target-ppc: Fix gdbstub for ppc64le-linux-user

The bswap that's needed for system mode isn't required for
user mode, and in fact breaks debugging.

Signed-off-by: Richard Henderson <rth@twiddle.net>
[agraf: fix apple gdbstub implementation]
Signed-off-by: Alexander Graf <agraf@suse.de>

target-ppc/gdbstub.c

@@ -83,16 +83,24 @@ static int ppc_gdb_register_len(int n)
     }
 }
 
-
-static void ppc_gdb_swap_register(uint8_t *mem_buf, int n, int len)
+/* We need to present the registers to gdb in the "current" memory ordering.
+   For user-only mode we get this for free; TARGET_WORDS_BIGENDIAN is set to
+   the proper ordering for the binary, and cannot be changed.
+   For system mode, TARGET_WORDS_BIGENDIAN is always set, and we must check
+   the current mode of the chip to see if we're running in little-endian.  */
+static void maybe_bswap_register(CPUPPCState *env, uint8_t *mem_buf, int len)
 {
-    if (len == 4) {
+#ifndef CONFIG_USER_ONLY
+    if (!msr_le) {
+        /* do nothing */
+    } else if (len == 4) {
         bswap32s((uint32_t *)mem_buf);
     } else if (len == 8) {
         bswap64s((uint64_t *)mem_buf);
     } else {
         g_assert_not_reached();
     }
+#endif
 }
 
 /* Old gdb always expects FP registers.  Newer (xml-aware) gdb only
@@ -150,10 +158,7 @@ int ppc_cpu_gdb_read_register(CPUState *cs, uint8_t *mem_buf, int n)
             break;
         }
     }
-    if (msr_le) {
-        /* If cpu is in LE mode, convert memory contents to LE. */
-        ppc_gdb_swap_register(mem_buf, n, r);
-    }
+    maybe_bswap_register(env, mem_buf, r);
     return r;
 }
 
@@ -209,10 +214,7 @@ int ppc_cpu_gdb_read_register_apple(CPUState *cs, uint8_t *mem_buf, int n)
             break;
         }
     }
-    if (msr_le) {
-        /* If cpu is in LE mode, convert memory contents to LE. */
-        ppc_gdb_swap_register(mem_buf, n, r);
-    }
+    maybe_bswap_register(env, mem_buf, r);
     return r;
 }
 
@@ -225,10 +227,7 @@ int ppc_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
     if (!r) {
         return r;
     }
-    if (msr_le) {
-        /* If cpu is in LE mode, convert memory contents to LE. */
-        ppc_gdb_swap_register(mem_buf, n, r);
-    }
+    maybe_bswap_register(env, mem_buf, r);
     if (n < 32) {
         /* gprs */
         env->gpr[n] = ldtul_p(mem_buf);
@@ -278,10 +277,7 @@ int ppc_cpu_gdb_write_register_apple(CPUState *cs, uint8_t *mem_buf, int n)
     if (!r) {
         return r;
     }
-    if (msr_le) {
-        /* If cpu is in LE mode, convert memory contents to LE. */
-        ppc_gdb_swap_register(mem_buf, n, r);
-    }
+    maybe_bswap_register(env, mem_buf, r);
     if (n < 32) {
         /* gprs */
         env->gpr[n] = ldq_p(mem_buf);