Re: [PATCH -mm] kprobes: kprobe-booster for ia64

Hello Shaohua,

Thank you for reviewing!

Shaohua Li wrote:
On Sat, 2008-03-08 at 00:01 +0800, Masami Hiramatsu wrote:
From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
+
+/* 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 ?

You are correct. I'll fix that.


+ 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?

I think that other cpu never change the flag, because the caller of this
function(__register_kprobe) locks kprobe_mutex in kernel/kprobes.c.

Thanks,
Shaohua

Thanks,

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@xxxxxxxxxx

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