[PATCH 1/2] linux-user/nios2: Properly emulate EXCP_TRAP

[Richard Henderson <richard.henderson@linaro.org>]

The real kernel has to load the instruction and extract
the imm5 field; for qemu, modify the translator to do this.

The use of R_AT for this in cpu_loop was a bug.  Handle
the other trap numbers as per the kernel's trap_table.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/nios2/cpu.h          |  5 +++--
 linux-user/nios2/cpu_loop.c | 35 ++++++++++++++++++-----------------
 target/nios2/translate.c    | 17 ++++++++++++++++-
 3 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/target/nios2/cpu.h b/target/nios2/cpu.h
index 2ab82fdc71..395e4d3281 100644
--- a/target/nios2/cpu.h
+++ b/target/nios2/cpu.h
@@ -158,9 +158,10 @@ struct Nios2CPUClass {
 struct CPUNios2State {
     uint32_t regs[NUM_CORE_REGS];
 
-#if !defined(CONFIG_USER_ONLY)
+#ifdef CONFIG_USER_ONLY
+    int trap_code;
+#else
     Nios2MMU mmu;
-
     uint32_t irq_pending;
 #endif
 };
diff --git a/linux-user/nios2/cpu_loop.c b/linux-user/nios2/cpu_loop.c
index 9869083fa1..d76bdb2891 100644
--- a/linux-user/nios2/cpu_loop.c
+++ b/linux-user/nios2/cpu_loop.c
@@ -37,9 +37,10 @@ void cpu_loop(CPUNios2State *env)
         case EXCP_INTERRUPT:
             /* just indicate that signals should be handled asap */
             break;
+
         case EXCP_TRAP:
-            if (env->regs[R_AT] == 0) {
-                abi_long ret;
+            switch (env->trap_code) {
+            case 0:
                 qemu_log_mask(CPU_LOG_INT, "\nSyscall\n");
 
                 ret = do_syscall(env, env->regs[2],
@@ -53,26 +54,26 @@ void cpu_loop(CPUNios2State *env)
 
                 env->regs[2] = abs(ret);
                 /* Return value is 0..4096 */
-                env->regs[7] = (ret > 0xfffffffffffff000ULL);
-                env->regs[CR_ESTATUS] = env->regs[CR_STATUS];
-                env->regs[CR_STATUS] &= ~0x3;
-                env->regs[R_EA] = env->regs[R_PC] + 4;
+                env->regs[7] = ret > 0xfffff000u;
                 env->regs[R_PC] += 4;
                 break;
-            } else {
-                qemu_log_mask(CPU_LOG_INT, "\nTrap\n");
 
-                env->regs[CR_ESTATUS] = env->regs[CR_STATUS];
-                env->regs[CR_STATUS] &= ~0x3;
-                env->regs[R_EA] = env->regs[R_PC] + 4;
-                env->regs[R_PC] = cpu->exception_addr;
-
-                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);
+            case 1:
+                qemu_log_mask(CPU_LOG_INT, "\nTrap 1\n");
+                force_sig_fault(TARGET_SIGUSR1, 0, env->regs[R_PC]);
+                break;
+            case 2:
+                qemu_log_mask(CPU_LOG_INT, "\nTrap 2\n");
+                force_sig_fault(TARGET_SIGUSR2, 0, env->regs[R_PC]);
+                break;
+            default:
+                qemu_log_mask(CPU_LOG_INT, "\nTrap %d\n", env->trap_code);
+                force_sig_fault(TARGET_SIGILL, TARGET_ILL_ILLTRP,
+                                env->regs[R_PC]);
                 break;
             }
+            break;
+
         case EXCP_DEBUG:
             info.si_signo = TARGET_SIGTRAP;
             info.si_errno = 0;
diff --git a/target/nios2/translate.c b/target/nios2/translate.c
index 08d7ac5398..485b487665 100644
--- a/target/nios2/translate.c
+++ b/target/nios2/translate.c
@@ -636,6 +636,21 @@ static void divu(DisasContext *dc, uint32_t code, uint32_t flags)
     tcg_temp_free(t0);
 }
 
+static void trap(DisasContext *dc, uint32_t code, uint32_t flags)
+{
+#ifdef CONFIG_USER_ONLY
+    /*
+     * The imm5 field is not stored anywhere on real hw; the kernel
+     * has to load the insn and extract the field.  But we can make
+     * things easier for cpu_loop if we pop this into env->trap_code.
+     */
+    R_TYPE(instr, code);
+    tcg_gen_st_i32(tcg_constant_i32(instr.imm5), cpu_env,
+                   offsetof(CPUNios2State, trap_code));
+#endif
+    t_gen_helper_raise_exception(dc, EXCP_TRAP);
+}
+
 static const Nios2Instruction r_type_instructions[] = {
     INSTRUCTION_ILLEGAL(),
     INSTRUCTION(eret),                                /* eret */
@@ -682,7 +697,7 @@ static const Nios2Instruction r_type_instructions[] = {
     INSTRUCTION_ILLEGAL(),
     INSTRUCTION_ILLEGAL(),
     INSTRUCTION_ILLEGAL(),
-    INSTRUCTION_FLG(gen_excp, EXCP_TRAP),             /* trap */
+    INSTRUCTION(trap),                                /* trap */
     INSTRUCTION(wrctl),                               /* wrctl */
     INSTRUCTION_ILLEGAL(),
     INSTRUCTION_FLG(gen_cmpxx, TCG_COND_LTU),         /* cmpltu */
-- 
2.25.1