util/clock.c: Apply clock skew

SEGA games are unplayable between 03:00 and 07:00 local time due
to a network maintenance period that is hard-coded into the games
themselves (no, guest play is not available).

Deal with this by slowing down time to avoid 02:00 (the time when
a warning appears and new credits eventually start being rejected),
then jump forward to sync up with real time when 07:00 hits.

chunihook/dllmain.c

@@ -43,7 +43,8 @@ static DWORD CALLBACK chuni_pre_startup(void)
 
     /* Hook Win32 APIs */
 
-    clock_hook_init();
+    clock_set_hook_init();
+    clock_skew_hook_init();
     gfx_hook_init();
     serial_hook_init();
 

minihook/dllmain.c

@@ -5,6 +5,7 @@
 #include "nu/ds.h"
 #include "nu/nusec.h"
 
+#include "util/clock.h"
 #include "util/dprintf.h"
 
 static process_entry_t app_startup;
@@ -15,6 +16,7 @@ static DWORD CALLBACK app_pre_startup(void)
 
     ds_hook_init();
     nusec_hook_init();
+    clock_skew_hook_init();
 
     dprintf("---  End  %s ---\n", __func__);
 

util/clock.c

@@ -1,39 +1,201 @@
+#include <windows.h>
+
+#include <stdint.h>
+
 #include "hook/table.h"
 
 #include "util/dprintf.h"
 
-static BOOL WINAPI my_SetSystemTime(void *whatever);
+static void WINAPI my_GetSystemTimeAsFileTime(FILETIME *out);
-static BOOL WINAPI my_SetTimeZoneInformation(void *whatever);
+static BOOL WINAPI my_GetLocalTime(SYSTEMTIME *out);
+static BOOL WINAPI my_GetSystemTime(SYSTEMTIME *out);
+static DWORD WINAPI my_GetTimeZoneInformation(TIME_ZONE_INFORMATION *tzinfo);
+static BOOL WINAPI my_SetSystemTime(SYSTEMTIME *in);
+static BOOL WINAPI my_SetTimeZoneInformation(TIME_ZONE_INFORMATION *tzinfo);
 
-static const struct hook_symbol clock_hook_syms[] = {
+static BOOL (WINAPI * next_GetSystemTimeAsFileTime)(FILETIME *out);
+static int64_t clock_current_day;
+
+static const struct hook_symbol clock_skew_hook_syms[] = {
+    /* Canonical time */
+
+    {
+        .name   = "GetSystemTimeAsFileTime",
+        .patch  = my_GetSystemTimeAsFileTime,
+        .link   = (void **) &next_GetSystemTimeAsFileTime,
+    },
+
+    /* Derived time */
+
+    {
+        .name   = "GetLocalTime",
+        .patch  = my_GetLocalTime,
+    }, {
+        .name   = "GetSystemTime",
+        .patch  = my_GetSystemTime,
+    }, {
+        .name   = "GetTimeZoneInformation",
+        .patch  = my_GetTimeZoneInformation,
+    },
+};
+
+static const struct hook_symbol clock_set_hook_syms[] = {
     {
         .name   = "SetSystemTime",
         .patch  = my_SetSystemTime,
     }, {
         .name   = "SetTimeZoneInformation",
         .patch  = my_SetTimeZoneInformation,
-    }
+    },
 };
 
-void clock_hook_init(void)
+/* FILETIME is expressed in 100ns i.e. 0.1us i.e. 10^-7 sec units.
+   No official name for these units is given so let's call them "jiffies". */
+
+static const int64_t jiffies_per_sec = 10000000LL;
+static const int64_t jiffies_per_hour = jiffies_per_sec * 3600LL;
+static const int64_t jiffies_per_day = jiffies_per_hour * 24LL;
+
+static void WINAPI my_GetSystemTimeAsFileTime(FILETIME *out)
 {
-    hook_table_apply(
+    FILETIME in;
-            NULL,
+    int64_t day;
-            "kernel32.dll",
+    int64_t real_jiffies;
-            clock_hook_syms,
+    int64_t real_jiffies_biased;
-            _countof(clock_hook_syms));
+    int64_t real_time;
+    int64_t fake_time;
+    int64_t fake_jiffies_biased;
+    int64_t fake_jiffies;
+
+    if (out == NULL) {
+        SetLastError(ERROR_INVALID_PARAMETER);
+
+        return;
+    }
+
+    /* Get and convert real jiffies */
+
+    next_GetSystemTimeAsFileTime(&in);
+    real_jiffies = (((int64_t) in.dwHighDateTime) << 32) | in.dwLowDateTime;
+
+    /* Apply bias: shift [02:00, 07:00) to [19:00, 24:00) */
+
+    real_jiffies_biased = real_jiffies + 17LL * jiffies_per_hour;
+
+    /* Split date and time */
+
+          day = real_jiffies_biased / jiffies_per_day;
+    real_time = real_jiffies_biased % jiffies_per_day;
+
+    /* Debug log */
+
+    if (clock_current_day != 0 && clock_current_day != day) {
+        dprintf("\n*** CLOCK JUMP! ***\n\n");
+    }
+
+    clock_current_day = day;
+
+    /* We want to skip the final five hours, so scale time-of-day by 19/24. */
+
+    fake_time = (real_time * 19LL) / 24LL;
+
+    /* Un-split date and time */
+
+    fake_jiffies_biased = day * jiffies_per_day + fake_time;
+
+    /* Remove bias */
+
+    fake_jiffies = fake_jiffies_biased - 17LL * jiffies_per_hour;
+
+    /* Return result */
+
+    out->dwLowDateTime  = fake_jiffies;
+    out->dwHighDateTime = fake_jiffies >> 32;
 }
 
-static BOOL WINAPI my_SetSystemTime(void *whatever)
+static BOOL WINAPI my_GetLocalTime(SYSTEMTIME *out)
+{
+    /* Use UTC to simplify things */
+    return my_GetSystemTime(out);
+}
+
+static BOOL WINAPI my_GetSystemTime(SYSTEMTIME *out)
+{
+    FILETIME linear;
+    BOOL ok;
+
+    my_GetSystemTimeAsFileTime(&linear);
+    ok = FileTimeToSystemTime(&linear, out);
+
+    if (!ok) {
+        return ok;
+    }
+
+#if 0
+    static int last_second;
+
+    if (out->wSecond != last_second) {
+        dprintf("%04i/%02i/%02i %02i:%02i:%02i\n",
+                out->wYear,
+                out->wMonth,
+                out->wDay,
+                out->wHour,
+                out->wMinute,
+                out->wSecond);
+    }
+
+    last_second = out->wSecond;
+#endif
+
+    return TRUE;
+}
+
+static DWORD WINAPI my_GetTimeZoneInformation(TIME_ZONE_INFORMATION *tzinfo)
+{
+    /* Use UTC to simplify things */
+
+    dprintf("%s\n", __func__);
+
+    if (tzinfo != NULL) {
+        memset(tzinfo, 0, sizeof(*tzinfo));
+        SetLastError(ERROR_SUCCESS);
+
+        return TIME_ZONE_ID_UNKNOWN;
+    } else {
+        SetLastError(ERROR_INVALID_PARAMETER);
+
+        return TIME_ZONE_ID_INVALID;
+    }
+}
+
+static BOOL WINAPI my_SetSystemTime(SYSTEMTIME *in)
 {
     dprintf("Prevented application from screwing with the system clock\n");
 
     return TRUE;
 }
 
-static BOOL WINAPI my_SetTimeZoneInformation(void *whatever)
+static BOOL WINAPI my_SetTimeZoneInformation(TIME_ZONE_INFORMATION *in)
 {
     dprintf("Prevented application from screwing with the timezone\n");
 
     return TRUE;
 }
+
+void clock_set_hook_init(void)
+{
+    hook_table_apply(
+            NULL,
+            "kernel32.dll",
+            clock_set_hook_syms,
+            _countof(clock_set_hook_syms));
+}
+
+void clock_skew_hook_init(void)
+{
+    hook_table_apply(
+            NULL,
+            "kernel32.dll",
+            clock_skew_hook_syms,
+            _countof(clock_skew_hook_syms));
+}

util/clock.h

@@ -1,3 +1,4 @@
 #pragma once
 
-void clock_hook_init(void);
+void clock_set_hook_init(void);
+void clock_skew_hook_init(void);