[Qemu-devel] qemu -boot d -cdrom /dev/cd0 on FreeBSD is not good

[Juergen Lock]

On Tue, Nov 16, 2004 at 02:48:34AM +0900, Norikatsu Shigemura wrote:
> 	I tried to install Windows XP SP2 on qemu over FreeBSD 6-current
> 	like following command, but failed.
> 
> 	# qemu -boot d -cdrom /dev/cd0 windows.img
> 
Yeah physical cdroms don't work currently as mentioned in the pkg-message...

> 	Because find_image_format on qemu/block.c is failed.  This
> 	problem can be confirmed like following program.
> - - - - - - - - - - - - - - - - - - - - - - - -
> #include <fcntl.h>
> #include <unistd.h>
> #include <stdio.h>
> int main(void)
> {
> 	char buf[2048];
> 	int fd = open("/dev/cd0", O_RDONLY);
> 	if(  read(fd, buf, sizeof(buf)) < 0  )  {	/* no problem */
> 		perror("[1] read error.");
> 	}
> 	if(  read(fd, buf, sizeof(buf) / 2) < 0  )  {	/* problem */
> 		perror("[2] read error.");
> 	}
> }
> - - - - - - - - - - - - - - - - - - - - - - - -
> 
> 	Adhoc-ly, I changed "buf" size to 2048. and confirmed this
> 	problem was fixed.
> - - - - - - - - - - - - - - - - - - - - - - - -
> static BlockDriver *find_image_format(const char *filename)
> {
>     int fd, ret, score, score_max;
>     BlockDriver *drv1, *drv;
>     uint8_t buf[1024];					=> buf[2048]
> (snip)
>     ret = read(fd, buf, sizeof(buf));
>     if (ret < 0) {
>         close(fd);
>         return NULL;
>     }
> (snip)
> - - - - - - - - - - - - - - - - - - - - - - - -
> Obtained from:	qemu-0.6.1
> 

 That's all there is to it?  Heh.  Antony made it sound like it needs
much more! :)

> 	I think magic number 2048 is sector size, but I don't know
> 	how to get valid read size.  Anyone, do you have any idea?
> 

 On 5.x and later you can use the DIOCGSECTORSIZE ioctl.  Here's
the relevant part of the patch I'll use in the next port update:

Index: qemu/block.c
@@ -103,14 +103,25 @@
 {
     int fd, ret, score, score_max;
     BlockDriver *drv1, *drv;
-    uint8_t buf[1024];
+    uint8_t *buf;
+    size_t bufsize = 1024;
+    u_int sectorsize = 512;
 
     fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
     if (fd < 0)
         return NULL;
-    ret = read(fd, buf, sizeof(buf));
+#ifdef DIOCGSECTORSIZE
+    if (!ioctl(fd, DIOCGSECTORSIZE, &sectorsize) &&
+        sectorsize > bufsize)
+        bufsize = sectorsize;
+#endif
+    buf = malloc(bufsize);
+    if (!buf)
+        return NULL;
+    ret = read(fd, buf, bufsize);
     if (ret < 0) {
         close(fd);
+        free(buf);
         return NULL;
     }
     close(fd);
@@ -124,6 +135,7 @@
             drv = drv1;
         }
     }
+    free(buf);
     return drv;
 }
 
 Cheers,
	Juergen