This patch implements arm64 specific part to support function tracers, such as function (CONFIG_FUNCTION_TRACER), function_graph (CONFIG_FUNCTION_GRAPH_TRACER) and function profiler (CONFIG_FUNCTION_PROFILER).
With 'function' tracer, all the functions in the kernel are traced with timestamps in ${sysfs}/tracing/trace. If function_graph tracer is specified, call graph is generated.
The kernel must be compiled with -pg option so that _mcount() is inserted at the beginning of functions. This function is called on every function's entry as long as tracing is enabled. In addition, function_graph tracer also needs to be able to probe function's exit. ftrace_graph_caller() & return_to_handler do this by faking link register's value to intercept function's return path.
More details on architecture specific requirements are described in 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 | 4 + arch/arm64/kernel/arm64ksyms.c | 4 + arch/arm64/kernel/entry-ftrace.S | 173 ++++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/ftrace.c | 64 ++++++++++++++ 6 files changed, 270 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 27bbcfc..5783641 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -33,6 +33,8 @@ config ARM64 select HAVE_DMA_ATTRS select HAVE_DMA_CONTIGUOUS select HAVE_EFFICIENT_UNALIGNED_ACCESS + 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..58ea595 --- /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 + +#include <asm/insn.h> + +#define MCOUNT_ADDR ((unsigned long)_mcount) +#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE + +#ifndef __ASSEMBLY__ +extern void _mcount(unsigned long); +#endif /* __ASSEMBLY__ */ + +#endif /* __ASM_FTRACE_H */ diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 2d4554b..ac67fd0 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -5,6 +5,9 @@ CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET) AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
+CFLAGS_REMOVE_ftrace.o = -pg +CFLAGS_REMOVE_insn.o = -pg + # Object file lists. arm64-obj-y := cputable.o debug-monitors.o entry.o irq.o fpsimd.o \ entry-fpsimd.o process.o ptrace.o setup.o signal.o \ @@ -13,6 +16,7 @@ arm64-obj-y := cputable.o debug-monitors.o entry.o irq.o fpsimd.o \
arm64-obj-$(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-$(CONFIG_SMP) += smp.o smp_spin_table.o arm64-obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o diff --git a/arch/arm64/kernel/arm64ksyms.c b/arch/arm64/kernel/arm64ksyms.c index 338b568..7f0512f 100644 --- a/arch/arm64/kernel/arm64ksyms.c +++ b/arch/arm64/kernel/arm64ksyms.c @@ -56,3 +56,7 @@ 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..2e8162e --- /dev/null +++ b/arch/arm64/kernel/entry-ftrace.S @@ -0,0 +1,173 @@ +/* + * 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> +#include <asm/insn.h> + +/* + * Gcc with -pg will put the following code in the beginning of each function: + * mov x0, x30 + * bl _mcount + * [function's body ...] + * "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic + * ftrace is enabled. + * + * Please note that x0 as an argument will not be used here because we can + * get lr(x30) of instrumented function at any time by winding up call stack + * as long as the kernel is compiled without -fomit-frame-pointer. + * (or CONFIG_FRAME_POINTER, this is forced on arm64) + * + * stack layout after mcount_enter: + * + * 0 ---------------------------------------- sp of _mcount() + * x29: fp of instrumented function fp is not winded + * -------------------- + * x30: lr of _mcount() (= instrumented function's pc) + * +16 ---------------------------------------- sp of instrumented function + * + * .... + * + * +xx ---------------------------------------- fp of instrumented function + * x29: fp of parent + * -------------------- + * x30: lr of instrumented function (= parent's pc) + * -------------------- + * xxx + */ + + .macro mcount_enter + stp x29, x30, [sp, #-16]! + .endm + + .macro mcount_exit + ldp x29, x30, [sp], #16 + ret + .endm + + .macro mcount_adjust_addr rd, rn + sub \rd, \rn, #AARCH64_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] + ldr \reg, [\reg, #8] + 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 + * + * This function makes calls, if enabled, to: + * - tracer function to probe instrumented function's entry, + * - ftrace_graph_caller to set up an exit hook + */ +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 // function's pc + mcount_get_lr x1 // function's lr (= parent's pc) + 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) + * + * Called from _mcount() or ftrace_caller() when function_graph tracer is + * selected. + * This function w/ prepare_ftrace_return() fakes link register's value on + * the call stack in order to intercept instrumented function's return path + * and run return_to_handler() later on its exit. + */ +ENTRY(ftrace_graph_caller) + mcount_get_saved_lr_addr x0 // pointer to function's saved lr + mcount_get_pc x1 // function's pc + 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) + * + * Run ftrace_return_to_handler() before going back to parent. + * @fp is checked against the value passed by 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..a559ab8 --- /dev/null +++ b/arch/arm64/kernel/ftrace.c @@ -0,0 +1,64 @@ +/* + * 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 +/* + * function_graph tracer expects ftrace_return_to_handler() to be called + * on the way back to parent. For this purpose, this function is called + * in _mcount() or ftrace_caller() to replace return address (*parent) on + * the call stack to return_to_handler. + * + * Note that @frame_pointer is used only for sanity check later. + */ +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; + struct ftrace_graph_ent trace; + int err; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + return; + + /* + * Note: + * No protection against faulting at *parent, which may be seen + * on other archs. It's unlikely on AArch64. + */ + old = *parent; + *parent = return_hooker; + + 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 */