From 7ba68b2172c19031fdc2a2caf37328edd146e299 Mon Sep 17 00:00:00 2001
From: Jordan Niethe <jniethe5@gmail.com>
Date: Wed, 6 May 2020 13:40:33 +1000
Subject: [PATCH] powerpc: Add a probe_user_read_inst() function

References: jsc#SLE-13847
Patch-mainline: v5.8-rc1
Git-commit: 7ba68b2172c19031fdc2a2caf37328edd146e299

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 <jniethe5@gmail.com>
Reviewed-by: Alistair Popple <alistair@popple.id.au>
[mpe: Don't write to *inst on error, fold in __user annotations]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200506034050.24806-14-jniethe5@gmail.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/include/asm/inst.h |  3 +++
 arch/powerpc/lib/Makefile       |  2 +-
 arch/powerpc/lib/inst.c         | 20 ++++++++++++++++++++
 arch/powerpc/mm/fault.c         |  4 ++--
 4 files changed, 26 insertions(+), 3 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 f9cbb24d2e34..4db0ecee2698 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 __user *nip);
+
 #endif /* _ASM_POWERPC_INST_H */
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
--- 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
+obj-y += alloc.o code-patching.o feature-fixups.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..605220dbb6ba
--- /dev/null
+++ b/arch/powerpc/lib/inst.c
@@ -0,0 +1,20 @@
+// 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 __user *nip)
+{
+	unsigned int val;
+	int err;
+
+	err = probe_user_read(&val, nip, sizeof(val));
+	if (!err)
+		*inst = ppc_inst(val);
+
+	return err;
+}
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 4f0ef68a7d31..2393ed9d84bb 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -282,7 +282,7 @@ static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address,
 	 * expand to 1MB without further checks.
 	 */
 	if (address + 0x100000 < vma->vm_end) {
-		unsigned int __user *nip = (unsigned int __user *)regs->nip;
+		struct ppc_inst __user *nip = (struct ppc_inst __user *)regs->nip;
 		/* get user regs even if this fault is in kernel mode */
 		struct pt_regs *uregs = current->thread.regs;
 		if (uregs == NULL)
@@ -307,7 +307,7 @@ 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, nip))
 				return !store_updates_sp(inst);
 			*must_retry = true;
 		}
-- 
2.26.2