See previous commit for what was done to `binutils` to make this
possible.
There were some uses of `forcedNativePackages` added. The
combination of overrides with that attribute is highly spooky: it's
often important that if an overridden package comes from it, the
replaced arguments for that package come from it. Long term this
package set and all the spookiness should be gone and irrelevant:
"Move along, nothing to see here!"
No hashes should be changed with this commit
Use `buildPackages.binutils` to get build = host != target binutils,
i.e. the old `binutilsCross`, and use
`buildPackages.buildPackages.binutils` to get build = host = target
binutils, i.e. the old `binutils`.
`buildPackages` chains like this are supposed to remove the need for
all such `*Cross` derivations. We start with binutils because it's
comparatively easy.
No hashes of cross-tests should be changed
stdenv.cross is a silly attribute that needs to go leaving the well-defined hostPlatform and targetPlatform. This PR doesn't remove it, but changes its definition: before it tracked the target platform which is sometimes more useful for compilers, and now it tracks the host platform which is more useful for everything else. Most usages are libraries, falling in the "everything else" category, so changing the definition makes sense to appease the majority. The few compiler (gcc in particular) uses that exist I remove to use targetPlatform --- preserving correctness and becoming more explicit in the process.
I would also update the documentation aside mentioning stdenv.cross as deprecated, but the definition given actually erroneously assumes this PR is already merged!
Before all overrides were also pruned in the previous stage, now
only gcc and binutils are, because they alone care about about the
target platform. The rest of the overrides don't, so it's better to
preserve them in order to avoid spurious rebuilds.
Each bootstrapping stage ought to just depend on the previous stage, but
poorly-written compilers break this elegence. This provides an easy-enough
way to depend on the next stage: targetPackages. PLEASE DO NOT USE IT
UNLESS YOU MUST!
I'm hoping someday in a pleasant future I can revert this commit :)
When not cross compiling, nativeBuildInputs and buildInputs have
identical behaviour. Currently that is implemented by having
mkDerivation do a concatenation of those variables in Nix code and pass
that to the builder via the nativeBuildInputs attribute.
However, that has some annoying side effects, like `foo.buildInputs`
evaluating to `[ ]` even if buildInputs were specified in the nix
expression for foo.
Instead, pass buildInputs and nativeBuildInputs in separate variables as
usual, and move the logic of cross compilation vs. native compilation to
the stdenv builder script. This is probably a tiny bit uglier but
fixes the previous problem.
Issue #4855.
If a package's meta has `knownVulnerabilities`, like so:
stdenv.mkDerivation {
name = "foobar-1.2.3";
...
meta.knownVulnerabilities = [
"CVE-0000-00000: remote code execution"
"CVE-0000-00001: local privilege escalation"
];
}
and a user attempts to install the package, they will be greeted with
a warning indicating that maybe they don't want to install it:
error: Package ‘foobar-1.2.3’ in ‘...default.nix:20’ is marked as insecure, refusing to evaluate.
Known issues:
- CVE-0000-00000: remote code execution
- CVE-0000-00001: local privilege escalation
You can install it anyway by whitelisting this package, using the
following methods:
a) for `nixos-rebuild` you can add ‘foobar-1.2.3’ to
`nixpkgs.config.permittedInsecurePackages` in the configuration.nix,
like so:
{
nixpkgs.config.permittedInsecurePackages = [
"foobar-1.2.3"
];
}
b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
‘foobar-1.2.3’ to `permittedInsecurePackages` in
~/.config/nixpkgs/config.nix, like so:
{
permittedInsecurePackages = [
"foobar-1.2.3"
];
}
Adding either of these configurations will permit this specific
version to be installed. A third option also exists:
NIXPKGS_ALLOW_INSECURE=1 nix-build ...
though I specifically avoided having a global file-based toggle to
disable this check. This way, users don't disable it once in order to
get a single package, and then don't realize future packages are
insecure.
If a package's meta has `knownVulnerabilities`, like so:
stdenv.mkDerivation {
name = "foobar-1.2.3";
...
meta.knownVulnerabilities = [
"CVE-0000-00000: remote code execution"
"CVE-0000-00001: local privilege escalation"
];
}
and a user attempts to install the package, they will be greeted with
a warning indicating that maybe they don't want to install it:
error: Package ‘foobar-1.2.3’ in ‘...default.nix:20’ is marked as insecure, refusing to evaluate.
Known issues:
- CVE-0000-00000: remote code execution
- CVE-0000-00001: local privilege escalation
You can install it anyway by whitelisting this package, using the
following methods:
a) for `nixos-rebuild` you can add ‘foobar-1.2.3’ to
`nixpkgs.config.permittedInsecurePackages` in the configuration.nix,
like so:
{
nixpkgs.config.permittedInsecurePackages = [
"foobar-1.2.3"
];
}
b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
‘foobar-1.2.3’ to `permittedInsecurePackages` in
~/.config/nixpkgs/config.nix, like so:
{
permittedInsecurePackages = [
"foobar-1.2.3"
];
}
Adding either of these configurations will permit this specific
version to be installed. A third option also exists:
NIXPKGS_ALLOW_INSECURE=1 nix-build ...
though I specifically avoided having a global file-based toggle to
disable this check. This way, users don't disable it once in order to
get a single package, and then don't realize future packages are
insecure.
This fixes the "sliding window" principle:
0. Run packages: build = native; host = foreign; target = foreign;
1. Build packages: build = native; host = native; target = foreign;
2. Vanilla packages: build = native; host = native; target = native;
3. Vanilla packages: build = native; host = native; target = native;
n+3. ...
Each stage's build dependencies are resolved against the previous stage,
and the "foreigns" are shifted accordingly. Vanilla packages alone are
built against themsevles, since there are no more "foreign"s to shift away.
Before, build packages' build dependencies were resolved against
themselves:
0. Run packages: build = native; host = foreign; target = foreign;
1. Build packages: build = native; host = native; target = foreign;
2. Build packages: build = native; host = native; target = foreign;
n+2. ...
This is wrong because that principle is violated by the target
platform staying foreign.
This will change the hashes of many build packages and run packages, but
that is OK. This is an unavoidable cost of fixing cross compiling.
The cross compilation docs have been updated to reflect this fix.
Our bootstrap tools are actually broken right now due to busybox not
working when invoked directly from a store path. (It says e.g.
"0qqqw19y4gmknajw8vg4fvhx9gxdqlhz-busybox: applet not found").
Make this test actually fail in such case, the next commit will fix the
problem with busybox.
This is required for Aarch64 since a lot of source tarballs ship with
outdated configure scripts that don't recognize aarch64. Simply
replacing the config.guess and config.sub with new versions from
upstream makes them build again.
This same approach is used by at least Buildroot and Fedora. In
principle this could be enabled for all architectures but
conditionalizing this on aarch64 avoids a mass rebuild on x86.
The long term goal is a big replace:
{ inherit system platform; } => buildPlatform
crossSystem => hostPlatform
stdenv.cross => targetPlatform
And additionally making sure each is defined even when not cross compiling.
This commit refactors the bootstrapping code along that vision, but leaves
the old identifiers with their null semantics in place so packages can be
modernized incrementally.
[N.B., this package also applies to the commits that follow it in the same
PR.]
In most cases, buildPackages = pkgs so things work just as before. For
cross compiling, however, buildPackages is resolved as the previous
bootstrapping stage. This allows us to avoid the mkDerivation hacks cross
compiling currently uses today.
To avoid a massive refactor, callPackage will splice together both package
sets. Again to avoid churn, it uses the old `nativeDrv` vs `crossDrv` to do
so. So now, whether cross compiling or not, packages with get a `nativeDrv`
and `crossDrv`---in the non-cross-compiling case they are simply the same
derivation. This is good because it reduces the divergence between the
cross and non-cross dataflow. See `pkgs/top-level/splice.nix` for a comment
along the lines of the preceding paragraph, and the code that does this
splicing.
Also, `forceNativeDrv` is replaced with `forceNativePackages`. The latter
resolves `pkgs` unless the host platform is different from the build
platform, in which case it resolves to `buildPackages`. Note that the
target platform is not important here---it will not prevent
`forcedNativePackages` from resolving to `pkgs`.
--------
Temporarily, we make preserve some dubious decisions in the name of preserving
hashes:
Most importantly, we don't distinguish between "host" and "target" in the
autoconf sense. This leads to the proliferation of *Cross derivations
currently used. What we ought to is resolve native deps of the cross "build
packages" (build = host != target) package set against the "vanilla
packages" (build = host = target) package set. Instead, "build packages"
uses itself, with (informally) target != build in all cases.
This is wrong because it violates the "sliding window" principle of
bootstrapping stages that shifting the platform triple of one stage to the
left coincides with the next stage's platform triple. Only because we don't
explicitly distinguish between "host" and "target" does it appear that the
"sliding window" principle is preserved--indeed it is over the reductionary
"platform double" of just "build" and "host/target".
Additionally, we build libc, libgcc, etc in the same stage as the compilers
themselves, which is wrong because they are used at runtime, not build
time. Fixing this is somewhat subtle, and the solution and problem will be
better explained in the commit that does fix it.
Commits after this will solve both these issues, at the expense of breaking
cross hashes. Native hashes won't be broken, thankfully.
--------
Did the temporary ugliness pan out? Of the packages that currently build in
`release-cross.nix`, the only ones that have their hash changed are
`*.gcc.crossDrv` and `bootstrapTools.*.coreutilsMinimal`. In both cases I
think it doesn't matter.
1. GCC when doing a `build = host = target = foreign` build (maximally
cross), still defines environment variables like `CPATH`[1] with
packages. This seems assuredly wrong because whether gcc dynamically
links those, or the programs built by gcc dynamically link those---I
have no idea which case is reality---they should be foreign. Therefore,
in all likelihood, I just made the gcc less broken.
2. Coreutils (ab)used the old cross-compiling infrastructure to depend on
a native version of itself. When coreutils was overwritten to be built
with fewer features, the native version it used would also be
overwritten because the binding was tight. Now it uses the much looser
`BuildPackages.coreutils` which is just fine as a richer build dep
doesn't cause any problems and avoids a rebuild.
So, in conclusion I'd say the conservatism payed off. Onward to actually
raking the muck in the next PR!
[1]: https://gcc.gnu.org/onlinedocs/gcc/Environment-Variables.html
This patch add a new argument to Nixpkgs default expression named "overlays".
By default, the value of the argument is either taken from the environment variable `NIXPKGS_OVERLAYS`,
or from the directory `~/.nixpkgs/overlays/`. If the environment variable does not name a valid directory
then this mechanism would fallback on the home directory. If the home directory does not exists it will
fallback on an empty list of overlays.
The overlays directory should contain the list of extra Nixpkgs stages which would be used to extend the
content of Nixpkgs, with additional set of packages. The overlays, i-e directory, files, symbolic links
are used in alphabetical order.
The simplest overlay which extends Nixpkgs with nothing looks like:
```nix
self: super: {
}
```
More refined overlays can use `super` as the basis for building new packages, and `self` as a way to query
the final result of the fix-point.
An example of overlay which extends Nixpkgs with a small set of packages can be found at:
https://github.com/nbp/nixpkgs-mozilla/blob/nixpkgs-overlay/moz-overlay.nix
To use this file, checkout the repository and add a symbolic link to
the `moz-overlay.nix` file in `~/.nixpkgs/overlays` directory.
