[ARM32,v4.4,V2,25/47] ARM: use __inttype() in get_user()

Message ID ee0c1251878b2ebd4da4bead196caa950274e98c.1564646727.git.viresh.kumar@linaro.org
State New
Headers show
Series
  • V4.4 backport of arm32 Spectre patches
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Commit Message

Viresh Kumar Aug. 1, 2019, 8:16 a.m.
From: Russell King <rmk+kernel@armlinux.org.uk>


Commit d09fbb327d670737ab40fd8bbb0765ae06b8b739 upstream.

Borrow the x86 implementation of __inttype() to use in get_user() to
select an integer type suitable to temporarily hold the result value.
This is necessary to avoid propagating the volatile nature of the
result argument, which can cause the following warning:

lib/iov_iter.c:413:5: warning: optimization may eliminate reads and/or writes to register variables [-Wvolatile-register-var]

Acked-by: Mark Rutland <mark.rutland@arm.com>

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

Signed-off-by: David A. Long <dave.long@linaro.org>

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

---
 arch/arm/include/asm/uaccess.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

-- 
2.21.0.rc0.269.g1a574e7a288b

Patch

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index cd8b589111ba..968b50063431 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -122,6 +122,13 @@  static inline void set_fs(mm_segment_t fs)
 		: "cc"); \
 	flag; })
 
+/*
+ * This is a type: either unsigned long, if the argument fits into
+ * that type, or otherwise unsigned long long.
+ */
+#define __inttype(x) \
+	__typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
+
 /*
  * Single-value transfer routines.  They automatically use the right
  * size if we just have the right pointer type.  Note that the functions
@@ -191,7 +198,7 @@  extern int __get_user_64t_4(void *);
 	({								\
 		unsigned long __limit = current_thread_info()->addr_limit - 1; \
 		register const typeof(*(p)) __user *__p asm("r0") = (p);\
-		register typeof(x) __r2 asm("r2");			\
+		register __inttype(x) __r2 asm("r2");			\
 		register unsigned long __l asm("r1") = __limit;		\
 		register int __e asm("r0");				\
 		unsigned int __ua_flags = uaccess_save_and_enable();	\