Comment 5 for bug 1853852

in GDB with follow-fork-mode child I can check which call is actually failing in the child:

It is this one:
p = mmap(NULL, page_size(), PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1,0);
assert_se(p == MAP_FAILED);

It expects a fail (due to seccomp block) but does not get that.

Take it with a grain of salt, that is the packaged binary with -Ox optimizations.