Jonathan Kollasch

ddb(4) tips

locating a softc

This locates a device's softc using it's cfdriver_t (e.g. &mainbus_cd, &cpu_cd) and its "device unit" (e.g. the 0 in mainbus0).

db{0}> call device_lookup_private(ohci_cd, 0)

locating structure members

This uses gdb(1) and a kernel with debugging symbols to find the offset to a element in a structure.

$ gdb netbsd.gdb
(gdb) print &((struct ohci_softc *)0)->iot
$3 = (bus_space_tag_t *) 0x478
(gdb) print &((struct ohci_softc *)0)->ioh
$4 = (bus_space_handle_t *) 0x480

peeking at mapped registers

db{0}> call bus_space_read_4(*(ffff800045fb2008+478), *(ffff800045fb2008+480), 0)

Unfinished Projects

x86 UEFI kernel loader

Needs more work and cleanup. Work has been done using the OVMF BIOS images for Qemu.

bcm47xx for evbmips

Boots multiuser on NFS root, needs more work and cleanup. This project is on hold until there's a miniature userland that fits in 4-8MiB flash storage devices, on a flash-oriented file system. bce(4) and bwi(4) would need refactoring to be bus-independent.

Memory-mapped PCI config access on x86

Needs cleanup, and maybe some more validation of MCFG tables.