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Subject[RFC v6 27/62] powerpc: helper to validate key-access permissions of a pte
Date
helper function that checks if the read/write/execute is allowed
on the pte.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
---
arch/powerpc/include/asm/book3s/64/pgtable.h | 4 +++
arch/powerpc/include/asm/pkeys.h | 12 +++++++++
arch/powerpc/mm/pkeys.c | 33 ++++++++++++++++++++++++++
3 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 30d7f55..0056e58 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -472,6 +472,10 @@ static inline void write_uamor(u64 value)
mtspr(SPRN_UAMOR, value);
}

+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+extern bool arch_pte_access_permitted(u64 pte, bool write, bool execute);
+#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
+
#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
unsigned long addr, pte_t *ptep)
diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index bbb5d85..7a9aade 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -53,6 +53,18 @@ static inline u64 pte_to_hpte_pkey_bits(u64 pteflags)
((pteflags & H_PAGE_PKEY_BIT4) ? HPTE_R_KEY_BIT4 : 0x0UL));
}

+static inline u16 pte_to_pkey_bits(u64 pteflags)
+{
+ if (!pkey_inited)
+ return 0x0UL;
+
+ return (((pteflags & H_PAGE_PKEY_BIT0) ? 0x10 : 0x0UL) |
+ ((pteflags & H_PAGE_PKEY_BIT1) ? 0x8 : 0x0UL) |
+ ((pteflags & H_PAGE_PKEY_BIT2) ? 0x4 : 0x0UL) |
+ ((pteflags & H_PAGE_PKEY_BIT3) ? 0x2 : 0x0UL) |
+ ((pteflags & H_PAGE_PKEY_BIT4) ? 0x1 : 0x0UL));
+}
+
static inline int vma_pkey(struct vm_area_struct *vma)
{
if (!pkey_inited)
diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index 403f5ae..1794e17 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -201,3 +201,36 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
*/
return vma_pkey(vma);
}
+
+static bool pkey_access_permitted(int pkey, bool write, bool execute)
+{
+ int pkey_shift;
+ u64 amr;
+
+ if (!pkey)
+ return true;
+
+ pkey_shift = pkeyshift(pkey);
+ if (!(read_uamor() & (0x3UL << pkey_shift)))
+ return true;
+
+ if (execute && !(read_iamr() & (IAMR_EX_BIT << pkey_shift)))
+ return true;
+
+ if (!write) {
+ amr = read_amr();
+ if (!(amr & (AMR_RD_BIT << pkey_shift)))
+ return true;
+ }
+
+ amr = read_amr(); /* delay reading amr uptil absolutely needed */
+ return (write && !(amr & (AMR_WR_BIT << pkey_shift)));
+}
+
+bool arch_pte_access_permitted(u64 pte, bool write, bool execute)
+{
+ if (!pkey_inited)
+ return true;
+ return pkey_access_permitted(pte_to_pkey_bits(pte),
+ write, execute);
+}
--
1.7.1
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