[PATCH v6 4/5] Add --disable-default-dt-relr
H.J. Lu
hjl.tools@gmail.com
Tue Mar 29 22:25:36 GMT 2022
On Tue, Mar 29, 2022 at 10:19 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 10/03/2022 17:03, H.J. Lu via Libc-alpha wrote:
> > Enable DT_RELR in glibc shared libraries and position independent
> > executables (PIE) automatically if linker supports -z pack-relative-relocs.
> >
> > Also add a new configuration option, --disable-default-dt-relr, to
> > avoid DT_RELR usage in glibc shared libraries and PIEs.
>
> LGTM, with two small nits below.
>
> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>
> > ---
> > INSTALL | 6 ++++++
> > Makeconfig | 19 +++++++++++++++++++
> > Makerules | 2 ++
> > configure | 18 ++++++++++++++++++
> > configure.ac | 13 +++++++++++++
> > elf/Makefile | 4 +++-
> > manual/install.texi | 5 +++++
> > 7 files changed, 66 insertions(+), 1 deletion(-)
> >
> > diff --git a/INSTALL b/INSTALL
> > index 63c022d6b9..4a6506f11f 100644
> > --- a/INSTALL
> > +++ b/INSTALL
> > @@ -133,6 +133,12 @@ if 'CFLAGS' is specified it must enable optimization. For example:
> > used with the GCC option, -static-pie, which is available with GCC
> > 8 or above, to create static PIE.
> >
> > +'--disable-default-dt-relr'
> > + Don't enable DT_RELR in glibc shared libraries and position
> > + independent executables (PIE). By default, DT_RELR is enabled in
>
> Two space after period.
INSTALL is a generated file. The original text in manual/install.texi has
2 spaces.
> > + glibc shared libraries and position independent executables on
> > + targets that support it.
> > +
> > '--enable-cet'
> > '--enable-cet=permissive'
> > Enable Intel Control-flow Enforcement Technology (CET) support.
> > diff --git a/Makeconfig b/Makeconfig
> > index 47db08d6ae..70c0acc065 100644
> > --- a/Makeconfig
> > +++ b/Makeconfig
> > @@ -358,6 +358,23 @@ else
> > real-static-start-installed-name = $(static-start-installed-name)
> > endif
> >
> > +# Linker option to enable and disable DT-RELR.
> > +ifeq ($(have-dt-relr),yes)
> > +dt-relr-ldflag = -Wl,-z,pack-relative-relocs
> > +no-dt-relr-ldflag = -Wl,-z,nopack-relative-relocs
> > +else
> > +dt-relr-ldflag =
> > +no-dt-relr-ldflag =
> > +endif
> > +
> > +# Default linker option for DT-RELR.
> > +ifeq (yes,$(build-dt-relr-default))
> > +default-rt-relr-ldflag = $(dt-relr-ldflag)
> > +else
> > +default-rt-relr-ldflag = $(no-dt-relr-ldflag)
> > +endif
> > +LDFLAGS-rtld += $(default-rt-relr-ldflag)
> > +
> > ifeq (yesyes,$(build-shared)$(have-z-combreloc))
> > combreloc-LDFLAGS = -Wl,-z,combreloc
> > LDFLAGS.so += $(combreloc-LDFLAGS)
> > @@ -419,6 +436,7 @@ link-extra-libs-tests = $(libsupport)
> > # Command for linking PIE programs with the C library.
> > ifndef +link-pie
> > +link-pie-before-inputs = $(if $($(@F)-no-pie),$(no-pie-ldflag),-pie) \
> > + $(if $($(@F)-no-dt-relr),$(no-dt-relr-ldflag),$(default-rt-relr-ldflag)) \
> > -Wl,-O1 -nostdlib -nostartfiles \
> > $(sysdep-LDFLAGS) $(LDFLAGS) $(LDFLAGS-$(@F)) \
> > $(combreloc-LDFLAGS) $(relro-LDFLAGS) $(hashstyle-LDFLAGS) \
> > @@ -451,6 +469,7 @@ endif
> > ifndef +link-static
> > +link-static-before-inputs = -nostdlib -nostartfiles -static \
> > $(if $($(@F)-no-pie),$(no-pie-ldflag),$(static-pie-ldflag)) \
> > + $(if $($(@F)-no-dt-relr),$(no-dt-relr-ldflag),$(default-rt-relr-ldflag)) \
> > $(sysdep-LDFLAGS) $(LDFLAGS) $(LDFLAGS-$(@F)) \
> > $(firstword $(CRT-$(@F)) $(csu-objpfx)$(real-static-start-installed-name)) \
> > $(+preinit) $(+prectorT)
> > diff --git a/Makerules b/Makerules
> > index 428464f092..7c1da551bf 100644
> > --- a/Makerules
> > +++ b/Makerules
> > @@ -536,6 +536,7 @@ lib%.so: lib%_pic.a $(+preinit) $(+postinit) $(link-libc-deps)
> > define build-shlib-helper
> > $(LINK.o) -shared -static-libgcc -Wl,-O1 $(sysdep-LDFLAGS) \
> > $(if $($(@F)-no-z-defs)$(no-z-defs),,-Wl,-z,defs) $(rtld-LDFLAGS) \
> > + $(if $($(@F)-no-dt-relr),$(no-dt-relr-ldflag),$(default-rt-relr-ldflag)) \
> > $(extra-B-$(@F:lib%.so=%).so) -B$(csu-objpfx) \
> > $(extra-B-$(@F:lib%.so=%).so) $(load-map-file) \
> > -Wl,-soname=lib$(libprefix)$(@F:lib%.so=%).so$($(@F)-version) \
> > @@ -595,6 +596,7 @@ endef
> > define build-module-helper
> > $(LINK.o) -shared -static-libgcc $(sysdep-LDFLAGS) $(rtld-LDFLAGS) \
> > $(if $($(@F)-no-z-defs)$(no-z-defs),,-Wl,-z,defs) \
> > + $(if $($(@F)-no-dt-relr),$(no-dt-relr-ldflag),$(default-rt-relr-ldflag)) \
> > -B$(csu-objpfx) $(load-map-file) \
> > $(LDFLAGS.so) $(LDFLAGS-$(@F:%.so=%).so) \
> > $(link-test-modules-rpath-link) \
>
> Ok.
>
> > diff --git a/configure b/configure
> > index 9156e29fe9..ee4137a977 100755
> > --- a/configure
> > +++ b/configure
> > @@ -768,6 +768,7 @@ enable_sanity_checks
> > enable_shared
> > enable_profile
> > enable_default_pie
> > +enable_default_dt_relr
> > enable_timezone_tools
> > enable_hardcoded_path_in_tests
> > enable_hidden_plt
> > @@ -1425,6 +1426,7 @@ Optional Features:
> > --enable-profile build profiled library [default=no]
> > --disable-default-pie Do not build glibc programs and the testsuite as PIE
> > [default=no]
> > + --disable-dt-relr Do not enable DT_RELR in glibc[default=no]
> > --disable-timezone-tools
> > do not install timezone tools [default=install]
> > --enable-hardcoded-path-in-tests
> > @@ -3441,6 +3443,13 @@ else
> > default_pie=yes
> > fi
> >
> > +# Check whether --enable-default-dt-relr was given.
> > +if test "${enable_default_dt_relr+set}" = set; then :
> > + enableval=$enable_default_dt_relr; default_dt_relr=$enableval
> > +else
> > + default_dt_relr=yes
> > +fi
> > +
> > # Check whether --enable-timezone-tools was given.
> > if test "${enable_timezone_tools+set}" = set; then :
> > enableval=$enable_timezone_tools; enable_timezone_tools=$enableval
> > @@ -7136,6 +7145,15 @@ fi
> > config_vars="$config_vars
> > enable-static-pie = $libc_cv_static_pie"
> >
> > +# Disable build-dt-relr-default if linker does not support it or glibc is
> > +# configured with --disable-default-dt-relr.
> > +build_dt_relr_default=$default_dt_relr
> > +if test "x$build_dt_relr_default" != xno; then
> > + build_dt_relr_default=$libc_cv_dt_relr
> > +fi
> > +config_vars="$config_vars
> > +build-dt-relr-default = $build_dt_relr_default"
> > +
> > # Set the `multidir' variable by grabbing the variable from the compiler.
> > # We do it once and save the result in a generated makefile.
> > libc_cv_multidir=`${CC-cc} $CFLAGS $CPPFLAGS -print-multi-directory`
> > diff --git a/configure.ac b/configure.ac
> > index 5c09871fee..680b036ffa 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -197,6 +197,11 @@ AC_ARG_ENABLE([default-pie],
> > [Do not build glibc programs and the testsuite as PIE @<:@default=no@:>@]),
> > [default_pie=$enableval],
> > [default_pie=yes])
> > +AC_ARG_ENABLE([default-dt-relr],
> > + AS_HELP_STRING([--disable-dt-relr],
> > + [Do not enable DT_RELR in glibc@<:@default=no@:>@]),
> > + [default_dt_relr=$enableval],
> > + [default_dt_relr=yes])
> > AC_ARG_ENABLE([timezone-tools],
> > AS_HELP_STRING([--disable-timezone-tools],
> > [do not install timezone tools @<:@default=install@:>@]),
> > @@ -1914,6 +1919,14 @@ if test "$libc_cv_static_pie" = "yes"; then
> > fi
> > LIBC_CONFIG_VAR([enable-static-pie], [$libc_cv_static_pie])
> >
> > +# Disable build-dt-relr-default if linker does not support it or glibc is
>
> Maybe 'or if'.
Fixed in v7.
> > +# configured with --disable-default-dt-relr.
> > +build_dt_relr_default=$default_dt_relr
> > +if test "x$build_dt_relr_default" != xno; then
> > + build_dt_relr_default=$libc_cv_dt_relr
> > +fi
> > +LIBC_CONFIG_VAR([build-dt-relr-default], [$build_dt_relr_default])
> > +
> > # Set the `multidir' variable by grabbing the variable from the compiler.
> > # We do it once and save the result in a generated makefile.
> > libc_cv_multidir=`${CC-cc} $CFLAGS $CPPFLAGS -print-multi-directory`
> > diff --git a/elf/Makefile b/elf/Makefile
> > index d3118b9777..c4384536ba 100644
> > --- a/elf/Makefile
> > +++ b/elf/Makefile
> > @@ -1567,6 +1567,7 @@ $(objpfx)nodlopen2.out: $(objpfx)nodlopenmod2.so
> >
> > $(objpfx)filtmod1.so: $(objpfx)filtmod1.os $(objpfx)filtmod2.so
> > $(LINK.o) -shared -o $@ -B$(csu-objpfx) $(LDFLAGS.so) \
> > + $(default-rt-relr-ldflag) \
> > -L$(subst :, -L,$(rpath-link)) \
> > -Wl,-rpath-link=$(rpath-link) \
> > $< -Wl,-F,$(objpfx)filtmod2.so
> > @@ -2366,7 +2367,7 @@ $(objpfx)tst-big-note: $(objpfx)tst-big-note-lib.so
> > # artificial, large note in tst-big-note-lib.o and invalidate the
> > # test.
> > $(objpfx)tst-big-note-lib.so: $(objpfx)tst-big-note-lib.o
> > - $(LINK.o) -shared -o $@ $(LDFLAGS.so) $<
> > + $(LINK.o) -shared -o $@ $(LDFLAGS.so) $(default-rt-relr-ldflag) $<
> >
> > $(objpfx)tst-unwind-ctor: $(objpfx)tst-unwind-ctor-lib.so
> >
> > @@ -2672,6 +2673,7 @@ $(objpfx)tst-ro-dynamic: $(objpfx)tst-ro-dynamic-mod.so
> > $(objpfx)tst-ro-dynamic-mod.so: $(objpfx)tst-ro-dynamic-mod.os \
> > tst-ro-dynamic-mod.map
> > $(LINK.o) -nostdlib -nostartfiles -shared -o $@ \
> > + $(default-rt-relr-ldflag) \
> > -Wl,--script=tst-ro-dynamic-mod.map \
> > $(objpfx)tst-ro-dynamic-mod.os
> >
> > diff --git a/manual/install.texi b/manual/install.texi
> > index 29c52f2927..04ea996561 100644
> > --- a/manual/install.texi
> > +++ b/manual/install.texi
> > @@ -161,6 +161,11 @@ and architecture support it, static executables are built as static PIE and the
> > resulting glibc can be used with the GCC option, -static-pie, which is
> > available with GCC 8 or above, to create static PIE.
> >
> > +@item --disable-default-dt-relr
> > +Don't enable DT_RELR in glibc shared libraries and position independent
> > +executables (PIE). By default, DT_RELR is enabled in glibc shared
> > +libraries and position independent executables on targets that support it.
> > +
> > @item --enable-cet
> > @itemx --enable-cet=permissive
> > Enable Intel Control-flow Enforcement Technology (CET) support. When
>
> Ok.
--
H.J.
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