Re: [Qemu-devel] [patch] Remove requirement for -hda with -kernel

[Ross Kendall Axe <ross@axe.homelinux.net>]

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Fabrice Bellard wrote:
> 
> Ross Kendall Axe wrote:
> 
>> The requirement to provide an -hda argument when doing a direct boot of
>> a linux kernel has irritated me for some time.  This patch removes that
>> requirement by creating a temporary 1 sector hda as needed.
>>
>> Ross
>
> I like the idea, but your patch may not compile for win32. Maybe
> creating a generic "dummy:[size]" block device would be interesting
> instead ?
>
> Fabrice.

Good point. It wouldn't compile, and, even if it did, it wouldn't run
correctly. Attached is a patch that *should* work.

The dummy block device idea is interesting. I'll see if I can implement
that; hopefully it won't be too difficult. However, IHMO a better,
albeit more ambitious solution would be to load the Linux boot code into
an emulated boot PROM.

Ross



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Index: hw/pc.c
===================================================================
RCS file: /cvsroot/qemu/qemu/hw/pc.c,v
retrieving revision 1.35
diff -u -p -r1.35 pc.c
--- hw/pc.c	15 Jan 2005 12:02:56 -0000	1.35
+++ hw/pc.c	28 Apr 2005 23:36:13 -0000
@@ -446,8 +446,40 @@ void pc_init(int ram_size, int vga_ram_s
         uint8_t old_bootsect[512];
 
         if (bs_table[0] == NULL) {
-            fprintf(stderr, "A disk image must be given for 'hda' when booting a Linux kernel\n");
-            exit(1);
+#ifdef WIN32
+	    char tmpfilename[L_tmpnam];
+#else
+	    char tmpfilename[] = "/tmp/qemu.XXXXXX";
+	    int tmpfilefd;
+#endif
+	    FILE *tmpfile;
+
+            fprintf(stderr, "qemu: Disk image not given for 'hda' when booting"
+                    " a Linux kernel; inventing one\n");
+#ifdef WIN32
+	    tmpnam(tmpfilename);
+	    tmpfile = fopen(tmpfilename, "wb");
+#else
+	    tmpfilefd = mkstemp(tmpfilename);
+	    tmpfile = (tmpfilefd == -1) ? NULL : fdopen(tmpfilefd, "wb");
+#endif
+            if(!tmpfile) {
+                fprintf(stderr, "qemu: couldn't create temporary diskimage\n");
+                exit(1);
+            }
+            fseek(tmpfile, 511, SEEK_SET);
+            fputc('0', tmpfile);
+            fclose(tmpfile);
+            bs_table[0] = bdrv_new("hda");
+            if (bdrv_open(bs_table[0], tmpfilename, 0) < 0) {
+                fprintf(stderr, "qemu: could not load temporary diskimage '%s'\n",
+                        tmpfilename);
+                exit(1);
+            }
+#ifndef WIN32
+            unlink(tmpfilename);
+#endif
+            boot_device = 'c';
         }
         snprintf(buf, sizeof(buf), "%s/%s", bios_dir, LINUX_BOOT_FILENAME);
         ret = load_image(buf, bootsect);

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