Running C code without translation enabled is fragile and could break at any time, since it's not running at right address. You're relying on PC-relative addressing being used for everything (i.e. not absolute and not GOT-indirect), which happens to be true today with -mcmodel=medany for this code and all it uses, but there's no guarantee of that. This should really be in assembly (which shouldn't be hard to do, given sbi_get_mvendorid is just a wrapper around ecall?).

In D47458#1082358, @jrtc27 wrote:

Running C code without translation enabled is fragile and could break at any time, since it's not running at right address. You're relying on PC-relative addressing being used for everything (i.e. not absolute and not GOT-indirect), which happens to be true today with -mcmodel=medany for this code and all it uses, but there's no guarantee of that. This should really be in assembly (which shouldn't be hard to do, given sbi_get_mvendorid is just a wrapper around ecall?).

I did find it was quite fragile what could be done this early, reads/writes to globals failed, for example. I am surprised that Linux is able to do as much as they do in this way.

Sure, I will convert it to asm.

In D47458#1082363, @mhorne wrote:

In D47458#1082358, @jrtc27 wrote:

Running C code without translation enabled is fragile and could break at any time, since it's not running at right address. You're relying on PC-relative addressing being used for everything (i.e. not absolute and not GOT-indirect), which happens to be true today with -mcmodel=medany for this code and all it uses, but there's no guarantee of that. This should really be in assembly (which shouldn't be hard to do, given sbi_get_mvendorid is just a wrapper around ecall?).

I did find it was quite fragile what could be done this early, reads/writes to globals failed, for example. I am surprised that Linux is able to do as much as they do in this way.

Sure, I will convert it to asm.

Yeah, we use -fPIE, which means GOT indirection for globals (with those GOT entries containing precomputed absolute virtual addresses from the linker), which we could jettison for modern LLVM as it was a workaround for undefined weak symbols. GCC+binutils never had that issue as GNU ld did some gross instruction rewriting for such references, so Linux doesn't use -fPIE, and I guess by the time Clang-built Linux was a thing for RISC-V we'd fixed the psABI and LLVM to not require such instruction rewriting.