linuxManualConfig: install GDB scripts #221707
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Looks like we're still missing the GDB entry point (vmlinux-gdb.py). All the rest of the scripts are installed into the build directory in the modules path, but not that one. |
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We can avoid the need to explicitly exclude it later if we just put it somewhere else to begin with.
linux is unusual in that we include its sources in an output. There's no point unpacking into /build when we're going to copy the sources into $dev later. Let's unpack directly into the final destination of the code, and save copying a whole kernel source tree (often across filesystems!). This also means that Kbuild knows the location of the sources, which will allow us to install the GDB scripts — some scripts are generated, and some are not, so the generated ones end up in the build directory, accompanied by symlinks to the non-generated ones in the source directory.
We've basically been reimplementing this — by default it contains vmlinux, dtbs (on applicable architectures), modules, and architecture specific stuff like $(KBUILD_IMAGE) and a couple of other miscellaneous files.
These are required to debug kernel modules. Since we're now able to
do that, there's another reason besides BTF to enable DEBUG_INFO, so
I've done that for pre-BTF kernel modules as well here.
For GDB to get configured correctly, vmlinux-gdb.py has to be two
directories up from scripts/gdb, and vmlinux has to be next to
vmlinux-gdb.py. The least invasive way to satisfy these constraints
is to make vmlinux a symlink, which GDB will resolve before looking
for vmlinux-gdb.py.
Tested both ways of getting the scripts into GDB that I know of:
gdb /nix/store/7n77ijlxkxr6d613h02lr707kvjx6j1k-linux-6.1.19-dev/vmlinux \
-iex 'add-auto-load-safe-path /nix/store/7n77ijlxkxr6d613h02lr707kvjx6j1k-linux-6.1.19-dev/lib/modules/6.1.19/build/vmlinux-gdb.py' \
-ex 'lx-version' \
-ex 'q'
gdb /nix/store/7n77ijlxkxr6d613h02lr707kvjx6j1k-linux-6.1.19-dev/vmlinux \
-ex 'source /nix/store/7n77ijlxkxr6d613h02lr707kvjx6j1k-linux-6.1.19-dev/lib/modules/6.1.19/build/vmlinux-gdb.py' \
-ex 'lx-version' \
-ex 'q'
Also tested that the strip changes don't result in meaningful output
size changes (there's some small variation due to BTF data not always
coming out the same size, which is unrelated), and built every kernel
I can on x86_64 to make sure I'm not relying on build system behaviour
specific to newer kernels.
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Might have been worth waiting to merge at the same time as some kernel updates to minimise rebuilds, but maybe it doesn't matter. |
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I believe this broke |
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Also noticed: https://hydra.nixos.org/build/213443349
(edited the above references to point to a "more common" variant) |
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There is a point. The point is not to have circular references in the outpaths, since Nix forbids that. This PR broke both powerpc and mips, and was incredibly frustrating to deal with because trying each fix requires a ~1hour build, and the end of which you get an unhelpful message from Nix about cycles so you need to inspect the failed build... but A much better strategy would have been to put the sources in their own separate output (either " |
| "vmlinux" # for "perf" and things like that | ||
| ] ++ optional isModular "modules" |
There was a problem hiding this comment.
This PR inadvertently destroyed the ability to build a kernel without the modules, which is a much faster build.
| kernelConf.target | ||
| "vmlinux" # for "perf" and things like that | ||
| ] ++ optional isModular "modules" | ||
| ++ optionals buildDTBs ["dtbs" "DTC_FLAGS=-@"] |
…iple-outputs linuxManualConfig: revert #221707
Description of changes
linux is unusual in that we include its sources in an output. There's no point unpacking into /build when we're going to copy the sources into $dev later. Let's unpack directly into the final destination of the code, and save copying a whole kernel source tree (often across filesystems!).
This also means that Kbuild knows the location of the sources, which will allow us to install the GDB scripts — some scripts are generated, and some are not, so the generated ones end up in the build directory, accompanied by symlinks to the non-generated ones in the source directory.
Things done
sandbox = trueset innix.conf? (See Nix manual)nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage./result/bin/)