arm64: percpu: Initialize ret in the default case

BugLink: https://bugs.launchpad.net/bugs/1836968
[ Upstream commit b5bb425871186303e6936fa2581521bdd1964a58 ]

Clang warns that if the default case is taken, ret will be
uninitialized.

./arch/arm64/include/asm/percpu.h:196:2: warning: variable 'ret' is used
uninitialized whenever switch default is taken
[-Wsometimes-uninitialized]
        default:
        ^~~~~~~
./arch/arm64/include/asm/percpu.h:200:9: note: uninitialized use occurs
here
        return ret;
               ^~~
./arch/arm64/include/asm/percpu.h:157:19: note: initialize the variable
'ret' to silence this warning
        unsigned long ret, loop;
                         ^
                          = 0

This warning appears several times while building the erofs filesystem.
While it's not strictly wrong, the BUILD_BUG will prevent this from
becoming a true problem. Initialize ret to 0 in the default case right
before the BUILD_BUG to silence all of these warnings.

Reported-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
index 43393208229eb8d64ec476f5b7b098bc73f498f9..d79eaa816f2949b8b941961aac21236c38a21545 100644 (file)
--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h
@@ -93,6 +93,7 @@ static inline unsigned long __percpu_##op(void *ptr,                  \
                : [val] "Ir" (val));                                    \
                break;                                                  \
        default:                                                        \
+               ret = 0;                                                \
                BUILD_BUG();                                            \
        }                                                               \
                                                                        \
@@ -122,6 +123,7 @@ static inline unsigned long __percpu_read(void *ptr, int size)
                ret = READ_ONCE(*(u64 *)ptr);
                break;
        default:
+               ret = 0;
                BUILD_BUG();
        }
 
@@ -191,6 +193,7 @@ static inline unsigned long __percpu_xchg(void *ptr, unsigned long val,
                : [val] "r" (val));
                break;
        default:
+               ret = 0;
                BUILD_BUG();
        }