On Tue, 21 May 2024 at 17:42, Jiaxun Yang jiaxun.yang@flygoat.com wrote:
在2024年5月21日五月 下午2:58，Ilias Apalodimas写道：
Hi Jiaxun,
On Fri, 17 May 2024 at 19:33, Jiaxun Yang jiaxun.yang@flygoat.com wrote:
Allow runtime relocate to be disabled because on MIPS we never do that. It's guaranteed that OS won't call set_virtual_address_map and convert_pointer as well.
Who guarantees that? Is it only for Linux?
Hi Ilias,
It's guarantee by all the existing implementations, ventoy, linux etc.
What's ventoy? Googling it seems to be a tool for writing images?
It's nearly impossible to run MIPS OS in virtual (or paged) segment. All MIPS OS and bootloaders are running in KSEG/XKPHYS segment, which directly mapping lower bits of virtual address into physical address. So I suppose set_virtual_address_map is unnecessary on MIPS because the mapping for U-Boot is always here and can't be disabled in hardware.
Fair enough, I am not too happy with the restriction but I think it's ok to start with
On MIPS KSEG0 is always mapped to memory and there is no way to disable it for kernel mode. Both EFI runtime and kernel lays in this segment, so relocation is totally unnecessary.
Also U-Boot does not use traditional .dyn.rel to perform relocation on MIPS, that makes implementation of runtime relocation pretty hard.
It already works on other architectures so I suppose it's only a matter of adding it?
MIPS is odd here, we are not compiling U-Boot with -fPIC, instead we use our own tools to generate relocation records and embedded them into U-Boot.
Adding relocation support requires modifications to that tool "tools/mips-relocs.c" and also processing our own record format here.
Given that set_virtual_address_map have no practice use on MIPS, I think the best way to handle it is to leave set_virtual_address_map alone.
hrrm any idea why? Was that a pre-existing state in mips? Perhaps we can fix it in the future.
That being said, I was away on a conference, I'll have a look at the mips patches, but probably next week
Cheers /Ilias
Thanks
Thanks /Ilias
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- Jiaxun