Piotr Jaroszyński: Usermode debugging under Linux

Allow gPXE to run as a usermode application under Linux on both i386 and x86_64. Hence opening new debugging possibilities and shortening the development cycle considerably.

Implementation details

How usermode under Linux is done

• Add a linux PLATFORM
  • Link against hacked stdlib
  • Add linker scripts for i386 and x86_64 with tables support
• Add the necessary subsystems for a tap network driver
  • CONSOLE_LINUX
  • TIMER_LINUX
  • UACCESS_LINUX
  • UMALLOC_LINUX
  • NAP_LINUX
  • SMBIOS_LINUX (empty)
• Add a tap network driver
• Add command-line arguments allowing configuration of the tap driver
• Drop the stdlib dep
  • Implement syscall() and linux_* on top of it where possible
  • Implement linux_realloc
  • Implement _start
  • Make it not too hard to switch to linking to stdlib for debugging purposes

• Making gPXE valgrindable

• Research how to map gPXE's driver API to hardware via kernel