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Subject[PATCH] arm64: Make sure permission updates happen for pmd/pud
Date
Commit 15122ee2c515 ("arm64: Enforce BBM for huge IO/VMAP mappings")
disallowed block mappings for ioremap since that code does not honor
break-before-make. The same APIs are also used for permission updating
though and the extra checks prevent the permission updates from happening,
even though this should be permitted. This results in read-only permissions
not being fully applied. Visibly, this can occasionaly be seen as a failure
on the built in rodata test when the test data ends up in a section or
as an odd RW gap on the page table dump. Fix this by keeping the check
for the top level p*d_set_huge APIs but using separate functions for the
update APIs.

Reported-by: Peter Robinson <pbrobinson@gmail.com>
Fixes: 15122ee2c515 ("arm64: Enforce BBM for huge IO/VMAP mappings")
Signed-off-by: Laura Abbott <labbott@redhat.com>
---
arch/arm64/mm/mmu.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2dbb2c9f1ec1..57517ad86910 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -66,6 +66,9 @@ static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;

+static void __pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot);
+static void __pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot);
+
pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
unsigned long size, pgprot_t vma_prot)
{
@@ -200,7 +203,7 @@ static void init_pmd(pud_t *pudp, unsigned long addr, unsigned long end,
/* try section mapping first */
if (((addr | next | phys) & ~SECTION_MASK) == 0 &&
(flags & NO_BLOCK_MAPPINGS) == 0) {
- pmd_set_huge(pmdp, phys, prot);
+ __pmd_set_huge(pmdp, phys, prot);

/*
* After the PMD entry has been populated once, we
@@ -299,7 +302,7 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end,
*/
if (use_1G_block(addr, next, phys) &&
(flags & NO_BLOCK_MAPPINGS) == 0) {
- pud_set_huge(pudp, phys, prot);
+ __pud_set_huge(pudp, phys, prot);

/*
* After the PUD entry has been populated once, we
@@ -929,31 +932,40 @@ int __init arch_ioremap_pmd_supported(void)
return 1;
}

-int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
+void __pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
{
pgprot_t sect_prot = __pgprot(PUD_TYPE_SECT |
pgprot_val(mk_sect_prot(prot)));

+ BUG_ON(phys & ~PUD_MASK);
+ set_pud(pudp, pfn_pud(__phys_to_pfn(phys), sect_prot));
+}
+
+int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
+{
/* ioremap_page_range doesn't honour BBM */
if (pud_present(READ_ONCE(*pudp)))
return 0;

- BUG_ON(phys & ~PUD_MASK);
- set_pud(pudp, pfn_pud(__phys_to_pfn(phys), sect_prot));
+ __pud_set_huge(pudp, phys, prot);
return 1;
}

-int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
+static void __pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
{
pgprot_t sect_prot = __pgprot(PMD_TYPE_SECT |
pgprot_val(mk_sect_prot(prot)));
+ BUG_ON(phys & ~PMD_MASK);
+ set_pmd(pmdp, pfn_pmd(__phys_to_pfn(phys), sect_prot));
+}

+int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
+{
/* ioremap_page_range doesn't honour BBM */
if (pmd_present(READ_ONCE(*pmdp)))
return 0;

- BUG_ON(phys & ~PMD_MASK);
- set_pmd(pmdp, pfn_pmd(__phys_to_pfn(phys), sect_prot));
+ __pmd_set_huge(pmdp, phys, prot);
return 1;
}

--
2.17.0
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