(2015/03/04 11:24), Wang Nan wrote: > On 2015/3/4 1:06, Petr Mladek wrote: >> On Tue 2015-03-03 13:09:05, Wang Nan wrote: >>> Before ftrace convertin instruction to nop, if an early kprobe is >>> registered then unregistered, without this patch its first bytes will >>> be replaced by head of NOP, which may confuse ftrace. >>> >>> Actually, since we have a patch which convert ftrace entry to nop >>> when probing, this problem should never be triggered. Provide it for >>> safety. >>> >>> Signed-off-by: Wang Nan <wangn...@huawei.com> >>> --- >>> arch/x86/kernel/kprobes/core.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c >>> index 87beb64..c7d304d 100644 >>> --- a/arch/x86/kernel/kprobes/core.c >>> +++ b/arch/x86/kernel/kprobes/core.c >>> @@ -225,6 +225,9 @@ __recover_probed_insn(kprobe_opcode_t *buf, unsigned >>> long addr) >>> struct kprobe *kp; >>> unsigned long faddr; >>> >>> + if (!kprobes_on_ftrace_initialized) >>> + return addr; >> >> This is not correct. The function has to return a buffer with the original >> code also when it is modified by normal kprobes. If it is a normal >> Kprobe, it reads the current code and replaces the first byte (INT3 >> instruction) with the saved kp->opcode. >> >>> + >>> kp = get_kprobe((void *)addr); >>> faddr = ftrace_location(addr); >> >> IMHO, the proper fix might be to replace the above line with >> >> if (kprobes_on_ftrace_initialized) >> faddr = ftrace_location(addr); >> else >> faddr = 0UL; >> >> By other words, it might pretend that it is not a ftrace location >> when the ftrace is not ready yet. >> > > Thanks for your reply. I'll follow your suggection in my next version. I > change > it as follow to enable the checking. > > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c > index 4e3d5a9..3241677 100644 > --- a/arch/x86/kernel/kprobes/core.c > +++ b/arch/x86/kernel/kprobes/core.c > @@ -234,6 +234,20 @@ __recover_probed_insn(kprobe_opcode_t *buf, unsigned > long addr) > */ > if (WARN_ON(faddr && faddr != addr)) > return 0UL; > + > + /* > + * If ftrace is not ready yet, pretend this is not an ftrace > + * location, because currently the target instruction has not > + * been replaced by a NOP yet. When ftrace trying to convert > + * it to NOP, kprobe should be notified and the kprobe data > + * should be fixed at that time. > + * > + * Since it is possible that an early kprobe already on that > + * place, don't return addr directly. > + */ > + if (likely(kprobes_on_ftrace_initialized)) > + faddr = 0UL; > + > /* > * Use the current code if it is not modified by Kprobe > * and it cannot be modified by ftrace >
This is better, but I don't think we need bool XXX_initialized flags for each subfunctions. Those should be serialized. Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
