From: Richard Henderson <richard.henderson@linaro.org>
Date: Thu, 21 Apr 2022 15:16:32 +0000 (-0700)
Subject: linux-user/nios2: Hoist pc advance to the top of EXCP_TRAP
X-Git-Tag: v7.1.0-rc0~128^2~67
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=892d0f4afb2614603157600e9d5d0aaa878b5d31;p=thirdparty%2Fqemu.git

linux-user/nios2: Hoist pc advance to the top of EXCP_TRAP

Note that this advance *should* be done by the translator, as
that's the pc value that's supposed to be generated by hardware.
However, that's a much larger change across sysemu as well.

In the meantime, produce the correct PC for any signals raised
by the trap instruction.  Note the special case of TRAP_BRKPT,
which itself is special cased within the kernel.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220421151735.31996-2-richard.henderson@linaro.org>
---

diff --git a/linux-user/nios2/cpu_loop.c b/linux-user/nios2/cpu_loop.c
index 1e93ef34e64..2e9296750d6 100644
--- a/linux-user/nios2/cpu_loop.c
+++ b/linux-user/nios2/cpu_loop.c
@@ -40,6 +40,12 @@ void cpu_loop(CPUNios2State *env)
             break;
 
         case EXCP_TRAP:
+            /*
+             * TODO: This advance should be done in the translator, as
+             * hardware produces an advanced pc as part of all exceptions.
+             */
+            env->regs[R_PC] += 4;
+
             switch (env->error_code) {
             case 0:
                 qemu_log_mask(CPU_LOG_INT, "\nSyscall\n");
@@ -56,7 +62,6 @@ void cpu_loop(CPUNios2State *env)
                 env->regs[2] = abs(ret);
                 /* Return value is 0..4096 */
                 env->regs[7] = ret > 0xfffff000u;
-                env->regs[R_PC] += 4;
                 break;
 
             case 1:
@@ -69,6 +74,8 @@ void cpu_loop(CPUNios2State *env)
                 break;
             case 31:
                 qemu_log_mask(CPU_LOG_INT, "\nTrap 31\n");
+                /* Match kernel's breakpoint_c(). */
+                env->regs[R_PC] -= 4;
                 force_sig_fault(TARGET_SIGTRAP, TARGET_TRAP_BRKPT, env->regs[R_PC]);
                 break;
             default:
@@ -99,7 +106,6 @@ void cpu_loop(CPUNios2State *env)
                     o = env->regs[5];
                     n = env->regs[6];
                     env->regs[2] = qatomic_cmpxchg(h, o, n) - o;
-                    env->regs[R_PC] += 4;
                 }
                 break;
             }