On Mon, 6 Jan 2020 at 17:09, Cédric Le Goater <c...@kaod.org> wrote: > ARM bootloaders are also embedded in QEMU's code. See hw/arm/boot.c. > You could improve a bit the definition though.
Given an opportunity to restart from scratch I don't know that I'd do things the way hw/arm/boot.c does. The initial idea was really simple and straightforward: 3 or 4 insns which just set some registers and jumped to the kernel. Fast-forward a decade or two, and the complexity has significantly increased as we added extra tweaks to deal with SMP systems, the GIC interrupt controller, boards which need to do some extra odd stuff, CPUs which start in Secure state, 64-bit CPUs, mangling the DTB, booting multiple flavours of image file format, implementing various 'firmware' functionality and APIs, and so on and on. Insisting from the start that QEMU emulates what bare metal hardware does, and doesn't get into the business of faking up the behaviour of firmware would have been a neater separation of concerns in the long run. To the narrower concern, yeah, on the arm side we just embed hand-assembled hex values in the C file; this is mostly to avoid needing a cross-compiler setup at QEMU build time, but it also lets us hand-patch the binary blob at runtime to fill in addresses and so on. thanks -- PMM
