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powerpc/mm: Update _PAGE_KERNEL_RO

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PS3 had used a PPP bit hack to implement a read only mapping in the
kernel area. Since we are bolting the ioremap area, it used the pte
flags _PAGE_PRESENT | _PAGE_USER to get a PPP value of 0x3 there by
resulting in a read only mapping. This means the area can be accessed by
user space, but kernel will never return such an address to user space.

But we can do better by implementing a read only kernel mapping using
PPP bits 0b110.

This also allows us to do read only kernel mapping for radix in later
patches.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Aneesh Kumar K.V
2016-04-29 23:25:36 +10:00
committed by Michael Ellerman
parent 96270b1fc2
commit e58e87adc8
3 changed files with 14 additions and 9 deletions
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2
arch/powerpc/platforms/ps3/spu.c
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@@ -205,7 +205,7 @@ static void spu_unmap(struct spu *spu)
static int __init setup_areas(struct spu *spu)
{
struct table {char* name; unsigned long addr; unsigned long size;};
static const unsigned long shadow_flags = _PAGE_NO_CACHE | 3;
unsigned long shadow_flags = pgprot_val(pgprot_noncached_wc(PAGE_KERNEL_RO));
spu_pdata(spu)->shadow = __ioremap(spu_pdata(spu)->shadow_addr,
sizeof(struct spe_shadow),