RISC-V: selftests: cbo: Ensure asm operands match constraints, take 2

Commit 0de6528 ("RISC-V: selftests: cbo: Ensure asm operands
match constraints") attempted to ensure MK_CBO() would always
provide to a compile-time constant when given a constant, but
cpu_to_le32() isn't necessarily going to do that. Switch to manually
shifting the bytes, when needed, to finally get this right.

Reported-by: Woodrow Shen <woodrow.shen@sifive.com>
Closes: https://lore.kernel.org/all/CABquHATcBTUwfLpd9sPObBgNobqQKEAZ2yxk+TWSpyO5xvpXpg@mail.gmail.com/
Fixes: a29e2a4 ("RISC-V: selftests: Add CBO tests")
Fixes: 0de6528 ("RISC-V: selftests: cbo: Ensure asm operands match constraints")
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20240322134728.151255-2-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

tools/testing/selftests/riscv/hwprobe/cbo.c

@@ -19,7 +19,7 @@
 #include "hwprobe.h"
 #include "../../kselftest.h"
 
-#define MK_CBO(fn) cpu_to_le32((fn) << 20 | 10 << 15 | 2 << 12 | 0 << 7 | 15)
+#define MK_CBO(fn) le32_bswap((uint32_t)(fn) << 20 | 10 << 15 | 2 << 12 | 0 << 7 | 15)
 
 static char mem[4096] __aligned(4096) = { [0 ... 4095] = 0xa5 };
 

tools/testing/selftests/riscv/hwprobe/hwprobe.h

@@ -4,6 +4,16 @@
 #include <stddef.h>
 #include <asm/hwprobe.h>
 
+#if __BYTE_ORDER == __BIG_ENDIAN
+# define le32_bswap(_x)				\
+	((((_x) & 0x000000ffU) << 24) |		\
+	 (((_x) & 0x0000ff00U) <<  8) |		\
+	 (((_x) & 0x00ff0000U) >>  8) |		\
+	 (((_x) & 0xff000000U) >> 24))
+#else
+# define le32_bswap(_x) (_x)
+#endif
+
 /*
  * Rather than relying on having a new enough libc to define this, just do it
  * ourselves.  This way we don't need to be coupled to a new-enough libc to