Hello Ludwig,
Why not use ex_regs() on the thread to trigger an exception. That way, the attached userland exception handler can introspect the thread's complete register set. It can also alter the registers, so that the thread continues to run with the modified register set.
Is there anything more you need?
I already tried ex_regs(). The problem with this function is, that it does not return all registers, if the thread is in a syscall. It only returns the PC and SP registers.
A thread's userland registers are stored on every entry to the kernel. The class in Fiasco is called Entry_frame.
The userland exception handler mentioned above modifies that Entry_frame.
Where does the kernel store the Entry_frame object for each thread? Is it the location where Context::regs() points to?
When the scheduler selects a thread, its userland state (Entry_frame) is restored on exit from kernel mode.
Can you point to the function that executes this code?
Yes, that PC line is the userland program counter. the USP is the userland stack pointer. All userland registers are located at the top of kernel stack for a particular thread.
In short mode, press 's' for a list of all tasks. Select the task in question and the press 'o' to see the capability space for that task.
Hope that helps,
- Christian
Thanks for your answer.
Kind regards, Denis