add gen_constants to generate IOCTL constants; add generated file

pkg/entropy/constants_linux.go

@@ -0,0 +1,14 @@
+// generated by gen_constants.c
+
+package entropy
+
+const (
+	RNDGETENTCNT   = 0x80045200
+	RNDADDTOENTCNT = 0x40045201
+	RNDGETPOOL     = 0x80085202
+	RNDADDENTROPY  = 0x40085203
+	RNDZAPENTCNT   = 0x5204
+	RNDCLEARPOOL   = 0x5206
+	RNDRESEEDCRNG  = 0x5207
+)
+

pkg/entropy/entropy_linux.go

@@ -2,6 +2,7 @@ package entropy
 
 import (
 	"fmt"
+	"syscall"
 	"unsafe"
 
 	"golang.org/x/sys/unix"
@@ -9,17 +10,6 @@ import (
 
 var entropy_device = "/dev/urandom"
 
-/* from linux/random.h */
-const (
-	RNDGETENTCNT   = 0b10>>30 | 'R'>>8 | 1>>16
-	RNDADDTOENTCNT = 0x01
-	RNDGETPOOL     = 0x02
-	RNDADDENTROPY  = 0x03
-	RNDZAPENTCNT   = 0x04
-	RNDCLEARPOOL   = 0x06
-	RNDRESEEDCRNG  = 0x07
-)
-
 // this is honestly easier through /proc, but in the spirit of completeness...
 func getEntropy() (ent int, err error) {
 	var fd int
@@ -28,13 +18,11 @@ func getEntropy() (ent int, err error) {
 	}
 	defer unix.Close(fd)
 
-	/*
+	var errno syscall.Errno
-		nrshift 0
+	_, _, errno = unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(RNDGETENTCNT), uintptr(unsafe.Pointer(&ent)))
-		typeshift 8
+	if errno != 0 {
-		sizeshift 16
+		err = errno
-		dirshift 30
+	}
-	*/
-	_, _, err = unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(RNDGETENTCNT), uintptr(unsafe.Pointer(&ent)))
 	return
 }
 

pkg/entropy/util/gen_constants.c

@@ -0,0 +1,34 @@
+// This simple program writes constants.go 
+// It uses the Linux headers to generate these contatns.
+
+#include <fcntl.h>
+#include <linux/random.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+const char * filename = "constants_linux.go";
+
+int main() {
+    int fd;
+    printf("Generating constants for entropy IOCTLs.\n");
+    fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0644);
+    if( fd == -1 ) {
+        printf("Failed to open output file: %s\n", filename);
+        return -1;
+    }
+    dprintf(fd, "// generated by gen_constants.c\n\n");
+    dprintf(fd, "package entropy\n\n");
+    dprintf(fd, "const (\n");
+    dprintf(fd, "\tRNDGETENTCNT   = %#x\n", RNDGETENTCNT);
+    dprintf(fd, "\tRNDADDTOENTCNT = %#x\n", RNDADDTOENTCNT);
+    dprintf(fd, "\tRNDGETPOOL     = %#x\n", RNDGETPOOL);
+    dprintf(fd, "\tRNDADDENTROPY  = %#x\n", RNDADDENTROPY);
+    dprintf(fd, "\tRNDZAPENTCNT   = %#x\n", RNDZAPENTCNT);
+    dprintf(fd, "\tRNDCLEARPOOL   = %#x\n", RNDCLEARPOOL);
+    dprintf(fd, "\tRNDRESEEDCRNG  = %#x\n", RNDRESEEDCRNG);
+    dprintf(fd, ")\n\n");
+    close(fd);
+    return 0;
+}