Re: git: 0d4f7723bc43 - main - libc: link libsys as a auxiliary filter library

On 5 Feb 2024, at 20:38, Brooks Davis <brooks@FreeBSD.org> wrote:
> 
> The branch main has been updated by brooks:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=0d4f7723bc43e06ca22025740cb826a7f282ea11
> 
> commit 0d4f7723bc43e06ca22025740cb826a7f282ea11
> Author:     Brooks Davis <brooks@FreeBSD.org>
> AuthorDate: 2023-11-15 23:35:16 +0000
> Commit:     Brooks Davis <brooks@FreeBSD.org>
> CommitDate: 2024-02-05 20:34:56 +0000
> 
>    libc: link libsys as a auxiliary filter library
> 
>    At runtime, when rtld loads libc it will also load libsys.  For each
>    symbol that is present in both, the libsys one will override the libc
>    one.  It continues to be the case that program need only link against
>    libc (usually implicitly).  The linkage to libsys is automatic.
> 
>    Reviewed by:    kib, emaste, imp
>    Pull Request:   https://github.com/freebsd/freebsd-src/pull/908
> ---
> Makefile.inc1            | 2 ++
> UPDATING                 | 6 ++++++
> lib/Makefile             | 2 +-
> lib/libc/Makefile        | 3 +++
> share/mk/src.libnames.mk | 2 +-
> 5 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile.inc1 b/Makefile.inc1
> index 7a9917fd8a74..f97e53cc7f9a 100644
> --- a/Makefile.inc1
> +++ b/Makefile.inc1
> @@ -3125,10 +3125,12 @@ _startup_libs= lib/csu
> _startup_libs+= lib/libc
> _startup_libs+= lib/libc_nonshared
> _startup_libs+= lib/libcxxrt
> +_startup_libs+= lib/libsys
> 
> _prereq_libs+= lib/libgcc_eh lib/libgcc_s
> _startup_libs+= lib/libgcc_eh lib/libgcc_s
> 
> +lib/libc__L: lib/libsys__L
> lib/libgcc_s__L: lib/libc__L
> lib/libgcc_s__L: lib/libc_nonshared__L
> lib/libcxxrt__L: lib/libgcc_s__L
> diff --git a/UPDATING b/UPDATING
> index 33bae2a42b9d..aae30936a8b5 100644
> --- a/UPDATING
> +++ b/UPDATING
> @@ -27,6 +27,12 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 15.x IS SLOW:
> world, or to merely disable the most expensive debugging functionality
> at runtime, run "ln -s 'abort:false,junk:false' /etc/malloc.conf".)
> 
> +20240205:
> + For dynamically linked programs, system calls are now made from
> + libsys rather than libc.  No change in linkage is required as
> + libsys is an auxiliary filter for libc.  People building custom
> + images must ensure that libsys.so.7 is included.
> +
> 20240202:
> Loader now also read configuration files listed in local_loader_conf_files.
> Files listed here are the last ones read. And /boot/loader.conf.local was
> diff --git a/lib/Makefile b/lib/Makefile
> index db07883e2b10..9d2531820c8b 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -123,7 +123,7 @@ SUBDIR_DEPEND_libbsnmp= ${_libnetgraph}
> SUBDIR_DEPEND_libc++:= libcxxrt
> # libssp_nonshared doesn't need to be linked into libc on every arch, but it is
> # small enough to build that this bit of serialization is likely insignificant.
> -SUBDIR_DEPEND_libc= libcompiler_rt libssp_nonshared
> +SUBDIR_DEPEND_libc= libsys libcompiler_rt libssp_nonshared
> SUBDIR_DEPEND_libcam= libsbuf
> SUBDIR_DEPEND_libcasper= libnv
> SUBDIR_DEPEND_libdevstat= libkvm
> diff --git a/lib/libc/Makefile b/lib/libc/Makefile
> index 72300e88d3d7..6a54f7641087 100644
> --- a/lib/libc/Makefile
> +++ b/lib/libc/Makefile
> @@ -62,6 +62,9 @@ CFLAGS+= -ftls-model=initial-exec
> #
> LDFLAGS+= -nodefaultlibs
> LIBADD+= compiler_rt
> +LIBADD+= sys
> +
> +LDFLAGS+=-Wl,--auxiliary,libsys.so

From reading documentation and implementation code (LLD + rtld), should
this not be the soname, i.e. libsys.so.7?

Jess

> .if ${MK_SSP} != "no" && \
>     (${LIBC_ARCH} == "i386" || ${LIBC_ARCH:Mpowerpc*} != "")
> diff --git a/share/mk/src.libnames.mk b/share/mk/src.libnames.mk
> index 5a6932614b29..3c19a4c45da3 100644
> --- a/share/mk/src.libnames.mk
> +++ b/share/mk/src.libnames.mk
> @@ -393,7 +393,7 @@ _DP_xo= util
> _DP_ztest= geom m nvpair umem zpool pthread avl zfs_core spl zutil zfs uutil icp
> # The libc dependencies are not strictly needed but are defined to make the
> # assert happy.
> -_DP_c= compiler_rt
> +_DP_c= sys compiler_rt
> # Use libssp_nonshared only on i386 and power*.  Other archs emit direct calls
> # to __stack_chk_fail, not __stack_chk_fail_local provided by libssp_nonshared.
> .if ${MK_SSP} != "no" && \