raw_syscalls: simplify assembly

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Co-developed-by: David Howells <dhowells@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>

diff --git a/src/lxc/raw_syscalls.c b/src/lxc/raw_syscalls.c
index a16f6edf76231563ad9d63dfa2c9f8829455e51c..bbf5409b0fc4560c1a4bbd9f68887629a2bdb611 100644 (file)
--- a/src/lxc/raw_syscalls.c
+++ b/src/lxc/raw_syscalls.c
@@ -56,31 +56,41 @@ __returns_twice pid_t lxc_raw_clone(unsigned long flags)
                 * boolean flag whether this is the child or the parent in %o1.
                 * Inline assembly is needed to get the flag returned in %o1.
                 */
-               int child_pid, in_child, ret;
+               register long g1 asm("g1") = __NR_clone;
+               register long o0 asm("o0") = flags | SIGCHLD;
+               register long o1 asm("o1") = 0; /* is parent/child indicator */
+               long is_error, retval, in_child;
+               pid_t child_pid;
 
-                asm volatile("mov %3, %%g1\n\t"
-                             "mov %4, %%o0\n\t"
-                             "mov 0 , %%o1\n\t"
+               asm volatile(
 #if defined(__arch64__)
-                             "t 0x6d\n\t"
+                   "t 0x6d\n\t" /* 64-bit trap */
 #else
-                             "t 0x10\n\t"
+                   "t 0x10\n\t" /* 32-bit trap */
 #endif
-                             "addx %%g0, 0, %2\n\t"
-                             "mov %%o1, %0\n\t"
-                             "mov %%o0, %1" :
-                             "=r"(in_child), "=r"(child_pid), "=r"(ret) :
-                             "i"(__NR_clone), "r"(flags | SIGCHLD) :
-                             "%o1", "%o0", "%g1", "cc" );
+                   /*
+                    * catch errors: On sparc, the carry bit (csr) in the
+                    * processor status register (psr) is used instead of a
+                    * full register.
+                    */
+                   "addx %%g0, 0, %g1"
+                   : "=r"(g1), "=r"(o0), "=r"(o1) /* outputs */
+                   : "r"(g1), "r"(o0), "r"(o1)    /* inputs */
+                   : "%cc");                      /* clobbers */
 
-               if (ret) {
-                       errno = child_pid;
+               is_error = g1;
+               retval = o0;
+               in_child = o1;
+
+               if (is_error) {
+                       errno = retval;
                        return -1;
                }
 
                if (in_child)
                        return 0;
 
+               child_pid = retval;
                return child_pid;
        }
 #elif defined(__ia64__)