Re: [Qemu-devel] [PATCH] fix multiboot loading if load_end_addr == 0 (fwd)

["Serge E. Hallyn" <serge@hallyn.com>]

Quoting Scott Moser (smoser@ubuntu.com):
> Re-sending to qemu-devel.  I'd originally sent this to kvm mailing list.
> 
> 
> ---------- Forwarded message ----------
> Date: Sat, 17 Mar 2012 00:08:06
> From: Scott Moser <smoser@ubuntu.com>
> To: kvm@vger.kernel.org
> Subject: [PATCH] fix multiboot loading if load_end_addr == 0
> 
> The previous code did not treat the case where load_end_addr was 0
> specially.  The multiboot specification says the following:
>  * load_end_addr
>    Contains the physical address of the end of the data segment.
>    (load_end_addr - load_addr) specifies how much data to load. This
>    implies that the text and data segments must be consecutive in the
>    OS image; this is true for existing a.out executable formats. If
>    this field is zero, the boot loader assumes that the text and data
>    segments occupy the whole OS image file.
> 
> This was raised initially as launchpad bug
> https://bugs.launchpad.net/qemu/+bug/957622
> 

Tested-by: Serge Hallyn <serge.hallyn@canonical.com>

> diff --git a/hw/multiboot.c b/hw/multiboot.c
> index b4484a3..b1e04c5 100644
> --- a/hw/multiboot.c
> +++ b/hw/multiboot.c
> @@ -202,10 +202,16 @@ int load_multiboot(void *fw_cfg,
>          uint32_t mh_bss_end_addr = ldl_p(header+i+24);
>          mh_load_addr = ldl_p(header+i+16);
>          uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
> -        uint32_t mb_load_size = mh_load_end_addr - mh_load_addr;
> -
> +        uint32_t mb_load_size = 0;
>          mh_entry_addr = ldl_p(header+i+28);
> -        mb_kernel_size = mh_bss_end_addr - mh_load_addr;
> +
> +        if (mh_load_end_addr) {
> +            mb_kernel_size = mh_bss_end_addr - mh_load_addr;
> +            mb_load_size = mh_load_end_addr - mh_load_addr;
> +        } else {
> +            mb_kernel_size = kernel_file_size - mb_kernel_text_offset;
> +            mb_load_size = mb_kernel_size;
> +        }
> 
>          /* Valid if mh_flags sets MULTIBOOT_HEADER_HAS_VBE.
>          uint32_t mh_mode_type = ldl_p(header+i+32);