Fix fake kernel entropy being entirely static.

kernel/random.cpp

@@ -24,19 +24,42 @@
 
 #include <errno.h>
 
+#include <sortix/clock.h>
+
 #include <sortix/kernel/copy.h>
+#include <sortix/kernel/interlock.h>
 #include <sortix/kernel/syscall.h>
+#include <sortix/kernel/time.h>
 
 namespace Sortix {
 
+static unsigned long sequence = 0;
+
 int sys_getentropy(void* user_buffer, size_t size)
 {
-	unsigned char buffer[256];
+	union
+	{
+		unsigned char buffer[256];
+		struct
+		{
+			struct timespec realtime;
+			struct timespec monotonic;
+			unsigned long sequence;
+		} seed;
+	};
 	if ( sizeof(buffer) < size )
 		return errno = EIO, -1;
 	// TODO: SECURITY: We need to actually gather entropy and deliver it.
 	for ( size_t i = 0; i < size; i++ )
 		buffer[i] = i;
+	// NOTE: This is not random and is not meant to be random, this is just
+	//       meant to make the returned entropy a little different each time
+	//       until we have real randomness, even across reboots. The userland
+	//       arc4random mixer will mix it around and the produced streams will
+	//       look random and should not repeat in practice.
+	seed.realtime = Time::Get(CLOCK_REALTIME);
+	seed.monotonic = Time::Get(CLOCK_MONOTONIC);
+	seed.sequence = InterlockedIncrement(&sequence).o;
 	if ( !CopyToUser(user_buffer, buffer, size) )
 		return -1;
 	return 0;