182 lines
7.2 KiB
Diff
182 lines
7.2 KiB
Diff
From d29ac2028078612c6b4c25fb5be857ca35b37a3b Mon Sep 17 00:00:00 2001
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From: XingLi <lixing@loongson.cn>
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Date: Thu, 27 Jul 2023 09:32:21 +0800
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Subject: [PATCH 2/3] LoongArch: Fix the condition to use PC-relative
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addressing in start.S
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A start.o compiled from start.S with -DPIC and no -DSHARED is used by
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both crt1.o and rcrt1.o. So the LoongArch static PIE patch
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unintentionally introduced PC-relative addressing for main and
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__libc_start_main into crt1.o.
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While the latest Binutils (trunk, which will be released as 2.40)
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supports the PC-relative relocs against an external function by creating
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a PLT entry, the 2.39 release branch doesn't (and won't) support this.
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An error is raised:
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"PLT stub does not represent and symbol not defined."
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So, we need the following changes:
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1. Check if ld supports the PC-relative relocs against an external
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function. If it's not supported, we deem static PIE unsupported.
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2. Change start.S. If static PIE is supported, use PC-relative
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addressing for main and __libc_start_main and rely on the linker to
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create PLT entries. Otherwise, restore the old behavior (using GOT
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to address these functions).
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An alternative would be adding a new "static-pie-start.S", and some
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custom logic into Makefile to build rcrt1.o with it. And, restore
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start.S to the state before static PIE change so crt1.o won't contain
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PC-relative relocs against external symbols. But I can't see any
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benefit of this alternative, so I'd just keep it simple.
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Tested by building glibc with the following configurations:
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1. Binutils trunk + GCC trunk. Static PIE enabled. All tests
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passed.
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2. Binutils 2.39 branch + GCC trunk. Static PIE disabled. Tests
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related to ifunc failed (it's a known issue). All other tests
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passed.
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3. Binutils 2.39 branch + GCC 12 branch, cross compilation with
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build-many-glibcs.py from x86_64-linux-gnu. Static PIE disabled.
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Build succeeded.
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From: Xi Ruoyao <xry111@xry111.site>
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Date: Sun, 2 Oct 2022 22:23:09 +0800
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---
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sysdeps/loongarch/configure | 29 +++++++++++++++++++++++++----
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sysdeps/loongarch/configure.ac | 18 ++++++++++++++----
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sysdeps/loongarch/start.S | 11 +++++++----
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3 files changed, 46 insertions(+), 12 deletions(-)
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diff --git a/sysdeps/loongarch/configure b/sysdeps/loongarch/configure
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index db6341e8..4f0ac252 100644
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--- a/sysdeps/loongarch/configure
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+++ b/sysdeps/loongarch/configure
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@@ -11,7 +11,7 @@ if ${libc_cv_static_pie_on_loongarch+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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- cat > conftest.S << EOF
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+ cat > conftest1.S << EOF
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.global _start
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.type _start, @function
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_start:
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@@ -27,14 +27,35 @@ x:
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/* This should produce an R_LARCH_RELATIVE in the static PIE. */
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.dword _start
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EOF
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+ cat > conftest2.S << EOF
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+.global f
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+.type f, @function
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+f:
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+ /* The linker should be able to handle this and produce a PLT entry. */
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+ la.pcrel \$t0, \$t0, external_func
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+ jirl \$zero, \$t0, 0
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+EOF
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+
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libc_cv_static_pie_on_loongarch=no
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- if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest conftest.S'
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+ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest1 conftest1.S'
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+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
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+ (eval $ac_try) 2>&5
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+ ac_status=$?
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+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
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+ test $ac_status = 0; }; } \
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+ && { ac_try='LC_ALL=C $READELF -Wr conftest1 | grep -q R_LARCH_RELATIVE'
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+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
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+ (eval $ac_try) 2>&5
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+ ac_status=$?
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+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
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+ test $ac_status = 0; }; } \
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+ && { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -shared -fPIC -o conftest2.so conftest2.S'
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{ { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
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(eval $ac_try) 2>&5
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ac_status=$?
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$as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
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test $ac_status = 0; }; } \
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- && { ac_try='LC_ALL=C $READELF -Wr conftest | grep -q R_LARCH_RELATIVE'
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+ && { ac_try='LC_ALL=C $READELF -Wr conftest2.so | grep -q 'R_LARCH_JUMP_SLOT.*external_func''
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{ { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
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(eval $ac_try) 2>&5
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ac_status=$?
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@@ -43,7 +64,7 @@ EOF
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then
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libc_cv_static_pie_on_loongarch=yes
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fi
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- rm -rf conftest.*
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+ rm -rf conftest*
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fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_static_pie_on_loongarch" >&5
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$as_echo "$libc_cv_static_pie_on_loongarch" >&6; }
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diff --git a/sysdeps/loongarch/configure.ac b/sysdeps/loongarch/configure.ac
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index 603085cd..bfe4e0f2 100644
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--- a/sysdeps/loongarch/configure.ac
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+++ b/sysdeps/loongarch/configure.ac
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@@ -13,7 +13,7 @@ dnl satisify the requirement, but a distro may backport static PIE support into
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dnl earlier GCC or Binutils releases as well.
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AC_CACHE_CHECK([if the toolchain is sufficient to build static PIE on LoongArch],
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libc_cv_static_pie_on_loongarch, [
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- cat > conftest.S << EOF
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+ cat > conftest1.S << EOF
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.global _start
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.type _start, @function
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_start:
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@@ -28,14 +28,24 @@ x:
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.word 0
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/* This should produce an R_LARCH_RELATIVE in the static PIE. */
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.dword _start
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+EOF
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+ cat > conftest2.S << EOF
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+.global f
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+.type f, @function
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+f:
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+ /* The linker should be able to handle this and produce a PLT entry. */
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+ la.pcrel \$t0, \$t0, external_func
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+ jirl \$zero, \$t0, 0
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EOF
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libc_cv_static_pie_on_loongarch=no
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- if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest conftest.S]) \
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- && AC_TRY_COMMAND([LC_ALL=C $READELF -Wr conftest | grep -q R_LARCH_RELATIVE])
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+ if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest1 conftest1.S]) \
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+ && AC_TRY_COMMAND([LC_ALL=C $READELF -Wr conftest1 | grep -q R_LARCH_RELATIVE]) \
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+ && AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -shared -fPIC -o conftest2.so conftest2.S]) \
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+ && AC_TRY_COMMAND([LC_ALL=C $READELF -Wr conftest2.so | grep -q 'R_LARCH_JUMP_SLOT.*external_func'])
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then
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libc_cv_static_pie_on_loongarch=yes
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fi
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- rm -rf conftest.*])
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+ rm -rf conftest* ])
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if test "$libc_cv_static_pie_on_loongarch" = yes; then
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AC_DEFINE(SUPPORT_STATIC_PIE)
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diff --git a/sysdeps/loongarch/start.S b/sysdeps/loongarch/start.S
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index cb2b6c5b..11e4cede 100644
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--- a/sysdeps/loongarch/start.S
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+++ b/sysdeps/loongarch/start.S
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@@ -44,13 +44,16 @@ ENTRY (ENTRY_POINT)
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cfi_undefined (1)
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or a5, a0, zero /* rtld_fini */
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-#if defined(PIC) && !defined(SHARED)
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+#if ENABLE_STATIC_PIE
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/* For static PIE, the GOT cannot be used in _start because the GOT entries are
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- offsets instead of real addresses before __libc_start_main. */
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+ offsets instead of real addresses before __libc_start_main.
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+ __libc_start_main and/or main may be not local, so we rely on the linker to
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+ produce PLT entries for them. GNU ld >= 2.40 supports this. */
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# define LA la.pcrel
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#else
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-/* We must get symbol main through GOT table, since main may not be local.
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- For instance: googletest defines main in dynamic library. */
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+/* Old GNU ld (< 2.40) cannot handle PC relative address against a non-local
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+ function correctly. We deem these old linkers failing to support static PIE
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+ and load the addresses from GOT. */
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# define LA la.got
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#endif
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--
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2.27.0
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