From 014c257cce65e9d1cd2d28ec1c89a37c536b151d Mon Sep 17 00:00:00 2001 From: Abhishek Sagar Date: Sat, 31 May 2008 14:23:50 +0530 Subject: ftrace: core support for ARM Core ftrace support for the ARM architecture, which includes support for dynamic function tracing. Signed-off-by: Abhishek Sagar Signed-off-by: Ingo Molnar --- arch/arm/kernel/ftrace.c | 128 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 128 insertions(+) create mode 100644 arch/arm/kernel/ftrace.c (limited to 'arch/arm/kernel/ftrace.c') 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 + * + * 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 +#include + +#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; +} -- cgit v1.2.2