On Tuesday 20 January 2009 12:52:28 am David Miller wrote:
> From: David Miller <davem@xxxxxxxxxxxxx>
> Date: Mon, 19 Jan 2009 22:35:17 -0800 (PST)
>
> > The code in sun4v_data_access_exception() needs some logic to properly
> > handle the case of the kernel doing a userspace access. Currently it
> > does an OOPS unconditionally when triggered from kernel space, which
> > is wrong.
> >
> > I'll fix this up and post a patch.
Dave,
The patch does fix the issue.
Dennis
> Dennis, here is a 2.6.27 based patch that should fix this bug.
>
> sparc64: Fix DAX handling via userspace access from kernel.
>
> If we do a userspace access from kernel mode, and get a
> data access exception, we need to check the exception
> table just like a normal fault does.
>
> The spitfire DAX handler was doing this, but such logic
> was missing from the sun4v DAX code.
>
> Reported-by: Dennis Gilmore <dgilmore@xxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
>
> diff --git a/arch/sparc64/kernel/traps.c b/arch/sparc64/kernel/traps.c
> index c824df1..eb19724 100644
> --- a/arch/sparc64/kernel/traps.c
> +++ b/arch/sparc64/kernel/traps.c
> @@ -1,6 +1,6 @@
> /* arch/sparc64/kernel/traps.c
> *
> - * Copyright (C) 1995,1997,2008 David S. Miller (davem@xxxxxxxxxxxxx)
> + * Copyright (C) 1995,1997,2008,2009 David S. Miller (davem@xxxxxxxxxxxxx)
> * Copyright (C) 1997,1999,2000 Jakub Jelinek (jakub@xxxxxxxxxx)
> */
>
> @@ -262,6 +262,21 @@ void sun4v_data_access_exception(struct pt_regs *regs,
> unsigned long addr, unsig return;
>
> if (regs->tstate & TSTATE_PRIV) {
> + /* Test if this comes from uaccess places. */
> + const struct exception_table_entry *entry;
> +
> + entry = search_exception_tables(regs->tpc);
> + if (entry) {
> + /* Ouch, somebody is trying VM hole tricks on us... */
> +#ifdef DEBUG_EXCEPTIONS
> + printk("Exception: PC<%016lx> faddr<UNKNOWN>\n", regs->tpc);
> + printk("EX_TABLE: insn<%016lx> fixup<%016lx>\n",
> + regs->tpc, entry->fixup);
> +#endif
> + regs->tpc = entry->fixup;
> + regs->tnpc = regs->tpc + 4;
> + return;
> + }
> printk("sun4v_data_access_exception: ADDR[%016lx] "
> "CTX[%04x] TYPE[%04x], going.\n",
> addr, ctx, type);
> --
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