https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107251
Bug ID: 107251
Summary: RISC-V linux kernel compiled with -mno-relax generates
a lot of local symbols
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: xnox at ubuntu dot com
Target Milestone: ---
Previous reported at
https://github.com/riscv-collab/riscv-gnu-toolchain/issues/1036
$ du -h btrfs.ko.*
76M btrfs.ko.riscv64
42M btrfs.ko.x86_64
$ strip --strip-debug btrfs.ko.x86_64
$ riscv64-linux-gnu-strip --strip-debug btrfs.ko.riscv64
$ du -h btrfs.ko.*
17M btrfs.ko.riscv64
2.8M btrfs.ko.x86_64
$ strip --strip-debug --discard-locals btrfs.ko.x86_64
$ riscv64-linux-gnu-strip --strip-debug --discard-locals btrfs.ko.riscv64
$ du -h btrfs.ko.*
4.2M btrfs.ko.riscv64
2.8M btrfs.ko.x86_64
The above demonstrates that RISCV kernel modules are compiled with -mno-relax
option, and yet a lot of relocation symbols are emitted and remain in the
modules keeping their size very large.
Over on github issue it was mentioned that "There is a known problem with GNU
as that we still emit extra symbols and relocations when -mno-relax is used.
Kernel modules are compiled -mno-relax. So fixing this would help reduce the
symtab size." However I was unable to find a bug report pointing this out.
Could you please ensure that when compiling code, the extra symbols and
relocations are not emitted, or otherwise stripped? Such that calling
--discard-locals would have no particular effect on the binary sizes. It is
inconvenient for distributions to call --discard-locals on riscv, even when
otherwise one is keeping the rest of the debug symbols for example.
I have observed this with gcc-10 and upwords, and most recently with gcc-12. I
can try newer builds of gcc and/or any patches to confirm behaviour.
