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Subject[PATCH] [2/5] Support range checking for required/advisory protections
Date

Previously these checks would only check a single address, which is ok
for 4k pages, but not for large pages

Needed for followup patches

Signed-off-by: Andi Kleen <ak@suse.de>

---
arch/x86/mm/pageattr.c | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)

Index: linux/arch/x86/mm/pageattr.c
===================================================================
--- linux.orig/arch/x86/mm/pageattr.c
+++ linux/arch/x86/mm/pageattr.c
@@ -35,6 +35,13 @@ within(unsigned long addr, unsigned long
return addr >= start && addr < end;
}

+static inline int
+within_range(unsigned long addr_start, unsigned long addr_end,
+ unsigned long start, unsigned long end)
+{
+ return addr_end >= start && addr_start < end;
+}
+
/*
* Flushing functions
*/
@@ -149,7 +156,8 @@ static unsigned long virt_to_highmap(voi
* right (again, ioremap() on BIOS memory is not uncommon) so this function
* checks and fixes these known static required protection bits.
*/
-static inline pgprot_t required_static_prot(pgprot_t prot, unsigned long address)
+static inline pgprot_t
+required_static_prot(pgprot_t prot, unsigned long start, unsigned long end)
{
pgprot_t forbidden = __pgprot(0);

@@ -157,19 +165,21 @@ static inline pgprot_t required_static_p
* The BIOS area between 640k and 1Mb needs to be executable for
* PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
*/
- if (within(__pa(address), BIOS_BEGIN, BIOS_END))
+ if (within_range(__pa(start), __pa(end), BIOS_BEGIN, BIOS_END))
pgprot_val(forbidden) |= _PAGE_NX;

/*
* The kernel text needs to be executable for obvious reasons
* Does not cover __inittext since that is gone later on
*/
- if (within(address, (unsigned long)_text, (unsigned long)_etext))
+ if (within_range(start, end,
+ (unsigned long)_text, (unsigned long)_etext))
pgprot_val(forbidden) |= _PAGE_NX;
/*
* Do the same for the x86-64 high kernel mapping
*/
- if (within(address, virt_to_highmap(_text), virt_to_highmap(_etext)))
+ if (within_range(start, end,
+ virt_to_highmap(_text), virt_to_highmap(_etext)))
pgprot_val(forbidden) |= _PAGE_NX;

prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
@@ -177,18 +187,19 @@ static inline pgprot_t required_static_p
return prot;
}

-static inline pgprot_t advised_static_prot(pgprot_t prot, unsigned long address)
+static inline pgprot_t
+advised_static_prot(pgprot_t prot, unsigned long start, unsigned long end)
{
pgprot_t forbidden = __pgprot(0);

/* The .rodata section needs to be read-only */
- if (within(address, (unsigned long)__start_rodata,
+ if (within_range(start, end, (unsigned long)__start_rodata,
(unsigned long)__end_rodata))
pgprot_val(forbidden) |= _PAGE_RW;
/*
* Do the same for the x86-64 high kernel mapping
*/
- if (within(address, virt_to_highmap(__start_rodata),
+ if (within_range(start, end, virt_to_highmap(__start_rodata),
virt_to_highmap(__end_rodata)))
pgprot_val(forbidden) |= _PAGE_RW;

@@ -313,8 +324,8 @@ try_preserve_large_page(pte_t *kpte, uns

pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);
- new_prot = required_static_prot(new_prot, address);
- new_prot = advised_static_prot(new_prot, address);
+ new_prot = required_static_prot(new_prot, address, address + psize - 1);
+ new_prot = advised_static_prot(new_prot, address, address + psize - 1);

/*
* If there are no changes, return. maxpages has been updated
@@ -438,6 +449,7 @@ repeat:
BUG_ON(PageCompound(kpte_page));

if (level == PG_LEVEL_4K) {
+ unsigned long end = address + PAGE_SIZE - 1;
pte_t new_pte, old_pte = *kpte;
pgprot_t new_prot = pte_pgprot(old_pte);

@@ -452,8 +464,8 @@ repeat:
pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);

- new_prot = required_static_prot(new_prot, address);
- new_prot = advised_static_prot(new_prot, address);
+ new_prot = required_static_prot(new_prot, address, end);
+ new_prot = advised_static_prot(new_prot, address, end);

/*
* We need to keep the pfn from the existing PTE,

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