This is a tough one because .gdb_index, .debug_gnu_pubnames,
.debug_gnu_pubtypes and DWARF are underdocumented, and DWARF is
complicated even if you have a right documentation. But, I believe I
managed to create a correct .gdb_index section.
Just like ld.lld, mold's --gdb-index needs all input object files to
have been compiled with -ggnu-pubnames. We read symbol names and type
names from the sections generated by -ggnu-pubnames.
Unlike ld.gold and ld.lld, we do not use an external library to read
DWARF debug info records.
As always, this feature is implemented with speed in mind. For Clang
15 which is built with -ggnu-pubnames, mold takes ~150 ms to create a
~300 MiB .gdb_index section on a simulated 16-core machine.
Fixes https://github.com/rui314/mold/issues/396
It is very rare, but technically you can create a shared object that
can also be executed directly. You can do that by giving a dynamic
linker path to the linker.
https://github.com/rui314/mold/issues/422
With this change, you can link a simple bootloader using mold.
To do so, compile bootloader source files to object files with
the `-fno-PIC` flag and then invoke mold on the object files with
`-Ttext=<bootloader-start-address>` and `--oformat=binary`.
The .text segment is usually at the beginning of the output file if
the file is created that way. By passing the startup code as the first
file argument to the linker, you can place that startup code at the
beginning of the file.
Fixes https://github.com/rui314/mold/issues/418
Previously, we make all PLT entries canonical if we are creating
a position dependent executable, because I was thinking that promoting
usual PLT entries to canonical ones is harmless; symbol equality still
holds.
However, it looks like Qt depends on the usual linker's behavior not
to make PLT canonical if not necessary. I believe they are maintaining
some hidden symbol as aliases for exported symbols and compare their
addresses at runtime.
Of course this doesn't work if your program is not compiled with -fPIC,
but qt5/QtCore/qglobal.h has a macro to abort compilation if PIC is
disabled. (They check for __PIC__ and __PIE__ macros.) So, all object
files are guaranteed to be compiled with -fPIC if they are using QT
functions, and they assume that the linker doesn't create a canonical
PLT for Qt functions.
This commit makes mold to create canonical PLTs only when needed.
That is, if an address of a function is directly taken (i.e. not via
GOT), then mold makes its PLT canonical.
Fixes https://github.com/rui314/mold/issues/352
With this change, you can now cross compile test cases and run
them on qemu-user. Here is an example to run our test suits in
an emulated ARM32 environment.
$ CC=arm-linux-gnueabihf-gcc \
CXX=arm-linux-gnueabihf-g++ \
GCC=arm-linux-gnueabihf-gcc \
GXX=arm-linux-gnueabihf-g++ \
OBJDUMP=arm-linux-gnueabihf-objdump \
MACHINE=arm \
QEMU='qemu-arm -L /usr/arm-linux-gnueabihf' \
make -j16 test
Currently, we do not support relaxations of TLS GD/LD relocations
for ARM64. This is in practice not a problem because TLSDESC is used
on ARM64 by default.
However, there's one situation in which not supporting TLS GD/LD
relaxation becomes an issue; static linking. If an executable is
statically-linked, relaxation is mandatory because we can't generate
dynamic relocations for GD/LD relocations.
In this patch, we simply report an error if an object file compiled
with TLS GD/LD is used for creating a statically-linked executable.
This commit fixes all tests on ARM64.
Some `ldd` impls don't support the --version option. We do not
want to show the error message but instead just skip the test
entirely.
https://github.com/rui314/mold/pull/385
After a certain point, it is not expected that there's a remaining
undefined symbol. -noinhibit-exec did not respect that invariant,
which caused a crash bug on ARM64.
This change forces all symbols to be resolved if --noinhibit-exec
is given.
Fixes https://github.com/rui314/mold/issues/383
We unset `LANG`, but it looks like `LC_ALL` takes precedence over `LANG`,
so we should set `LC_ALL` to `C`.
Reported at https://github.com/rui314/mold/pull/385
mold 1.1.1 generates `-static-pie` code that works with glibc 2.35 but
segfaults with glibc 2.34 or older.
Signed-off-by: Christoph Erhardt <github@sicherha.de>
Previously, mold did not work with the -static-pie compiler flag.
In order to support static PIE, we need the following:
1. Create a .dynamic section even if it is not a dynamic executable, and
2. do not define __rel_iplt_start/end symbols.
The second part is required to workaround a glibc issue.
Even with these changes, mold-generated executable doesn't work with
old glibc versions. But I think it's OK because -static-pie is relatively
new option and you need a newer toolchain anyway.
It looks like the glibc loader does not use this field in the dynamic
section. GNU ld, gold and LLVM lld don't create this. So I think we
can just follow suit.
