在 2022/5/20 14:52, Ard Biesheuvel 写道:
On Thu, 19 May 2022 at 13:09, mawupeng <mawupeng1@xxxxxxxxxx> wrote:
在 2022/5/7 17:28, mawupeng 写道:
在 2022/5/3 17:58, Ard Biesheuvel 写道:
On Tue, 19 Apr 2022 at 08:43, Wupeng Ma <mawupeng1@xxxxxxxxxx> wrote:
From: Ma Wupeng <mawupeng1@xxxxxxxxxx>
Now system image will perfer to be located to mirrored regions both KASLR
on and off.
Hello Ma Wupeng,
I wonder if we could simplify this as follows:
- ignore the non-KASLR case for now, and rely on the bootloader > load the image into mirrored memory if it exists;
In grub, memory for static image is allocated via the following path:
grub_cmd_linux
kernel = grub_malloc(filelen)
kernel_alloc_addr = grub_efi_allocate_any_pages (kernel_alloc_pages)
grub_memcpy (kernel_addr, kernel, grub_min(filelen, kernel_size))
grub_loader_set (grub_linux_boot, grub_linux_unload, 0)
Can we get memory from mirrored region by the following steps:
1. get memory map by calling grub_efi_get_memory_map()
2. iter all memory map to find a suitable mirrored memory area
3. locate kernel image to this area
So, if kaslr is not enabled
- grub will load kernel into mirrored region
else
- arm64-stub.c will relocate kernel image to mirrored region
Is this feasible?
Is this a feasible proposal to relocate the static kernel image itself
into more reliable memory?
I'm not sure, it all depends on the firmware.
When GRUB calls LoadImage(), the firmware will reallocate the image
and unpack it there. So it is really the firmware's job to ensure that
the image is loaded into a suitable location.
I have some code here that implements a EFI based decompressor, and
which loads the kernel image into mirrored memory if it exists,
without the need to move it again. It could trivially be modified to
deal with non-randomized loads as well.
But the bottom line is that UEFI should expose the ability to target
mirrored memory, hacking around it like this is not a sustainable
approach.
Since firmware is responsible for put kernel static image into mirrored
region and kernel is responsible for relocate this image into mirrored
region if kaslr is enabled. There is no conflict between these two.
Can we integrate the kernel part(introduce mirrored support to arm64) first?
.
