vasilito
155d01b11e
The MSR R/W scheme lets root request an arbitrary wrmsr/rdmsr on any CPU (used by cpufreqd/thermald). A bad MSR number or reserved-bit value raises #GP; on the raw wrmsr/rdmsr that is a kernel-mode fault that panics the whole machine at exit_this_context (unreachable!) — i.e. root userspace can crash the kernel. Observed on KVM: cpufreqd writing a legacy P-state MSR (#GP in the msr IPI handler) halted the boot right before the console/login. Add wrmsr_safe/rdmsr_safe (arch/x86_64): the faulting instruction sits in a __wrmsr_safe_start/end (resp. rdmsr) region, and the #GP handler recognises a fault inside those bounds and returns an error via recover_and_efault — the same fault-recovery mechanism already used for usercopy page faults. The MSR scheme (local path) and the cross-CPU msr IPI handler now use these and surface EIO to the caller (IPI failures propagated via a new MsrMailbox faulted flag) instead of panicking. 32-bit x86 keeps the raw path (untested).
Kernel
Redox OS Microkernel
Requirements
nasmneeds to be available on the PATH at build time.
Building The Documentation
Use this command:
cargo doc --open --target x86_64-unknown-none
Debugging
QEMU
Running QEMU with the -s flag will set up QEMU to listen on port 1234 for a GDB client to connect to it. To debug the redox kernel run.
make qemu gdb=yes
This will start a virtual machine with and listen on port 1234 for a GDB or LLDB client.
GDB
If you are going to use GDB, run these commands to load debug symbols and connect to your running kernel:
(gdb) symbol-file build/kernel.sym
(gdb) target remote localhost:1234
LLDB
If you are going to use LLDB, run these commands to start debugging:
(lldb) target create -s build/kernel.sym build/kernel
(lldb) gdb-remote localhost:1234
After connecting to your kernel you can set some interesting breakpoints and continue
the process. See your debuggers man page for more information on useful commands to run.
Notes
-
Always use
foo.get(n)instead offoo[n]and try to cover for the possibility ofOption::None. Doing the regular way may work fine for applications, but never in the kernel. No possible panics should ever exist in kernel space, because then the whole OS would just stop working. -
If you receive a kernel panic in QEMU, use
pkill qemu-systemto kill the frozen QEMU process.
How To Contribute
To learn how to contribute to this system component you need to read the following document:
Development
To learn how to do development with this system component inside the Redox build system you need to read the Build System and Coding and Building pages.
How To Build
To build this system component you need to download the Redox build system, you can learn how to do it on the Building Redox page.
This is necessary because they only work with cross-compilation to a Redox virtual machine, but you can do some testing from Linux.
Funding - Unix-style Signals and Process Management
This project is funded through NGI Zero Core, a fund established by NLnet with financial support from the European Commission's Next Generation Internet program. Learn more at the NLnet project page.
