Re: RTLD_DEEPBIND question

On 23/04/2025 21:56, Andriy Gapon wrote:
> BTW, I've been wondering how illumos avoids the problem even though they do not 
> use any special dlopen flags.
> It turns out that they link almost all system shared libraries with -Bdirect 
> option (which is Solaris/illumos specific).
> It's somewhat similar to, but different from, -Bsymbolic.
> https://docs.oracle.com/cd/E23824_01/html/819-0690/aehzq.html#scrolltoc
> https://docs.oracle.com/cd/E36784_01/html/E36857/gejfe.html

Oh, and it looks like there is an even better explanation for illumos.
There is a version map file for libdtrace which explicitly lists API functions 
and makes everything else local.
https://github.com/illumos/illumos-gate/blob/master/usr/src/lib/libdtrace/common/mapfile-vers

I wonder why we didn't do the same when porting.
Maybe we should do that now?

> I think that on FreeBSD we should use symbol visibility attributes or a symbol 
> map to hide (make local) symbols that are not expected to be interposed or have 
> a high chance to be interposed by accident.
> 
> IMO, yyparse should definitely get that treatment.
> 
> I think that approach would be better than magic rtld tricks.
> Especially because the tricks do not work with the current rtld.
> I'd rather make a change to libdtrace.so than to rtld.

This, while not as nice as the illumos solution, fixes my specific issue:
diff --git a/cddl/lib/libdtrace/Makefile b/cddl/lib/libdtrace/Makefile
index d086fffb07bc..58054d129b49 100644
--- a/cddl/lib/libdtrace/Makefile
+++ b/cddl/lib/libdtrace/Makefile
@@ -146,7 +146,8 @@ CFLAGS+=    -fsanitize=address -fsanitize=undefined
  LDFLAGS+=      -fsanitize=address -fsanitize=undefined
  .endif

-LIBADD=        ctf elf proc pthread rtld_db xo
+VERSION_MAP=   ${.CURDIR}/Symbol.map
+LIBADD=                ctf elf proc pthread rtld_db xo

  CLEANFILES=    dt_errtags.c dt_names.c

diff --git a/cddl/lib/libdtrace/Symbol.map b/cddl/lib/libdtrace/Symbol.map
new file mode 100644
index 000000000000..89ee9de65209
--- /dev/null
+++ b/cddl/lib/libdtrace/Symbol.map
@@ -0,0 +1,4 @@
+{
+       local:
+               yy*;
+};

-- 
Andriy Gapon