Hi Alex,
On 7 June 2018 at 12:36, Alexander Graf agraf@suse.de wrote:
On 07.06.18 22:25, Simon Glass wrote:
Hi Alex,
On 3 June 2018 at 04:13, Alexander Graf agraf@suse.de wrote:
On 25.05.18 04:42, Simon Glass wrote:
Hi Alex,
On 24 May 2018 at 06:24, Alexander Graf agraf@suse.de wrote:
On 16.05.18 17:42, Simon Glass wrote:
At present this code casts addresses to pointers so cannot be used with sandbox. Update it to use mapmem instead.
Signed-off-by: Simon Glass sjg@chromium.org
I really dislike the whole fact that you have to call map_sysmem() at all. I don't quite understand the whole point of it either - it just seems to clutter the code and make it harder to follow.
The purpose is to map U-Boot addresses (e.g. 0x1234) to actual user-space addresses in sandbox (gd->arch.ram_buf + 0x1234).
Otherwise we cannot write tests which use particular addresses, and people have to worry about the host memory layout when using sandbox.
Not if we write a smart enough linker script. I can try to see when I get around to give you an example. But basically all we need to do is reserve a section for guest ram at a constant virtual address.
Yes, but ideally that would be 0, or something small.
You can't do 0 because 0 is protected on a good number of OSs. And if it can't be 0, better use something that makes pointers easy to read.
Yes this is one reason for map_sysmem().
Can't we just simply make sandbox behave like any other target instead?
Actually that's the goal of the sandbox support. Memory is modelled as a contiguous chunk starting at 0x0, regardless of what the OS actually gives U-Boot in terms of addresses.
Most platforms don't have RAM start at 0x0 (and making sure nobody assumes it does start at 0 is a good thing). The only bit we need to make sure is that it always starts at *the same* address on every invocation. But if that address is 256MB, things should still be fine.
Yes but putting a 10000000 base address on everything is a bit of a pain.
Why? It's what we do on arm systems that have ram starting at higher offsets already.
It's a pain because you have to type 1 and 5-6 zeroes before you can get to the address you want. Otherwise sandbox just segfaults, which is annoying.
Regards, Simon