this commit adds the facilities to extract eh_frame[_header]
sections and pass it to each process.
A bump is required to `std` to extract the passed parameters.
it works with e.g. shellchat, but not vault.
still scratching my head on what's gone wrong -- it's
crashing in the pre-boot, which means something is not
mapped right for some case that wasn't caught in the
earlier testing.
Atomic operations were previously broken. RISC-V breaks atomic
operations into multiple instructions, and there is some state kept
between those instructions. This state is not visible, and is internal
to the processor.
We were ignoring this state, which resulted in inconsistencies
throughout the system. The following sequence was possible:
1. A thread loads a value, and obtains the `reservation set`
2. A context switch happens on the following instruction
3. A different thread loads the value, modifies it, and continues
4. A third thread (or a different process) loads a value and obtains the
`reservation set`
5. The original thread runs, sees the `reservation set` is held, and
updates the value, clobbering what the second thread did in #3
A workaround for this is to perform a dummy `sc` as part of the context
switch. This invalidates any atomic operations that may be pending.
Signed-off-by: Sean Cross <sean@xobs.io>
The previous patch didn't properly restore thread IDs when switching
contexts -- there were spots where we missed things, and spots where we
were double-borrowing.
Fix these corner cases.
Signed-off-by: Sean Cross <sean@xobs.io>
Note the current thread in the original process when its quantum
expires. This will allow us to clean up after ourselves when a context
switch occurs, and will help to prevent thread starvation.
Signed-off-by: Sean Cross <sean@xobs.io>
Currently, returning a Message (e.g. a Scalar1, Scalar2, or
MemoryMessage) always results in a context switch from the server to the
client. This is what makes these syscalls cheaper.
However, this results in process starvation. For example, if three
processes send a message to a server, then the server will only be able
to respond to one of those messages at a time. This works well with a
lightly-loaded system, but quickly falls apart when many threads are
running.
Keep track of which process and thread were originally switched to as
part of the `SwitchTo` call. If the Server is responding to a message
and owns the current quantum, don't immediately switch to the Client
thread.
Signed-off-by: Sean Cross <sean@xobs.io>
For some reason, the current thread becomes 0 during suspend or resume.
This causes an error during boot.
Patch this up while we figure out what's causing it.
Signed-off-by: Sean Cross <sean@xobs.io>
Unify scalar return calls so that we only have one return path rather
than three.
We can almost unify memory returning as well, but it's not quite there.
Signed-off-by: Sean Cross <sean@xobs.io>
There were a few corner cases when it came to thread selection. Namely,
the same thread had a higher chance of repeatedly being executed.
Clean up these corner cases, and as a result get libstd tests to pass.
Signed-off-by: Sean Cross <sean@xobs.io>
Add notes on how to properly hand memory to userspace. This does not yet
work, but is committed here as a work-in-progress.
Signed-off-by: Sean Cross <sean@xobs.io>
The default mem size got shrunk down to 4 MB earlier, but there is a
lingering issue that prevents specifying virtual addresses. As a result,
pddb and others don't work.
Temporarily revert this change.
Signed-off-by: Sean Cross <sean@xobs.io>
The process search now uses iterators properly. It's still not ideal
because it needs to investigate every process, but it's better than it
was.
Signed-off-by: Sean Cross <sean@xobs.io>
Use a multiply-based algorithm to count the number of leading zeroes.
This results in a function that's just 20 instructions long.
Signed-off-by: Sean Cross <sean@xobs.io>
THe act of finding a runnable thread is so common, yet the kernel
contains three ways of doing this.
Use a unified function to select the next available thread.
Signed-off-by: Sean Cross <sean@xobs.io>
Previously the `current_thread` was set to 0, which is invalid. Set the
`current_thread` so that it defaults to the initial thread ID.
Signed-off-by: Sean Cross <sean@xobs.io>
This memory region is much smaller than the previous value of 256 MB,
but it will limit the amount of memory used by superpages in
long-running processes.
Previously, we would march through memory as messages were passed back
and forth and a process' memory space would quickly be eaten up by 1024
pages.
Signed-off-by: Sean Cross <sean@xobs.io>
When waiting on a thread, it may be the case that the thread we're
joining has exited already. In this case, the correct approach is to
resume execution rather than switching to the parent process.
This fixes an issue where `SWITCHTO_CALLER` is None when joining a
short-lived thread.
Signed-off-by: Sean Cross <sean@xobs.io>
When attempting to return an invalid item, return `DoubleFree`. This is
because such cases are most likely due to instances where a message was
responded to twice.
Signed-off-by: Sean Cross <sean@xobs.io>
- we don't need a general memset call -- just a zero page call
- use native rust semantics to embody the call. some alignment checking is
done on the arguments on the way in and out that seem worth it
- the unrolled loop doesn't pay off because we're at the limit of
write bandwidth on the CPU at this point. we would need write-back
caches to gain more performance through unrolling.
@xobs found a scheduler bug that would trigger a runnable process
search every time a scalar message returned. This fixes the problem,
causing the quantum to go back to the caller as intended.
Improves performance on the syscall by about 40%.
Fix a segfault that occurred when using ReplyAndReceiveNext on hosted
mode. This now properly passes memory messages back to the client.
Signed-off-by: Sean Cross <sean@xobs.io>
Implement `ReplyAndReceiveNext` as a syscall. This will reply to a
message, pull the next message out of the queue, and then re-queue the
server to run. This should make servers much more responsive.
This patch has been tested on both hosted and native modes.
Signed-off-by: Sean Cross <sean@xobs.io>
I've added a `platform` module to store all platform specific code, (not
architecture specific) as some platforms will require custom drivers, e.g.
for debug output and for the random number generation code. The platform
code is in charge of mapping any peripherals needed to work, also to
initialize any other parts of the kernel that require drivers, for example
the debug shell.
Signed-off-by: Jean-Pierre De Jesus DIAZ <me@jeandudey.tech>
The rationale is that xous-rs should have only architecture
specific code, e.g.: riscv, arm, x86, etc. To make other
crates that depend on it not specify the features.
This could be useful when using xous-rs with `libstd`
for example.
Signed-off-by: Jean-Pierre De Jesus DIAZ <me@jeandudey.tech>
This allows for a more reliable detection of target_os configuration
in build scripts. The target is inconsistent between some architectures,
notably armv7a is `armv7a-none-eabi` skipping the `unknown` (the vendor,
I guess) part. This happen with some of the unrelated Cortex-M targets
present, and others may also be.
Signed-off-by: Jean-Pierre De Jesus DIAZ <me@jeandudey.tech>
- strip out gdb-stub. Per xobs, the feature never worked, and it
depends upon a branch of a git repo which is not allowed by crates.io
Since the feature hasn't been developed, and crates.io will not
allow even an optional feature that points to a git repo, the feature
was stripped out.
- rename "kernel" to "xous-kernel", so that we can live in a crates.io
package namespace that is specific to Xous.
still have to figure out the riscv package issue.
this will help speed up performance profiling as we can
resolve the physical address of the performance buffer allocated
in RAM and use a USB command to read it out, instead of streaming
it over serial.
Instead of passing a constructed mutable ref from the pagetable entry,
pass a raw pointer and use `read_volatile()` / `write_volatile(x)` on
this pointer.
This should remove a little bit of UB from the kernel.
Signed-off-by: Sean Cross <sean@xobs.io>
Previously, the kernel would dutifully try to map memory that was in the
kernel space. It did this by investigating the kernel memory offset,
which immediately causes a double-fault.
Check to make sure a userspace process is not trying to map kernel
memory before checking the valid page.
Signed-off-by: Sean Cross <sean@xobs.io>
Implement the syscall to adjust a process' limit. Currently this
only supports adjusting the heap maximum and the heap size.
In order to adjust a limit, you must first present the current limit.
This can be obtained by requesting a bogus value. The current limit is
returned as part of the result.
Signed-off-by: Sean Cross <sean@xobs.io>
Return the heap size and offset when decreasing the heap. Additionally,
return the heap size when increasing the heap by 0 bytes.
Signed-off-by: Sean Cross <sean@xobs.io>
this contains a dependency to `failure` two levels down that has a critical
vulnerability. Unfortunately no new versions of debug-here have been
published in a while. It's no longer used, so just stripping it out
altogether.
Hosted mode spawns processes very differently, and this difference was
not reflected after changes were made to native mode.
Signed-off-by: Sean Cross <sean@xobs.io>
Unmap the pages from the child process after we're done setting them up.
This ensures they're not still aliased by our process, despite being
marked as "owned" by the other process.
Signed-off-by: Sean Cross <sean@xobs.io>
Implement a functioning CreateProcess syscall on riscv. This call
creates a server in the child process, and connects the server to the
parent. The parent can communicate with the child process using this
server.
The Server ID is passed as four `u32` values to the entrypoint function.
This can be reassembled into something that can then be passed to the
`ReceiveMessage` syscall.
Signed-off-by: Sean Cross <sean@xobs.io>
We now us `ProcessStartup` as the return type. This builds in tset
mode, hosted mode, and RISC-V mode.
Process Startup is still not implemented for RISC-V mode.
Signed-off-by: Sean Cross <sean@xobs.io>
Turns out we didn't end up needing this capability, so, commenting it
out because it is a shy too powerful and is like packing a live
mortar shell in a storage unit: eventually, someone is going to
get hurt, even though it seems mostly harmless at the moment.
Code just commented out in case we need this feature in the future,
but, the main reason it was asked for (the PDDB) was accomplished
without it.
This moves the kernel into the main monorepo, allowing it to share
packages with the rest of the system. This change will allow us to
reduce the number of rebuilds that take place, as well as reducing disk
usage.
Note that the loader is still an indepenent project, and the integration
of that into the monorepo is pending.
Signed-off-by: Sean Cross <sean@xobs.io>
Each Cargo.toml now includes a comment which remnids maintainers
of the dependency policy for Xous (that is, nail down every dependency
to the minor number).
