diff options
Diffstat (limited to 'arch/arm/kernel/ftrace.c')
-rw-r--r-- | arch/arm/kernel/ftrace.c | 288 |
1 files changed, 288 insertions, 0 deletions
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c new file mode 100644 index 00000000..c0062ad1 --- /dev/null +++ b/arch/arm/kernel/ftrace.c @@ -0,0 +1,288 @@ +/* + * Dynamic function tracing support. + * + * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com> + * Copyright (C) 2010 Rabin Vincent <rabin@rab.in> + * + * 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 with NOP till they are enabled. + * All code mutation routines here are called under stop_machine(). + */ + +#include <linux/ftrace.h> +#include <linux/uaccess.h> + +#include <asm/cacheflush.h> +#include <asm/ftrace.h> + +#ifdef CONFIG_THUMB2_KERNEL +#define NOP 0xeb04f85d /* pop.w {lr} */ +#else +#define NOP 0xe8bd4000 /* pop {lr} */ +#endif + +#ifdef CONFIG_DYNAMIC_FTRACE +#ifdef CONFIG_OLD_MCOUNT +#define OLD_MCOUNT_ADDR ((unsigned long) mcount) +#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) + +#define OLD_NOP 0xe1a00000 /* mov r0, r0 */ + +static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) +{ + return rec->arch.old_mcount ? OLD_NOP : NOP; +} + +static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr) +{ + if (!rec->arch.old_mcount) + return addr; + + if (addr == MCOUNT_ADDR) + addr = OLD_MCOUNT_ADDR; + else if (addr == FTRACE_ADDR) + addr = OLD_FTRACE_ADDR; + + return addr; +} +#else +static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) +{ + return NOP; +} + +static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr) +{ + return addr; +} +#endif + +#ifdef CONFIG_THUMB2_KERNEL +static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr, + bool link) +{ + unsigned long s, j1, j2, i1, i2, imm10, imm11; + unsigned long first, second; + long offset; + + offset = (long)addr - (long)(pc + 4); + if (offset < -16777216 || offset > 16777214) { + WARN_ON_ONCE(1); + return 0; + } + + s = (offset >> 24) & 0x1; + i1 = (offset >> 23) & 0x1; + i2 = (offset >> 22) & 0x1; + imm10 = (offset >> 12) & 0x3ff; + imm11 = (offset >> 1) & 0x7ff; + + j1 = (!i1) ^ s; + j2 = (!i2) ^ s; + + first = 0xf000 | (s << 10) | imm10; + second = 0x9000 | (j1 << 13) | (j2 << 11) | imm11; + if (link) + second |= 1 << 14; + + return (second << 16) | first; +} +#else +static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr, + bool link) +{ + unsigned long opcode = 0xea000000; + long offset; + + if (link) + opcode |= 1 << 24; + + offset = (long)addr - (long)(pc + 8); + if (unlikely(offset < -33554432 || offset > 33554428)) { + /* Can't generate branches that far (from ARM ARM). Ftrace + * doesn't generate branches outside of kernel text. + */ + WARN_ON_ONCE(1); + return 0; + } + + offset = (offset >> 2) & 0x00ffffff; + + return opcode | offset; +} +#endif + +static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr) +{ + return ftrace_gen_branch(pc, addr, true); +} + +static int ftrace_modify_code(unsigned long pc, unsigned long old, + unsigned long new) +{ + unsigned long replaced; + + if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE)) + return -EFAULT; + + if (replaced != old) + return -EINVAL; + + if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE)) + return -EPERM; + + flush_icache_range(pc, pc + MCOUNT_INSN_SIZE); + + return 0; +} + +int ftrace_update_ftrace_func(ftrace_func_t func) +{ + unsigned long pc, old; + unsigned long new; + int ret; + + pc = (unsigned long)&ftrace_call; + memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE); + new = ftrace_call_replace(pc, (unsigned long)func); + + ret = ftrace_modify_code(pc, old, new); + +#ifdef CONFIG_OLD_MCOUNT + if (!ret) { + pc = (unsigned long)&ftrace_call_old; + memcpy(&old, &ftrace_call_old, MCOUNT_INSN_SIZE); + new = ftrace_call_replace(pc, (unsigned long)func); + + ret = ftrace_modify_code(pc, old, new); + } +#endif + + return ret; +} + +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long new, old; + unsigned long ip = rec->ip; + + old = ftrace_nop_replace(rec); + new = ftrace_call_replace(ip, adjust_address(rec, addr)); + + return ftrace_modify_code(rec->ip, old, new); +} + +int ftrace_make_nop(struct module *mod, + struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long ip = rec->ip; + unsigned long old; + unsigned long new; + int ret; + + old = ftrace_call_replace(ip, adjust_address(rec, addr)); + new = ftrace_nop_replace(rec); + ret = ftrace_modify_code(ip, old, new); + +#ifdef CONFIG_OLD_MCOUNT + if (ret == -EINVAL && addr == MCOUNT_ADDR) { + rec->arch.old_mcount = true; + + old = ftrace_call_replace(ip, adjust_address(rec, addr)); + new = ftrace_nop_replace(rec); + ret = ftrace_modify_code(ip, old, new); + } +#endif + + return ret; +} + +int __init ftrace_dyn_arch_init(void *data) +{ + *(unsigned long *)data = 0; + + return 0; +} +#endif /* CONFIG_DYNAMIC_FTRACE */ + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, + unsigned long frame_pointer) +{ + unsigned long return_hooker = (unsigned long) &return_to_handler; + struct ftrace_graph_ent trace; + unsigned long old; + int err; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + return; + + old = *parent; + *parent = return_hooker; + + err = ftrace_push_return_trace(old, self_addr, &trace.depth, + frame_pointer); + if (err == -EBUSY) { + *parent = old; + return; + } + + trace.func = self_addr; + + /* Only trace if the calling function expects to */ + if (!ftrace_graph_entry(&trace)) { + current->curr_ret_stack--; + *parent = old; + } +} + +#ifdef CONFIG_DYNAMIC_FTRACE +extern unsigned long ftrace_graph_call; +extern unsigned long ftrace_graph_call_old; +extern void ftrace_graph_caller_old(void); + +static int __ftrace_modify_caller(unsigned long *callsite, + void (*func) (void), bool enable) +{ + unsigned long caller_fn = (unsigned long) func; + unsigned long pc = (unsigned long) callsite; + unsigned long branch = ftrace_gen_branch(pc, caller_fn, false); + unsigned long nop = 0xe1a00000; /* mov r0, r0 */ + unsigned long old = enable ? nop : branch; + unsigned long new = enable ? branch : nop; + + return ftrace_modify_code(pc, old, new); +} + +static int ftrace_modify_graph_caller(bool enable) +{ + int ret; + + ret = __ftrace_modify_caller(&ftrace_graph_call, + ftrace_graph_caller, + enable); + +#ifdef CONFIG_OLD_MCOUNT + if (!ret) + ret = __ftrace_modify_caller(&ftrace_graph_call_old, + ftrace_graph_caller_old, + enable); +#endif + + return ret; +} + +int ftrace_enable_ftrace_graph_caller(void) +{ + return ftrace_modify_graph_caller(true); +} + +int ftrace_disable_ftrace_graph_caller(void) +{ + return ftrace_modify_graph_caller(false); +} +#endif /* CONFIG_DYNAMIC_FTRACE */ +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |