target/nios2: Advance pc when raising exceptions

The exception return address for nios2 is the instruction
after the one that was executing at the time of the exception.

We have so far implemented this by advancing the pc during the
process of raising the exception.  It is perhaps a little less
confusing to do this advance in the translator (and helpers)
when raising the exception in the first place, so that we may
more closely match kernel sources.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220421151735.31996-58-richard.henderson@linaro.org>

diff --git a/linux-user/nios2/cpu_loop.c b/linux-user/nios2/cpu_loop.c
index 30a27f252b6972e523616c8b7f33d07a8fe4727c..a5e86990e2d45b869d5ed40352bf7d2c77ea138f 100644 (file)
--- a/linux-user/nios2/cpu_loop.c
+++ b/linux-user/nios2/cpu_loop.c
@@ -39,6 +39,8 @@ void cpu_loop(CPUNios2State *env)
             break;
 
         case EXCP_DIV:
+            /* Match kernel's handle_diverror_c(). */
+            env->pc -= 4;
             force_sig_fault(TARGET_SIGFPE, TARGET_FPE_INTDIV, env->pc);
             break;
 
@@ -49,12 +51,6 @@ 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->pc += 4;
-
             switch (env->error_code) {
             case 0:
                 qemu_log_mask(CPU_LOG_INT, "\nSyscall\n");

diff --git a/target/nios2/cpu.h b/target/nios2/cpu.h
index 5474b1c40456b42427cb578e34fe1f99627a6170..f85581ee560a3726a314f3cb5e88d6560a3536f2 100644 (file)
--- a/target/nios2/cpu.h
+++ b/target/nios2/cpu.h
@@ -266,6 +266,8 @@ hwaddr nios2_cpu_get_phys_page_debug(CPUState *cpu, vaddr addr);
 G_NORETURN void nios2_cpu_do_unaligned_access(CPUState *cpu, vaddr addr,
                                               MMUAccessType access_type, int mmu_idx,
                                               uintptr_t retaddr);
+G_NORETURN void nios2_cpu_loop_exit_advance(CPUNios2State *env,
+                                            uintptr_t retaddr);
 
 void do_nios2_semihosting(CPUNios2State *env);
 

diff --git a/target/nios2/helper.c b/target/nios2/helper.c
index e256d1528e9e6c7f187716ddecf98b89313575a6..bb3b09e5a7738370e8fc162fa81905a8684a6f8d 100644 (file)
--- a/target/nios2/helper.c
+++ b/target/nios2/helper.c
@@ -49,7 +49,7 @@ static void do_exception(Nios2CPU *cpu, uint32_t exception_addr,
             cr_es = CR_BSTATUS;
         }
         env->ctrl[cr_es] = old_status;
-        env->regs[r_ea] = env->pc + 4;
+        env->regs[r_ea] = env->pc;
 
         if (cpu->mmu_present) {
             new_status |= CR_STATUS_EH;
@@ -113,7 +113,7 @@ static void do_eic_irq(Nios2CPU *cpu)
             }
             env->shadow_regs[new_rs][R_SSTATUS] = old_status;
         }
-        env->shadow_regs[new_rs][R_EA] = env->pc + 4;
+        env->shadow_regs[new_rs][R_EA] = env->pc;
     }
 
     env->ctrl[CR_STATUS] = new_status;
@@ -187,6 +187,8 @@ void nios2_cpu_do_interrupt(CPUState *cs)
 
     switch (cs->exception_index) {
     case EXCP_IRQ:
+        /* Note that PC is advanced for interrupts as well. */
+        env->pc += 4;
         if (cpu->eic_present) {
             do_eic_irq(cpu);
         } else {
@@ -249,7 +251,6 @@ void nios2_cpu_do_interrupt(CPUState *cs)
         break;
 
     case EXCP_SEMIHOST:
-        env->pc += 4;
         do_nios2_semihosting(env);
         break;
 
@@ -291,7 +292,7 @@ void nios2_cpu_do_unaligned_access(CPUState *cs, vaddr addr,
 
     env->ctrl[CR_BADADDR] = addr;
     cs->exception_index = EXCP_UNALIGN;
-    cpu_loop_exit_restore(cs, retaddr);
+    nios2_cpu_loop_exit_advance(env, retaddr);
 }
 
 bool nios2_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
@@ -330,7 +331,7 @@ bool nios2_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
             cs->exception_index = (access_type == MMU_INST_FETCH
                                    ? EXCP_SUPERA_X : EXCP_SUPERA_D);
             env->ctrl[CR_BADADDR] = address;
-            cpu_loop_exit_restore(cs, retaddr);
+            nios2_cpu_loop_exit_advance(env, retaddr);
         }
     }
 
@@ -367,5 +368,5 @@ bool nios2_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
 
     cs->exception_index = excp;
     env->ctrl[CR_BADADDR] = address;
-    cpu_loop_exit_restore(cs, retaddr);
+    nios2_cpu_loop_exit_advance(env, retaddr);
 }

diff --git a/target/nios2/op_helper.c b/target/nios2/op_helper.c
index 94040102f4aef4760bca3942a74f5ca957682d31..2e30d0a908d35ad4de2c64f842b9dd678eb8f567 100644 (file)
--- a/target/nios2/op_helper.c
+++ b/target/nios2/op_helper.c
@@ -31,6 +31,20 @@ void helper_raise_exception(CPUNios2State *env, uint32_t index)
     cpu_loop_exit(cs);
 }
 
+void nios2_cpu_loop_exit_advance(CPUNios2State *env, uintptr_t retaddr)
+{
+    CPUState *cs = env_cpu(env);
+
+    /*
+     * Note that PC is advanced for all hardware exceptions.
+     * Do this here, rather than in restore_state_to_opc(),
+     * lest we affect QEMU internal exceptions, like EXCP_DEBUG.
+     */
+    cpu_restore_state(cs, retaddr, true);
+    env->pc += 4;
+    cpu_loop_exit(cs);
+}
+
 static void maybe_raise_div(CPUNios2State *env, uintptr_t ra)
 {
     Nios2CPU *cpu = env_archcpu(env);
@@ -38,7 +52,7 @@ static void maybe_raise_div(CPUNios2State *env, uintptr_t ra)
 
     if (cpu->diverr_present) {
         cs->exception_index = EXCP_DIV;
-        cpu_loop_exit_restore(cs, ra);
+        nios2_cpu_loop_exit_advance(env, ra);
     }
 }
 
@@ -69,7 +83,7 @@ void helper_eret(CPUNios2State *env, uint32_t new_status, uint32_t new_pc)
     if (unlikely(new_pc & 3)) {
         env->ctrl[CR_BADADDR] = new_pc;
         cs->exception_index = EXCP_UNALIGND;
-        cpu_loop_exit_restore(cs, GETPC());
+        nios2_cpu_loop_exit_advance(env, GETPC());
     }
 
     /*

diff --git a/target/nios2/translate.c b/target/nios2/translate.c
index b52f98180d4c3b18bd2336fcb7976b5df57cc8f5..3a037a68cc46790278561fb9206f22e4a4505ea1 100644 (file)
--- a/target/nios2/translate.c
+++ b/target/nios2/translate.c
@@ -202,10 +202,10 @@ static TCGv dest_gpr(DisasContext *dc, unsigned reg)
 #endif
 }
 
-static void t_gen_helper_raise_exception(DisasContext *dc,
-                                         uint32_t index)
+static void t_gen_helper_raise_exception(DisasContext *dc, uint32_t index)
 {
-    tcg_gen_movi_tl(cpu_pc, dc->pc);
+    /* Note that PC is advanced for all hardware exceptions. */
+    tcg_gen_movi_tl(cpu_pc, dc->base.pc_next);
     gen_helper_raise_exception(cpu_env, tcg_constant_i32(index));
     dc->base.is_jmp = DISAS_NORETURN;
 }