[RFC PATCH 6/7 v1]powerpc: Handle exceptions caused by violation of key protection.
Ram Pai
linuxram at us.ibm.com
Tue Jun 6 11:05:08 AEST 2017
Handle Data and Instruction exceptions caused by memory
protection-key.
Signed-off-by: Ram Pai <linuxram at us.ibm.com>
---
arch/powerpc/include/asm/mmu_context.h | 12 +++++
arch/powerpc/include/asm/pkeys.h | 9 ++++
arch/powerpc/include/asm/reg.h | 10 +++-
arch/powerpc/kernel/exceptions-64s.S | 2 +-
arch/powerpc/mm/fault.c | 21 +++++++-
arch/powerpc/mm/pkeys.c | 90 ++++++++++++++++++++++++++++++++++
6 files changed, 140 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index da7e943..71fffe0 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -175,11 +175,23 @@ static inline void arch_bprm_mm_init(struct mm_struct *mm,
{
}
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+bool arch_pte_access_permitted(pte_t pte, bool write);
+bool arch_vma_access_permitted(struct vm_area_struct *vma,
+ bool write, bool execute, bool foreign);
+#else /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
+static inline bool arch_pte_access_permitted(pte_t pte, bool write)
+{
+ /* by default, allow everything */
+ return true;
+}
static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
bool write, bool execute, bool foreign)
{
/* by default, allow everything */
return true;
}
+#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
+
#endif /* __KERNEL__ */
#endif /* __ASM_POWERPC_MMU_CONTEXT_H */
diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
index 9b6820d..405e7db 100644
--- a/arch/powerpc/include/asm/pkeys.h
+++ b/arch/powerpc/include/asm/pkeys.h
@@ -14,6 +14,15 @@
VM_PKEY_BIT3 | \
VM_PKEY_BIT4)
+static inline u16 pte_flags_to_pkey(unsigned long pte_flags)
+{
+ return ((pte_flags & H_PAGE_PKEY_BIT4) ? 0x1 : 0x0) |
+ ((pte_flags & H_PAGE_PKEY_BIT3) ? 0x2 : 0x0) |
+ ((pte_flags & H_PAGE_PKEY_BIT2) ? 0x4 : 0x0) |
+ ((pte_flags & H_PAGE_PKEY_BIT1) ? 0x8 : 0x0) |
+ ((pte_flags & H_PAGE_PKEY_BIT0) ? 0x10 : 0x0);
+}
+
#define pkey_to_vmflag_bits(key) (((key & 0x1UL) ? VM_PKEY_BIT0 : 0x0UL) | \
((key & 0x2UL) ? VM_PKEY_BIT1 : 0x0UL) | \
((key & 0x4UL) ? VM_PKEY_BIT2 : 0x0UL) | \
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 7e50e47..c1ec880 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -272,16 +272,24 @@
#define SPRN_DAR 0x013 /* Data Address Register */
#define SPRN_DBCR 0x136 /* e300 Data Breakpoint Control Reg */
#define SPRN_DSISR 0x012 /* Data Storage Interrupt Status Register */
+#define DSISR_BIT32 0x80000000 /* not defined */
#define DSISR_NOHPTE 0x40000000 /* no translation found */
+#define DSISR_PAGEATTR_CONFLT 0x20000000 /* page attribute conflict */
+#define DSISR_BIT35 0x10000000 /* not defined */
#define DSISR_PROTFAULT 0x08000000 /* protection fault */
#define DSISR_BADACCESS 0x04000000 /* bad access to CI or G */
#define DSISR_ISSTORE 0x02000000 /* access was a store */
#define DSISR_DABRMATCH 0x00400000 /* hit data breakpoint */
-#define DSISR_NOSEGMENT 0x00200000 /* SLB miss */
#define DSISR_KEYFAULT 0x00200000 /* Key fault */
+#define DSISR_BIT43 0x00100000 /* Not defined */
#define DSISR_UNSUPP_MMU 0x00080000 /* Unsupported MMU config */
#define DSISR_SET_RC 0x00040000 /* Failed setting of R/C bits */
#define DSISR_PGDIRFAULT 0x00020000 /* Fault on page directory */
+#define DSISR_PAGE_FAULT_MASK (DSISR_BIT32 | \
+ DSISR_PAGEATTR_CONFLT | \
+ DSISR_BADACCESS | \
+ DSISR_KEYFAULT | \
+ DSISR_BIT43)
#define SPRN_TBRL 0x10C /* Time Base Read Lower Register (user, R/O) */
#define SPRN_TBRU 0x10D /* Time Base Read Upper Register (user, R/O) */
#define SPRN_CIR 0x11B /* Chip Information Register (hyper, R/0) */
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index ae418b8..5226a9d 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1411,7 +1411,7 @@ USE_TEXT_SECTION()
.balign IFETCH_ALIGN_BYTES
do_hash_page:
#ifdef CONFIG_PPC_STD_MMU_64
- andis. r0,r4,0xa410 /* weird error? */
+ andis. r0,r4,DSISR_PAGE_FAULT_MASK at h /* weird error? */
bne- handle_page_fault /* if not, try to insert a HPTE */
andis. r0,r4,DSISR_DABRMATCH at h
bne- handle_dabr_fault
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 3a7d580..c31624f 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -216,9 +216,10 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
* bits we are interested in. But there are some bits which
* indicate errors in DSISR but can validly be set in SRR1.
*/
- if (trap == 0x400)
+ if (trap == 0x400) {
error_code &= 0x48200000;
- else
+ flags |= FAULT_FLAG_INSTRUCTION;
+ } else
is_write = error_code & DSISR_ISSTORE;
#else
is_write = error_code & ESR_DST;
@@ -261,6 +262,13 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
}
#endif
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+ if (error_code & DSISR_KEYFAULT) {
+ code = SEGV_PKUERR;
+ goto bad_area_nosemaphore;
+ }
+#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
+
/* We restore the interrupt state now */
if (!arch_irq_disabled_regs(regs))
local_irq_enable();
@@ -441,6 +449,15 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
#endif /* CONFIG_PPC_STD_MMU */
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+ if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE,
+ flags & FAULT_FLAG_INSTRUCTION,
+ 0)) {
+ code = SEGV_PKUERR;
+ goto bad_area;
+ }
+#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
+
/*
* If for any reason at all we couldn't handle the fault,
* make sure we exit gracefully rather than endlessly redo
diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index 11a32b3..a9545f1 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -27,6 +27,37 @@ static inline bool pkey_allows_readwrite(int pkey)
return !(read_amr() & ((AMR_AD_BIT|AMR_WD_BIT) << pkey_shift));
}
+static inline bool pkey_allows_read(int pkey)
+{
+ int pkey_shift = (arch_max_pkey()-pkey-1) * AMR_BITS_PER_PKEY;
+
+ if (!(read_uamor() & (0x3ul << pkey_shift)))
+ return true;
+
+ return !(read_amr() & (AMR_AD_BIT << pkey_shift));
+}
+
+static inline bool pkey_allows_write(int pkey)
+{
+ int pkey_shift = (arch_max_pkey()-pkey-1) * AMR_BITS_PER_PKEY;
+
+ if (!(read_uamor() & (0x3ul << pkey_shift)))
+ return true;
+
+ return !(read_amr() & (AMR_WD_BIT << pkey_shift));
+}
+
+static inline bool pkey_allows_execute(int pkey)
+{
+ int pkey_shift = (arch_max_pkey()-pkey-1) * AMR_BITS_PER_PKEY;
+
+ if (!(read_uamor() & (0x3ul << pkey_shift)))
+ return true;
+
+ return !(read_iamr() & (IAMR_EX_BIT << pkey_shift));
+}
+
+
/*
* set the access right in AMR IAMR and UAMOR register
* for @pkey to that specified in @init_val.
@@ -175,3 +206,62 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
*/
return vma_pkey(vma);
}
+
+bool arch_pte_access_permitted(pte_t pte, bool write)
+{
+ int pkey = pte_flags_to_pkey(pte_val(pte));
+
+ if (!pkey_allows_read(pkey))
+ return false;
+ if (write && !pkey_allows_write(pkey))
+ return false;
+ return true;
+}
+
+/*
+ * We only want to enforce protection keys on the current process
+ * because we effectively have no access to PKRU for other
+ * processes or any way to tell *which * PKRU in a threaded
+ * process we could use.
+ *
+ * So do not enforce things if the VMA is not from the current
+ * mm, or if we are in a kernel thread.
+ */
+static inline bool vma_is_foreign(struct vm_area_struct *vma)
+{
+ if (!current->mm)
+ return true;
+ /*
+ * if the VMA is from another process, then PKRU has no
+ * relevance and should not be enforced.
+ */
+ if (current->mm != vma->vm_mm)
+ return true;
+
+ return false;
+}
+
+bool arch_vma_access_permitted(struct vm_area_struct *vma,
+ bool write, bool execute, bool foreign)
+{
+ int pkey;
+ /* allow access if the VMA is not one from this process */
+ if (foreign || vma_is_foreign(vma))
+ return true;
+
+ pkey = vma_pkey(vma);
+
+ if (!pkey)
+ return true;
+
+ if (execute)
+ return pkey_allows_execute(pkey);
+
+ if (!pkey_allows_read(pkey))
+ return false;
+
+ if (write)
+ return pkey_allows_write(pkey);
+
+ return true;
+}
--
1.8.3.1
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