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Discussion on u32
by Lawrence Esswood Oct. 7, 2024

Oct. 7, 2024

I think this is a good discussion for Friday, but I wanted to send out an advance email to give time for people to gather their thoughts in advance The current set of return codes include a type. e.g. calls like allow/brk currently return SyscallReturnU32U32 or SyscallReturnU32. Clearly this is not true for 64-bit platforms. Or for CHERI where the size of an address is not the size of a pointer.I think there are a few options: 1. 1) They should return different codes on different platforms: SyscallReturnu32 on 32-bit, SyscallReturnu64on 64-bit, SyscallReturnMetaPtr on CHERI etc with some meta constructors to help choose. Userspace should expect the same and be If-Defed appropriately. 2. 2) They should return a new more specific code SyscallReturnPtr / SyscallReturnUsize on all platforms, and user space should check for just that one.e 3. 3) These calls are already made type safe because of the wrappers in libtock-c / libtock-rs. Just use SyscallSuccess for these built in syscalls. Wrappers know what they are getting. 4. 4) A true evil one. Option 3, but SyscallReturnu32 is the code for legacy reasons. You know what you are actually getting. What I actually did on my fork was just 3 (because all these different codes were getting in the way), but this does break compatibility unless there is a matching change in libtock-c/libtock-rs and it would probably be better not to do so. In fact, both 2 and 3 are breaking API changes. This means that possibly we should prefer (1), simply for backwards compatibility? This is roughly what the consttructor I added for SyscallReturnUsize does: selects one of SyscallReturnu32 or SyscallReturnu64 as appropriate. But possibly we will need a few more as soon as CHERI comes into play.As for types for commands:Currently in the kernel commands are:fn command(&self, cmd_num: usize, arg1: usize, arg2: usize, appid: ProcessId) Which is already usize-ified.In libtock-c: syscall_return_t command(uint32_t driver, uint32_t command, size_t arg1, size_t arg2); There is clearly a mismatch there on command number. I am of the mind that the driver/command being u32 is fine, and args should really be usize. For instance, a command might realistically take an offset to a previously allowed buffer. This is usize, not u32.Upcalls: in the kernel were all u32, I changed most of the arguments usize apart from data/fn pointer which are MetaPtr. i.e., the type in C should be:typedef void (subscribe_upcall)(size_t, size_t, size_t, void*);where currently it istypedef void (subscribe_upcall)(int, int, int, void*);And I think its worth some discussion whether people are happy with this. It means nothing for 32-bit libtock-c because the ABI for passing usize is the same as int on 32-bit platforms. In libtock-rs I have the patches ready to go to define the upcall trait on both u32 and usize so it won't break any code there. Lawrence

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Tock meeting agenda 2024-10-04
by Amit Levy Oct. 4, 2024

Oct. 4, 2024

Meeting Link: https://meetings.dialpad.com/room/tock/1vnk9r3e1b Agenda - Updates - Pointer returns from syscalls on non-32-bit platforms (https://lists.tockos.org/hyperkitty/list/devel@lists.tockos.org/thread/ACZB…)

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Call for Tock meeting agenda items 2024-10-04
by Amit Levy Oct. 3, 2024

Oct. 3, 2024

Please response with proposed agenda items and +1s for tomorrows core meeting

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Tock meeting agenda 2024-09-27
by Amit Levy Sept. 27, 2024

Sept. 27, 2024

Meeting Link: https://meetings.dialpad.com/room/tock/1vnk9r3e1b Agenda - Updates - PR status - Raw 802.15.4 support - what to do about it? - https://github.com/tock/libtock-rs/pull/551 * Needs someone knowledgeable about libtock-rs to look at it and review * What's the bar for merging self-contained changes in libtock-rs? - PIO - how should we handle programmable I/O bytecode? https://github.com/tock/tock/pull/4179 * Example: https://github.com/tock/tock/blob/5ad547c0998320b30b0b66ee7ff799dcb65f0f0e/… * Zephyr deals with this similarly: https://github.com/zephyrproject-rtos/zephyr/blob/main/drivers/serial/uart_…

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Re: Tock meeting agenda 2024-09-27
by Branden Ghena Sept. 27, 2024

Sept. 27, 2024

A couple of last-minute, low-priority items. Raw 802.15.4 support - what to do about it? https://github.com/tock/libtock-rs/pull/551 * Needs someone knowledgeable about libtock-rs to look at it and review (this can't all fall on Jonathan's lap) * What's the bar for merging self-contained changes in libtock-rs? PIO - how should we handle programmable I/O bytecode? https://github.com/tock/tock/pull/4179 * Example: https://github.com/tock/tock/blob/5ad547c0998320b30b0b66ee7ff799dcb65f0f0e/… * Zephyr deals with this similarly: https://github.com/zephyrproject-rtos/zephyr/blob/main/drivers/serial/uart_… Thanks, Branden Ghena Northwestern University On Thu, Sep 26, 2024 at 12:46 PM Amit Levy via Devel <devel(a)lists.tockos.org> wrote: > Please response with proposed agenda items and +1s for tomorrows core > meeting > _______________________________________________ > Devel mailing list -- devel(a)lists.tockos.org > To unsubscribe send an email to devel-leave(a)lists.tockos.org >

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Tock meeting agenda 2024-09-27
by Amit Levy Sept. 26, 2024

Sept. 26, 2024

Please response with proposed agenda items and +1s for tomorrows core meeting

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Tock meeting agenda 2024-09-20
by Amit Levy Sept. 20, 2024

Sept. 20, 2024

Meeting Link: https://meetings.dialpad.com/room/tock/1vnk9r3e1b Agenda - Updates - VeeR EL2 PR check-in, readiness - https://github.com/tock/tock/pull/4118 - How to review and approach external x86 crate dependency in x86 PR - https://github.com/tock/tock/pull/4171#discussion_r1757119032 - Supporting different (older) compiler versions for CHERI - AKA, are `cfg`s ever acceptable?

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Re: Call for Tock meeting agenda items 2024-09-20
by Branden Ghena Sept. 20, 2024

Sept. 20, 2024

Quick check-in on https://github.com/tock/tock/pull/4118 I think it's good to merge (module one simple update from the PR author). But I want to check on CI error and more importantly what our bar is for a PR like this. On Fri, Sep 20, 2024 at 9:45 AM Brad Campbell via Devel < devel(a)lists.tockos.org> wrote: > Guidance for external x86 crate. > https://github.com/tock/tock/pull/4171#discussion_r1757119032 > <https://urldefense.com/v3/__https://github.com/tock/tock/pull/4171*discussi…> > > On Fri, Sep 20, 2024 at 2:02 AM Amit Levy via Devel < > devel(a)lists.tockos.org> wrote: > >> Handling different compiler versions upstream (e.g. for forked Rustc for >> CHERI) >> _______________________________________________ >> Devel mailing list -- devel(a)lists.tockos.org >> To unsubscribe send an email to devel-leave(a)lists.tockos.org >> >

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Call for Tock meeting agenda items 2024-09-20
by Amit Levy Sept. 20, 2024

Sept. 20, 2024

Please respond with suggestions for agenda items for tomorrow's meeting

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Call for Tock meeting agenda items 2024-09-13
by Amit Levy Sept. 13, 2024

Sept. 13, 2024

Please respond with suggestions for agenda items for tomorrow's meeting

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