On Mon, Apr 15, 2019 at 03:01:51PM -0700, Nathan Chancellor wrote:
On Mon, Apr 15, 2019 at 08:44:36PM +0200, Greg Kroah-Hartman wrote:
From: Will Deacon will.deacon@arm.com
[...]
@@ -53,29 +53,29 @@ static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr) {
- int oldval = 0, ret, tmp;
- int oldval, ret, tmp;
pagefault_disable(); switch (op) { case FUTEX_OP_SET:
__futex_atomic_op("mov %w0, %w4",
__futex_atomic_op("mov %w3, %w4", ret, oldval, uaddr, tmp, oparg);
__futex_atomic_op("add %w0, %w1, %w4",
__futex_atomic_op("add %w3, %w1, %w4", ret, oldval, uaddr, tmp, oparg);
__futex_atomic_op("orr %w0, %w1, %w4",
__futex_atomic_op("orr %w3, %w1, %w4", ret, oldval, uaddr, tmp, oparg);
__futex_atomic_op("and %w0, %w1, %w4",
__futex_atomic_op("and %w3, %w1, %w4", ret, oldval, uaddr, tmp, ~oparg);
__futex_atomic_op("eor %w0, %w1, %w4",
__futex_atomic_op("eor %w3, %w1, %w4", ret, oldval, uaddr, tmp, oparg);This causes a (false) build warning with AOSP's GCC 4.9.4 (which is used to build nearly all arm64 Android kernels before 4.14):
CC kernel/futex.o ../kernel/futex.c: In function 'do_futex': ../kernel/futex.c:1492:17: warning: 'oldval' may be used uninitialized in this function [-Wmaybe-uninitialized] return oldval == cmparg; ^ In file included from ../kernel/futex.c:69:0: ../arch/arm64/include/asm/futex.h:56:6: note: 'oldval' was declared here int oldval, ret, tmp; ^
The only reason I bring this up is Qualcomm based kernels have a Python script that emulates -Werror, meaning this will be fatal for a large number of kernels, when this eventually gets merged into them.
Thanks. Does restoring the initial assignment of 0 suppress the bogus warning? If so, please could you send a patch on top for stable (assuming Greg is ok with the simple change for this)?
Will