Macro TO_NATIVE() directly takes a reference to its argument @x
without making an intermediate variable. This makes compilers
emit build warnings and errors if @x is an expression or a deref
of a const pointer (when target Endianness != host Endianness):
>> scripts/mod/modpost.h:87:18: error: lvalue required as unary '&' operand
87 | __endian(&(x), &(__x), sizeof(__x)); \
| ^
scripts/mod/sympath.c:19:25: note: in expansion of macro 'TO_NATIVE'
19 | #define t(x) TO_NATIVE(x)
| ^~~~~~~~~
scripts/mod/sympath.c:100:31: note: in expansion of macro 't'
100 | eh->e_shoff = t(h(eh->e_shoff) + off);
>> scripts/mod/modpost.h:87:24: warning: passing argument 2 of '__endian'
discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
87 | __endian(&(x), &(__x), sizeof(__x)); \
| ^~~~~~
scripts/mod/sympath.c:18:25: note: in expansion of macro 'TO_NATIVE'
18 | #define h(x) TO_NATIVE(x)
| ^~~~~~~~~
scripts/mod/sympath.c:178:48: note: in expansion of macro 'h'
178 | iter < end; iter = (void *)iter + h(eh->e_shentsize)) {
Create a temporary variable, assign @x to it and don't use @x after
that. This makes it possible to pass expressions as an argument.
Also, do a cast-away for the second argument when calling __endian()
to avoid 'discarded qualifiers' warning, as typeof() preserves
qualifiers and makes compilers think that we're passing pointer
to a const.
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx # 4.9+
Signed-off-by: Alexander Lobakin <alexandr.lobakin@xxxxxxxxx>
---
scripts/mod/modpost.h | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 1178f40a73f3..29f440f18414 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -83,9 +83,10 @@ static inline void __endian(const void *src, void *dest, unsigned int size)
#define TO_NATIVE(x) \
({ \
- typeof(x) __x; \
- __endian(&(x), &(__x), sizeof(__x)); \
- __x; \
+ typeof(x) __src = (x); \
+ typeof(__src) __dst; \
+ __endian(&__src, (void *)&__dst, sizeof(__src)); \
+ __dst; \
})
#else /* endianness matches */
--
2.37.2
