Does not work on binaries linked with mold

[tumanovm]

Hello!

When I tried to use uftrace 0.16 in project I noticed that it does not work on binaries linked with mold. It works fine when linking with gold in the same environment, so I've tried to make a minimal example for you.

I attached an archive with a Dockerfile and a couple of shell scripts for your convinience.
uftrace-mold.tar.gz

Here is a short overview:

• Extract contents somewhere and cd into directory
• Use ./build-image.sh to build image (then ./remove-image.sh later to clean up your environment)
• Use ./in-container.sh <COMMAND> to run command inside container as if your working directory is project (For example ./in-container.sh make <TARGET>)
• See project/Makefile to learn and edit compile command and uftrace record command
• Use ./in-container.sh make record to compile a simple hello world executable and run uftrace record on it
• See project/output directory to find uftrace log file and uftrace.data directory

Instead of getting "Hello world!" message in stdout when running ./in-container.sh make record, uftrace exits with code 2 and uftrace.log contains this message:
WARN: child terminated by signal: 5: Trace/breakpoint trap

Environment:

• uftrace 0.16
• gcc 13.2
• mold 2.33.0

Thanks for the great tool. It is very helpful and convinient!

[tumanovm]

When running uftrace on a real executable linked with mold I could find these lines in log:

WARN: Segmentation fault: address not mapped (addr: 0x1)
WARN: Backtrace from uftrace  ( x86_64 dwarf perf sched )
WARN: =====================================
WARN: [0] (OPENSSL_cpuid_setup[55963b1b17c0] <= <559639f4e92b>[559639f4e92b])
uftrace: MSG START: /uftrace-6de1a0c1d3f49a0b-60-000
uftrace: MSG TASK_START : 60/60
uftrace: all process/thread exited
WARN: child terminated by signal: 11: Segmentation fault

After switching linker from mold to gold there are no such lines in log and everything works as expected

[namhyung]

Thanks for the report. I've never tried mold linker by myself yet, but it looks like a cool project. I'll take a look what difference it caused the trouble.