Add newly released mold version 2.33.0 from upstream
https://github.com/rui314/mold
New features
- mold gained a new linker flag --separate-debug-file to bundle debug
info sections into a separate file instead of putting them into a main
output file. You can optionally specify a filename in the form of
--separate-debug-file=<filename>. By default, a debug info file is
created in the same directory as the main output file with the .dbg
extension. mold embeds the debug file's filename into the main output
file so that gdb can automatically follow the link to find debug info
when debugging the main output file.
- The main objective of this flag is to speed up the mold linker even
more. By default, mold creates a separate debug file in the background
after creating a main output file, so that you can start running the
executable as soon as possible while mold is still working on linking
its debug info sections. For example, linking clang with debug info
normally takes ~1.70s on a Threadripper 7980X machine, while it takes
only ~0.52s with --separate-debug-info. Shaving off a full second in
quick edit-rebuild-run cycles should improve programmers'
productivity. If you do not want mold to work in the background, pass
the --no-detach option. (596ffa9)
- mold now supports the --no-allow-shlib-undefined flag. If the option
is given, mold checks if all undefined symbols are resolved not only
for input object files but also for shared libraries passed to the
linker. To use the feature, you need to pass all shared libraries,
including transitively dependent ones, to the linker so that the
linker can resolve all symbols that are available at runtime.
(3001f02)
- mold gained the --dynamic-list-data flag for the sake of compatibility
with GNU ld. If the flag is given, all data symbols are exported as
dynamic symbols. (dd8d971)
- [x86-64] -z x86-64-v2, -z x86-64-v3, -z x86-64-v4 flags are supported.
(5606087)
Bug fixes and compatibility improvements
- [x86-64] Recent x86-64 processors support Intel CET to protect control
flow integrity. When the feature is enabled, the instruction that is
executed immediately after an indirect branch must be endbr64 or a CPU
fault will raise. In other words, it restricts the locations where the
control can transfer to with indirect branches. Doing that makes ROP
attacks harder to conduct.
- A problem with that is the compiler needs to conservatively emit an
endbr64 at the beginning of each global function because the compiler
doesn't know whether or not the function's address is taken in other
translation units. As a result, the resulting binary contains more
endbr64s than necessary, weakening the protection.
- mold supports the -z rewrite-endbr option to conduct a whole program
analysis and rewrite endbr64 with nop if a function's address is not
actually taken within the program. Previously, mold didn't take
section symbols into account when conducting the analysis, which
resulted in culling some endbr64s that must not be removed. Now, the
bug has been fixed. We confirmed that mold can build itself with -z
rewrite-endbr, and the resulting mold executable works fine with Intel
CET. (ed7eec5)
- mold now creates a .eh_frame section even if it's empty. (14a4b05)
- [LoongArch] The following relocations are now supported:
R_LARCH_TLS_LE_HI20_R, R_LARCH_TLS_LE_ADD_R, R_LARCH_TLS_LE_LO12_R,
R_LARCH_CALL36, R_LARCH_RELAX (36e5b4b, 98a7cff, 2c6f379)
- [LoongArch] Some relaxations that reduce the section size are now
supported. (74b359f, 121f917)
- [LoongArch] Range extension thunk support has been removed in favor of
R_LARCH_CALL36 relocations. (47c092a)
Signed-off-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
Add newly released mold version 2.32.0 from upstream
https://github.com/rui314/mold
New features
- mold supports a feature called Identical Code Folding, or ICF. As the
name suggests, ICF finds identical functions and merges them to reduce
the size of an output file. This is especially effective for
template-heavy C++ programs since templates tend to be instantiated to
the same machine code for different types. For example,
std::vector<int> is likely to be instantiated to the same code as
std::vector<unsigned>. We've made an improvement to our ICF algorithm
so that the --icf feature is ~50% faster than the previous version.
(fa8e95a)
- The -z rodynamic option is now supported for compatibility with LLVM
lld. With the option, mold places the .dynamic section into a
read-only segment. (9a233df)
Bug fixes and compatibility improvements
- Previously, mold behaved differently compared to other linkers if both
-z defs and --undefined=ignore-in-object-files were given (#1270).
Now, they override each other so that the mold's behavior is
compatible with others. (8cd85aa)
- Previously, --dependency-file mistakenly recorded response files as
dependencies (#1258). This bug has been fixed. (4281f45)
- There was a bug that mold corrupted debug info section contents when
the --relocatable option was given (#1265). This issue has been fixed.
(08b0a16)
- [PPC64] The R_PPC64_TPREL16_LO_DS relocation type is supported.
(a8cd2e8)
- [ARM64, PPC64, LoongArch] mold 2.31.0 or earlier may have failed with
an assertion failure when creating a large output file (#1224). This
issue has been resolved. (c7c8583)
Signed-off-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
Allows building the #mold linker, which can then be used in the
cross-toolchain by passing the -fuse-ld=mold to the gcc flags. It is
much faster than ld or gold.
This requires a C++20 compiler and cmake.
Initially implemented by Arnaud, and HC added configure check for cmake.
Outstanding task to validate compiler is C++20 compatible.
Signed-off-by: Arnaud Vrac <avrac@freebox.fr>
Signed-off-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
