On Thu, 10 Feb 2011, Catalin Marinas wrote:
> On Thu, 2011-02-10 at 13:04 +0000, Russell King - ARM Linux wrote:
> > On Wed, Feb 09, 2011 at 10:01:33AM +0000, Catalin Marinas wrote:
> > > Could we make the domains usage a run-time feature based on the
> > > architecture version? For ARMv7, we need to have the vectors page
> > > read-only anyway if the SWP emulation is enabled (and I posted a
> > > simple patch in a reply to your email).
> > >
> > > The issue I see is that ARM11MPCore is reported as v7 though we still
> > > use domains on this processor (we could always remove the domains if
> > > TLS register is available or use some more precise architecture
> > > version identification).
> >
> > We could also do the below, which I think is more logical - SWP emulation
> > requires that CPU domains aren't enabled, so let's make that explicit
> > in the Kconfig.
>
> This may work but it is to restrictive IMHO. SWP emulation only requires
> that RO user pages are also RO for the kernel. And there is a simple fix
> for this:
>
The patch below is making the code more straight forward regardless of
any swp emulation issues.
Acked-by: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>
> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
> index ee57640..6e0b349 100644
> --- a/arch/arm/kernel/traps.c
> +++ b/arch/arm/kernel/traps.c
> @@ -758,17 +758,21 @@ static void __init kuser_get_tls_init(unsigned long vectors)
>
> void __init early_trap_init(void)
> {
> -#if defined(CONFIG_CPU_USE_DOMAINS)
> - unsigned long vectors = CONFIG_VECTORS_BASE;
> -#else
> - unsigned long vectors = (unsigned long)vectors_page;
> -#endif
> + unsigned long vectors;
> extern char __stubs_start[], __stubs_end[];
> extern char __vectors_start[], __vectors_end[];
> extern char __kuser_helper_start[], __kuser_helper_end[];
> int kuser_sz = __kuser_helper_end - __kuser_helper_start;
>
> /*
> + * On ARMv7, user RO pages are mapped as kernel RO.
> + */
> + if (cpu_architecture() >= 7)
> + vectors = (unsigned long)vectors_page;
> + else
> + vectors = CONFIG_VECTORS_BASE;
> +
> + /*
> * Copy the vectors, stubs and kuser helpers (in entry-armv.S)
> * into the vector page, mapped at 0xffff0000, and ensure these
> * are visible to the instruction stream.
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index 0c1172b..5f51592 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -146,11 +146,6 @@ ENTRY(cpu_v7_set_pte_ext)
>
> tst r1, #L_PTE_USER
> orrne r3, r3, #PTE_EXT_AP1
> -#ifdef CONFIG_CPU_USE_DOMAINS
> - @ allow kernel read/write access to read-only user pages
> - tstne r3, #PTE_EXT_APX
> - bicne r3, r3, #PTE_EXT_APX | PTE_EXT_AP0
> -#endif
>
> tst r1, #L_PTE_XN
> orrne r3, r3, #PTE_EXT_XN
>
>
> --
> Catalin
>
>
>
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>
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