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Date: Wed, 21 Jun 2006 10:34:36 -0700
From: Mike Grundy <grundym@us.ibm.com>
To: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: jan.glauber@de.ibm.com, linux-kernel@vger.kernel.org,
       systemtap@sources.redhat.com
Subject: Re: [PATCH] kprobes for s390 architecture
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On Wed, Jun 21, 2006 at 06:38:40PM +0200, Martin Schwidefsky wrote:
> You misunderstood me here. I'm not talking about storing the same piece
> of data to memory on each processor. I'm talking about isolating all
> other cpus so that the initiating cpu can store the breakpoint to memory
> without running into the danger that another cpu is trying to execute it
> at the same time. But probably the store should be atomic in regard to
> instruction fetching on the other cpus. It is only two bytes and it
> should be aligned.

So maybe something like this:

void smp_replace_instruction(void *info) {
        struct ins_replace_args *parms;
        parms = (struct ins_replace_args *) info;
        *parms->addr = *parms->insn
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
        struct ins_replace_args parms;
        parms.addr = p->addr;
        parms.insn = BREAKPOINT_INSTRUCTION

        preempt_disable();
        smp_call_function(smp_replace_instruction, &parms, 0, 1);
        preempt_enable();
}

Thanks
Mike