riscv/atomic: Fix sign extension for RV64I

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>

diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
index d969bab4a26b5f588a5284ae7c8cdf7fa14cbf85..262e5bbb27760840d598e4e940a340fc5d820178 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:                                                         \