diff options
Diffstat (limited to 'arch/x86/kernel/ftrace.c')
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 311bcf338..29408d6d6 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -105,14 +105,14 @@ ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code, { unsigned char replaced[MCOUNT_INSN_SIZE]; + ftrace_expected = old_code; + /* - * Note: Due to modules and __init, code can - * disappear and change, we need to protect against faulting - * as well as code changing. We do this by using the - * probe_kernel_* functions. - * - * No real locking needed, this code is run through - * kstop_machine, or before SMP starts. + * Note: + * We are paranoid about modifying text, as if a bug was to happen, it + * could cause us to read or write to someplace that could cause harm. + * Carefully read and modify the code with probe_kernel_*(), and make + * sure what we read is what we expected it to be before modifying it. */ /* read the text we want to modify */ @@ -154,6 +154,8 @@ int ftrace_make_nop(struct module *mod, if (addr == MCOUNT_ADDR) return ftrace_modify_code_direct(rec->ip, old, new); + ftrace_expected = NULL; + /* Normal cases use add_brk_on_nop */ WARN_ONCE(1, "invalid use of ftrace_make_nop"); return -EINVAL; @@ -220,6 +222,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr) { WARN_ON(1); + ftrace_expected = NULL; return -EINVAL; } @@ -314,6 +317,8 @@ static int add_break(unsigned long ip, const char *old) if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) return -EFAULT; + ftrace_expected = old; + /* Make sure it is what we expect it to be */ if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0) return -EINVAL; @@ -413,6 +418,8 @@ static int remove_breakpoint(struct dyn_ftrace *rec) ftrace_addr = ftrace_get_addr_curr(rec); nop = ftrace_call_replace(ip, ftrace_addr); + ftrace_expected = nop; + if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) return -EINVAL; } |