riscv/atomic: Fix sign extension for RV64I

[ Upstream commit 6c58f25e6938c073198af8b1e1832f83f8f0df33 ]

The argument passed to cmpxchg is not guaranteed to be sign
extended, but lr.w sign extends on RV64I. This makes cmpxchg
fail on clang built kernels when __old is negative.

To fix this, we just cast __old to long which sign extends on
RV64I. With this fix, clang built RISC-V kernels now boot.

Link: https://github.com/ClangBuiltLinux/linux/issues/867
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
index d969bab..262e5bb 100644 (file)
--- a/arch/riscv/include/asm/cmpxchg.h
+++ b/arch/riscv/include/asm/cmpxchg.h
@@ -179,7 +179,7 @@
                        "       bnez %1, 0b\n"                          \
                        "1:\n"                                          \
                        : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr)    \
-                       : "rJ" (__old), "rJ" (__new)                    \
+                       : "rJ" ((long)__old), "rJ" (__new)              \
                        : "memory");                                    \
                break;                                                  \
        case 8:                                                         \
@@ -224,7 +224,7 @@
                        RISCV_ACQUIRE_BARRIER                           \
                        "1:\n"                                          \
                        : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr)    \
-                       : "rJ" (__old), "rJ" (__new)                    \
+                       : "rJ" ((long)__old), "rJ" (__new)              \
                        : "memory");                                    \
                break;                                                  \
        case 8:                                                         \
@@ -270,7 +270,7 @@
                        "       bnez %1, 0b\n"                          \
                        "1:\n"                                          \
                        : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr)    \
-                       : "rJ" (__old), "rJ" (__new)                    \
+                       : "rJ" ((long)__old), "rJ" (__new)              \
                        : "memory");                                    \
                break;                                                  \
        case 8:                                                         \
@@ -316,7 +316,7 @@
                        "       fence rw, rw\n"                         \
                        "1:\n"                                          \
                        : "=&r" (__ret), "=&r" (__rc), "+A" (*__ptr)    \
-                       : "rJ" (__old), "rJ" (__new)                    \
+                       : "rJ" ((long)__old), "rJ" (__new)              \
                        : "memory");                                    \
                break;                                                  \
        case 8:                                                         \