[v10,3/7] elf: Support DT_RELR relative relocation format [BZ #27924]
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Commit Message
From: Fangrui Song <maskray@google.com>
PIE and shared objects usually have many relative relocations. In
2017/2018, SHT_RELR/DT_RELR was proposed on
https://groups.google.com/g/generic-abi/c/bX460iggiKg/m/GxjM0L-PBAAJ
("Proposal for a new section type SHT_RELR") and is a pre-standard. RELR
usually takes 3% or smaller space than R_*_RELATIVE relocations. The
virtual memory size of a mostly statically linked PIE is typically 5~10%
smaller.
---
Notes I will not include in the submitted commit:
Available on https://sourceware.org/git/?p=glibc.git;a=shortlog;h=refs/heads/maskray/relr
"pre-standard": even Solaris folks are happy with the refined generic-abi
proposal. Cary Coutant will apply the change
https://sourceware.org/pipermail/libc-alpha/2021-October/131781.html
This patch is simpler than Chrome OS's glibc patch and makes ELF_DYNAMIC_DO_RELR
available to all ports. I don't think the current glibc implementation
supports ia64 in an ELFCLASS32 container. That said, the style I used is
works with an ELFCLASS32 container for 64-bit machine if ElfW(Addr) is
64-bit.
* Chrome OS folks have carried a local patch since 2018 (latest version:
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-libs/glibc/files/local/glibc-2.32).
I.e. this feature has been battle tested.
* Android bionic supports 2018 and switched to DT_RELR==36 in 2020.
* The Linux kernel has supported CONFIG_RELR since 2019-08
(https://git.kernel.org/linus/5cf896fb6be3effd9aea455b22213e27be8bdb1d).
* A musl patch (by me) exists but is not applied:
https://www.openwall.com/lists/musl/2019/03/06/3
* rtld-elf from FreeBSD 14 will support DT_RELR.
I believe upstream glibc should support DT_RELR to benefit all Linux
distributions. I filed some feature requests to get their attention:
* Gentoo: https://bugs.gentoo.org/818376
* Arch Linux: https://bugs.archlinux.org/task/72433
* Debian https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=996598
* Fedora https://bugzilla.redhat.com/show_bug.cgi?id=2014699
As of linker support (to the best of my knowledge):
* LLD support DT_RELR.
* https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-devel/binutils/files/
has a gold patch.
* GNU ld feature request https://sourceware.org/bugzilla/show_bug.cgi?id=27923
Changes from the original patch:
1. Check the linker option, -z pack-relative-relocs, which add a
GLIBC_ABI_DT_RELR symbol version dependency on the shared C library if
it provides a GLIBC_2.XX symbol version.
2. Change make variale to have-dt-relr.
3. Rename tst-relr-no-pie to tst-relr-pie for --disable-default-pie.
4. Use TEST_VERIFY in tst-relr.c.
5. Add the check-tst-relr-pie.out test to check for linker generated
libc.so version dependency on GLIBC_ABI_DT_RELR.
6. Move ELF_DYNAMIC_DO_RELR before ELF_DYNAMIC_DO_REL.
---
configure | 37 ++++++++++++++++++++++++
configure.ac | 5 ++++
elf/Makefile | 25 ++++++++++++++++
elf/dynamic-link.h | 34 ++++++++++++++++++++++
elf/get-dynamic-info.h | 3 ++
elf/tst-relr-pie.c | 1 +
elf/tst-relr.c | 65 ++++++++++++++++++++++++++++++++++++++++++
7 files changed, 170 insertions(+)
create mode 100644 elf/tst-relr-pie.c
create mode 100644 elf/tst-relr.c
Comments
On 14/04/2022 20:21, H.J. Lu wrote:
> From: Fangrui Song <maskray@google.com>
>
> PIE and shared objects usually have many relative relocations. In
> 2017/2018, SHT_RELR/DT_RELR was proposed on
> https://groups.google.com/g/generic-abi/c/bX460iggiKg/m/GxjM0L-PBAAJ
> ("Proposal for a new section type SHT_RELR") and is a pre-standard. RELR
> usually takes 3% or smaller space than R_*_RELATIVE relocations. The
> virtual memory size of a mostly statically linked PIE is typically 5~10%
> smaller.
>
> ---
>
> Notes I will not include in the submitted commit:
>
> Available on https://sourceware.org/git/?p=glibc.git;a=shortlog;h=refs/heads/maskray/relr
>
> "pre-standard": even Solaris folks are happy with the refined generic-abi
> proposal. Cary Coutant will apply the change
> https://sourceware.org/pipermail/libc-alpha/2021-October/131781.html
>
> This patch is simpler than Chrome OS's glibc patch and makes ELF_DYNAMIC_DO_RELR
> available to all ports. I don't think the current glibc implementation
> supports ia64 in an ELFCLASS32 container. That said, the style I used is
> works with an ELFCLASS32 container for 64-bit machine if ElfW(Addr) is
> 64-bit.
>
> * Chrome OS folks have carried a local patch since 2018 (latest version:
> https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-libs/glibc/files/local/glibc-2.32).
> I.e. this feature has been battle tested.
> * Android bionic supports 2018 and switched to DT_RELR==36 in 2020.
> * The Linux kernel has supported CONFIG_RELR since 2019-08
> (https://git.kernel.org/linus/5cf896fb6be3effd9aea455b22213e27be8bdb1d).
> * A musl patch (by me) exists but is not applied:
> https://www.openwall.com/lists/musl/2019/03/06/3
> * rtld-elf from FreeBSD 14 will support DT_RELR.
>
> I believe upstream glibc should support DT_RELR to benefit all Linux
> distributions. I filed some feature requests to get their attention:
>
> * Gentoo: https://bugs.gentoo.org/818376
> * Arch Linux: https://bugs.archlinux.org/task/72433
> * Debian https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=996598
> * Fedora https://bugzilla.redhat.com/show_bug.cgi?id=2014699
>
> As of linker support (to the best of my knowledge):
>
> * LLD support DT_RELR.
> * https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-devel/binutils/files/
> has a gold patch.
> * GNU ld feature request https://sourceware.org/bugzilla/show_bug.cgi?id=27923
>
> Changes from the original patch:
>
> 1. Check the linker option, -z pack-relative-relocs, which add a
> GLIBC_ABI_DT_RELR symbol version dependency on the shared C library if
> it provides a GLIBC_2.XX symbol version.
> 2. Change make variale to have-dt-relr.
> 3. Rename tst-relr-no-pie to tst-relr-pie for --disable-default-pie.
> 4. Use TEST_VERIFY in tst-relr.c.
> 5. Add the check-tst-relr-pie.out test to check for linker generated
> libc.so version dependency on GLIBC_ABI_DT_RELR.
> 6. Move ELF_DYNAMIC_DO_RELR before ELF_DYNAMIC_DO_REL.
Patch looks good, only a small nit below.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> configure | 37 ++++++++++++++++++++++++
> configure.ac | 5 ++++
> elf/Makefile | 25 ++++++++++++++++
> elf/dynamic-link.h | 34 ++++++++++++++++++++++
> elf/get-dynamic-info.h | 3 ++
> elf/tst-relr-pie.c | 1 +
> elf/tst-relr.c | 65 ++++++++++++++++++++++++++++++++++++++++++
> 7 files changed, 170 insertions(+)
> create mode 100644 elf/tst-relr-pie.c
> create mode 100644 elf/tst-relr.c
>
> diff --git a/configure b/configure
> index d2f413d05d..c0c2246597 100755
> --- a/configure
> +++ b/configure
> @@ -6076,6 +6076,43 @@ $as_echo "$libc_linker_feature" >&6; }
> config_vars="$config_vars
> have-depaudit = $libc_cv_depaudit"
>
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z pack-relative-relocs" >&5
> +$as_echo_n "checking for linker that supports -z pack-relative-relocs... " >&6; }
> +libc_linker_feature=no
> +if test x"$gnu_ld" = x"yes"; then
> + cat > conftest.c <<EOF
> +int _start (void) { return 42; }
> +EOF
> + if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
> + -Wl,-z,pack-relative-relocs -nostdlib -nostartfiles
> + -fPIC -shared -o conftest.so conftest.c
> + 1>&5'
> + { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> + (eval $ac_try) 2>&5
> + ac_status=$?
> + $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> + test $ac_status = 0; }; }
> + then
> + if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,-z,pack-relative-relocs -nostdlib \
> + -nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
> + | grep "warning: -z pack-relative-relocs ignored" > /dev/null 2>&1; then
> + true
> + else
> + libc_linker_feature=yes
> + fi
> + fi
> + rm -f conftest*
> +fi
> +if test $libc_linker_feature = yes; then
> + libc_cv_dt_relr=yes
> +else
> + libc_cv_dt_relr=no
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
> +$as_echo "$libc_linker_feature" >&6; }
> +config_vars="$config_vars
> +have-dt-relr = $libc_cv_dt_relr"
> +
> { $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports --no-dynamic-linker" >&5
> $as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6; }
> libc_linker_feature=no
> diff --git a/configure.ac b/configure.ac
> index b6a747dece..66cad71431 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -1336,6 +1336,11 @@ LIBC_LINKER_FEATURE([--depaudit], [-Wl,--depaudit,x],
> [libc_cv_depaudit=yes], [libc_cv_depaudit=no])
> LIBC_CONFIG_VAR([have-depaudit], [$libc_cv_depaudit])
>
> +LIBC_LINKER_FEATURE([-z pack-relative-relocs],
> + [-Wl,-z,pack-relative-relocs],
> + [libc_cv_dt_relr=yes], [libc_cv_dt_relr=no])
> +LIBC_CONFIG_VAR([have-dt-relr], [$libc_cv_dt_relr])
> +
> LIBC_LINKER_FEATURE([--no-dynamic-linker],
> [-Wl,--no-dynamic-linker],
> [libc_cv_no_dynamic_linker=yes],
Ok.
> diff --git a/elf/Makefile b/elf/Makefile
> index ee8778c3a2..3f3e711dd2 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -541,6 +541,25 @@ tests-special += \
> # tests-special
> endif
> endif
> +ifeq ($(have-dt-relr),yes)
> +tests += \
> + tst-relr \
> +# tests
> +ifeq ($(have-fpie),yes)
> +tests += \
> + tst-relr-pie \
> +# tests
> +tests-pie += \
> + tst-relr-pie \
> +# tests-pie
> +tests-special += \
> + $(objpfx)check-tst-relr-pie.out \
> +# tests-special
> +endif
> +CFLAGS-tst-relr-pie.c += $(pie-ccflag)
> +LDFLAGS-tst-relr += -Wl,-z,pack-relative-relocs
> +LDFLAGS-tst-relr-pie += -Wl,-z,pack-relative-relocs
> +endif
> endif
>
> ifeq ($(run-built-tests),yes)
> @@ -2743,3 +2762,9 @@ $(objpfx)check-abi-version-libc.out: $(common-objpfx)libc.so
> | sed -ne '/.gnu.version_d/, /.gnu.version_r/ p' \
> | grep GLIBC_ABI_DT_RELR > $@; \
> $(evaluate-test)
> +
> +$(objpfx)check-tst-relr-pie.out: $(objpfx)tst-relr-pie
> + LC_ALL=C $(OBJDUMP) -p $< \
> + | sed -ne '/required from libc.so/,$$ p' \
> + | grep GLIBC_ABI_DT_RELR > $@; \
> + $(evaluate-test)
Ok.
> diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
> index 25dd7ca4f2..7325e0d9fc 100644
> --- a/elf/dynamic-link.h
> +++ b/elf/dynamic-link.h
> @@ -146,12 +146,46 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
> # define ELF_DYNAMIC_DO_RELA(map, scope, lazy, skip_ifunc) /* Nothing to do. */
> # endif
>
> +# define ELF_DYNAMIC_DO_RELR(map) \
> + do { \
> + ElfW(Addr) l_addr = (map)->l_addr, *where = 0; \
> + const ElfW(Relr) *r, *end; \
> + if (!(map)->l_info[DT_RELR]) \
Maybe check against NULL?
> + break; \
> + r = (const ElfW(Relr) *)D_PTR((map), l_info[DT_RELR]); \
> + end = (const ElfW(Relr) *)((const char *)r + \
> + (map)->l_info[DT_RELRSZ]->d_un.d_val); \
> + for (; r < end; r++) \
> + { \
> + ElfW(Relr) entry = *r; \
> + if ((entry & 1) == 0) \
> + { \
> + where = (ElfW(Addr) *)(l_addr + entry); \
> + *where++ += l_addr; \
> + } \
> + else \
> + { \
> + for (long int i = 0; (entry >>= 1) != 0; i++) \
> + if ((entry & 1) != 0) \
> + where[i] += l_addr; \
> + where += CHAR_BIT * sizeof(ElfW(Relr)) - 1; \
> + } \
> + } \
> + } while (0);
> +
Ok.
> /* This can't just be an inline function because GCC is too dumb
> to inline functions containing inlines themselves. */
> +# ifdef RTLD_BOOTSTRAP
> +# define DO_RTLD_BOOTSTRAP 1
> +# else
> +# define DO_RTLD_BOOTSTRAP 0
> +# endif
> # define ELF_DYNAMIC_RELOCATE(map, scope, lazy, consider_profile, skip_ifunc) \
> do { \
> int edr_lazy = elf_machine_runtime_setup ((map), (scope), (lazy), \
> (consider_profile)); \
> + if (((map) != &GL(dl_rtld_map) || DO_RTLD_BOOTSTRAP)) \
> + ELF_DYNAMIC_DO_RELR (map); \
> ELF_DYNAMIC_DO_REL ((map), (scope), edr_lazy, skip_ifunc); \
> ELF_DYNAMIC_DO_RELA ((map), (scope), edr_lazy, skip_ifunc); \
> } while (0)
Ok.
> diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
> index 6c2ccd6db4..6c2a3a12b1 100644
> --- a/elf/get-dynamic-info.h
> +++ b/elf/get-dynamic-info.h
> @@ -89,6 +89,7 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
> # if ! ELF_MACHINE_NO_REL
> ADJUST_DYN_INFO (DT_REL);
> # endif
> + ADJUST_DYN_INFO (DT_RELR);
> ADJUST_DYN_INFO (DT_JMPREL);
> ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
> ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
> @@ -113,6 +114,8 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
> if (info[DT_REL] != NULL)
> assert (info[DT_RELENT]->d_un.d_val == sizeof (ElfW(Rel)));
> #endif
> + if (info[DT_RELR] != NULL)
> + assert (info[DT_RELRENT]->d_un.d_val == sizeof (ElfW(Relr)));
> if (bootstrap || static_pie_bootstrap)
> {
> assert (info[DT_RUNPATH] == NULL);
Ok.
> diff --git a/elf/tst-relr-pie.c b/elf/tst-relr-pie.c
> new file mode 100644
> index 0000000000..7df0cdbfd6
> --- /dev/null
> +++ b/elf/tst-relr-pie.c
> @@ -0,0 +1 @@
> +#include "tst-relr.c"
> diff --git a/elf/tst-relr.c b/elf/tst-relr.c
> new file mode 100644
> index 0000000000..c634ce0d21
> --- /dev/null
> +++ b/elf/tst-relr.c
> @@ -0,0 +1,65 @@
> +/* Basic tests for DT_RELR.
> + Copyright (C) 2022 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +#include <link.h>
> +#include <stdbool.h>
> +#include <array_length.h>
> +#include <support/check.h>
> +
> +static int o, x;
> +
> +#define ELEMS O O O O O O O O X X X X X X X O O X O O X X X E X E E O X O E
> +#define E 0,
> +
> +#define O &o,
> +#define X &x,
> +void *arr[] = { ELEMS };
> +#undef O
> +#undef X
> +
> +#define O 1,
> +#define X 2,
> +static char val[] = { ELEMS };
> +
> +static int
> +do_test (void)
> +{
> + ElfW(Dyn) *d = _DYNAMIC;
> + if (d)
> + {
> + bool has_relr = false;
> + for (; d->d_tag != DT_NULL; d++)
> + if (d->d_tag == DT_RELR)
> + has_relr = true;
> +
> +#if defined __PIE__ || defined __pie__ || defined PIE || defined pie
> + TEST_VERIFY (has_relr);
> +#else
> + TEST_VERIFY (!has_relr);
> +#endif
> + }
> +
> + for (int i = 0; i < array_length (arr); i++)
> + TEST_VERIFY ((arr[i] == 0 && val[i] == 0)
> + || (arr[i] == &o && val[i] == 1)
> + || (arr[i] == &x && val[i] == 2));
> +
> + return 0;
> +}
> +
> +#include <support/test-driver.c>
Ok.
On Wed, Apr 20, 2022 at 6:44 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 14/04/2022 20:21, H.J. Lu wrote:
> > From: Fangrui Song <maskray@google.com>
> >
> > PIE and shared objects usually have many relative relocations. In
> > 2017/2018, SHT_RELR/DT_RELR was proposed on
> > https://groups.google.com/g/generic-abi/c/bX460iggiKg/m/GxjM0L-PBAAJ
> > ("Proposal for a new section type SHT_RELR") and is a pre-standard. RELR
> > usually takes 3% or smaller space than R_*_RELATIVE relocations. The
> > virtual memory size of a mostly statically linked PIE is typically 5~10%
> > smaller.
> >
> > ---
> >
> > Notes I will not include in the submitted commit:
> >
> > Available on https://sourceware.org/git/?p=glibc.git;a=shortlog;h=refs/heads/maskray/relr
> >
> > "pre-standard": even Solaris folks are happy with the refined generic-abi
> > proposal. Cary Coutant will apply the change
> > https://sourceware.org/pipermail/libc-alpha/2021-October/131781.html
> >
> > This patch is simpler than Chrome OS's glibc patch and makes ELF_DYNAMIC_DO_RELR
> > available to all ports. I don't think the current glibc implementation
> > supports ia64 in an ELFCLASS32 container. That said, the style I used is
> > works with an ELFCLASS32 container for 64-bit machine if ElfW(Addr) is
> > 64-bit.
> >
> > * Chrome OS folks have carried a local patch since 2018 (latest version:
> > https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-libs/glibc/files/local/glibc-2.32).
> > I.e. this feature has been battle tested.
> > * Android bionic supports 2018 and switched to DT_RELR==36 in 2020.
> > * The Linux kernel has supported CONFIG_RELR since 2019-08
> > (https://git.kernel.org/linus/5cf896fb6be3effd9aea455b22213e27be8bdb1d).
> > * A musl patch (by me) exists but is not applied:
> > https://www.openwall.com/lists/musl/2019/03/06/3
> > * rtld-elf from FreeBSD 14 will support DT_RELR.
> >
> > I believe upstream glibc should support DT_RELR to benefit all Linux
> > distributions. I filed some feature requests to get their attention:
> >
> > * Gentoo: https://bugs.gentoo.org/818376
> > * Arch Linux: https://bugs.archlinux.org/task/72433
> > * Debian https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=996598
> > * Fedora https://bugzilla.redhat.com/show_bug.cgi?id=2014699
> >
> > As of linker support (to the best of my knowledge):
> >
> > * LLD support DT_RELR.
> > * https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-devel/binutils/files/
> > has a gold patch.
> > * GNU ld feature request https://sourceware.org/bugzilla/show_bug.cgi?id=27923
> >
> > Changes from the original patch:
> >
> > 1. Check the linker option, -z pack-relative-relocs, which add a
> > GLIBC_ABI_DT_RELR symbol version dependency on the shared C library if
> > it provides a GLIBC_2.XX symbol version.
> > 2. Change make variale to have-dt-relr.
> > 3. Rename tst-relr-no-pie to tst-relr-pie for --disable-default-pie.
> > 4. Use TEST_VERIFY in tst-relr.c.
> > 5. Add the check-tst-relr-pie.out test to check for linker generated
> > libc.so version dependency on GLIBC_ABI_DT_RELR.
> > 6. Move ELF_DYNAMIC_DO_RELR before ELF_DYNAMIC_DO_REL.
>
> Patch looks good, only a small nit below.
>
> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>
> > ---
> > configure | 37 ++++++++++++++++++++++++
> > configure.ac | 5 ++++
> > elf/Makefile | 25 ++++++++++++++++
> > elf/dynamic-link.h | 34 ++++++++++++++++++++++
> > elf/get-dynamic-info.h | 3 ++
> > elf/tst-relr-pie.c | 1 +
> > elf/tst-relr.c | 65 ++++++++++++++++++++++++++++++++++++++++++
> > 7 files changed, 170 insertions(+)
> > create mode 100644 elf/tst-relr-pie.c
> > create mode 100644 elf/tst-relr.c
> >
> > diff --git a/configure b/configure
> > index d2f413d05d..c0c2246597 100755
> > --- a/configure
> > +++ b/configure
> > @@ -6076,6 +6076,43 @@ $as_echo "$libc_linker_feature" >&6; }
> > config_vars="$config_vars
> > have-depaudit = $libc_cv_depaudit"
> >
> > +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z pack-relative-relocs" >&5
> > +$as_echo_n "checking for linker that supports -z pack-relative-relocs... " >&6; }
> > +libc_linker_feature=no
> > +if test x"$gnu_ld" = x"yes"; then
> > + cat > conftest.c <<EOF
> > +int _start (void) { return 42; }
> > +EOF
> > + if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
> > + -Wl,-z,pack-relative-relocs -nostdlib -nostartfiles
> > + -fPIC -shared -o conftest.so conftest.c
> > + 1>&5'
> > + { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> > + (eval $ac_try) 2>&5
> > + ac_status=$?
> > + $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> > + test $ac_status = 0; }; }
> > + then
> > + if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,-z,pack-relative-relocs -nostdlib \
> > + -nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
> > + | grep "warning: -z pack-relative-relocs ignored" > /dev/null 2>&1; then
> > + true
> > + else
> > + libc_linker_feature=yes
> > + fi
> > + fi
> > + rm -f conftest*
> > +fi
> > +if test $libc_linker_feature = yes; then
> > + libc_cv_dt_relr=yes
> > +else
> > + libc_cv_dt_relr=no
> > +fi
> > +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
> > +$as_echo "$libc_linker_feature" >&6; }
> > +config_vars="$config_vars
> > +have-dt-relr = $libc_cv_dt_relr"
> > +
> > { $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports --no-dynamic-linker" >&5
> > $as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6; }
> > libc_linker_feature=no
> > diff --git a/configure.ac b/configure.ac
> > index b6a747dece..66cad71431 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -1336,6 +1336,11 @@ LIBC_LINKER_FEATURE([--depaudit], [-Wl,--depaudit,x],
> > [libc_cv_depaudit=yes], [libc_cv_depaudit=no])
> > LIBC_CONFIG_VAR([have-depaudit], [$libc_cv_depaudit])
> >
> > +LIBC_LINKER_FEATURE([-z pack-relative-relocs],
> > + [-Wl,-z,pack-relative-relocs],
> > + [libc_cv_dt_relr=yes], [libc_cv_dt_relr=no])
> > +LIBC_CONFIG_VAR([have-dt-relr], [$libc_cv_dt_relr])
> > +
> > LIBC_LINKER_FEATURE([--no-dynamic-linker],
> > [-Wl,--no-dynamic-linker],
> > [libc_cv_no_dynamic_linker=yes],
>
> Ok.
>
> > diff --git a/elf/Makefile b/elf/Makefile
> > index ee8778c3a2..3f3e711dd2 100644
> > --- a/elf/Makefile
> > +++ b/elf/Makefile
> > @@ -541,6 +541,25 @@ tests-special += \
> > # tests-special
> > endif
> > endif
> > +ifeq ($(have-dt-relr),yes)
> > +tests += \
> > + tst-relr \
> > +# tests
> > +ifeq ($(have-fpie),yes)
> > +tests += \
> > + tst-relr-pie \
> > +# tests
> > +tests-pie += \
> > + tst-relr-pie \
> > +# tests-pie
> > +tests-special += \
> > + $(objpfx)check-tst-relr-pie.out \
> > +# tests-special
> > +endif
> > +CFLAGS-tst-relr-pie.c += $(pie-ccflag)
> > +LDFLAGS-tst-relr += -Wl,-z,pack-relative-relocs
> > +LDFLAGS-tst-relr-pie += -Wl,-z,pack-relative-relocs
> > +endif
> > endif
> >
> > ifeq ($(run-built-tests),yes)
> > @@ -2743,3 +2762,9 @@ $(objpfx)check-abi-version-libc.out: $(common-objpfx)libc.so
> > | sed -ne '/.gnu.version_d/, /.gnu.version_r/ p' \
> > | grep GLIBC_ABI_DT_RELR > $@; \
> > $(evaluate-test)
> > +
> > +$(objpfx)check-tst-relr-pie.out: $(objpfx)tst-relr-pie
> > + LC_ALL=C $(OBJDUMP) -p $< \
> > + | sed -ne '/required from libc.so/,$$ p' \
> > + | grep GLIBC_ABI_DT_RELR > $@; \
> > + $(evaluate-test)
>
> Ok.
>
> > diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
> > index 25dd7ca4f2..7325e0d9fc 100644
> > --- a/elf/dynamic-link.h
> > +++ b/elf/dynamic-link.h
> > @@ -146,12 +146,46 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
> > # define ELF_DYNAMIC_DO_RELA(map, scope, lazy, skip_ifunc) /* Nothing to do. */
> > # endif
> >
> > +# define ELF_DYNAMIC_DO_RELR(map) \
> > + do { \
> > + ElfW(Addr) l_addr = (map)->l_addr, *where = 0; \
> > + const ElfW(Relr) *r, *end; \
> > + if (!(map)->l_info[DT_RELR]) \
>
> Maybe check against NULL?
Fixed in v11.
> > + break; \
> > + r = (const ElfW(Relr) *)D_PTR((map), l_info[DT_RELR]); \
> > + end = (const ElfW(Relr) *)((const char *)r + \
> > + (map)->l_info[DT_RELRSZ]->d_un.d_val); \
> > + for (; r < end; r++) \
> > + { \
> > + ElfW(Relr) entry = *r; \
> > + if ((entry & 1) == 0) \
> > + { \
> > + where = (ElfW(Addr) *)(l_addr + entry); \
> > + *where++ += l_addr; \
> > + } \
> > + else \
> > + { \
> > + for (long int i = 0; (entry >>= 1) != 0; i++) \
> > + if ((entry & 1) != 0) \
> > + where[i] += l_addr; \
> > + where += CHAR_BIT * sizeof(ElfW(Relr)) - 1; \
> > + } \
> > + } \
> > + } while (0);
> > +
>
> Ok.
>
> > /* This can't just be an inline function because GCC is too dumb
> > to inline functions containing inlines themselves. */
> > +# ifdef RTLD_BOOTSTRAP
> > +# define DO_RTLD_BOOTSTRAP 1
> > +# else
> > +# define DO_RTLD_BOOTSTRAP 0
> > +# endif
> > # define ELF_DYNAMIC_RELOCATE(map, scope, lazy, consider_profile, skip_ifunc) \
> > do { \
> > int edr_lazy = elf_machine_runtime_setup ((map), (scope), (lazy), \
> > (consider_profile)); \
> > + if (((map) != &GL(dl_rtld_map) || DO_RTLD_BOOTSTRAP)) \
> > + ELF_DYNAMIC_DO_RELR (map); \
> > ELF_DYNAMIC_DO_REL ((map), (scope), edr_lazy, skip_ifunc); \
> > ELF_DYNAMIC_DO_RELA ((map), (scope), edr_lazy, skip_ifunc); \
> > } while (0)
>
> Ok.
>
> > diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
> > index 6c2ccd6db4..6c2a3a12b1 100644
> > --- a/elf/get-dynamic-info.h
> > +++ b/elf/get-dynamic-info.h
> > @@ -89,6 +89,7 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
> > # if ! ELF_MACHINE_NO_REL
> > ADJUST_DYN_INFO (DT_REL);
> > # endif
> > + ADJUST_DYN_INFO (DT_RELR);
> > ADJUST_DYN_INFO (DT_JMPREL);
> > ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
> > ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
> > @@ -113,6 +114,8 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
> > if (info[DT_REL] != NULL)
> > assert (info[DT_RELENT]->d_un.d_val == sizeof (ElfW(Rel)));
> > #endif
> > + if (info[DT_RELR] != NULL)
> > + assert (info[DT_RELRENT]->d_un.d_val == sizeof (ElfW(Relr)));
> > if (bootstrap || static_pie_bootstrap)
> > {
> > assert (info[DT_RUNPATH] == NULL);
>
> Ok.
>
> > diff --git a/elf/tst-relr-pie.c b/elf/tst-relr-pie.c
> > new file mode 100644
> > index 0000000000..7df0cdbfd6
> > --- /dev/null
> > +++ b/elf/tst-relr-pie.c
> > @@ -0,0 +1 @@
> > +#include "tst-relr.c"
> > diff --git a/elf/tst-relr.c b/elf/tst-relr.c
> > new file mode 100644
> > index 0000000000..c634ce0d21
> > --- /dev/null
> > +++ b/elf/tst-relr.c
> > @@ -0,0 +1,65 @@
> > +/* Basic tests for DT_RELR.
> > + Copyright (C) 2022 Free Software Foundation, Inc.
> > + This file is part of the GNU C Library.
> > +
> > + The GNU C Library is free software; you can redistribute it and/or
> > + modify it under the terms of the GNU Lesser General Public
> > + License as published by the Free Software Foundation; either
> > + version 2.1 of the License, or (at your option) any later version.
> > +
> > + The GNU C Library is distributed in the hope that it will be useful,
> > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > + Lesser General Public License for more details.
> > +
> > + You should have received a copy of the GNU Lesser General Public
> > + License along with the GNU C Library; if not, see
> > + <https://www.gnu.org/licenses/>. */
> > +
> > +#include <link.h>
> > +#include <stdbool.h>
> > +#include <array_length.h>
> > +#include <support/check.h>
> > +
> > +static int o, x;
> > +
> > +#define ELEMS O O O O O O O O X X X X X X X O O X O O X X X E X E E O X O E
> > +#define E 0,
> > +
> > +#define O &o,
> > +#define X &x,
> > +void *arr[] = { ELEMS };
> > +#undef O
> > +#undef X
> > +
> > +#define O 1,
> > +#define X 2,
> > +static char val[] = { ELEMS };
> > +
> > +static int
> > +do_test (void)
> > +{
> > + ElfW(Dyn) *d = _DYNAMIC;
> > + if (d)
> > + {
> > + bool has_relr = false;
> > + for (; d->d_tag != DT_NULL; d++)
> > + if (d->d_tag == DT_RELR)
> > + has_relr = true;
> > +
> > +#if defined __PIE__ || defined __pie__ || defined PIE || defined pie
> > + TEST_VERIFY (has_relr);
> > +#else
> > + TEST_VERIFY (!has_relr);
> > +#endif
> > + }
> > +
> > + for (int i = 0; i < array_length (arr); i++)
> > + TEST_VERIFY ((arr[i] == 0 && val[i] == 0)
> > + || (arr[i] == &o && val[i] == 1)
> > + || (arr[i] == &x && val[i] == 2));
> > +
> > + return 0;
> > +}
> > +
> > +#include <support/test-driver.c>
>
> Ok.
@@ -6076,6 +6076,43 @@ $as_echo "$libc_linker_feature" >&6; }
config_vars="$config_vars
have-depaudit = $libc_cv_depaudit"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z pack-relative-relocs" >&5
+$as_echo_n "checking for linker that supports -z pack-relative-relocs... " >&6; }
+libc_linker_feature=no
+if test x"$gnu_ld" = x"yes"; then
+ cat > conftest.c <<EOF
+int _start (void) { return 42; }
+EOF
+ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
+ -Wl,-z,pack-relative-relocs -nostdlib -nostartfiles
+ -fPIC -shared -o conftest.so conftest.c
+ 1>&5'
+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+ (eval $ac_try) 2>&5
+ ac_status=$?
+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+ test $ac_status = 0; }; }
+ then
+ if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,-z,pack-relative-relocs -nostdlib \
+ -nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
+ | grep "warning: -z pack-relative-relocs ignored" > /dev/null 2>&1; then
+ true
+ else
+ libc_linker_feature=yes
+ fi
+ fi
+ rm -f conftest*
+fi
+if test $libc_linker_feature = yes; then
+ libc_cv_dt_relr=yes
+else
+ libc_cv_dt_relr=no
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
+$as_echo "$libc_linker_feature" >&6; }
+config_vars="$config_vars
+have-dt-relr = $libc_cv_dt_relr"
+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports --no-dynamic-linker" >&5
$as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6; }
libc_linker_feature=no
@@ -1336,6 +1336,11 @@ LIBC_LINKER_FEATURE([--depaudit], [-Wl,--depaudit,x],
[libc_cv_depaudit=yes], [libc_cv_depaudit=no])
LIBC_CONFIG_VAR([have-depaudit], [$libc_cv_depaudit])
+LIBC_LINKER_FEATURE([-z pack-relative-relocs],
+ [-Wl,-z,pack-relative-relocs],
+ [libc_cv_dt_relr=yes], [libc_cv_dt_relr=no])
+LIBC_CONFIG_VAR([have-dt-relr], [$libc_cv_dt_relr])
+
LIBC_LINKER_FEATURE([--no-dynamic-linker],
[-Wl,--no-dynamic-linker],
[libc_cv_no_dynamic_linker=yes],
@@ -541,6 +541,25 @@ tests-special += \
# tests-special
endif
endif
+ifeq ($(have-dt-relr),yes)
+tests += \
+ tst-relr \
+# tests
+ifeq ($(have-fpie),yes)
+tests += \
+ tst-relr-pie \
+# tests
+tests-pie += \
+ tst-relr-pie \
+# tests-pie
+tests-special += \
+ $(objpfx)check-tst-relr-pie.out \
+# tests-special
+endif
+CFLAGS-tst-relr-pie.c += $(pie-ccflag)
+LDFLAGS-tst-relr += -Wl,-z,pack-relative-relocs
+LDFLAGS-tst-relr-pie += -Wl,-z,pack-relative-relocs
+endif
endif
ifeq ($(run-built-tests),yes)
@@ -2743,3 +2762,9 @@ $(objpfx)check-abi-version-libc.out: $(common-objpfx)libc.so
| sed -ne '/.gnu.version_d/, /.gnu.version_r/ p' \
| grep GLIBC_ABI_DT_RELR > $@; \
$(evaluate-test)
+
+$(objpfx)check-tst-relr-pie.out: $(objpfx)tst-relr-pie
+ LC_ALL=C $(OBJDUMP) -p $< \
+ | sed -ne '/required from libc.so/,$$ p' \
+ | grep GLIBC_ABI_DT_RELR > $@; \
+ $(evaluate-test)
@@ -146,12 +146,46 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
# define ELF_DYNAMIC_DO_RELA(map, scope, lazy, skip_ifunc) /* Nothing to do. */
# endif
+# define ELF_DYNAMIC_DO_RELR(map) \
+ do { \
+ ElfW(Addr) l_addr = (map)->l_addr, *where = 0; \
+ const ElfW(Relr) *r, *end; \
+ if (!(map)->l_info[DT_RELR]) \
+ break; \
+ r = (const ElfW(Relr) *)D_PTR((map), l_info[DT_RELR]); \
+ end = (const ElfW(Relr) *)((const char *)r + \
+ (map)->l_info[DT_RELRSZ]->d_un.d_val); \
+ for (; r < end; r++) \
+ { \
+ ElfW(Relr) entry = *r; \
+ if ((entry & 1) == 0) \
+ { \
+ where = (ElfW(Addr) *)(l_addr + entry); \
+ *where++ += l_addr; \
+ } \
+ else \
+ { \
+ for (long int i = 0; (entry >>= 1) != 0; i++) \
+ if ((entry & 1) != 0) \
+ where[i] += l_addr; \
+ where += CHAR_BIT * sizeof(ElfW(Relr)) - 1; \
+ } \
+ } \
+ } while (0);
+
/* This can't just be an inline function because GCC is too dumb
to inline functions containing inlines themselves. */
+# ifdef RTLD_BOOTSTRAP
+# define DO_RTLD_BOOTSTRAP 1
+# else
+# define DO_RTLD_BOOTSTRAP 0
+# endif
# define ELF_DYNAMIC_RELOCATE(map, scope, lazy, consider_profile, skip_ifunc) \
do { \
int edr_lazy = elf_machine_runtime_setup ((map), (scope), (lazy), \
(consider_profile)); \
+ if (((map) != &GL(dl_rtld_map) || DO_RTLD_BOOTSTRAP)) \
+ ELF_DYNAMIC_DO_RELR (map); \
ELF_DYNAMIC_DO_REL ((map), (scope), edr_lazy, skip_ifunc); \
ELF_DYNAMIC_DO_RELA ((map), (scope), edr_lazy, skip_ifunc); \
} while (0)
@@ -89,6 +89,7 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
# if ! ELF_MACHINE_NO_REL
ADJUST_DYN_INFO (DT_REL);
# endif
+ ADJUST_DYN_INFO (DT_RELR);
ADJUST_DYN_INFO (DT_JMPREL);
ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
@@ -113,6 +114,8 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
if (info[DT_REL] != NULL)
assert (info[DT_RELENT]->d_un.d_val == sizeof (ElfW(Rel)));
#endif
+ if (info[DT_RELR] != NULL)
+ assert (info[DT_RELRENT]->d_un.d_val == sizeof (ElfW(Relr)));
if (bootstrap || static_pie_bootstrap)
{
assert (info[DT_RUNPATH] == NULL);
new file mode 100644
@@ -0,0 +1 @@
+#include "tst-relr.c"
new file mode 100644
@@ -0,0 +1,65 @@
+/* Basic tests for DT_RELR.
+ Copyright (C) 2022 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <link.h>
+#include <stdbool.h>
+#include <array_length.h>
+#include <support/check.h>
+
+static int o, x;
+
+#define ELEMS O O O O O O O O X X X X X X X O O X O O X X X E X E E O X O E
+#define E 0,
+
+#define O &o,
+#define X &x,
+void *arr[] = { ELEMS };
+#undef O
+#undef X
+
+#define O 1,
+#define X 2,
+static char val[] = { ELEMS };
+
+static int
+do_test (void)
+{
+ ElfW(Dyn) *d = _DYNAMIC;
+ if (d)
+ {
+ bool has_relr = false;
+ for (; d->d_tag != DT_NULL; d++)
+ if (d->d_tag == DT_RELR)
+ has_relr = true;
+
+#if defined __PIE__ || defined __pie__ || defined PIE || defined pie
+ TEST_VERIFY (has_relr);
+#else
+ TEST_VERIFY (!has_relr);
+#endif
+ }
+
+ for (int i = 0; i < array_length (arr); i++)
+ TEST_VERIFY ((arr[i] == 0 && val[i] == 0)
+ || (arr[i] == &o && val[i] == 1)
+ || (arr[i] == &x && val[i] == 2));
+
+ return 0;
+}
+
+#include <support/test-driver.c>