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NixOS RISC-V

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NixOS on RISC-V https://wiki.nixos.org/wiki/RISC-V https://pad.lassul.us/NixOS-riscv64-linux https://github.com/orgs/NixOS/teams/risc-v65 Servers

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14 Nov 2025
@no-mood:matrix.orgno-mood *

Hi all, I have a few questions on RISC-V cross-compilation in Nix

I need a bare-metal RISC-V toolchain (riscv32-none-elf with newlib, not Linux).
I'm using pkgs.pkgsCross.riscv32-embedded.buildPackages.gcc which provides the correct riscv32-none-elf-gcc.
Now:

  1. Is pkgsCross just syntactic sugar over crossSystem, or are there functional differences?
  2. For bare-metal embedded: should I use pkgsCross.riscv32-embedded.buildPackages.gcc
    or is there a better package?

For context, I'm writing a SpinalHDL/Verilog project, with RISC-V firmware for an FPGA (no OS, pure embedded)

11:49:53
@no-mood:matrix.orgno-mood *

Hi all, I have a few questions on RISC-V cross-compilation in Nix

I need a bare-metal RISC-V toolchain (riscv32-none-elf with newlib, not Linux).
I'm using pkgs.pkgsCross.riscv32-embedded.buildPackages.gcc which provides the correct riscv32-none-elf-gcc. Now:

  1. Is pkgsCross just syntactic sugar over crossSystem, or are there functional differences?
  2. For bare-metal embedded: should I use pkgsCross.riscv32-embedded.buildPackages.gcc
    or is there a better package?

For context, I'm writing a SpinalHDL/Verilog project, with RISC-V firmware for an FPGA (no OS, pure embedded)

11:50:02
@alex:tunstall.xyzAlexAnswer to 1: yes.11:50:17
@alex:tunstall.xyzAlex * Answer to 1: yes, it is just sugar (and crossSystem is far more flexible). 11:50:45
@rosscomputerguy:matrix.orgTristan Ross
FAIL: lookup_test
=================

AddressSanitizer:DEADLYSIGNAL
=================================================================
==12600==ERROR: AddressSanitizer: SEGV on unknown address 0x100d5554fbe8 (pc 0x7ffff7877a26 bp 0x7fffffffdf60 sp 0x7fffffffd710 T-1)
==12600==The signal is caused by a READ memory access.
AddressSanitizer: CHECK failed: asan_suppressions.cpp:47 "((suppression_ctx)) != (0)" (0x0, 0x0) (tid=12600)
AddressSanitizer: CHECK failed: asan_suppressions.cpp:47 "((suppression_ctx)) != (0)" (0x0, 0x0) (tid=12600)
FAIL lookup_test (exit status: 133)

FAIL: auparse_extra_test
========================

AddressSanitizer:DEADLYSIGNAL
=================================================================
==12629==ERROR: AddressSanitizer: SEGV on unknown address 0x100d5554fbe8 (pc 0x7ffff7877a26 bp 0x7fffffffdf50 sp 0x7fffffffd700 T-1)
==12629==The signal is caused by a READ memory access.
AddressSanitizer: CHECK failed: asan_suppressions.cpp:47 "((suppression_ctx)) != (0)" (0x0, 0x0) (tid=12629)
AddressSanitizer: CHECK failed: asan_suppressions.cpp:47 "((suppression_ctx)) != (0)" (0x0, 0x0) (tid=12629)
FAIL auparse_extra_test (exit status: 133)

Oh no, audit fails to build...

19:04:45
@rosscomputerguy:matrix.orgTristan Ross(This is native btw)19:04:52
@rosscomputerguy:matrix.orgTristan Ross *
FAIL: lookup_test
=================

AddressSanitizer:DEADLYSIGNAL
=================================================================
==12600==ERROR: AddressSanitizer: SEGV on unknown address 0x100d5554fbe8 (pc 0x7ffff7877a26 bp 0x7fffffffdf60 sp 0x7fffffffd710 T-1)
==12600==The signal is caused by a READ memory access.
AddressSanitizer: CHECK failed: asan_suppressions.cpp:47 "((suppression_ctx)) != (0)" (0x0, 0x0) (tid=12600)
AddressSanitizer: CHECK failed: asan_suppressions.cpp:47 "((suppression_ctx)) != (0)" (0x0, 0x0) (tid=12600)
FAIL lookup_test (exit status: 133)

FAIL: auparse_extra_test
========================

AddressSanitizer:DEADLYSIGNAL
=================================================================
==12629==ERROR: AddressSanitizer: SEGV on unknown address 0x100d5554fbe8 (pc 0x7ffff7877a26 bp 0x7fffffffdf50 sp 0x7fffffffd700 T-1)
==12629==The signal is caused by a READ memory access.
AddressSanitizer: CHECK failed: asan_suppressions.cpp:47 "((suppression_ctx)) != (0)" (0x0, 0x0) (tid=12629)
AddressSanitizer: CHECK failed: asan_suppressions.cpp:47 "((suppression_ctx)) != (0)" (0x0, 0x0) (tid=12629)
FAIL auparse_extra_test (exit status: 133)

Oh no, audit's tests fail...

19:05:11
15 Nov 2025
@rosscomputerguy:matrix.orgTristan Ross

https://github.com/linux-audit/audit-userspace/issues/504#issuecomment-3535532063

Wouldn't the AddressSanitizer: "CHECK failed: asan_suppressions.cpp:47 "((suppression_ctx)) != (0)" (0x0, 0x0)" be an internal assertion failure within ASAN? The suppression_ctx (suppression context) pointer is null when it shouldn't be, causing ASAN to crash while trying to handle a memory error.

Recommend not using ASAN in the build process until it's support is better. Check for compiler issues around ASAN on RISC-V. Let "make check" run without ASAN and see if it passes.

Hmm, how do you even turn off ASAN?

03:53:04
@dramforever:matrix.orgdramforever Tristan Ross: audit unconditionally enables asan if found 03:58:31
@rosscomputerguy:matrix.orgTristan RossOh03:58:43

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