From: Fangrui Song <maskray@google.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: libc-alpha@sourceware.org, Joseph Myers <joseph@codesourcery.com>
Subject: Re: [PATCH v3 4/5] Add --disable-default-dt-relr
Date: Mon, 28 Feb 2022 20:25:03 -0800 [thread overview]
Message-ID: <20220301042503.ujwp3cidhdmjhprf@google.com> (raw)
In-Reply-To: <20220207235127.1807294-5-hjl.tools@gmail.com>
On 2022-02-07, H.J. Lu 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.
>---
> 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
>+ 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 5de2cec6be..260c7b7253 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) \
> $(link-test-modules-rpath-link) \
>diff --git a/configure b/configure
>index 9156e29fe9..ee4137a977 100755
>--- a/configure
>+++ b/configure
>@@ -768,6 +768,7 @@ enable_sanity_checks
> enable_shared
> enable_profile
> enable_default_pie
>+enable_default_dt_relr
> enable_timezone_tools
> enable_hardcoded_path_in_tests
> enable_hidden_plt
>@@ -1425,6 +1426,7 @@ Optional Features:
> --enable-profile build profiled library [default=no]
> --disable-default-pie Do not build glibc programs and the testsuite as PIE
> [default=no]
>+ --disable-dt-relr Do not enable DT_RELR in glibc[default=no]
> --disable-timezone-tools
> do not install timezone tools [default=install]
> --enable-hardcoded-path-in-tests
>@@ -3441,6 +3443,13 @@ else
> default_pie=yes
> fi
>
>+# Check whether --enable-default-dt-relr was given.
>+if test "${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], [$libc_cv_static_pie])
>
>+# Disable build-dt-relr-default if linker does not support it or glibc is
>+# configured with --disable-default-dt-relr.
>+build_dt_relr_default=$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 a6515e8a21..1727f5acc0 100644
>--- a/elf/Makefile
>+++ b/elf/Makefile
>@@ -1570,6 +1570,7 @@ $(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
>@@ -2376,7 +2377,7 @@ $(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
>
>@@ -2682,6 +2683,7 @@ $(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
>--
>2.34.1
>
I have read an early version of this serires. This still looks good to
me.
Reviewed-by: Fangrui Song <maskray@google.com>
next prev parent reply other threads:[~2022-03-01 4:25 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-07 23:51 [PATCH v3 0/5] Support DT_RELR relative relocation format H.J. Lu
2022-02-07 23:51 ` [PATCH v3 1/5] elf: Support DT_RELR relative relocation format [BZ #27924] H.J. Lu
2022-02-07 23:51 ` [PATCH v3 2/5] elf: Properly handle zero DT_RELA/DT_REL values H.J. Lu
2022-02-07 23:51 ` [PATCH v3 3/5] Add GLIBC_ABI_DT_RELR for DT_RELR support H.J. Lu
2022-03-01 4:22 ` Fangrui Song
2022-03-01 14:42 ` H.J. Lu
2022-03-01 15:10 ` H.J. Lu
2022-03-01 19:13 ` Fangrui Song
2022-02-07 23:51 ` [PATCH v3 4/5] Add --disable-default-dt-relr H.J. Lu
2022-03-01 4:25 ` Fangrui Song [this message]
2022-02-07 23:51 ` [PATCH v3 5/5] NEWS: Mention DT_RELR support H.J. Lu
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