riscv: add optional architectural trap entry

Author: Kreijstal

include/uc_priv.h

@@ -335,6 +335,7 @@ struct uc_struct {
     TargetPageBits *init_target_page;
     int target_bits; // User defined page bits by uc_ctl
     int cpu_model;
+    bool architectural_exceptions;
     BounceBuffer bounce;                // qemu/cpu-exec.c
     volatile sig_atomic_t exit_request; // qemu/cpu-exec.c
     /* qemu/accel/tcg/cpu-exec-common.c */

include/unicorn/unicorn.h

@@ -605,6 +605,11 @@ typedef enum uc_control_type {
     // controle if context_save/restore should work with snapshots
     // Write: @args = (int)
     UC_CTL_CONTEXT_MODE,
+    // Let the target CPU perform architectural exception entry before
+    // UC_HOOK_INTR is invoked. Disabled by default for compatibility.
+    // Write: @args = (int)
+    // Read: @args = (int*)
+    UC_CTL_UC_ARCHITECTURAL_EXCEPTIONS,
 } uc_control_type;
 
 /*
@@ -688,6 +693,10 @@ See sample_ctl.c for a detailed example.
     uc_ctl(uc, UC_CTL_WRITE(UC_CTL_TCG_BUFFER_SIZE, 1), (size))
 #define uc_ctl_context_mode(uc, mode)                                          \
     uc_ctl(uc, UC_CTL_WRITE(UC_CTL_CONTEXT_MODE, 1), (mode))
+#define uc_ctl_get_architectural_exceptions(uc, enabled)                       \
+    uc_ctl(uc, UC_CTL_READ(UC_CTL_UC_ARCHITECTURAL_EXCEPTIONS, 1), (enabled))
+#define uc_ctl_set_architectural_exceptions(uc, enabled)                       \
+    uc_ctl(uc, UC_CTL_WRITE(UC_CTL_UC_ARCHITECTURAL_EXCEPTIONS, 1), (enabled))
 
 // Opaque storage for CPU context, used with uc_context_*()
 struct uc_context;

qemu/accel/tcg/cpu-exec.c

@@ -392,7 +392,12 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
 #endif
 #if defined(TARGET_RISCV)
         CPURISCVState *env = &(RISCV_CPU(uc->cpu)->env);
-        env->pc += 4;
+        int riscv_hook_exception = cpu->exception_index;
+        if (uc->architectural_exceptions) {
+            riscv_cpu_do_interrupt(cpu);
+        } else {
+            env->pc += 4;
+        }
 #endif
 #if defined(TARGET_SPARC)
         CPUSPARCState *env = &(SPARC_CPU(uc->cpu)->env);
@@ -409,7 +414,13 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
             if (hook->to_delete) {
                 continue;
             }
-            JIT_CALLBACK_GUARD(((uc_cb_hookintr_t)hook->callback)(uc, cpu->exception_index, hook->user_data));
+            JIT_CALLBACK_GUARD(((uc_cb_hookintr_t)hook->callback)(uc,
+#if defined(TARGET_RISCV)
+                                riscv_hook_exception,
+#else
+                                cpu->exception_index,
+#endif
+                                hook->user_data));
             catched = true;
         }
         // Unicorn: If un-catched interrupt, stop executions.

tests/unit/test_riscv.c

@@ -459,6 +459,36 @@ static void test_riscv64_ecall(void)
     OK(uc_close(uc));
 }
 
+static void test_riscv32_architectural_exception_entry(void)
+{
+    uc_engine *uc;
+    char code[] = "\x73\x00\x00\x00"; // ecall
+    uint32_t mtvec = 0x1800;
+    uint32_t pc, mepc, mcause, priv;
+    int enabled = 0;
+    uc_hook h;
+
+    uc_common_setup(&uc, UC_ARCH_RISCV, UC_MODE_RISCV32, code,
+                    sizeof(code) - 1);
+    OK(uc_reg_write(uc, UC_RISCV_REG_MTVEC, &mtvec));
+    OK(uc_ctl_set_architectural_exceptions(uc, 1));
+    OK(uc_ctl_get_architectural_exceptions(uc, &enabled));
+    TEST_CHECK(enabled == 1);
+    OK(uc_hook_add(uc, &h, UC_HOOK_INTR, test_riscv64_ecall_cb, NULL, 1, 0));
+    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));
+
+    OK(uc_reg_read(uc, UC_RISCV_REG_PC, &pc));
+    OK(uc_reg_read(uc, UC_RISCV_REG_MEPC, &mepc));
+    OK(uc_reg_read(uc, UC_RISCV_REG_MCAUSE, &mcause));
+    OK(uc_reg_read(uc, UC_RISCV_REG_PRIV, &priv));
+    TEST_CHECK(pc == mtvec);
+    TEST_CHECK(mepc == code_start);
+    TEST_CHECK(mcause == 11); // machine-mode ecall
+    TEST_CHECK(priv == 3);    // machine mode
+
+    OK(uc_close(uc));
+}
+
 static uint64_t test_riscv32_mmio_map_read_cb(uc_engine *uc, uint64_t offset,
                                               unsigned size, void *data)
 {
@@ -810,6 +840,8 @@ TEST_LIST = {
      test_riscv64_fp_move_from_int_reg_write},
     {"test_riscv64_fp_move_to_int", test_riscv64_fp_move_to_int},
     {"test_riscv64_ecall", test_riscv64_ecall},
+    {"test_riscv32_architectural_exception_entry",
+     test_riscv32_architectural_exception_entry},
     {"test_riscv32_mmio_map", test_riscv32_mmio_map},
     {"test_riscv64_mmio_map", test_riscv64_mmio_map},
     {"test_riscv32_map", test_riscv32_map},

uc.c

@@ -2632,6 +2632,19 @@ uc_err uc_ctl(uc_engine *uc, uc_control_type control, ...)
     va_start(args, control);
 
     switch (type) {
+    case UC_CTL_UC_ARCHITECTURAL_EXCEPTIONS: {
+        if (uc->arch != UC_ARCH_RISCV) {
+            err = UC_ERR_ARCH;
+        } else if (rw == UC_CTL_IO_READ) {
+            int *enabled = va_arg(args, int *);
+            *enabled = uc->architectural_exceptions;
+        } else if (rw == UC_CTL_IO_WRITE) {
+            uc->architectural_exceptions = !!va_arg(args, int);
+        } else {
+            err = UC_ERR_ARG;
+        }
+        break;
+    }
     case UC_CTL_UC_MODE: {
         if (rw == UC_CTL_IO_READ) {
             int *pmode = va_arg(args, int *);