These are the changes to HdrSrc for the Linux Port.

• The Linux port runs as an ordinary Linux process entirely in user mode.
• SWI calls are intercepted using seccomp or ptrace.
• The macros pvMRS and psMSR emulate MRS and MSR instructions by calling the HAL, those HAL routines are linked in a similar way to the SharedCLibrary.
• fvSWI and pvSWI are a performance optimisation, to avoid calling the Linux SWI handler on every SWI call.
• I am considering moving the contents of PVOps into Generic32 and combining pvMRS and psMSR with mymrs and mymsr, with the names MyMRS and MyMSR.

See !7 (merged) for changes to mymrs and mymsr. Forum thread: https://www.riscosopen.org/forum/forums/3/topics/9068 Full port on github: https://github.com/TimothyEBaldwin/RISC_OS_Linux_Source/tree/Linux2-rebased