[PATCH 6.1 121/473] x86/pat: Introduce lookup_address_in_pgd_attr()

Greg Kroah-Hartman
2024-06-06T14:14:04Z

From: Juergen Gross <jgross@suse.com>

[ Upstream commit ceb647b4b529fdeca9021cd34486f5a170746bda ]

Add lookup_address_in_pgd_attr() doing the same as the already
existing lookup_address_in_pgd(), but returning the effective settings
of the NX and RW bits of all walked page table levels, too.

This will be needed in order to match hardware behavior when looking
for effective access rights, especially for detecting writable code
pages.

In order to avoid code duplication, let lookup_address_in_pgd() call
lookup_address_in_pgd_attr() with dummy parameters.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240412151258.9171-2-jgross@suse.com
Stable-dep-of: 5bc8b0f5dac0 ("x86/pat: Fix W^X violation false-positives when running as Xen PV guest")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/include/asm/pgtable_types.h | 2 ++
arch/x86/mm/pat/set_memory.c | 33 +++++++++++++++++++++++++---
2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index f0b9b37c4609b..e3028373f0b45 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -544,6 +544,8 @@ static inline void update_page_count(int level, unsigned long pages) { }
extern pte_t *lookup_address(unsigned long address, unsigned int *level);
extern pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
unsigned int *level);
+pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
+ unsigned int *level, bool *nx, bool *rw);
extern pmd_t *lookup_pmd_address(unsigned long address);
extern phys_addr_t slow_virt_to_phys(void *__address);
extern int __init kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn,
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 68d4f328f1696..a26a9e3608cb2 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -625,20 +625,26 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star

/*
* Lookup the page table entry for a virtual address in a specific pgd.
- * Return a pointer to the entry and the level of the mapping.
+ * Return a pointer to the entry, the level of the mapping, and the effective
+ * NX and RW bits of all page table levels.
*/
-pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
- unsigned int *level)
+pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
+ unsigned int *level, bool *nx, bool *rw)
{
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;

*level = PG_LEVEL_NONE;
+ *nx = false;
+ *rw = true;

if (pgd_none(*pgd))
return NULL;

+ *nx |= pgd_flags(*pgd) & _PAGE_NX;
+ *rw &= pgd_flags(*pgd) & _PAGE_RW;
+
p4d = p4d_offset(pgd, address);
if (p4d_none(*p4d))
return NULL;
@@ -647,6 +653,9 @@ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
if (p4d_large(*p4d) || !p4d_present(*p4d))
return (pte_t *)p4d;

+ *nx |= p4d_flags(*p4d) & _PAGE_NX;
+ *rw &= p4d_flags(*p4d) & _PAGE_RW;
+
pud = pud_offset(p4d, address);
if (pud_none(*pud))
return NULL;
@@ -655,6 +664,9 @@ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
if (pud_large(*pud) || !pud_present(*pud))
return (pte_t *)pud;

+ *nx |= pud_flags(*pud) & _PAGE_NX;
+ *rw &= pud_flags(*pud) & _PAGE_RW;
+
pmd = pmd_offset(pud, address);
if (pmd_none(*pmd))
return NULL;
@@ -663,11 +675,26 @@ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
if (pmd_large(*pmd) || !pmd_present(*pmd))
return (pte_t *)pmd;

+ *nx |= pmd_flags(*pmd) & _PAGE_NX;
+ *rw &= pmd_flags(*pmd) & _PAGE_RW;
+
*level = PG_LEVEL_4K;

return pte_offset_kernel(pmd, address);
}

+/*
+ * Lookup the page table entry for a virtual address in a specific pgd.
+ * Return a pointer to the entry and the level of the mapping.
+ */
+pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
+ unsigned int *level)
+{
+ bool nx, rw;
+
+ return lookup_address_in_pgd_attr(pgd, address, level, &nx, &rw);
+}
+
/*
* Lookup the page table entry for a virtual address. Return a pointer
* to the entry and the level of the mapping.
--
2.43.0