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)
/*
* Do it the simple way for now and invalidate the entire tlb
--
2.26.0.rc2
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