Hi Alex, On 7 June 2018 at 12:36, Alexander Graf <[email protected]> wrote: > > > On 07.06.18 22:25, Simon Glass wrote: >> Hi Alex, >> >> On 3 June 2018 at 04:13, Alexander Graf <[email protected]> wrote: >>> >>> >>> On 25.05.18 04:42, Simon Glass wrote: >>>> Hi Alex, >>>> >>>> On 24 May 2018 at 06:24, Alexander Graf <[email protected]> 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 <[email protected]> >>>>> >>>>> 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 _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
