diff options
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 88 |
1 files changed, 72 insertions, 16 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 2407a6d81cb7..c3a7cb4bf6e6 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -100,7 +100,7 @@ static const unsigned char *ftrace_nop_replace(void) } static int -ftrace_modify_code(unsigned long ip, unsigned const char *old_code, +ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code, unsigned const char *new_code) { unsigned char replaced[MCOUNT_INSN_SIZE]; @@ -141,7 +141,20 @@ int ftrace_make_nop(struct module *mod, old = ftrace_call_replace(ip, addr); new = ftrace_nop_replace(); - return ftrace_modify_code(rec->ip, old, new); + /* + * On boot up, and when modules are loaded, the MCOUNT_ADDR + * is converted to a nop, and will never become MCOUNT_ADDR + * again. This code is either running before SMP (on boot up) + * or before the code will ever be executed (module load). + * We do not want to use the breakpoint version in this case, + * just modify the code directly. + */ + if (addr == MCOUNT_ADDR) + return ftrace_modify_code_direct(rec->ip, old, new); + + /* Normal cases use add_brk_on_nop */ + WARN_ONCE(1, "invalid use of ftrace_make_nop"); + return -EINVAL; } int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) @@ -152,20 +165,8 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) old = ftrace_nop_replace(); new = ftrace_call_replace(ip, addr); - return ftrace_modify_code(rec->ip, old, new); -} - -int ftrace_update_ftrace_func(ftrace_func_t func) -{ - unsigned long ip = (unsigned long)(&ftrace_call); - unsigned char old[MCOUNT_INSN_SIZE], *new; - int ret; - - memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE); - new = ftrace_call_replace(ip, (unsigned long)func); - ret = ftrace_modify_code(ip, old, new); - - return ret; + /* Should only be called when module is loaded */ + return ftrace_modify_code_direct(rec->ip, old, new); } /* @@ -201,6 +202,29 @@ int ftrace_update_ftrace_func(ftrace_func_t func) */ atomic_t modifying_ftrace_code __read_mostly; +static int +ftrace_modify_code(unsigned long ip, unsigned const char *old_code, + unsigned const char *new_code); + +int ftrace_update_ftrace_func(ftrace_func_t func) +{ + unsigned long ip = (unsigned long)(&ftrace_call); + unsigned char old[MCOUNT_INSN_SIZE], *new; + int ret; + + memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE); + new = ftrace_call_replace(ip, (unsigned long)func); + + /* See comment above by declaration of modifying_ftrace_code */ + atomic_inc(&modifying_ftrace_code); + + ret = ftrace_modify_code(ip, old, new); + + atomic_dec(&modifying_ftrace_code); + + return ret; +} + /* * A breakpoint was added to the code address we are about to * modify, and this is the handle that will just skip over it. @@ -520,6 +544,38 @@ void ftrace_replace_code(int enable) } } +static int +ftrace_modify_code(unsigned long ip, unsigned const char *old_code, + unsigned const char *new_code) +{ + int ret; + + ret = add_break(ip, old_code); + if (ret) + goto out; + + run_sync(); + + ret = add_update_code(ip, new_code); + if (ret) + goto fail_update; + + run_sync(); + + ret = ftrace_write(ip, new_code, 1); + if (ret) { + ret = -EPERM; + goto out; + } + run_sync(); + out: + return ret; + + fail_update: + probe_kernel_write((void *)ip, &old_code[0], 1); + goto out; +} + void arch_ftrace_update_code(int command) { /* See comment above by declaration of modifying_ftrace_code */ |