From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: "H.J. Lu" <hjl.tools@gmail.com>, libc-alpha@sourceware.org
Subject: Re: [PATCH v10 6/7] Add --disable-default-dt-relr
Date: Wed, 20 Apr 2022 14:49:02 -0300 [thread overview]
Message-ID: <1bd5e1b8-6753-cc72-a548-2dcf8154cc38@linaro.org> (raw)
In-Reply-To: <20220414232129.1886210-7-hjl.tools@gmail.com>
On 14/04/2022 20:21, 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.
Patch looks ok but I am trying to see which would be a usercase for the
--disable-default-dt-relr since loader and libc are tied together and
we don't really support mixing up build with different configure
options (although in practice I think most combination would work).
I take that DT_RELR is always an improvement for shared libraries and
PIE, specially the ones with a lot o irelative relocations.
> ---
> 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.
> + 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 0aa5fb0099..b75f28f837 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)
> +
> relro-LDFLAGS = -Wl,-z,relro
> LDFLAGS.so += $(relro-LDFLAGS)
> LDFLAGS-rtld += $(relro-LDFLAGS)
> @@ -413,6 +430,7 @@ 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)) \
> $(relro-LDFLAGS) $(hashstyle-LDFLAGS) \
> @@ -445,6 +463,7 @@ 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) \
> $(link-test-modules-rpath-link) \
> diff --git a/configure b/configure
> index c0c2246597..d230c2c673 100755
> --- a/configure
> +++ b/configure
> @@ -767,6 +767,7 @@ enable_sanity_checks
> enable_shared
> enable_profile
> enable_default_pie
> +enable_default_dt_relr
> enable_timezone_tools
> enable_hardcoded_path_in_tests
> enable_hidden_plt
> @@ -1424,6 +1425,7 @@ Optional Features:
> --enable-profile build profiled library [default=no]
> --disable-default-pie Do not build glibc programs and the testsuite as PIE
> [default=no]
> + --disable-dt-relr Do not enable DT_RELR in glibc[default=no]
> --disable-timezone-tools
> do not install timezone tools [default=install]
> --enable-hardcoded-path-in-tests
> @@ -3440,6 +3442,13 @@ else
> default_pie=yes
> fi
>
> +# Check whether --enable-default-dt-relr was given.
> +if test "${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=$enableval
> @@ -7092,6 +7101,15 @@ fi
> config_vars="$config_vars
> enable-static-pie = $libc_cv_static_pie"
>
> +# Disable build-dt-relr-default if linker does not support it or if glibc
> +# is configured with --disable-default-dt-relr.
> +build_dt_relr_default=$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 $CPPFLAGS -print-multi-directory`
> diff --git a/configure.ac b/configure.ac
> index 66cad71431..1aa152b901 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -197,6 +197,11 @@ AC_ARG_ENABLE([default-pie],
> [Do not build glibc programs and the testsuite as PIE @<:@default=no@:>@]),
> [default_pie=$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@:>@]),
Missing space after 'glibc'.
> + [default_dt_relr=$enableval],
> + [default_dt_relr=yes])
> AC_ARG_ENABLE([timezone-tools],
> AS_HELP_STRING([--disable-timezone-tools],
> [do not install timezone tools @<:@default=install@:>@]),
> @@ -1878,6 +1883,14 @@ if test "$libc_cv_static_pie" = "yes"; then
> fi
> LIBC_CONFIG_VAR([enable-static-pie], [$libc_cv_static_pie])
>
> +# Disable build-dt-relr-default if linker does not support it or if glibc
> +# is configured with --disable-default-dt-relr.
> +build_dt_relr_default=$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 07ac9ec3ef..bf8a61dc30 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -1603,6 +1603,7 @@ $(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
> @@ -2402,7 +2403,7 @@ $(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
>
> @@ -2711,6 +2712,7 @@ $(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
next prev parent reply other threads:[~2022-04-20 17:49 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-14 23:21 [PATCH v10 0/7] Support DT_RELR relative relocation format H.J. Lu
2022-04-14 23:21 ` [PATCH v10 1/7] elf: Define DT_RELR related macros and types H.J. Lu
2022-04-20 12:45 ` Adhemerval Zanella
2022-04-14 23:21 ` [PATCH v10 2/7] Add GLIBC_ABI_DT_RELR for DT_RELR support H.J. Lu
2022-04-20 13:32 ` Adhemerval Zanella
2022-04-14 23:21 ` [PATCH v10 3/7] elf: Support DT_RELR relative relocation format [BZ #27924] H.J. Lu
2022-04-20 13:44 ` Adhemerval Zanella
2022-04-22 18:47 ` H.J. Lu
2022-04-14 23:21 ` [PATCH v10 4/7] elf: Properly handle zero DT_RELA/DT_REL values H.J. Lu
2022-04-20 17:10 ` Adhemerval Zanella
2022-04-14 23:21 ` [PATCH v10 5/7] elf: Add more DT_RELR tests H.J. Lu
2022-04-20 17:24 ` Adhemerval Zanella
2022-04-20 17:41 ` Adhemerval Zanella
2022-04-22 18:44 ` H.J. Lu
2022-04-14 23:21 ` [PATCH v10 6/7] Add --disable-default-dt-relr H.J. Lu
2022-04-20 17:49 ` Adhemerval Zanella [this message]
2022-04-22 18:41 ` H.J. Lu
2022-04-14 23:21 ` [PATCH v10 7/7] NEWS: Mention DT_RELR support H.J. Lu
2022-04-20 17:49 ` Adhemerval Zanella
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1bd5e1b8-6753-cc72-a548-2dcf8154cc38@linaro.org \
--to=adhemerval.zanella@linaro.org \
--cc=hjl.tools@gmail.com \
--cc=libc-alpha@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).