(2013/07/11 6:31), Jiri Kosina wrote:
> +/*
> + * text_poke_bp() -- update instructions on live kernel on SMP
> + * @addr: address to patch
> + * @opcode: opcode of new instruction
> + * @len: length to copy
> + * @handler: address to jump to when the temporary breakpoint is hit
> + *
> +
> + * Modify multi-byte instruction by using int3 breakpoint on SMP.
> + * In contrary to text_poke_smp(), we completely avoid stop_machine() here,
> + * and achieve the synchronization using int3 breakpoint.
> + *
> + * The way it is done:
> + * - add a int3 trap to the address that will be patched
> + * - sync cores
You don't need this "sync cores". (and your code didn't) :)
> + * - update all but the first byte of the patched range
> + * - sync cores
> + * - replalace the first byte (int3) by the first byte of
> + * replacing opcode
> + * - sync cores
> + *
> + * Note: must be called under text_mutex.
> + */
> +void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
> +{
> + unsigned char int3 = 0xcc;
> +
Here, you have to protect this code from others, since bp_* are
global.
> + bp_int3_handler = handler;
> + bp_int3_addr = (u8 *)addr + sizeof(int3);
> + bp_patching_in_progress = true;
> + /*
> + * corresponding read barrier in int3 notifier for
> + * making sure the in_progress flags is correctly ordered wrt.
> + * patching */
> + smp_wmb();
> +
> + text_poke(addr, &int3, sizeof(int3));
> +
> + if (len - sizeof(int3) > 0) {
> + /* patch all but the first byte */
> + text_poke((char *)addr + sizeof(int3),
> + (const char *) opcode + sizeof(int3),
> + len - sizeof(int3));
> +
> + on_each_cpu(do_sync_core, NULL, 1);
> + }
> +
> + /* patch the first byte */
> + text_poke(addr, opcode, sizeof(int3));
> +
> + on_each_cpu(do_sync_core, NULL, 1);
> +
> + bp_patching_in_progress = false;
> + smp_wmb();
> +
> + return addr;
> +}
> +
> +/* this one needs to run before anything else handles it as a
> + * regular exception */
> +static struct notifier_block int3_nb = {
> + .priority = 0x7fffffff,
> + .notifier_call = int3_notify
> +};
> +
> +static int __init int3_init(void)
> +{
> + return register_die_notifier(&int3_nb);
> +}
> +
> +arch_initcall(int3_init);
> /*
> * Cross-modifying kernel text with stop_machine().
> * This code originally comes from immediate value.
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index bddf3b2..d6db7bd 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1709,7 +1709,7 @@ EXPORT_SYMBOL_GPL(unregister_kprobes);
>
> static struct notifier_block kprobe_exceptions_nb = {
> .notifier_call = kprobe_exceptions_notify,
> - .priority = 0x7fffffff /* we need to be notified first */
> + .priority = 0x7ffffff0 /* High priority, but not first. */
> };
>
> unsigned long __weak arch_deref_entry_point(void *entry)
>
Thanks,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu...@hitachi.com
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