The newly updated version "0.2.13" cannot run on mipsel

[vnt-dev]

It can run normally before you update 0.2.13

thread 'main' panicked at 'could not initialize thread_rng: Function not implemented', /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/rand-0.8.5/src/rngs/thread.rs:72:17
note: run with RUST_BACKTRACE=1 environment variable to display a backtrace
Aborted

[josephlr]

This is almost certainly caused by #396

That PR removed certain fallback code on certain Linux CPU architectures (all CPU architectures that aren't ARM, x86, PowerPC, or s390). On such architectures (like mipsel), a sufficiently new kernel is already required. Looking at the list of Rust Targets the mipsel-unknown-linux-gnu target requires kernel 4.4, which should have support for the getrandom syscall.

@lbl8603 to help us debug further:

• which Rust target are you using (is it mipsel-unknown-linux-gnu)?
• which Rust version are you using?
• which Linux distro are you using?
• which version of the linux kernel are you running on?

[josephlr]

CC @newpavlov @briansmith (who worked on #396)

[vnt-dev]

• target: mipsel-unknown-linux-musl
• Rust version: rustc 1.71.1 (eb26296b5 2023-08-03)
• linux:
  Linux RM2100 3.4.113 #2 SMP Sat Mar 19 17:12:12 CST 2022 mips GNU/Linux
Linux version 3.4.113 (root@hiboy-VirtualBox) (gcc version 4.4.7 (GCC) ) #2 SMP Sat Mar 19 17:12:12 CST 2022

[josephlr]

Looking at the platform list, it seems like the musl targets don't list a minimum kernel version (they just require MUSL 1.2.3 which requires kernel 2.6 or later), while for mipsel-unknown-linux-gnu the minim kernel version is 4.4. I'm wondering if we should reach out to see what the actual minimum supported kernel version for Rust is on -musl targets.

@lbl8603 out of curiosity what system/distro are you running on? Based on the uname it looks like some sort of old router?

@newpavlov @briansmith should we support MUSL systems with kernels older than 3.17?

[newpavlov]

Hm, mipsel-unknown-linux-gnu requires kernel 4.4, so we assumed that mipsel-unknown-linux-musl would require it as well. Could you please find an official link that Rust officially supports pre-4.4 kernels for this target?

Adding a MUSL exception looks like an obvious solution for now.

[josephlr]

Hm, mipsel-unknown-linux-gnu requires kernel 4.4, so we assumed that mipsel-unknown-linux-musl would require it as well. Could you please find an official link that Rust officially supports pre-4.4 kernels for this target?

I'm wondering if MUSL might target an older kernel version. It seems like a lot of the folks who target very old kernels intentionally use MUSL to avoid depending on an ancient glibc.

EDIT: Looking at rust-lang/compiler-team#493 it seems like the only reason Linux 3.2 is even required by rust is to support GLIBC (whose newer versions have that as the minimum kernel version).

[vnt-dev]

Compiling target mipsel-unknown-linux-musl requires using versions prior to Rust 1.71.1. I encountered this bug on the router