Add wrapper for linux kernel module loading #930

bachp · 2018-07-20T20:00:10Z

init_module and finit_module to load kernel modules
delete_module to unload kernel modules

bachp · 2018-07-20T20:01:13Z

src/kmod.rs

+/// init_module(&mut contents, &CString::new("").unwrap()).unwrap();
+/// ```
+/// 
+pub fn init_module(module_image: &[u8], param_values: &CStr) -> Result<i64> {


Is there a more flexible way then passing the binary as &[u8]?

bachp · 2018-07-20T20:02:20Z

src/lib.rs

@@ -43,6 +43,8 @@ pub mod fcntl;
          target_os = "openbsd"))]
 pub mod ifaddrs;
 #[cfg(any(target_os = "linux", target_os = "android"))]
+pub mod kmod;


Not sure if this is the right place to put this nor if this is the proper name. Inputs are welcome.

asomers

I think it looks good overall, but it could use some tests. Is there a trivial kernel module that you could use for testing? It's ok to have tests that can only run as root; we already have a few.

bachp · 2018-08-04T08:44:52Z

@asomers A simple hello world module as describe here could be used. But as the kernel ABI is not stable it needs to be compiled for the currently running version of Linux. I'm trying to get it compiled during the test using the cc crate, but with no luck so far.

bachp · 2018-08-04T10:02:28Z

@asomers What is the best way to run tests as root? Should I run all of the build as root or is there a better way?

asomers · 2018-08-04T14:44:04Z

Do it just like the test_setgroups test. The test should quit early if it's not running as root. When you want to actually run that test by hand, run all of the tests as root.

bachp · 2018-08-04T21:00:49Z

@asomers I added some tests

asomers · 2018-08-05T14:31:44Z

test/test_kmod/hello_mod/hello-1.c

+	printk(KERN_INFO "Goodbye world 1.\n");
+}
+
+MODULE_LICENSE("GPL");


Why GPL? The rest of Nix uses MIT.

The module is taken from tldp.org where it is licensed GPL.

This also isn't specific enough, as the GPL has versions. I assume that means 2.0. Let's get a new one written that we can license MIT. Also, can we name it hello.c. That -1 is really killing me.

A pure MIT licensed module would taint the kernel if loaded. The option I see would be: Dual MIT/GPL. I willl create a new module and license it accordingly.

asomers · 2018-08-05T14:31:44Z

test/test_kmod/mod.rs

+use std::process::Command;
+
+fn compile_kernel_module() -> String {
+    #[allow(unused_variables)]


The #[allow(unused_variables)] syntax is holdover from an older version of rustc. Nowadays you can just do let _, = ... and it won't complain.

I tried it and it doesn't work. I'm not sure what's the scope of _ but it seems it doesn't stick around till the end of the block.

Sorry, my last comment had a typo. You need to use let _m = ..., not let _ = .... There is a difference between _m and _.

Good to know. I didn't know they behave differently. I update the code.

asomers · 2018-08-05T14:53:44Z

On my Debian system the test_finit_and_delete_module test fails with this error:

make -C /lib/modules/4.9.0-7-amd64/build M=/home/somers/src/rust/nix/test/test_kmod/hello_mod modules
make[1]: *** /lib/modules/4.9.0-7-amd64/build: No such file or directory.  Stop.
Makefile:4: recipe for target 'all' failed
make: *** [all] Error 2
FAILED

failures:

---- test_kmod::test_finit_and_delete_module stdout ----
        thread 'test_kmod::test_finit_and_delete_module' panicked at 'assertion failed: status.success()', test/test_kmod/mod.rs:12:5
note: Run with `RUST_BACKTRACE=1` for a backtrace.

bachp · 2018-08-05T16:16:15Z

@asomers You most probably don't have the kernel sources installed on your system. Building a kernel module requires the kernel source. I'm not sure what packages provides these on Debian.

asomers · 2018-08-05T20:13:52Z

I installed the linux-source package, and now I have sources in /usr/src, but I still get the same error. The fact that the error message mentions a "build" directory suggests that maybe there's a missing step?

bachp · 2018-08-05T22:00:29Z

I tried on a debian system and the required package is linux-headers-*.

You can install it via:

apt install linux-headers-$(uname -r)

asomers · 2018-08-05T22:20:27Z

Ok, installing linux-headers did the trick. But now "cargo test" is trying to create some temporary files in nix's test directory. Could you fix it so those are created in TMPDIR instead?

running 1 test
test test_kmod::test_finit_and_delete_module ... make -C /lib/modules/4.9.0-7-amd64/build M=/home/somers/src/rust/nix/test/test_kmod/hello_mod modules
make[1]: Entering directory '/usr/src/linux-headers-4.9.0-7-amd64'
arch/x86/Makefile:140: CONFIG_X86_X32 enabled but no binutils support
mkdir: cannot create directory ‘/home/somers/src/rust/nix/test/test_kmod/hello_mod/.tmp_versions’: Permission denied
  CC [M]  /home/somers/src/rust/nix/test/test_kmod/hello_mod/hello-1.o
/home/somers/src/rust/nix/test/test_kmod/hello_mod/hello-1.c:1:0: error: code model kernel does not support PIC mode
 /*
 
Assembler messages:
Fatal error: can't create /home/somers/src/rust/nix/test/test_kmod/hello_mod/.tmp_hello-1.o: Permission denied
/usr/src/linux-headers-4.9.0-7-common/scripts/Makefile.build:307: recipe for target '/home/somers/src/rust/nix/test/test_kmod/hello_mod/hello-1.o' failed
make[4]: *** [/home/somers/src/rust/nix/test/test_kmod/hello_mod/hello-1.o] Error 1
/usr/src/linux-headers-4.9.0-7-common/Makefile:1526: recipe for target '_module_/home/somers/src/rust/nix/test/test_kmod/hello_mod' failed
make[3]: *** [_module_/home/somers/src/rust/nix/test/test_kmod/hello_mod] Error 2
Makefile:152: recipe for target 'sub-make' failed
make[2]: *** [sub-make] Error 2
Makefile:8: recipe for target 'all' failed
make[1]: *** [all] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-4.9.0-7-amd64'
Makefile:4: recipe for target 'all' failed
make: *** [all] Error 2

Susurrus

I'd really like to see the kernel module we use allow for parameters to be passed. I don't see those tested as part of this, and I think it's important that it get tested, ideally having 2 parameters or more.

Susurrus · 2018-08-06T03:33:08Z

test/test_kmod/hello_mod/hello-1.c

+	printk(KERN_INFO "Goodbye world 1.\n");
+}
+
+MODULE_LICENSE("GPL");


This also isn't specific enough, as the GPL has versions. I assume that means 2.0. Let's get a new one written that we can license MIT. Also, can we name it hello.c. That -1 is really killing me.

Susurrus · 2018-08-06T03:33:08Z

test/test_kmod/hello_mod/Makefile

@@ -0,0 +1,7 @@
+obj-m += hello-1.o


Also make this hello.o

Susurrus · 2018-08-06T03:33:08Z

test/test.rs

 mod sys;
 mod test_fcntl;
+#[cfg(any(target_os = "linux", target_os = "android"))]


Please alphabetize the OSes

Susurrus · 2018-08-06T03:33:08Z

src/lib.rs

@@ -43,6 +43,8 @@ pub mod fcntl;
          target_os = "openbsd"))]
 pub mod ifaddrs;
 #[cfg(any(target_os = "linux", target_os = "android"))]
+pub mod kmod;
+#[cfg(any(target_os = "linux", target_os = "android"))]


Please alphabetize here.

Susurrus · 2018-08-06T03:33:08Z

src/lib.rs

@@ -43,6 +43,8 @@ pub mod fcntl;
          target_os = "openbsd"))]
 pub mod ifaddrs;
 #[cfg(any(target_os = "linux", target_os = "android"))]


Please alphabetize this.

Susurrus · 2018-08-06T03:33:08Z

src/kmod.rs

+
+/// Loads a kernel module from a given file descriptor.
+///
+/// Example usage:


Same as the above, use # Example instead.

Susurrus · 2018-08-06T03:33:08Z

src/kmod.rs

+libc_bitflags!(
+    /// Flags used by `delete_module`.
+    pub struct OFlags: libc::c_int {
+        O_NONBLOCK;


Please add doccomments for these items.

Susurrus · 2018-08-06T03:33:08Z

src/kmod.rs

+
+libc_bitflags!(
+    /// Flags used by `delete_module`.
+    pub struct OFlags: libc::c_int {


Can we rename this to OutputFlags or something less short-hand?

Susurrus · 2018-08-06T03:33:08Z

src/kmod.rs

+
+/// Unloads the kernel module with the given name.
+///
+/// Example usage:


# Example

src/kmod.rs

bachp · 2018-08-06T07:54:19Z

@Susurrus Kernel module rewritten, it is now dual licensed MIT or GPL-2.0+ and includes parameters. These are also used in tests.

@asomers I didn't find a way how to build external kernel modules with a separate build directory.

asomers · 2018-08-06T14:53:42Z

Did you try simply cd'ing to ${TMPDIR:-/tmp} before running make?

bachp · 2018-08-07T07:27:10Z

@asomers I don't think switching the workdir before doing make would work as the workdir needs to be in the same directory. One option would be to copy everything to a TMP location, do the build and then delete it again after the test. But it seems hacky.

asomers · 2018-08-08T16:05:07Z

@bachp could you try that then? No test should be creating files in the source directory. I can't even run these tests, because my source directory is mounted over NFS with rootsquash on.

bachp · 2018-08-09T10:13:49Z

@asomers I bumped the minimum required rust version to 1.24.1 as this is the version packaged in Debian. So it should allow them to still package rust tools depending on nix.

I think the freebsd jobs should be updated to this version too.

bachp · 2018-08-09T21:24:12Z

@Susurrus I incorporated your feedback into the documentation and added some additional information and links.

asomers · 2018-08-10T16:01:20Z

Why 1.24.1? If Nix only depends on 1.22.0 features, then the minimum rustc version should be 1.22.0. That shouldn't be a problem for building Debian packages. Nor should Nix depend in any way on Debian.

bachp · 2018-08-10T17:39:20Z

@asomers Rust 1.22 produces some compile errors that are not present in 1.20 and are no longer present in 1.24.1. See: https://travis-ci.org/nix-rust/nix/builds/413801114 for details on the error.

asomers · 2018-08-10T17:47:16Z

That looks like a bug in Nix. ptr may be a mutable reference. But since it's passed by value to encode_into, it itself does not need to be declared mutable. Try removing the mut and rebuilding on 1.22.0.

bachp · 2018-08-10T18:00:04Z

But why does this warning only pop up with 1.22 and not with 1.24.1 or 1.28?

bachp · 2018-08-14T14:40:47Z

I updated the MR to build with 1.22.1 and changed the offending code. But travis seems to have failed for some other reason now. Seems unrelated to the change.

asomers · 2018-08-14T14:52:33Z

The Travis failures were spurious. Restarting the jobs fixed them. I'm upgrading buildbot now.

bachp · 2018-08-14T20:42:20Z

Anything else that needs to be fixed?

Susurrus · 2018-08-15T01:35:29Z

CHANGELOG.md


 ### Changed
+- Bump minimum tested Rust version to 1.22.1.


"tested" -> "required"

This commit/change will be removed once #900 is merged

Susurrus · 2018-08-15T01:40:18Z

There are a bunch of changes unrelated to adding kmod, like the tempfile update and the various style changes. I'd prefer to merge #900 and then rebase and squash this merge into 2 commits:

updating the Rust requirements to 1.22.1
Adding kmod

We'll give #900 a couple of days.

bachp · 2018-08-15T09:34:56Z

@Susurrus I think the 1.22.1 update should go into #900 as it is related to tempfile.

bachp · 2018-09-02T21:56:44Z

Rebased after #900 got merged

Cargo.toml

bachp · 2018-09-04T19:56:59Z

I rebased again to fix the changelog conflict.

Susurrus

This looks pretty good to me, so I think it's time to refactor the commits and then we can merge. Please refactor this PR into 4 commits in the following order:

Update rand crate
Remove allow(unused_variables)
Factor out skipping tests if not root into a macro
Adding the kmod module

This avoids having both 0.4 and 0.5 (required by tempfile)

This macro can be used in tests to skip the test if it requires root to sucssfully run.

- init_module and finit_module to load kernel modules - delete_module to unload kernel modules Signed-off-by: Pascal Bach <pascal.bach@nextrem.ch>

bachp · 2018-09-05T20:02:58Z

@Susurrus PR reworked into 4 logical commits.

bachp · 2018-09-13T18:14:40Z

Anything still missing?

asomers

LGTM. @Susurrus do you have any more concerns?

Susurrus · 2018-09-23T04:16:47Z

bors r+

930: Add wrapper for linux kernel module loading r=Susurrus a=bachp - init_module and finit_module to load kernel modules - delete_module to unload kernel modules Co-authored-by: Pascal Bach <pascal.bach@nextrem.ch>

bors · 2018-09-23T04:40:50Z

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insmod and rmmod uutils/coreutils#1272

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deps: update tempfile to 3 #900

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bachp added 4 commits Aug 9, 2018

Update to rand 0.5 crate

da089f8

This avoids having both 0.4 and 0.5 (required by tempfile)

Replace allow unused directive with _ prefix

57603c6

Refactor skip_if_not_root into macro

81088ab

This macro can be used in tests to skip the test if it requires root to sucssfully run.

Add wrapper for linux kernel module loading

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- init_module and finit_module to load kernel modules - delete_module to unload kernel modules Signed-off-by: Pascal Bach <pascal.bach@nextrem.ch>

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nix-rust / nix

Add wrapper for linux kernel module loading #930

Add wrapper for linux kernel module loading #930

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