From: Bibo Mao <maobibo@loongson.cn>

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>
(cherry picked from commit 7bd4eaa847fcdbc4505d9ab95dafa21791d8302a)
(Mjt: context fix due to missing v9.1.0-913-g2a99b2af2c
 "target/loongarch: Use explicit little-endian LD/ST API")
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/target/loongarch/gdbstub.c b/target/loongarch/gdbstub.c
index 5fc2f19e96..320a6f2fcc 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)
     LoongArchCPU *cpu = LOONGARCH_CPU(cs);
     CPULoongArchState *env = &cpu->env;
     target_ulong tmp;
-    int read_length;
     int length = 0;
 
+    if (n < 0 || n > 34) {
+        return 0;
+    }
+
     if (is_la64(env)) {
         tmp = ldq_p(mem_buf);
-        read_length = 8;
+        length = 8;
     } else {
         tmp = ldl_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;
 }
-- 
2.39.5