On 07.06.18 22:25, Simon Glass wrote: > Hi Alex, > > On 3 June 2018 at 04:13, Alexander Graf <ag...@suse.de> wrote: >> >> >> On 25.05.18 04:42, Simon Glass wrote: >>> Hi Alex, >>> >>> On 24 May 2018 at 06:24, Alexander Graf <ag...@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 <s...@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. > >> >>>> 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. Alex _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
