On Wed, Sep 20, 2017 at 8:50 PM, Jon Brawn <j...@brawn.org> wrote: > Wotcha! > > I work for Arm for my sins, and in my spare time I’ve been playing with > FreeBSD. In my day job I work with the CPU core validation team, and one of > the things we do is take the hardware design of a new core and run it on a > machine called an emulator. This emulator isn’t the same thing as QEMU, nor > is it just an FPGA, it’s something in the middle - you compile the hardware > design and download it to the emulator, and it can then run programs on > your design at about 1MHz. Which is lovely. Our main bread and butter is to > take such a design and get it to boot Arm Linux, a very cut down version, > and then run some tests hosted in the Linux environment. These tests would > typically thrash the snot out of some particular aspect of the > architecture, such as memory sharing amongst multiple processor cores. Now, > we would like to use other operating systems that behave differently to > Linux, there are some obvious candidates that I’m not going to talk about > for legal reasons, but one that was suggested was using FreeBSD under > emulation. > > So, what is needed is someway of telling the operating system that it is > going to use a ram disk for its root filesystem, and that the ram disk is > going to be at a fixed physical address in the memory map. That way we can > pre-load root from a file in the emulation environment. In the Linux > environment we would package the kernel, it’s DRB and the root filesystem > memory image inside a light-weight bootloader wrapper, load that at the > right offset into the emulator’s memory map, and twang the virtual reset > line of the emulated processor. There’s some magic jiggery pokery to get > console output from what the OS thinks is an AMBA UART, but that’s about > size of it. > > So, what does FreeBSD have to offer in the way of ramdisk functionality? >
Yes. See MD_ROOT and friends. Warner _______________________________________________ freebsd-current@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
