Thayne Harbaugh wrote: > There are several things that I'd like to see addressed in linux-user. > Some of these are to fix bugs, some are to make qemu linux-user more > like the Linux kernel, some are to make the internal qemu interfaces > more consistent. > > An internal coding practice that is being addressed bit-by-bit is that > of managing the interface between the host and the target. Currently > this is a bit sloppy and inconsistent (some of which I've contributed > to). There are examples of using target addresses for host pointers and > host errnos for target errnos, using different types between target and > host that don't sign-extend properly, as well as other things. This > causes compiler warnings to actual run-time bugs. Currently I'm > reviewing all of the linux-user code (mostly syscall.c) to fix these > inconsistencies. I will be writing developer documentation describing > the coding practices that should govern the target/host interface and > submitting patches for the fixes. > > As obvious as it may seem I'll re-state that the linux-user emulation is > emulating the Linux kernel (duh!). There are portions of qemu > linux-user that are even excerpted directly from the Linux kernel. > Consequently it is useful for internal qemu data and functions to > closely mimic the kernel for best code sharing. There are also > advantages to even structuring qemu directly and file organization in > similar divisions, groupings and locations. Some of this organization > might lead to good division so that other user/kernel divisions are > cleaner (different kernel versions, other OSes - darwin-user and > others). > > Internal qemu interfaces are consistent - except when they aren't. This > causes coding errors when passing target and host arguments or return > codes. I'll be documenting the coding practices as well as submitting > patches to make these consistent. (That sounds a bit redundant with > other things I've mentioned). > > I have about 40 patches already worked up that do this. Some of those > patches might be broken up smaller. The qemu that we've been working > with is nearly rock solid (still a few more bugs being wrung out). It > can nearly build an entire Debian arm distribution for an arm target > being hosted on x86_64. We're quite excited to get our patches upstream > so that others can benefit and to ease our maintenance overhead. We're > also turning our focus to PPC and other archs. > > Please let me know if you support the general idea of the coding changes > above: General clean-up, consistent target/host interfaces, file > splitting/reorganizing, etc.. In the meantime I'll be putting together > the developer documentation/coding guidelines for review.
FWIW, I agree with everything you said above. Thiemo
