Re: [PATCH v7 13/28] powerpc: Add a probe_user_read_inst() function

Introduce a probe_user_read_inst() function to use in cases where
probe_user_read() is used for getting an instruction. This will be more
useful for prefixed instructions.

Signed-off-by: Jordan Niethe <redacted>
---
v6: - New to series
---
 arch/powerpc/include/asm/inst.h |  3 +++
 arch/powerpc/lib/Makefile       |  2 +-
 arch/powerpc/lib/inst.c         | 18 ++++++++++++++++++
 arch/powerpc/mm/fault.c         |  2 +-
 4 files changed, 23 insertions(+), 2 deletions(-)
 create mode 100644 arch/powerpc/lib/inst.c

diff --git a/arch/powerpc/include/asm/inst.h

b/arch/powerpc/include/asm/inst.h index 552e953bf04f..3e9a58420151 100644

--- a/arch/powerpc/include/asm/inst.h
+++ b/arch/powerpc/include/asm/inst.h

@@ -37,4 +37,7 @@ static inline bool ppc_inst_equal(struct ppc_inst x,

struct ppc_inst y) return ppc_inst_val(x) == ppc_inst_val(y);
 }

+int probe_user_read_inst(struct ppc_inst *inst,
+			 struct ppc_inst *nip);
+
 #endif /* _ASM_INST_H */

diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index b8de3be10eb4..546591848219 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile

@@ -16,7 +16,7 @@ CFLAGS_code-patching.o += -DDISABLE_BRANCH_PROFILING
 CFLAGS_feature-fixups.o += -DDISABLE_BRANCH_PROFILING
 endif

-obj-y += alloc.o code-patching.o feature-fixups.o pmem.o
+obj-y += alloc.o code-patching.o feature-fixups.o pmem.o inst.o

 ifndef CONFIG_KASAN
 obj-y	+=	string.o memcmp_$(BITS).o

diff --git a/arch/powerpc/lib/inst.c b/arch/powerpc/lib/inst.c
new file mode 100644
index 000000000000..eaf786afad2b
--- /dev/null
+++ b/arch/powerpc/lib/inst.c

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright 2020, IBM Corporation.
+ */
+
+#include <linux/uaccess.h>
+#include <asm/inst.h>
+
+int probe_user_read_inst(struct ppc_inst *inst,
+			 struct ppc_inst *nip)
+{
+	unsigned int val;
+	int err;
+
+	err = probe_user_read(&val, nip, sizeof(val));
+	*inst = ppc_inst(val);
+	return err;
+}

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 4a50f125ec18..f3a943eae305 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c

@@ -281,7 +281,7 @@ static bool bad_stack_expansion(struct pt_regs *regs,

unsigned long address, access_ok(nip, sizeof(*nip))) {
 			struct ppc_inst inst;

-			if (!probe_user_read(&inst, nip, sizeof(inst)))
+			if (!probe_user_read_inst(&inst, (struct ppc_inst __user *)nip))
 				return !store_updates_sp(inst);
 			*must_retry = true;
 		}