Rust toolchain can't figure out what version of rustc to run

[amanuel2]

I'm getting the error below while trying to build an out of tree rust-module:

~/Documents/rust-out-of-tree-module λ sudo make -C /lib/modules/$(uname -r)/build M=$PWD                                                                                      
make: Entering directory '/usr/lib/modules/6.10.1-zen1-1-zen/build'
  RUSTC [M] /home/aman/Documents/rust-out-of-tree-module/rust_out_of_tree.o
error: rustup could not choose a version of rustc to run, because one wasn't specified explicitly, and no default is configured.
help: run 'rustup default stable' to download the latest stable release of Rust and set it as your default toolchain.
make[2]: *** [scripts/Makefile.build:294: /home/aman/Documents/rust-out-of-tree-module/rust_out_of_tree.o] Error 1
make[1]: *** [/usr/lib/modules/6.10.1-zen1-1-zen/build/Makefile:1932: /home/aman/Documents/rust-out-of-tree-module] Error 2
make: *** [Makefile:240: __sub-make] Error 2
make: Leaving directory '/usr/lib/modules/6.10.1-zen1-1-zen/build'

~/Documents/rust-out-of-tree-module λ    

I have already tried rustup default stable, reinstalled rust with rustup as well as all the components and followed the entire guide labeled here: https://docs.kernel.org/rust/quick-start.html

[amanuel2]

To add to this, found something weird. I was compiling a new kernel and found incosensties which is strange to say the least...

~/Documents/linux-6.10.2 λ sudo make LLVM=1 modules -j10                                                           5s 
  SYNC    include/generated/autoconf.h
  HOSTCC  scripts/basic/fixdep
  UPD     include/generated/compile.h
mkdir -p /home/aman/Documents/linux-6.10.2/tools/objtool && make O=/home/aman/Documents/linux-6.10.2 subdir=tools/objtool --no-print-directory -C objtool 
  INSTALL libsubcmd_headers
  HOSTCC  scripts/kconfig/expr.o
  HOSTCC  scripts/kconfig/conf.o
  HOSTCC  scripts/kconfig/lexer.lex.o
  HOSTCC  scripts/kconfig/confdata.o
  HOSTCC  scripts/kconfig/menu.o
  HOSTCC  scripts/kconfig/parser.tab.o
  HOSTCC  scripts/kconfig/preprocess.o
  HOSTCC  scripts/kconfig/util.o
  HOSTCC  scripts/kconfig/symbol.o
  HOSTLD  scripts/kconfig/conf
error: rustup could not choose a version of rustc to run, because one wasn't specified explicitly, and no default is configured.
help: run 'rustup default stable' to download the latest stable release of Rust and set it as your default toolchain.
  CALL    scripts/checksyscalls.sh
***
*** Running 'rustc' to check the Rust compiler version failed with
*** code 1. See output and docs below for details:
***

***
***
*** Please see Documentation/rust/quick-start.rst for details
*** on how to set up the Rust support.
***
make[1]: *** [/home/aman/Documents/linux-6.10.2/Makefile:1213: prepare] Error 1
make: *** [Makefile:240: __sub-make] Error 2

~/Documents/linux-6.10.2 λ rustc                                                                                   2s 
Usage: rustc [OPTIONS] INPUT

Options:
    -h, --help          Display this message
        --cfg SPEC      Configure the compilation environment.
                        SPEC supports the syntax `NAME[="VALUE"]`.
    -L [KIND=]PATH      Add a directory to the library search path. The


..... opted out for brevity


~/Documents/linux-6.10.2 λ sudo make LLVM=1 modules -j10                                                              
mkdir -p /home/aman/Documents/linux-6.10.2/tools/objtool && make O=/home/aman/Documents/linux-6.10.2 subdir=tools/objtool --no-print-directory -C objtool 
  CALL    scripts/checksyscalls.sh
  INSTALL libsubcmd_headers
  MODPOST Module.symvers

~/Documents/linux-6.10.2 λ   

Right after I ran rustc, ran the make modules command again, and somehow it works?

[ojeda]

Something that stands out right away is that you are using sudo for some reason.

In addition (and it may be related), rustup should not be complaining about not having a default toolchain.

[bjorn3]

You shouldn't run the make command as root. That has entirely separate rustup state and thua isn't affected by rustup default stable as regular user. If you run make as your own user it should work fine.

[amanuel2]

Not running as sudo is giving me permission errors:

~/Documents/linux-6.10.2 λ make LLVM=1 modules_install -j10                                                        2s 
rm: cannot remove '/lib/modules/6.10.2/kernel/fs/efivarfs/efivarfs.ko': Permission denied
rm: cannot remove '/lib/modules/6.10.2/kernel/drivers/thermal/intel/x86_pkg_temp_thermal.ko': Permission denied
rm: cannot remove '/lib/modules/6.10.2/kernel/net/netfilter/xt_addrtype.ko': Permission denied
rm: cannot remove '/lib/modules/6.10.2/kernel/net/netfilter/nf_log_syslog.ko': Permission denied
rm: cannot remove '/lib/modules/6.10.2/kernel/net/netfilter/xt_MASQUERADE.ko': Permission denied
rm: cannot remove '/lib/modules/6.10.2/kernel/net/netfilter/xt_mark.ko': Permission denied
rm: cannot remove '/lib/modules/6.10.2/kernel/net/netfilter/xt_nat.ko': Permission denied
rm: cannot remove '/lib/modules/6.10.2/kernel/net/netfilter/xt_LOG.ko': Permission denied
rm: cannot remove '/lib/modules/6.10.2/kernel/net/ipv4/netfilter/iptable_nat.ko': Permission denied
rm: cannot remove '/lib/modules/6.10.2/build': Permission denied
  INSTALL /lib/modules/6.10.2/modules.builtin
  SYMLINK /lib/modules/6.10.2/build
  INSTALL /lib/modules/6.10.2/modules.builtin.modinfo
  INSTALL /lib/modules/6.10.2/kernel/fs/efivarfs/efivarfs.ko
  INSTALL /lib/modules/6.10.2/modules.order
ln: failed to create symbolic link '/lib/modules/6.10.2/build/linux-6.10.2': File exists
  INSTALL /lib/modules/6.10.2/kernel/drivers/thermal/intel/x86_pkg_temp_thermal.ko
cp: cannot create regular file '/lib/modules/6.10.2/modules.builtin': Permission denied
make[2]: *** [scripts/Makefile.modinst:22: /lib/modules/6.10.2/build] Error 1
make[2]: *** Waiting for unfinished jobs....
cp: cannot create regular file '/lib/modules/6.10.2/modules.builtin.modinfo': Permission denied
make[2]: *** [scripts/Makefile.modinst:37: /lib/modules/6.10.2/modules.builtin] Error 1
/bin/sh: line 1: /lib/modules/6.10.2/modules.order: Permission denied
  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/nf_log_syslog.ko
make[2]: *** [scripts/Makefile.modinst:37: /lib/modules/6.10.2/modules.builtin.modinfo] Error 1
cp: cannot create regular file '/lib/modules/6.10.2/kernel/fs/efivarfs/efivarfs.ko': Permission denied
make[2]: *** [scripts/Makefile.modinst:28: /lib/modules/6.10.2/modules.order] Error 1
cp: cannot create regular file '/lib/modules/6.10.2/kernel/drivers/thermal/intel/x86_pkg_temp_thermal.ko': Permission denied
make[2]: *** [scripts/Makefile.modinst:119: /lib/modules/6.10.2/kernel/fs/efivarfs/efivarfs.ko] Error 1
make[2]: *** [scripts/Makefile.modinst:119: /lib/modules/6.10.2/kernel/drivers/thermal/intel/x86_pkg_temp_thermal.ko] Error 1
cp: cannot create regular file '/lib/modules/6.10.2/kernel/net/netfilter/nf_log_syslog.ko': Permission denied
make[2]: *** [scripts/Makefile.modinst:119: /lib/modules/6.10.2/kernel/net/netfilter/nf_log_syslog.ko] Error 1
  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/xt_LOG.ko
  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/xt_mark.ko
cp: cannot create regular file '/lib/modules/6.10.2/kernel/net/netfilter/xt_LOG.ko'  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/xt_nat.ko
: Permission denied
make[2]: *** [scripts/Makefile.modinst:119: /lib/modules/6.10.2/kernel/net/netfilter/xt_LOG.ko] Error 1
cp: cannot create regular file '/lib/modules/6.10.2/kernel/net/netfilter/xt_mark.ko': Permission denied
make[2]: *** [scripts/Makefile.modinst:119: /lib/modules/6.10.2/kernel/net/netfilter/xt_mark.ko] Error 1
cp: cannot create regular file '/lib/modules/6.10.2/kernel/net/netfilter/xt_nat.ko': Permission denied
make[2]: *** [scripts/Makefile.modinst:119: /lib/modules/6.10.2/kernel/net/netfilter/xt_nat.ko] Error 1
make[1]: *** [/home/aman/Documents/linux-6.10.2/Makefile:1842: modules_install] Error 2
make: *** [Makefile:240: __sub-make] Error 2

~/Documents/linux-6.10.2 λ sudo make LLVM=1 modules_install -j10                                                      
[sudo] password for aman:         
  INSTALL /lib/modules/6.10.2/modules.builtin
  INSTALL /lib/modules/6.10.2/modules.builtin.modinfo
  INSTALL /lib/modules/6.10.2/kernel/fs/efivarfs/efivarfs.ko
  SYMLINK /lib/modules/6.10.2/build
  INSTALL /lib/modules/6.10.2/modules.order
  INSTALL /lib/modules/6.10.2/kernel/drivers/thermal/intel/x86_pkg_temp_thermal.ko
  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/nf_log_syslog.ko
  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/xt_nat.ko
  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/xt_LOG.ko
  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/xt_mark.ko
  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/xt_addrtype.ko
  INSTALL /lib/modules/6.10.2/kernel/net/netfilter/xt_MASQUERADE.ko
  INSTALL /lib/modules/6.10.2/kernel/net/ipv4/netfilter/iptable_nat.ko
  DEPMOD  /lib/modules/6.10.2

~/Documents/linux-6.10.2 λ   

[bjorn3]

You can run the install command as root, but don't run the build command as root.

[ojeda]

I think this can be closed. If you need more help, please feel free to ask in our Zulip: https://rust-for-linux.com/contact.