Date: Fri, 16 May 2025 10:11:12 -0400 From: Mark Johnston <markj@freebsd.org> To: Andriy Gapon <avg@freebsd.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, FreeBSD Current <current@freebsd.org> Subject: Re: RTLD_DEEPBIND question Message-ID: <aCdHgFCQA1ghPfYJ@nuc> In-Reply-To: <5b887290-a6aa-49ff-aa92-f335ed09b9a5@freebsd.org> References: <aALjHwFnFKChuAdR@kib.kiev.ua> <900c8521-559a-47b5-acaa-ae941f6852c4@freebsd.org> <fd12cce4-7e6b-4ab6-bced-b36e98c995ba@FreeBSD.org> <7c4e1682-d797-493c-8326-08d51dde3359@FreeBSD.org> <aAN69URjEJFuOLxR@kib.kiev.ua> <aAN9NH1IR-gZceP4@kib.kiev.ua> <e528f630-9d6e-4ec6-b7e6-30b5a978f5c8@freebsd.org> <59db8ace-770f-4f73-976f-411f6de0885a@FreeBSD.org> <aA4-hQ6xrF2dD-sJ@nuc> <5b887290-a6aa-49ff-aa92-f335ed09b9a5@freebsd.org>
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On Fri, May 16, 2025 at 03:22:52PM +0300, Andriy Gapon wrote: > On 27/04/2025 17:26, Mark Johnston wrote: > > On Thu, Apr 24, 2025 at 08:56:44AM +0300, Andriy Gapon wrote: > > > 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 don't have any objection, but I believe adding a version map after the > > fact doesn't accomplish much, assuming that we care deeply about ABI > > stability in libdtrace.so (I'm not sure we do though). > > My primary goal here is not ABI stability, but hiding symbols that really > should not be exported. See more at the end. > > At the same time I am not sure why it could be too late to start caring > about ABI stability now. Assuming we actually would want to do that. I just mean that the version map helps only helps provide stability for binaries linked to libdtrace.so after the version map is introduced. > And I don't want to single out libtrace here. > It seems that the story is the same for all libraries that have been ported > from illumos. > E.g., libzfs_core was supposed to be a library that cares greatly about its > API / ABI stability. > > > > > 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*; > > > +}; > > > > This just gives the lexer/parser symbols in libdtrace.so local > > visibility? I think that's fine. > Yes, that's the intention. > > I tested locally two versions of Symbol.map for libdtrace. > The basic one quoted here and a more extended one based on illumos > lib/libdtrace/common/mapfile-vers. > The latter version does not define any symbol versions, its purpose is only > to be a white-list of things to make public / global: > https://people.freebsd.org/~avg/libdtrace-Symbol.map Do we really want to export _dtrace_debug? > Comparing to illumos I only had to add 3 dtrace_oformat* symbols, > > Both versions worked equally well in my tests, but maybe I missed more of > FreeBSD extensions. > > Which one would be better to get into the tree? Having a full whitelist seems preferable to me. Did you test lockstat as well? I believe it and dtrace(8) are the only users of libdtrace.so in the base system.home | help
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