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Subject[PATCH] nospec: Move array_index_nospec parameter checking into separate macro
Date
For architectures providing their own implementation of
array_index_mask_nospec in asm/barrier.h, attempting to use WARN_ONCE to
complain about out-of-range parameters using WARN_ON results in a mess
of mutually-dependent include files.

Rather than unpick the dependencies, simply have the core code in nospec.h
perform the checking for us.

Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
include/linux/nospec.h | 36 +++++++++++++++++++++---------------
1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/include/linux/nospec.h b/include/linux/nospec.h
index b99bced39ac2..fbc98e2c8228 100644
--- a/include/linux/nospec.h
+++ b/include/linux/nospec.h
@@ -20,20 +20,6 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
unsigned long size)
{
/*
- * Warn developers about inappropriate array_index_nospec() usage.
- *
- * Even if the CPU speculates past the WARN_ONCE branch, the
- * sign bit of @index is taken into account when generating the
- * mask.
- *
- * This warning is compiled out when the compiler can infer that
- * @index and @size are less than LONG_MAX.
- */
- if (WARN_ONCE(index > LONG_MAX || size > LONG_MAX,
- "array_index_nospec() limited to range of [0, LONG_MAX]\n"))
- return 0;
-
- /*
* Always calculate and emit the mask even if the compiler
* thinks the mask is not needed. The compiler does not take
* into account the value of @index under speculation.
@@ -44,6 +30,26 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
#endif

/*
+ * Warn developers about inappropriate array_index_nospec() usage.
+ *
+ * Even if the CPU speculates past the WARN_ONCE branch, the
+ * sign bit of @index is taken into account when generating the
+ * mask.
+ *
+ * This warning is compiled out when the compiler can infer that
+ * @index and @size are less than LONG_MAX.
+ */
+#define array_index_mask_nospec_check(index, size) \
+({ \
+ if (WARN_ONCE(index > LONG_MAX || size > LONG_MAX, \
+ "array_index_nospec() limited to range of [0, LONG_MAX]\n")) \
+ _mask = 0; \
+ else \
+ _mask = array_index_mask_nospec(index, size); \
+ _mask; \
+})
+
+/*
* array_index_nospec - sanitize an array index after a bounds check
*
* For a code sequence like:
@@ -61,7 +67,7 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
({ \
typeof(index) _i = (index); \
typeof(size) _s = (size); \
- unsigned long _mask = array_index_mask_nospec(_i, _s); \
+ unsigned long _mask = array_index_mask_nospec_check(_i, _s); \
\
BUILD_BUG_ON(sizeof(_i) > sizeof(long)); \
BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \
--
2.1.4
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