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@intel.com Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org # 4.9+ Signed-off-by: Alexander Lobakin alexandr.lobakin@intel.com --- 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 */