From: James Hogan <james.hogan@mips.com>

nanoMIPS has no ISA bit in the PC, so remove the handling of the low bit
of the PC in the MIPS gdbstub for nanoMIPS. This prevents the PC being
read as e.g. 0xbfc00001, and prevents writing to the PC clearing
MIPS_HFLAG_M16.

Signed-off-by: James Hogan <james.hogan@mips.com>
Signed-off-by: Yongbok Kim <yongbok.kim@mips.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Signed-off-by: Stefan Markovic <smarkovic@wavecomp.com>
---
 target/mips/gdbstub.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/target/mips/gdbstub.c b/target/mips/gdbstub.c
index 18e0e6d..559b69f 100644
--- a/target/mips/gdbstub.c
+++ b/target/mips/gdbstub.c
@@ -60,7 +60,8 @@ int mips_cpu_gdb_read_register(CPUState *cs, uint8_t *mem_buf, int n)
         return gdb_get_regl(mem_buf, (int32_t)env->CP0_Cause);
     case 37:
         return gdb_get_regl(mem_buf, env->active_tc.PC |
-                                     !!(env->hflags & MIPS_HFLAG_M16));
+                                     (!(env->insn_flags & ISA_NANOMIPS32) &&
+                                      env->hflags & MIPS_HFLAG_M16));
     case 72:
         return gdb_get_regl(mem_buf, 0); /* fp */
     case 89:
@@ -131,10 +132,12 @@ int mips_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
         break;
     case 37:
         env->active_tc.PC = tmp & ~(target_ulong)1;
-        if (tmp & 1) {
-            env->hflags |= MIPS_HFLAG_M16;
-        } else {
-            env->hflags &= ~(MIPS_HFLAG_M16);
+        if (!(env->insn_flags & ISA_NANOMIPS32)) {
+            if (tmp & 1) {
+                env->hflags |= MIPS_HFLAG_M16;
+            } else {
+                env->hflags &= ~(MIPS_HFLAG_M16);
+            }
         }
         break;
     case 72: /* fp, ignored */
-- 
2.7.4

On 07/30/2018 12:12 PM, Aleksandar Markovic wrote:
> From: James Hogan <james.hogan@mips.com>
> 
> nanoMIPS has no ISA bit in the PC, so remove the handling of the low bit
> of the PC in the MIPS gdbstub for nanoMIPS. This prevents the PC being
> read as e.g. 0xbfc00001, and prevents writing to the PC clearing
> MIPS_HFLAG_M16.
> 
> Signed-off-by: James Hogan <james.hogan@mips.com>
> Signed-off-by: Yongbok Kim <yongbok.kim@mips.com>
> Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
> Signed-off-by: Stefan Markovic <smarkovic@wavecomp.com>
> ---
>  target/mips/gdbstub.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)

Likewise re nanomips not setting M16.


r~