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author | Abhishek Sagar <sagar.abhishek@gmail.com> | 2008-05-31 14:23:50 +0530 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-06-02 11:32:20 +0200 |
commit | 014c257cce65e9d1cd2d28ec1c89a37c536b151d (patch) | |
tree | c7a28fbf6f295538964539d5b8c552ea786f7072 /arch/arm/kernel | |
parent | b1829d2705daa7cb72eb1e08bdc8b7e9fad34266 (diff) | |
download | linux-014c257cce65e9d1cd2d28ec1c89a37c536b151d.tar.bz2 |
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>
Diffstat (limited to 'arch/arm/kernel')
-rw-r--r-- | arch/arm/kernel/Makefile | 5 | ||||
-rw-r--r-- | arch/arm/kernel/armksyms.c | 5 | ||||
-rw-r--r-- | arch/arm/kernel/entry-common.S | 47 | ||||
-rw-r--r-- | arch/arm/kernel/ftrace.c | 128 |
4 files changed, 185 insertions, 0 deletions
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; +} |