The nios2 main loop code's code does some odd
things with gdb_handlesig() that no other target
CPU does: it has some signals that are delivered
to gdb and only to gdb. Stop doing this, and instead
behave like all the other targets:
 * a trap instruction becomes a SIGTRAP
 * an unhandled exception type returned from cpu_exec()
   causes us to abort(), not to try to hand gdb a SIGILL

This fixes in passing Coverity issue CID 1390853,
which was a complaint that the old code failed to
check the return value from gdb_handlesig().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Disclaimer: compile tested, and the change makes conceptual
sense, but I have no nios2 test environment.
---
 linux-user/nios2/cpu_loop.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/linux-user/nios2/cpu_loop.c b/linux-user/nios2/cpu_loop.c
index dac7a061813..973dd54d791 100644
--- a/linux-user/nios2/cpu_loop.c
+++ b/linux-user/nios2/cpu_loop.c
@@ -68,7 +68,10 @@ void cpu_loop(CPUNios2State *env)
                 env->regs[R_EA] = env->regs[R_PC] + 4;
                 env->regs[R_PC] = cpu->exception_addr;
 
-                gdbsig = TARGET_SIGTRAP;
+                info.si_signo = TARGET_SIGTRAP;
+                info.si_errno = 0;
+                info.si_code = TARGET_TRAP_BRKPT;
+                queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
                 break;
             }
         case 0xaa:
@@ -106,14 +109,7 @@ kuser_fail:
         default:
             EXCP_DUMP(env, "\nqemu: unhandled CPU exception %#x - aborting\n",
                      trapnr);
-            gdbsig = TARGET_SIGILL;
-            break;
-        }
-        if (gdbsig) {
-            gdb_handlesig(cs, gdbsig);
-            if (gdbsig != TARGET_SIGTRAP) {
-                exit(EXIT_FAILURE);
-            }
+            abort();
         }
 
         process_pending_signals(env);
-- 
2.19.1

On 19/10/2018 19:49, Peter Maydell wrote:
> The nios2 main loop code's code does some odd
> things with gdb_handlesig() that no other target
> CPU does: it has some signals that are delivered
> to gdb and only to gdb. Stop doing this, and instead
> behave like all the other targets:
>  * a trap instruction becomes a SIGTRAP
>  * an unhandled exception type returned from cpu_exec()
>    causes us to abort(), not to try to hand gdb a SIGILL
> 
> This fixes in passing Coverity issue CID 1390853,
> which was a complaint that the old code failed to
> check the return value from gdb_handlesig().
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> Disclaimer: compile tested, and the change makes conceptual
> sense, but I have no nios2 test environment.

I'll push a slightly modified version of this patch: gdbsig is now
unused and my compiler complains about that.

Thanks,
Laurent

> ---
>  linux-user/nios2/cpu_loop.c | 14 +++++---------
>  1 file changed, 5 insertions(+), 9 deletions(-)
> 
> diff --git a/linux-user/nios2/cpu_loop.c b/linux-user/nios2/cpu_loop.c
> index dac7a061813..973dd54d791 100644
> --- a/linux-user/nios2/cpu_loop.c
> +++ b/linux-user/nios2/cpu_loop.c
> @@ -68,7 +68,10 @@ void cpu_loop(CPUNios2State *env)
>                  env->regs[R_EA] = env->regs[R_PC] + 4;
>                  env->regs[R_PC] = cpu->exception_addr;
>  
> -                gdbsig = TARGET_SIGTRAP;
> +                info.si_signo = TARGET_SIGTRAP;
> +                info.si_errno = 0;
> +                info.si_code = TARGET_TRAP_BRKPT;
> +                queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
>                  break;
>              }
>          case 0xaa:
> @@ -106,14 +109,7 @@ kuser_fail:
>          default:
>              EXCP_DUMP(env, "\nqemu: unhandled CPU exception %#x - aborting\n",
>                       trapnr);
> -            gdbsig = TARGET_SIGILL;
> -            break;
> -        }
> -        if (gdbsig) {
> -            gdb_handlesig(cs, gdbsig);
> -            if (gdbsig != TARGET_SIGTRAP) {
> -                exit(EXIT_FAILURE);
> -            }
> +            abort();
>          }
>  
>          process_pending_signals(env);
>