e895cff59a
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.
66 lines
1.7 KiB
C
66 lines
1.7 KiB
C
/* 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>
|