feat: add x86 RDRAND instruction hook

include/unicorn/x86.h

@@ -85,6 +85,13 @@ typedef void (*uc_cb_insn_syscall_t)(struct uc_struct *uc, void *user_data);
 //          indicates cpuid instruction will still be executed.
 typedef int (*uc_cb_insn_cpuid_t)(struct uc_struct *uc, void *user_data);
 
+// Callback function for modifying the random value generated by RDRAND.
+// @value: generated random value, which may be modified by the callback.
+// @success: generated random value validity, which may be modified by the callback.
+// @user_data: user data passed to tracing APIs.
+typedef void (*uc_cb_insn_rdrand_t)(struct uc_struct *uc, uint64_t *value,
+                                    bool *success, void *user_data);
+
 //> X86 registers
 typedef enum uc_x86_reg {
     UC_X86_REG_INVALID = 0,

qemu/target/i386/int_helper.c

@@ -23,6 +23,7 @@
 #include "qemu/host-utils.h"
 #include "exec/helper-proto.h"
 #include "qemu/guest-random.h"
+#include "uc_priv.h"
 
 //#define DEBUG_MULDIV
 
@@ -487,9 +488,38 @@ void helper_cr4_testbit(CPUX86State *env, uint32_t bit)
 
 target_ulong HELPER(rdrand)(CPUX86State *env)
 {
-    target_ulong ret;
+    target_ulong ret = 0;
+    bool success;
+    uc_engine *uc = env->uc;
+    struct hook *hook;
+    bool synced = false;
+
+    success = qemu_guest_getrandom(&ret, sizeof(ret)) == 0;
+
+    // Unicorn: call registered RDRAND hooks.
+    HOOK_FOREACH_VAR_DECLARE;
+    HOOK_FOREACH(uc, hook, UC_HOOK_INSN) {
+        if (hook->to_delete)
+            continue;
+        if (!HOOK_BOUND_CHECK(hook, env->eip))
+            continue;
+
+        if (hook->insn == UC_X86_INS_RDRAND) {
+            uintptr_t pc = GETPC();
+            if (!synced && !uc->skip_sync_pc_on_exit && pc) {
+                cpu_restore_state(uc->cpu, pc, false);
+                synced = true;
+            }
+            JIT_CALLBACK_GUARD(
+                ((uc_cb_insn_rdrand_t)hook->callback)(uc, (uint64_t *)&ret,
+                                                      &success, hook->user_data));
+        }
+
+        if (uc->stop_request)
+            break;
+    }
 
-    if (qemu_guest_getrandom(&ret, sizeof(ret)) < 0) {
+    if (!success) {
         // qemu_log_mask(LOG_UNIMP, "rdrand: Crypto failure: %s",
         //               error_get_pretty(err));
         // error_free(err);

qemu/target/i386/unicorn.c

@@ -2041,11 +2041,12 @@ static bool x86_stop_interrupt(struct uc_struct *uc, int intno)
 
 static bool x86_insn_hook_validate(uint32_t insn_enum)
 {
-    // for x86 we can only hook IN, OUT, SYSCALL, SYSENTER, CPUID, RDTSC, RDTSCP, RDMSR and WRMSR
+    // for x86 we can only hook IN, OUT, SYSCALL, SYSENTER, CPUID, RDTSC, RDTSCP, RDRAND, RDMSR and WRMSR
     if (insn_enum != UC_X86_INS_IN && insn_enum != UC_X86_INS_OUT &&
         insn_enum != UC_X86_INS_SYSCALL && insn_enum != UC_X86_INS_SYSENTER &&
         insn_enum != UC_X86_INS_CPUID && insn_enum != UC_X86_INS_RDTSC &&
-        insn_enum != UC_X86_INS_RDTSCP && insn_enum != UC_X86_INS_RDMSR &&
+        insn_enum != UC_X86_INS_RDTSCP && insn_enum != UC_X86_INS_RDRAND &&
+        insn_enum != UC_X86_INS_RDMSR &&
         insn_enum != UC_X86_INS_WRMSR) {
         return false;
     }

tests/unit/test_x86.c

@@ -2377,6 +2377,74 @@ static void test_x86_hook_insn_rdtscp(void)
     OK(uc_close(uc));
 }
 
+static void test_x86_hook_insn_rdrand_cb(uc_engine *uc, uint64_t *value,
+                                          bool *success, void *user_data)
+{
+    (*(int *)user_data)++;
+    *value = 0x0123456789ABCDEF;
+}
+
+static void test_x86_hook_insn_rdrand(void)
+{
+    char code[] = "\x48\x0F\xC7\xF3"; // RDRAND RBX
+    uc_engine *uc;
+    uint64_t rbx = 0;
+    uint64_t eflags = 0;
+    int called = 0;
+    uc_hook hook;
+
+    OK(uc_open(UC_ARCH_X86, UC_MODE_64, &uc));
+    OK(uc_ctl_set_cpu_model(uc, UC_CPU_X86_HASWELL));
+    OK(uc_mem_map(uc, code_start, code_len, UC_PROT_ALL));
+    OK(uc_mem_write(uc, code_start, code, sizeof(code) - 1));
+    OK(uc_hook_add(uc, &hook, UC_HOOK_INSN, test_x86_hook_insn_rdrand_cb, &called,
+                   1, 0, UC_X86_INS_RDRAND));
+    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));
+    OK(uc_hook_del(uc, hook));
+
+    OK(uc_reg_read(uc, UC_X86_REG_RBX, &rbx));
+    OK(uc_reg_read(uc, UC_X86_REG_EFLAGS, &eflags)); // check carry flag is set
+    TEST_CHECK(called == 1);
+    TEST_CHECK(rbx == 0x0123456789ABCDEF);
+    TEST_CHECK((eflags & 1) != 0);
+    OK(uc_close(uc));
+}
+
+static void test_x86_hook_insn_rdrand_failure_cb(uc_engine *uc,
+                                                  uint64_t *value, bool *success,
+                                                  void *user_data)
+{
+    (*(int *)user_data)++;
+    *success = false;
+}
+
+static void test_x86_hook_insn_rdrand_failure(void)
+{
+    char code[] = "\x48\x0F\xC7\xF3"; // RDRAND RBX
+    uc_engine *uc;
+    uint64_t rbx = 1;
+    uint64_t eflags = 0;
+    int called = 0;
+    uc_hook hook;
+
+    OK(uc_open(UC_ARCH_X86, UC_MODE_64, &uc));
+    OK(uc_ctl_set_cpu_model(uc, UC_CPU_X86_HASWELL));
+    OK(uc_mem_map(uc, code_start, code_len, UC_PROT_ALL));
+    OK(uc_mem_write(uc, code_start, code, sizeof(code) - 1));
+    OK(uc_hook_add(uc, &hook, UC_HOOK_INSN,
+                   test_x86_hook_insn_rdrand_failure_cb, &called, 1, 0,
+                   UC_X86_INS_RDRAND));
+    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));
+    OK(uc_hook_del(uc, hook));
+
+    OK(uc_reg_read(uc, UC_X86_REG_RBX, &rbx));
+    OK(uc_reg_read(uc, UC_X86_REG_EFLAGS, &eflags));
+    TEST_CHECK(called == 1);
+    TEST_CHECK(rbx == 0);
+    TEST_CHECK((eflags & 1) == 0);
+    OK(uc_close(uc));
+}
+
 static int test_x86_hook_insn_wrmsr_cb(uc_engine *uc, void *user_data)
 {
     *(int *)user_data = 1;
@@ -2802,6 +2870,8 @@ TEST_LIST = {
     {"test_x86_ro_segfault", test_x86_ro_segfault},
     {"test_x86_hook_insn_rdtsc", test_x86_hook_insn_rdtsc},
     {"test_x86_hook_insn_rdtscp", test_x86_hook_insn_rdtscp},
+    {"test_x86_hook_insn_rdrand", test_x86_hook_insn_rdrand},
+    {"test_x86_hook_insn_rdrand_failure", test_x86_hook_insn_rdrand_failure},
     {"test_x86_hook_insn_wrmsr", test_x86_hook_insn_wrmsr},
     {"test_x86_hook_insn_rdmsr", test_x86_hook_insn_rdmsr},
     {"test_x86_dr7", test_x86_dr7},