boot_loader_openfirmware: Fix system_time()

system_time() was based on of_milliseconds(), which returns the number of
milliseconds since power-on. This would produce very similar or identical
results for subsequent boots due to limited clock resolution; therefore it
was unsuited as PRNG seed, e.g., for TCP ports.

Try to inquire the RTC device node with get-time to return an improved time
value, if possible.

Closes ticket #6061.

Changes from proposed patch:
* Obtain the RTC handle once and reuse it for each inquiry.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@38465 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/system/boot/platform/openfirmware/real_time_clock.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright 2006, Ingo Weinhold <[email protected]>.
+ * Copyright 2010, Andreas Färber <[email protected]>
  * All rights reserved. Distributed under the terms of the MIT License.
  */
 
@@ -14,6 +15,9 @@
 #include <platform/openfirmware/openfirmware.h>
 
 
+int gRTC = OF_FAILED;
+
+
 status_t
 init_real_time_clock(void)
 {
@@ -26,6 +30,12 @@ init_real_time_clock(void)
 		return B_ERROR;
 	}
 
+	gRTC = of_open(gKernelArgs.platform_args.rtc_path);
+	if (gRTC == OF_FAILED) {
+		printf("%s(): Could not open RTC device!\n", __func__);
+		return B_ERROR;
+	}
+
 	return B_OK;
 }
 

src/system/boot/platform/openfirmware/real_time_clock.h

@@ -12,6 +12,8 @@
 extern "C" {
 #endif
 
+extern int gRTC;
+
 status_t init_real_time_clock(void);
 
 #ifdef __cplusplus

src/system/boot/platform/openfirmware/support.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright 2005, Ingo Weinhold <[email protected]>.
+ * Copyright 2010, Andreas Färber <[email protected]>
  * All rights reserved. Distributed under the terms of the MIT License.
  */
 
@@ -8,10 +9,27 @@
 
 #include <platform/openfirmware/openfirmware.h>
 
+#include "real_time_clock.h"
+
 
 bigtime_t
 system_time(void)
 {
-	int result = of_milliseconds();
+	int milliseconds = of_milliseconds();
-	return (result == OF_FAILED ? 0 : bigtime_t(result) * 1000);
+	if (milliseconds == OF_FAILED)
+		milliseconds = 0;
+	bigtime_t result = milliseconds;
+	int second, minute, hour, day, month, year;
+	if (gRTC != OF_FAILED) {
+		if (of_call_method(gRTC, "get-time", 0, 6, &year, &month, &day,
+ 				&hour, &minute, &second) != OF_FAILED) {
+ 			result %= 1000;
+ 			int days = day;
+				// TODO: Apply algorithm from kernel
+				// to assure monotonically increasing date.
+ 			result += (((days * 24 + hour) * 60ULL + minute) * 60ULL + second)
+				* 1000ULL;
+		}
+	}
+	return result * 1000;
 }