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SubjectRe: [PATCH -mm] kprobes: kprobe-booster for ia64
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On Sat, 2008-03-08 at 00:01 +0800, Masami Hiramatsu wrote:
> From: Masami Hiramatsu <mhiramat@redhat.com>
>

> +
> +/*
> + * In this function, we check whether the target bundle modifies IP
> or
> + * it triggers an exception. If so, it cannot be boostable.
> + */
> +static int __kprobes can_boost(bundle_t *bundle, uint slot,
> + unsigned long bundle_addr)
> +{
> + unsigned int template = bundle->quad0.template;
> +
> + do {
> + if (search_exception_tables(bundle_addr + slot) ||
> + __is_ia64_break_inst(bundle, slot))
> + return 0; /* exception may occur in this
> bundle*/
> + } while ((++slot) < 3);
> + template &= 0x1e;
> + if (template >= 0x10 /* including B unit */ ||
> + template == 0x04 /* including X unit */ ||
> + template == 0x06) /* undefined */
> + return 0;
> +
> + return 1;
> +}
> +
> +/* Prepare long jump bundle and disables other boosters if need */
> +static void __kprobes prepare_booster(struct kprobe *p)
> +{
> + unsigned long addr = (unsigned long)p->addr & ~0xFULL;
> + unsigned int slot = addr & 0xf;
slot = (unsigned long)p->addr & 0xf ?

> + struct kprobe *other_kp;
> +
> + if (can_boost(&p->ainsn.insn[0].bundle, slot, addr)) {
> + set_brl_inst(&p->ainsn.insn[1].bundle, (bundle_t
> *)addr + 1);
> + p->ainsn.inst_flag |= INST_FLAG_BOOSTABLE;
> + }
> +
> + /* disables boosters in previous slots */
> + for (; addr < (unsigned long)p->addr; addr++) {
> + other_kp = get_kprobe((void *)addr);
> + if (other_kp)
> + other_kp->ainsn.inst_flag &=
> ~INST_FLAG_BOOSTABLE;
> + }
> +}
> +
There is no lock to protect the flag. If one cpu invokes other_kp and
the other cpu is changing the flag, what's the result?

Thanks,
Shaohua



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