m68k version of Eric's patch series 'alpha/ptrace: Improved switch_stack handling'. Registers d6, d7, a3-a6 are not saved on the stack by default on every syscall entry by the m68k kernel. A separate switch stack frame is pushed to save those registers as needed. This leaves the majority of syscalls with only a subset of registers on the stack, and access to unsaved registers in those would expose or modify random stack addresses. Patch 1 and 2 add a switch stack for all syscalls that were found to need one to allow ptrace access to all registers outside of syscall entry/exit tracing, as well as kernel worker threads. This ought to protect against accidents. Patch 3 adds safety checks and debug output to m68k get_reg() and put_reg() functions. Any unsafe register access during process tracing will be prevented and reported. Suggestions for optimizations or improvements welcome! Cheers, Michael Link: https://lore.kernel.org/r/<87pmwlek8d.fsf_-_@disp2133>
