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

[Michael Olbrich]

On Thu, Jan 04, 2024 at 12:17:12PM +0100, Ahmad Fatoum wrote:
> On 03.01.24 19:58, Michael Olbrich wrote:
> > 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.
> 
> The limit for x86 remains at 1G. It's only for other architectures, that we
> remove the limit. I suspect that other architectures won't have this kind
> of problems though , because they would boot the kernel image via EFI load
> and start image boot services, where the EFI firmware takes care to layout
> the boot artifacts.
> 
> Once we have that in place, we could even use it on x86 instead of
> using struct linux_kernel_header, but I haven't investigated this yet.

How do you load the initrd via EFI? As far as I know, that only works as a
filename in the EFI boot partition. That was the reason for implementing
the "legacy" boot mode. And what about the device-tree?

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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> 

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Pengutronix e.K.                           |                             |
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