[PATCH v6 3/6] kexec, x86: Fix bzImage real-mode booting

[H. Peter Anvin]

On 12/13/2012 02:18 PM, Yinghai Lu wrote:

> +	if (real_mode_entry) {
> +		/* restore can use heap and load high */
> +		real_mode->loader_flags = 0x81;
> +		if (real_mode->protocol_version >= 0x0201)
> +			real_mode->heap_end_ptr += heap_size - 0x200; /*stack*/
> +	}
> +

This code is wrong: the bits at the bottom of this field (LOADED_HIGH) 
are kernel->bootloader flags.

The right behavior is:

	if (real_mode->protocol_version >= 0x0201) {
		real_mode->loader_flag |= CAN_USE_HEAP;
		real_mode->heap_end_ptr += heap_size - 0x200; /*stack*/
	}


> +		regs16.ds = regs16.es = regs16.fs = regs16.gs = setup_base >> 4;
> +		regs16.cs = regs16.ds + 0x20;
> +		regs16.ip = 0;
> +		/* XXX: Documentation/i386/boot.txt says 'ss' must equal 'ds' */
> +		regs16.ss = (elf_rel_get_addr(&info->rhdr, "stack_end") - 64*1024) >> 4;
> +		/* XXX: Documentation/i386/boot.txt says 'sp' must equal heap_end */
> +		regs16.esp = 0xFFFC;
> +

And, pray tell, why aren't they?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.