On 31.01.25 7:58 PM, Christian Schrefl wrote: > On 31.01.25 5:05 PM, Andrew Lunn wrote: >>> To fix this Rust would have to provide a way to build the core >>> library without float support. I don't know if there is a plan >>> already to allow this. >> >> Floating point is banned within the kernel, except for in very narrow >> conditions, because the floating point registers are lazy saved on >> context switch. If the kernel uses the floating point registers, you >> can break user space in bad ways. >> >> I expect this has been discussed, since it is well known kernel >> restriction. Maybe go see what happened to that discussion within RfL? > > After checking again, it seems the float intrinsics are actually not > needed anymore at least for my config. Only `__aeabi_uldivmod` is still > required for `parse_u64_into` since [0] allows disabling float formatting. Seems like Rust 1.78 still needs at least __aeabi_fcmpeq __aeabi_fcmpun __aeabi_dcmpun and __aeabi_uldivmod. > > Link error without the `__aeabi_uldivmod` symbol defined: > > ld.lld: error: undefined symbol: __aeabi_uldivmod >>>> referenced by num.rs:580 (/home/chrisi/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/num.rs:580) >>>> rust/core.o:(core::fmt::num::parse_u64_into::<39>) in archive vmlinux.a >>>> referenced by num.rs:589 (/home/chrisi/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/num.rs:589) >>>> rust/core.o:(core::fmt::num::parse_u64_into::<39>) in archive vmlinux.a >>>> referenced by num.rs:589 (/home/chrisi/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/num.rs:589) >>>> rust/core.o:(core::fmt::num::parse_u64_into::<39>) in archive vmlinux.a >>>> referenced 34 more times >>>> did you mean: __aeabi_uidivmod >>>> defined in: vmlinux.a(arch/arm/lib/lib1funcs.o) > > Not sure if we should just implement `__aeabi_uldivmod`, keep the > panicking intrinsic for it or somehow fix it in upstream Rust? > > Miguel do you know how this is best handled? > > Link: https://github.com/rust-lang/rust/pull/86048 [0] > > Cheers > Christian
