakes instrumented function's return address to make a hook + * on function return path by calling prepare_ftrace_return(). This function + * is assumed to be jumped into from _mcount() or ftrace_caller() and so no + * context need be saved here. + */ +ENTRY(ftrace_graph_caller) + mcount_get_saved_lr_addr x0 // pointer to callsite's saved lr + mcount_get_pc x1 // pc in callsite + mcount_get_parent_fp x2 // parent's fp + bl prepare_ftrace_return // prepare_ftrace_return(&lr, pc, fp) + + mcount_exit +ENDPROC(ftrace_graph_caller) + +/* + * void return_to_handler(void) + * + * return hook handler + * @fp is used to check against the value specified in ftrace_graph_caller() + * only when CONFIG_FUNCTION_GRAPH_FP_TEST is enabled. + */ + .global return_to_handler +return_to_handler: + str x0, [sp, #-16]! + mov x0, x29 // parent's fp + bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp); + mov x30, x0 // restore the original return address + ldr x0, [sp], #16 + ret +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c new file mode 100644 index 0000000..e779e16 --- /dev/null +++ b/arch/arm64/kernel/ftrace.c @@ -0,0 +1,83 @@ +/* + * arch/arm64/kernel/ftrace.c + * + * Copyright (C) 2013 Linaro Limited + * Author: AKASHI Takahiro takahiro.akashi@linaro.org + * + * 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 <linux/ftrace.h> +#include <linux/swab.h> +#include <linux/uaccess.h> + +#include <asm/cacheflush.h> +#include <asm/ftrace.h> +#include <asm/insn.h> + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, + unsigned long frame_pointer) +{ + unsigned long return_hooker = (unsigned long)&return_to_handler; + unsigned long old, faulted; + struct ftrace_graph_ent trace; + int err; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + return; + +#if 1 /* FIXME */ + /* + * Protect against fault, even if it shouldn't + * happen. This tool is too much intrusive to + * ignore such a protection. + * Actually we want to do + * old = *parent; + * parent = return_hooker; + */ + asm volatile( +"1: ldr %0, [%2]\n" +"2: str %3, [%2]\n" +" mov %1, #0\n" +"3:\n" +" .pushsection .fixup, "ax"\n" +"4: mov %1, #1\n" +" b 3b\n" +" .popsection\n" +" .pushsection __ex_table, "a"\n" +" .align 3\n" +" .quad 1b, 4b, 2b, 4b\n" +" .popsection\n" + : "=&r" (old), "=r" (faulted) : "r" (parent), "r" (return_hooker) + ); + + if (unlikely(faulted)) { + ftrace_graph_stop(); + WARN_ON(1); + return; + } +#else + old = *parent; + *parent = return_hooker; +#endif + + trace.func = self_addr; + trace.depth = current->curr_ret_stack + 1; + + /* Only trace if the calling function expects to */ + if (!ftrace_graph_entry(&trace)) { + *parent = old; + return; + } + + err = ftrace_push_return_trace(old, self_addr, &trace.depth, + frame_pointer); + if (err == -EBUSY) { + *parent = old; + return; + } +} +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */