From 014c257cce65e9d1cd2d28ec1c89a37c536b151d Mon Sep 17 00:00:00 2001
From: Abhishek Sagar <sagar.abhishek@gmail.com>
Date: Sat, 31 May 2008 14:23:50 +0530
Subject: [PATCH] ftrace: core support for ARM
Core ftrace support for the ARM architecture, which includes support
for dynamic function tracing.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/arm/Kconfig | 2 +
arch/arm/boot/compressed/Makefile | 6 ++
arch/arm/kernel/Makefile | 5 ++
arch/arm/kernel/armksyms.c | 5 ++
arch/arm/kernel/entry-common.S | 47 +++++++++++
arch/arm/kernel/ftrace.c | 128 ++++++++++++++++++++++++++++++
6 files changed, 193 insertions(+)
create mode 100644 arch/arm/kernel/ftrace.c
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b786e68914d4..3845e5c8a34f 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -14,6 +14,8 @@ config ARM
select HAVE_OPROFILE
select HAVE_KPROBES if (!XIP_KERNEL)
select HAVE_KRETPROBES if (HAVE_KPROBES)
+ select HAVE_FTRACE if (!XIP_KERNEL)
+ select HAVE_DYNAMIC_FTRACE if (HAVE_FTRACE)
help
The ARM series is a line of low-power-consumption RISC chip designs
licensed by ARM Ltd and targeted at embedded applications and
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index de9d9ee50958..95baac4939e0 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -69,6 +69,12 @@ SEDFLAGS = s/TEXT_START/$(ZTEXTADDR)/;s/BSS_START/$(ZBSSADDR)/
targets := vmlinux vmlinux.lds piggy.gz piggy.o font.o font.c \
head.o misc.o $(OBJS)
+
+ifeq ($(CONFIG_FTRACE),y)
+ORIG_CFLAGS := $(KBUILD_CFLAGS)
+KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
+endif
+
EXTRA_CFLAGS := -fpic -fno-builtin
EXTRA_AFLAGS :=
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index ad455ff5aebe..eb9092ca8008 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -4,6 +4,10 @@
AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
+ifdef CONFIG_DYNAMIC_FTRACE
+CFLAGS_REMOVE_ftrace.o = -pg
+endif
+
# Object file lists.
obj-y := compat.o entry-armv.o entry-common.o irq.o \
@@ -18,6 +22,7 @@ obj-$(CONFIG_ARTHUR) += arthur.o
obj-$(CONFIG_ISA_DMA) += dma-isa.o
obj-$(CONFIG_PCI) += bios32.o isa.o
obj-$(CONFIG_SMP) += smp.o
+obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
obj-$(CONFIG_KPROBES) += kprobes.o kprobes-decode.o
obj-$(CONFIG_ATAGS_PROC) += atags.o
diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
index 688b7b1ee416..3b132215cbf8 100644
--- a/arch/arm/kernel/armksyms.c
+++ b/arch/arm/kernel/armksyms.c
@@ -48,6 +48,11 @@ extern void __aeabi_ulcmp(void);
extern void fpundefinstr(void);
extern void fp_enter(void);
+#ifdef CONFIG_FTRACE
+extern void mcount(void);
+EXPORT_SYMBOL(mcount);
+#endif
+
/*
* This has a special calling convention; it doesn't
* modify any of the usual registers, except for LR.
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 597ed00a08d8..8f79a4789ed4 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -99,6 +99,53 @@ ENTRY(ret_from_fork)
#undef CALL
#define CALL(x) .long x
+#ifdef CONFIG_FTRACE
+#ifdef CONFIG_DYNAMIC_FTRACE
+ENTRY(mcount)
+ stmdb sp!, {r0-r3, lr}
+ mov r0, lr
+
+ .globl mcount_call
+mcount_call:
+ bl ftrace_stub
+ ldmia sp!, {r0-r3, pc}
+
+ENTRY(ftrace_caller)
+ stmdb sp!, {r0-r3, lr}
+ ldr r1, [fp, #-4]
+ mov r0, lr
+
+ .globl ftrace_call
+ftrace_call:
+ bl ftrace_stub
+ ldmia sp!, {r0-r3, pc}
+
+#else
+
+ENTRY(mcount)
+ stmdb sp!, {r0-r3, lr}
+ ldr r0, =ftrace_trace_function
+ ldr r2, [r0]
+ adr r0, ftrace_stub
+ cmp r0, r2
+ bne trace
+ ldmia sp!, {r0-r3, pc}
+
+trace:
+ ldr r1, [fp, #-4]
+ mov r0, lr
+ mov lr, pc
+ mov pc, r2
+ ldmia sp!, {r0-r3, pc}
+
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+ .globl ftrace_stub
+ftrace_stub:
+ mov pc, lr
+
+#endif /* CONFIG_FTRACE */
+
/*=============================================================================
* SWI handler
*-----------------------------------------------------------------------------
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
new file mode 100644
index 000000000000..f4cb4cc3fa0c
--- /dev/null
+++ b/arch/arm/kernel/ftrace.c
@@ -0,0 +1,128 @@
+/*
+ * Dynamic function tracing support.
+ *
+ * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
+ *
+ * For licencing details, see COPYING.
+ *
+ * Defines low-level handling of mcount calls when the kernel
+ * is compiled with the -pg flag. When using dynamic ftrace, the
+ * mcount call-sites get patched lazily with NOP till they are
+ * enabled. All code mutation routines here take effect atomically.
+ */
+
+#include <linux/ftrace.h>
+#include <asm/cacheflush.h>
+
+#define INSN_SIZE 4
+#define PC_OFFSET 8
+#define BL_OPCODE 0xeb000000
+#define BL_OFFSET_MASK 0x00ffffff
+
+static unsigned long bl_insn;
+static const unsigned long NOP = 0xe1a00000; /* mov r0, r0 */
+
+/* return true if mcount call site is already patched/no-op'ed */
+int ftrace_ip_converted(unsigned long pc)
+{
+ unsigned long save;
+
+ pc -= INSN_SIZE;
+ save = *(unsigned long *)pc;
+ return save == NOP;
+}
+
+unsigned char *ftrace_nop_replace(void)
+{
+ return (char *)&NOP;
+}
+
+/* construct a branch (BL) instruction to addr */
+unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
+{
+ long offset;
+
+ offset = (long)addr - (long)(pc - INSN_SIZE + PC_OFFSET);
+ if (unlikely(offset < -33554432 || offset > 33554428)) {
+ /* Can't generate branches that far (from ARM ARM). Ftrace
+ * doesn't generate branches outside of core kernel text.
+ */
+ WARN_ON_ONCE(1);
+ return NULL;
+ }
+ offset = (offset >> 2) & BL_OFFSET_MASK;
+ bl_insn = BL_OPCODE | offset;
+ return (unsigned char *)&bl_insn;
+}
+
+int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
+ unsigned char *new_code)
+{
+ unsigned long err = 0, replaced = 0, old, new;
+
+ old = *(unsigned long *)old_code;
+ new = *(unsigned long *)new_code;
+ pc -= INSN_SIZE;
+
+ __asm__ __volatile__ (
+ "1: ldr %1, [%2] \n"
+ " cmp %1, %4 \n"
+ "2: streq %3, [%2] \n"
+ " cmpne %1, %3 \n"
+ " movne %0, #2 \n"
+ "3:\n"
+
+ ".section .fixup, \"ax\"\n"
+ "4: mov %0, #1 \n"
+ " b 3b \n"
+ ".previous\n"
+
+ ".section __ex_table, \"a\"\n"
+ " .long 1b, 4b \n"
+ " .long 2b, 4b \n"
+ ".previous\n"
+
+ : "=r"(err), "=r"(replaced)
+ : "r"(pc), "r"(new), "r"(old), "0"(err), "1"(replaced)
+ : "memory");
+
+ if (!err && (replaced == old))
+ flush_icache_range(pc, pc + INSN_SIZE);
+
+ return err;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ int ret;
+ unsigned long pc, old;
+ unsigned char *new;
+
+ pc = (unsigned long)&ftrace_call;
+ pc += INSN_SIZE;
+ memcpy(&old, &ftrace_call, INSN_SIZE);
+ new = ftrace_call_replace(pc, (unsigned long)func);
+ ret = ftrace_modify_code(pc, (unsigned char *)&old, new);
+ return ret;
+}
+
+int ftrace_mcount_set(unsigned long *data)
+{
+ unsigned long pc, old;
+ unsigned long *addr = data;
+ unsigned char *new;
+
+ pc = (unsigned long)&mcount_call;
+ pc += INSN_SIZE;
+ memcpy(&old, &mcount_call, INSN_SIZE);
+ new = ftrace_call_replace(pc, *addr);
+ *addr = ftrace_modify_code(pc, (unsigned char *)&old, new);
+ return 0;
+}
+
+/* run from kstop_machine */
+int __init ftrace_dyn_arch_init(void *data)
+{
+ ftrace_mcount_set(data);
+ return 0;
+}
--
GitLab