From: Masami Hiramatsu <mhiramat@redhat.com>
To: Arjan van de Ven <arjan@infradead.org>
Cc: ananth@in.ibm.com, Jim Keniston <jkenisto@us.ibm.com>,
Roland McGrath <roland@redhat.com>,
prasanna@in.ibm.com, anil.s.keshavamurthy@intel.com,
davem@davemloft.net,
systemtap-ml <systemtap@sources.redhat.com>
Subject: Re: [RFC -mm][PATCH 5/6] prepare kprobes code for x86 unification
Date: Tue, 11 Dec 2007 16:41:00 -0000 [thread overview]
Message-ID: <475EBD9B.2050504@redhat.com> (raw)
In-Reply-To: <20071211080259.0877708c@laptopd505.fenrus.org>
Hi Arjan,
Thank you for comment.
Arjan van de Ven wrote:
> On Mon, 10 Dec 2007 17:53:22 -0500
> Masami Hiramatsu <mhiramat@redhat.com> wrote:
>> +#define stack_addr(regs) ((unsigned long *)®s->sp)
>
> Hi,
>
> thanks for taking up this work again, however this line has a bug (yes it's a bug in the 32 bit retprobes);
> the address of the stack is regs->sp not ®s->sp, since ®s->sp is the address of the
> memory we store the stackpointer in, not the actual address on the stack...
As far as I know, it is true on x86-64, but it's not true on x86-32(kernel mode).
I checked it in __show_registers()@arch/x86/kernel/process_32.c.
Here is that code:
> if (user_mode_vm(regs)) {
> sp = regs->sp;
> ss = regs->ss & 0xffff;
> savesegment(gs, gs);
> } else {
> sp = (unsigned long) (®s->sp);
> savesegment(ss, ss);
> savesegment(gs, gs);
> }
So, in kernel mode, ®s->sp is the address of the top of stack.
Best Regards,
>
> Greetings,
> Arjan van de Ven
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division
e-mail: mhiramat@redhat.com, masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2007-12-11 16:41 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-10 22:53 Masami Hiramatsu
2007-12-11 13:52 ` Srinivasa Ds
2007-12-11 17:57 ` Masami Hiramatsu
2007-12-12 13:38 ` Srinivasa Ds
2007-12-12 17:30 ` Masami Hiramatsu
2007-12-12 21:20 ` Masami Hiramatsu
2007-12-13 1:21 ` Masami Hiramatsu
2007-12-13 7:48 ` Ananth N Mavinakayanahalli
2007-12-13 8:18 ` Srinivasa Ds
2007-12-13 8:23 ` Ananth N Mavinakayanahalli
2007-12-13 11:21 ` [RFC -mm][PATCH ] Patch to avoid probing __init functions using kprobes Srinivasa Ds
2007-12-13 15:35 ` Ananth N Mavinakayanahalli
2007-12-13 18:50 ` Masami Hiramatsu
2007-12-11 16:06 ` [RFC -mm][PATCH 5/6] prepare kprobes code for x86 unification Arjan van de Ven
2007-12-11 16:41 ` Masami Hiramatsu [this message]
2007-12-11 18:44 ` Jim Keniston
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