On Tue, Mar 31, 2020 at 12:12:58PM +0200, Sascha Hauer wrote:
> The attributes should be set to avoid speculative access to memory-mapped
> peripherals.
>
> The patch has been tested with:
>
> noinline unsigned long nox(void)
> {
> return get_pc();
> }
>
> static void xn_test(void)
> {
> void *adr = (void *)SOME_SRAM_ADDRESS;
> unsigned long ret;
> unsigned long (*fn)(void) = adr;
>
> memcpy(adr, nox, 0x1000);
>
> sync_caches_for_execution();
>
> ret = fn();
> printf("pc: 0x%08lx\n", ret);
> }
>
> Without this patch nox() gets executed in SRAM, with it runs into a
> abort as expected.
>
> Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> ---
> Changes since v1:
> - Select correct PXN/UXN bits based on current exception level
>
> arch/arm/cpu/mmu_64.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/cpu/mmu_64.h b/arch/arm/cpu/mmu_64.h
> index a2a5477569..f5b7624037 100644
> --- a/arch/arm/cpu/mmu_64.h
> +++ b/arch/arm/cpu/mmu_64.h
> @@ -6,7 +6,8 @@
> PTE_BLOCK_AF)
> #define UNCACHED_MEM (PTE_BLOCK_MEMTYPE(MT_DEVICE_nGnRnE) | \
> PTE_BLOCK_OUTER_SHARE | \
> - PTE_BLOCK_AF)
> + PTE_BLOCK_AF | \
> + PTE_BLOCK_UXN)
Wrong patch, please ignore.
Sascha
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