linux-kernel - [RFC v5 29/38] powerpc: Handle exceptions caused by pkey violation

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Date:   Wed,  5 Jul 2017 14:22:06 -0700
From:   Ram Pai <linuxram@...ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org
Cc:     benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, dave.hansen@...el.com, hbabu@...ibm.com,
        linuxram@...ibm.com, arnd@...db.de, akpm@...ux-foundation.org,
        corbet@....net, mingo@...hat.com
Subject: [RFC v5 29/38] powerpc: Handle exceptions caused by pkey violation

Handle Data and  Instruction exceptions caused by memory
protection-key.

The CPU will detect the key fault if the HPTE is already
programmed with the key.

However if the HPTE is not  hashed, a key fault will not
be detected by the  hardware. The   software will detect
pkey violation in such a case.

Signed-off-by: Ram Pai <linuxram@...ibm.com>
---
 arch/powerpc/include/asm/reg.h |    2 +-
 arch/powerpc/mm/fault.c        |   21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index ba110dd..6e2a860 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -286,7 +286,7 @@
 #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_BIT43)
+			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/mm/fault.c b/arch/powerpc/mm/fault.c
index 3a7d580..ea74fe2 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -261,6 +261,13 @@ 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 +448,20 @@ 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,
+			is_exec, 0)) {
+		code = SEGV_PKUERR;
+		goto bad_area;
+	}
+#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
+
+
+	/* handle_mm_fault() needs to know if its a instruction access
+	 * fault.
+	 */
+	if (is_exec)
+		flags |= FAULT_FLAG_INSTRUCTION;
 	/*
 	 * If for any reason at all we couldn't handle the fault,
 	 * make sure we exit gracefully rather than endlessly redo
-- 
1.7.1