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authorAKASHI Takahiro <takahiro.akashi@linaro.org>2014-04-30 18:54:33 +0900
committerWill Deacon <will.deacon@arm.com>2014-05-29 09:08:08 +0100
commit819e50e25d0ce8a75f5cba815416a6a8573655c4 (patch)
tree006f9d7dc3f97f47709430357651a83ffdc1f86d /arch/arm64
parentaf64d2aa872a174772ffc00e2558083f70193acb (diff)
downloadlinux-linaro-stable-819e50e25d0ce8a75f5cba815416a6a8573655c4.tar.gz
arm64: Add ftrace support
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. Reviewed-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/Kconfig2
-rw-r--r--arch/arm64/include/asm/ftrace.h23
-rw-r--r--arch/arm64/kernel/Makefile4
-rw-r--r--arch/arm64/kernel/arm64ksyms.c4
-rw-r--r--arch/arm64/kernel/entry-ftrace.S175
-rw-r--r--arch/arm64/kernel/ftrace.c64
6 files changed, 272 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c7022a9d5eeb..8a25a4ad3159 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -38,6 +38,8 @@ config ARM64
select HAVE_DMA_CONTIGUOUS
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select HAVE_FTRACE_MCOUNT_RECORD
+ 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 000000000000..58ea5951b198
--- /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 7d811d9522bc..1ebcb4c6b5d8 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-$(CONFIG_SMP) += smp.o smp_spin_table.o topology.o
arm64-obj-$(CONFIG_PERF_EVENTS) += perf_regs.o
diff --git a/arch/arm64/kernel/arm64ksyms.c b/arch/arm64/kernel/arm64ksyms.c
index 1edc792b4a1f..a85843ddbde8 100644
--- a/arch/arm64/kernel/arm64ksyms.c
+++ b/arch/arm64/kernel/arm64ksyms.c
@@ -61,3 +61,7 @@ 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 000000000000..b2d8c4559cd8
--- /dev/null
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -0,0 +1,175 @@
+/*
+ * 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 in _mcount():
+ *
+ * current sp/fp => 0:+-----+
+ * in _mcount() | x29 | -> instrumented function's fp
+ * +-----+
+ * | x30 | -> _mcount()'s lr (= instrumented function's pc)
+ * old sp => +16:+-----+
+ * when instrumented | |
+ * function calls | ... |
+ * _mcount() | |
+ * | |
+ * instrumented => +xx:+-----+
+ * function's fp | x29 | -> parent's fp
+ * +-----+
+ * | x30 | -> instrumented function's lr (= parent's pc)
+ * +-----+
+ * | ... |
+ */
+
+ .macro mcount_enter
+ stp x29, x30, [sp, #-16]!
+ mov x29, sp
+ .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, [x29]
+ 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, [x29, #8]
+ mcount_adjust_addr \reg, \reg
+ .endm
+
+ .macro mcount_get_lr reg
+ ldr \reg, [x29]
+ ldr \reg, [\reg, #8]
+ mcount_adjust_addr \reg, \reg
+ .endm
+
+ .macro mcount_get_lr_addr reg
+ ldr \reg, [x29]
+ 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_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.
+ */
+ENTRY(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
+END(return_to_handler)
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
new file mode 100644
index 000000000000..a559ab86999b
--- /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(&current->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 */