Subject: [PATCH 20/25] powerpc: Handle exceptions caused by pkey violation

From: Ram Pai <[email-masked]>
Date: Fri, 8 Sep 2017 15:45:08 -0700

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 <[email-masked]>
---
 arch/powerpc/mm/fault.c |   37 ++++++++++++++++++++++++++++++++-----
 1 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 4797d08..a16bc43 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -145,6 +145,23 @@ static noinline int bad_area(struct pt_regs *regs, unsigned long address)
 	return __bad_area(regs, address, SEGV_MAPERR);
 }
 
+static int bad_page_fault_exception(struct pt_regs *regs, unsigned long address,
+					int si_code)
+{
+	int sig = SIGBUS;
+	int code = BUS_OBJERR;
+
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+	if (si_code & DSISR_KEYFAULT) {
+		sig = SIGSEGV;
+		code = SEGV_PKUERR;
+	}
+#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
+
+	_exception(sig, regs, code, address);
+	return 0;
+}
+
 static int do_sigbus(struct pt_regs *regs, unsigned long address,
 		     unsigned int fault)
 {
@@ -391,11 +408,9 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
 		return 0;
 
 	if (unlikely(page_fault_is_bad(error_code))) {
-		if (is_user) {
-			_exception(SIGBUS, regs, BUS_OBJERR, address);
-			return 0;
-		}
-		return SIGBUS;
+		if (!is_user)
+			return SIGBUS;
+		return bad_page_fault_exception(regs, address, error_code);
 	}
 
 	/* Additional sanity check(s) */
@@ -492,6 +507,18 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
 	if (unlikely(access_error(is_write, is_exec, vma)))
 		return bad_area(regs, address);
 
+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+	if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE,
+			is_exec, 0))
+		return __bad_area(regs, address, SEGV_PKUERR);
+#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