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powerpc/mm: add exec protection on powerpc 603

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The 603 doesn't have a HASH table, TLB misses are handled by
software. It is then possible to generate page fault when
_PAGE_EXEC is not set like in nohash/32.

There is one "reserved" PTE bit available, this patch uses
it for _PAGE_EXEC.

In order to support it, set_pte_filter() and
set_access_flags_filter() are made common, and the handling
is made dependent on MMU_FTR_HPTE_TABLE

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy
2018-11-28 17:21:10 +00:00
committed by Michael Ellerman
parent badb9687ce
commit 385e89d5b2
6 changed files with 26 additions and 25 deletions
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20
arch/powerpc/mm/pgtable.c
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@@ -74,7 +74,7 @@ static struct page *maybe_pte_to_page(pte_t pte)
* support falls into the same category.
*/
static pte_t set_pte_filter(pte_t pte)
static pte_t set_pte_filter_hash(pte_t pte)
{
if (radix_enabled())
return pte;
@@ -93,14 +93,12 @@ static pte_t set_pte_filter(pte_t pte)
return pte;
}
static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma,
int dirty)
{
return pte;
}
#else /* CONFIG_PPC_BOOK3S */
static pte_t set_pte_filter_hash(pte_t pte) { return pte; }
#endif /* CONFIG_PPC_BOOK3S */
/* Embedded type MMU with HW exec support. This is a bit more complicated
* as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so
* instead we "filter out" the exec permission for non clean pages.
@@ -109,6 +107,9 @@ static pte_t set_pte_filter(pte_t pte)
{
struct page *pg;
if (mmu_has_feature(MMU_FTR_HPTE_TABLE))
return set_pte_filter_hash(pte);
/* No exec permission in the first place, move on */
if (!pte_exec(pte) || !pte_looks_normal(pte))
return pte;
@@ -138,6 +139,9 @@ static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma,
{
struct page *pg;
if (mmu_has_feature(MMU_FTR_HPTE_TABLE))
return pte;
/* So here, we only care about exec faults, as we use them
* to recover lost _PAGE_EXEC and perform I$/D$ coherency
* if necessary. Also if _PAGE_EXEC is already set, same deal,
@@ -172,8 +176,6 @@ static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma,
return pte_mkexec(pte);
}
#endif /* CONFIG_PPC_BOOK3S */
/*
* set_pte stores a linux PTE into the linux page table.
*/