Date: Mon, 20 Aug 2012 08:04:31 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: Monthadar Al Jaberi <monthadar@gmail.com> Subject: Re: kernel page fult for a valid pointer? Message-ID: <201208200804.31932.jhb@freebsd.org> In-Reply-To: <CA%2BsBSo%2BG7ovJk5O17YB-ZjCe%2BEQSntdx6MvBftKx9S=p4w8hvA@mail.gmail.com> References: <CA%2BsBSo%2BG7ovJk5O17YB-ZjCe%2BEQSntdx6MvBftKx9S=p4w8hvA@mail.gmail.com>
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On Saturday, August 18, 2012 2:29:26 pm Monthadar Al Jaberi wrote: > Hi, > > I am wondering is there a reason for getting "Fatal trap 12: page > fault while in kernel mode" "supervisor read, page not present" for an > address used to be valid in kernel space? > > I dont really understand why I am getting this, I added a hardware > watchpoint on the address, and when I got to the debuger I could read > the memory content and dump for that address. But when I continue from > the debugger I get the panic and now when I try to read the memory > content I get *** error reading from address ce733000 ***. Whatever memory was there might have been unmapped? For example, memory pointed to by I/O buffers (struct buf/bio) use transient mappings that are only valid while an I/O request is in progress. -- John Baldwin
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