[PATCH 059/112] efi: payload: init: restrict barebox mem to first 1G only on x86

[Michael Olbrich]

On Wed, Jan 03, 2024 at 07:12:19PM +0100, Ahmad Fatoum wrote:
> When run as EFI payload, barebox will not have full access to DRAM and will
> have to ask the EFI firmware for memory. It does so once at the beginning
> and since commit 356aaef5a37d ("efi: improve malloc pool allocation"),
> the buffer was always placed beneath the 1G boundary.
> 
> Aforementioned commit didn't elaborate why a maximum of 1G in particular
> was chosen. Anyways, non-PC architectures have different memory maps, so
> a 1G limit doesn't make sense there. Therefore restrict the limit to
> ARCH_X86. On non-x86, we allow the memory pages to be located anywhere.

The 1G is somewhat arbitrary but if you don't restrict the memory to 32bit,
then loading the kernel may fail: The addresses in "struct
linux_kernel_header" are only 32bit. So if you impose no restrictions at
all, then this memory cannot be used for the kernel and initrd.

Regards,
Michael

> This can break PCI drivers on systems that so far assumed barebox memory
> is located in the first 4G, but that's ok. That code will need to be
> fixed eventually anyway.
> 
> Cc: Michael Olbrich <m.olbrich at pengutronix.de>
> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
> ---
>  efi/payload/init.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/efi/payload/init.c b/efi/payload/init.c
> index 4b612e61afb3..0c2f38e9c86a 100644
> --- a/efi/payload/init.c
> +++ b/efi/payload/init.c
> @@ -292,7 +292,7 @@ void efi_main(efi_handle_t image, struct efi_system_table *sys_table)
>  		BS->handle_protocol(efi_loaded_image->device_handle,
>  				&efi_device_path_protocol_guid, (void **)&efi_device_path);
>  
> -	mem = 0x3fffffff;
> +	mem = IS_ENABLED(CONFIG_X86) ? 0x3fffffff : ~0ULL;
>  	for (memsize = SZ_256M; memsize >= SZ_8M; memsize /= 2) {
>  		efiret  = BS->allocate_pages(EFI_ALLOCATE_MAX_ADDRESS,
>  					     EFI_LOADER_DATA,
> -- 
> 2.39.2
> 
> 

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