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Add handling of the .symver asm directives - #994

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marxin merged 12 commits into
wild-linker:mainfrom
marxin:symver-fix-emission
Sep 26, 2025
Merged

Add handling of the .symver asm directives#994
marxin merged 12 commits into
wild-linker:mainfrom
marxin:symver-fix-emission

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@marxin

@marxin marxin commented Jul 7, 2025 •
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After reworking of changes, the PR includes rudimentary .symver support that leads to successful linking of the alsa-lib shared library. When we encounter a symbol defined by .symver, we correctly mark it in the .gnu.version section.

There might still be missing gaps when it comes to symbol resolution if any other symbol points to a one defined via .symver, but let's see where can we get with this change.

@marxin marxin mentioned this pull request Jul 15, 2025
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marxin marked this pull request as ready for review September 25, 2025 18:27
davidlattimore
davidlattimore approved these changes Sep 26, 2025
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Awesome! I had assumed that this might have a slight performance impact, but it seems fine.

@marxin
marxin merged commit c4b19d1 into wild-linker:main Sep 26, 2025
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marxin deleted the symver-fix-emission branch September 26, 2025 16:55
@marxin marxin mentioned this pull request Sep 26, 2025
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@mati865

mati865 commented Sep 27, 2025 •
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I'm back from hiking and upon @marxin request I've run his Gentoo test build.

As the first step I have removed RUN emerge alsa-lib elfutils from https://github.com/marxin/gentoo-docker-testing/blob/main/Dockerfile and it works much better than before but it's still incomplete. Great work though!
Lvm2 build failed with:

make[1]: Entering directory '/var/tmp/portage/sys-fs/lvm2-2.03.22-r7/work/LVM2.2.03.22/libdm'
if x86_64-pc-linux-gnu-readelf -Ws ioctl/libdevmapper.so | grep -q dm_stats_create_region@@; then \
SYM=$(x86_64-pc-linux-gnu-readelf -Ws ioctl/libdevmapper.so | grep dm_stats_create_region@DM_1_02_106); \
if test -n "$SYM"; then touch .symver_check; \
else echo >&2 "Missing versioned symbols in ioctl/libdevmapper.so"; false; fi; \
else touch .symver_check; fi
Missing versioned symbols in ioctl/libdevmapper.so

The symbols inside the shared object:

cd /var/tmp/portage/sys-fs/lvm2-2.03.22-r7/work/LVM2.2.03.22/libdm
readelf -Ws ioctl/libdevmapper.so | grep dm_stats_create_region@
   359: 0000000000027330   322 FUNC    GLOBAL DEFAULT   13 dm_stats_create_region@@DM_1_02_107
   360: 000000000002bac0    28 FUNC    GLOBAL DEFAULT   13 dm_stats_create_region@@DM_1_02_106
   361: 000000000002bae0    29 FUNC    GLOBAL DEFAULT   13 dm_stats_create_region@@DM_1_02_104

Notice @ vs @@ difference.

According to https://maskray.me/blog/2020-11-26-all-about-symbol-versioning we should create symbol with only one @ if the symbol is defined.

@marxin

marxin commented Sep 29, 2025

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Thanks @mati865 for the testing effort and I think I have a fix: #1129. Feel free to continue with the gentoo-docker if you have spare cycles.

@mati865

mati865 commented Sep 29, 2025 •
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@marxin it doesn't fix lvm2 build.
The part that I was referring to, is "If foo is defined, produce foo and foo@v1 with the same binding and st_other value.".

@marxin

marxin commented Oct 1, 2025

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@mati865 I've just re-run locally the build of lvm2 and the build process finishes correctly (with #1129) with the following symbol listing:

readelf -Ws libdm/ioctl/libdevmapper.so | grep dm_stats_create_region@
   354: 0000000000049400    28 FUNC    GLOBAL DEFAULT   14 dm_stats_create_region@DM_1_02_106
   355: 0000000000049420    29 FUNC    GLOBAL DEFAULT   14 dm_stats_create_region@DM_1_02_104
   356: 0000000000044d30   317 FUNC    GLOBAL DEFAULT   14 dm_stats_create_region@@DM_1_02_107

While running on the main branch, I hit the aforementioned issue:

    [CHECK] ioctl/libdevmapper.so
Missing versioned symbols in ioctl/libdevmapper.so

@mati865

mati865 commented Oct 1, 2025

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Hmm, I'm sure I've copied the binary after building it. Perhaps I've built the debug one by mistake, I'll try later.

@mati865

mati865 commented Oct 1, 2025

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🤦🏻‍♂️ I had run cp target/release/wild /usr/bin in Gentoo container ...

Sorry for the confusion.

@marxin

marxin commented Oct 2, 2025

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No worries, that happens. Anyways, thanks for the testing effort.

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