This is a simple patch to parse and read the multiboot table in libpayload. It doesn't do much more then read the memory map for now, but the important thing is that we are storing off %eax and %ebx in the init code and using it when we need it.
The next step is probably an API where upon a multiboot aware payload could insert new things into the table (say, the drive structure, or the cmdline or other interesting information), and then pass it to a child payload.
I'm not sure what else we would need to do to libpayload so that grub will load the payloads, but I'm sure Robert will enlighten us.
Jordan
On Thu, Sep 25, 2008 at 12:51:47PM -0600, Jordan Crouse wrote:
This is a simple patch to parse and read the multiboot table in libpayload. It doesn't do much more then read the memory map for now, but the important thing is that we are storing off %eax and %ebx in the init code and using it when we need it.
Nice!
The next step is probably an API where upon a multiboot aware payload could insert new things into the table (say, the drive structure, or the cmdline or other interesting information), and then pass it to a child payload.
If you want to preserve the table for future use, I recommend that you copy it early in the code. Per spec the loader doesn't make any promises on its location (other than not overwriting your code with it, of course).
I'm not sure what else we would need to do to libpayload so that grub will load the payloads, but I'm sure Robert will enlighten us.
You also need a Multiboot header in the resulting image. It has to be 32bit-aligned and in the first 8k. For what your patch does, the following should suffice:
0x1BADB002 (magic) 0x00000002 (flag for memory info) (-0x1BADB002 -0x00000002) (checksum)
For details see http://www.gnu.org/software/grub/manual/multiboot/html_node/Header-layout.ht...
On 25/09/08 22:02 +0200, Robert Millan wrote:
On Thu, Sep 25, 2008 at 12:51:47PM -0600, Jordan Crouse wrote:
This is a simple patch to parse and read the multiboot table in libpayload. It doesn't do much more then read the memory map for now, but the important thing is that we are storing off %eax and %ebx in the init code and using it when we need it.
Nice!
The next step is probably an API where upon a multiboot aware payload could insert new things into the table (say, the drive structure, or the cmdline or other interesting information), and then pass it to a child payload.
If you want to preserve the table for future use, I recommend that you copy it early in the code. Per spec the loader doesn't make any promises on its location (other than not overwriting your code with it, of course).
Right - I thought about this during lunch, and the more I think about it, the more I think we're going to have to end up rewriting ithe tables for reentrant payloads (I totally made that term up) like bayou that will need to exclude themselves from memory so they don't get blown away.
I'm not sure what else we would need to do to libpayload so that grub will load the payloads, but I'm sure Robert will enlighten us.
You also need a Multiboot header in the resulting image. It has to be 32bit-aligned and in the first 8k. For what your patch does, the following should suffice:
0x1BADB002 (magic) 0x00000002 (flag for memory info) (-0x1BADB002 -0x00000002) (checksum)
For details see http://www.gnu.org/software/grub/manual/multiboot/html_node/Header-layout.ht...
Okay - I'll add that if I get a chance.
Jordan
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Jordan Crouse -
Robert Millan