diff options
Diffstat (limited to 'arch/arm/kernel/ftrace.c')
| -rw-r--r-- | arch/arm/kernel/ftrace.c | 188 |
1 files changed, 140 insertions, 48 deletions
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c index 0298286ad4ad..971ac8c36ea7 100644 --- a/arch/arm/kernel/ftrace.c +++ b/arch/arm/kernel/ftrace.c @@ -2,102 +2,194 @@ * 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 lazily with NOP till they are - * enabled. All code mutation routines here take effect atomically. + * 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> -#define PC_OFFSET 8 -#define BL_OPCODE 0xeb000000 -#define BL_OFFSET_MASK 0x00ffffff +#ifdef CONFIG_THUMB2_KERNEL +#define NOP 0xeb04f85d /* pop.w {lr} */ +#else +#define NOP 0xe8bd4000 /* pop {lr} */ +#endif -static unsigned long bl_insn; -static const unsigned long NOP = 0xe1a00000; /* mov r0, r0 */ +#ifdef CONFIG_OLD_MCOUNT +#define OLD_MCOUNT_ADDR ((unsigned long) mcount) +#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) -unsigned char *ftrace_nop_replace(void) +#define OLD_NOP 0xe1a00000 /* mov r0, r0 */ + +static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) { - return (char *)&NOP; + 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 + /* construct a branch (BL) instruction to addr */ -unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr) +#ifdef CONFIG_THUMB2_KERNEL +static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr) { + unsigned long s, j1, j2, i1, i2, imm10, imm11; + unsigned long first, second; long offset; - offset = (long)addr - (long)(pc + PC_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 = 0xd000 | (j1 << 13) | (j2 << 11) | imm11; + + return (second << 16) | first; +} +#else +static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr) +{ + long offset; + + 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 NULL; + return 0; } - 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; + offset = (offset >> 2) & 0x00ffffff; - old = *(unsigned long *)old_code; - new = *(unsigned long *)new_code; + return 0xeb000000 | offset; +} +#endif - __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" +static int ftrace_modify_code(unsigned long pc, unsigned long old, + unsigned long new) +{ + unsigned long replaced; - ".pushsection .fixup, \"ax\"\n" - "4: mov %0, #1 \n" - " b 3b \n" - ".popsection\n" + if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE)) + return -EFAULT; - ".pushsection __ex_table, \"a\"\n" - " .long 1b, 4b \n" - " .long 2b, 4b \n" - ".popsection\n" + if (replaced != old) + return -EINVAL; - : "=r"(err), "=r"(replaced) - : "r"(pc), "r"(new), "r"(old), "0"(err), "1"(replaced) - : "memory"); + if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE)) + return -EPERM; - if (!err && (replaced == old)) - flush_icache_range(pc, pc + MCOUNT_INSN_SIZE); + flush_icache_range(pc, pc + MCOUNT_INSN_SIZE); - return err; + return 0; } int ftrace_update_ftrace_func(ftrace_func_t func) { - int ret; unsigned long pc, old; - unsigned char *new; + 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, (unsigned char *)&old, new); + + 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; } -/* run from ftrace_init with irqs disabled */ int __init ftrace_dyn_arch_init(void *data) { - ftrace_mcount_set(data); + *(unsigned long *)data = 0; + return 0; } |