On Tue, 2020-01-14 at 09:59 +0000, Peter Maydell wrote: > Note that semihosting is not a "here's a handy QEMU feature" > thing. It's an architecture-specific API and ABI, which should > be defined somewhere in a standard external to QEMU.
There is no such standard for powerpc today that I know of. > You need to start by having a definition for PPC of what > semihosting is. If you're starting from scratch there, there > are some important things you should do differently to Arm -- > there is no benefit to repeating the mistakes of API definition > that we made! Most notably, you want to specify and require > that any unrecognized semihosting call function fails in a > clean and detectable way; you also should have a semihosting > function for "ask for a feature bit mask" so you don't need > the silly magic-filename approach Arm had to go for. You > also want to standardize what the errno values are, which Arm > forgot to do and which makes the errno handling in the spec > pretty useless. Keith and I are somewhat of a different mind here. From the perspective of the user of that API (picolibc is one), it's easier to deal with a single one and have everybody inherit the same bugs. Now I understand the point of wanting to fix the mistakes made but I would suggest we do so by proposing extensions to the existing one to do so. > TLDR: don't start by writing code, start by writing the *API/ABI > spec*. > I tried to push the RISCV folks in this direction as well. AFAIK they are still just doing what ARM does for the above reason. Cheers, Ben.
