Re: [OpenBIOS] x86 multiboot header?

[Nathan Kunkee]

> Date: Tue, 21 Sep 2010 10:07:19 +0100
> From: [e-mail]
> To: [e-mail]
> Subject: Re: [OpenBIOS] x86 multiboot header?
>
> Nathan Kunkee wrote:
> > Hi all,
> >
> > As of revision 861, I am unable to build a working multiboot image. I am working on Ubuntu 10.4, gcc 4.4. Although OpenSolaris b134, gcc4, also doesn't work.
> >
> > Grub 1.95 doesn't recognize the file as a multiboot file. QEMU crashes when passed this via -kernel (something about running code near 0xa000). Sure enough, I can find the second header for 0x2BAD but not 0x1BAD. Is the linker script that prefixes the header off?
> >
> > Thank you in advance for any assistance!
> > Nathan
>
> Interesting. Did you find r861 as the result of an SVN bisect? If so,
> posting a link to your test image so that someone could debug this would
> be very helpful.
>
> ATB,
>
> Mark.

Hello,

I should have said "As of the latest commit (r861)..." since I wanted to convey that I'd tried the latest sources, not that a particular revision introduced this, nor that I found it with a bisect.

I found the following change enabled the multiboot image to load with the embedded utils/iso/boot/grub:

Index: arch/x86/multiboot.c
===================================================================
--- arch/x86/multiboot.c    (revision 872)
+++ arch/x86/multiboot.c    (working copy)
@@ -15,8 +15,10 @@
     unsigned int magic, flags, checksum;
 };
 
-static const struct mbheader multiboot_header
-    __attribute__((section (".hdr"))) =
+//static 
+const struct mbheader multiboot_header
+    __attribute__ ((section (".hdr"))) 
+=
 {
     MULTIBOOT_HEADER_MAGIC,
     MULTIBOOT_HEADER_FLAGS,

However, even with this, qemu doesn't successfully load the multiboot image:

nathan@fangorn:~/openbios-devel/obj-x86$ /usr/local/build/qemu/i386-softmmu/qemu -L /usr/local/src/qemu/pc-bios/ -kernel openbios.multiboot -initrd openbios-x86.dict
qemu: I believe we found a multiboot image!
multiboot: mh_header_addr = 0
multiboot: mh_load_addr = 0x8
multiboot: mh_load_end_addr = 0x9
multiboot: mh_bss_end_addr = 0x1
qemu: loading multiboot kernel (0x14d28 bytes) at 0x8
multiboot loading module: openbios-x86.dict
mod00: 00016008 - 0002dd44
mod_start: 0x9b73cd0
mod_end:   0x9b8ba0c
cmdline: 00015018
multiboot: mh_entry_addr = 0x42464c45
mb_buf_phys   = 00000008
mod_start     = 00016008
mb_mods_count = 1
qemu: fatal: Trying to execute code outside RAM or ROM at 0x42464c45

I've uploaded a zip (openbios-multi.zip) to http://filebin.ca/boqpcs/openbios-multi.zip [filebin.ca] if you'd like to look at my test image.

Thank you for your assistance!
Nathan

x86 multiboot header?

[Mark Cave-Ayland]

Nathan Kunkee wrote:
> However, even with this, qemu doesn't successfully load the multiboot image:
>
> nathan@fangorn:~/openbios-devel/obj-x86$ /usr/local/build/qemu/i386-softmmu/qemu -L /usr/local/src/qemu/pc-bios/ -kernel openbios.multiboot -initrd openbios-x86.dict
> qemu: I believe we found a multiboot image!
> multiboot: mh_header_addr = 0
> multiboot: mh_load_addr = 0x8
> multiboot: mh_load_end_addr = 0x9
> multiboot: mh_bss_end_addr = 0x1
> qemu: loading multiboot kernel (0x14d28 bytes) at 0x8
> multiboot loading module: openbios-x86.dict
> mod00: 00016008 - 0002dd44
> mod_start: 0x9b73cd0
> mod_end:   0x9b8ba0c
> cmdline: 00015018
> multiboot: mh_entry_addr = 0x42464c45
> mb_buf_phys   = 00000008
> mod_start     = 00016008
> mb_mods_count = 1
> qemu: fatal: Trying to execute code outside RAM or ROM at 0x42464c45
>
> I've uploaded a zip (openbios-multi.zip) to http://filebin.ca/boqpcs/openbios-multi.zip [filebin.ca] if you'd like to look at my test image.
>
> Thank you for your assistance!
> Nathan

Hi Nathan,

Thanks for the detailed information. Is there any chance that you can 
keep a constant QEMU version and then svn bisect OpenBIOS until you find 
the last version that works? Otherwise looking at the information above, 
I'm going to struggle to find the time to do this part myself :(

ATB,

Mark.