target/loongarch/gdbstub: Fix gdbstub incorrectly handling some registers

Write operation with R32 (orig_a0) and R34 (CSR_BADV) is discarded on
gdbstub implementation for LoongArch system. And return value should
be register size rather than 0, since it is used to calculate offset of
next register such as R33 (PC) in function handle_write_all_regs().

Cc: qemu-stable@nongnu.org
Fixes: ca61e75071c6 ("target/loongarch: Add gdb support.")
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Bibo Mao <maobibo@loongson.cn>

1 files changed, 6 insertions, 5 deletions

diff --git a/target/loongarch/gdbstub.c b/target/loongarch/gdbstub.c
index dafa4feb75..471eda28c7 100644
--- a/target/loongarch/gdbstub.c
+++ b/target/loongarch/gdbstub.c
@@ -63,23 +63,24 @@ int loongarch_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
 {
     CPULoongArchState *env = cpu_env(cs);
     target_ulong tmp;
-    int read_length;
     int length = 0;
 
+    if (n < 0 || n > 34) {
+        return 0;
+    }
+
     if (is_la64(env)) {
         tmp = ldq_le_p(mem_buf);
-        read_length = 8;
+        length = 8;
     } else {
         tmp = ldl_le_p(mem_buf);
-        read_length = 4;
+        length = 4;
     }
 
     if (0 <= n && n < 32) {
         env->gpr[n] = tmp;
-        length = read_length;
     } else if (n == 33) {
         set_pc(env, tmp);
-        length = read_length;
     }
     return length;
 }