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410 lines
14 KiB
410 lines
14 KiB
commit 198abcbb94618730dae1b3f4393efaa49e0ec8c7
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Mon Apr 11 11:30:31 2022 +0200
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Default to --with-default-link=no (bug 25812)
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This is necessary to place the libio vtables into the RELRO segment.
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New tests elf/tst-relro-ldso and elf/tst-relro-libc are added to
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verify that this is what actually happens.
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The new tests fail on ia64 due to lack of (default) RELRO support
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inbutils, so they are XFAILed there.
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Conflicts:
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elf/Makefile
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(missing valgrind smoke test)
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diff --git a/INSTALL b/INSTALL
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index b3a4370f592c5047..b69672b283c0b774 100644
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--- a/INSTALL
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+++ b/INSTALL
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@@ -90,6 +90,12 @@ if 'CFLAGS' is specified it must enable optimization. For example:
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library will still be usable, but functionality may be lost--for
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example, you can't build a shared libc with old binutils.
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+'--with-default-link=FLAG'
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+ With '--with-default-link=yes', the build system does not use a
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+ custom linker script for linking shared objects. The default for
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+ FLAG is the opposite, 'no', because the custom linker script is
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+ needed for full RELRO protection.
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+
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'--with-nonshared-cflags=CFLAGS'
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Use additional compiler flags CFLAGS to build the parts of the
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library which are always statically linked into applications and
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diff --git a/configure b/configure
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index 8b3681d2e28310c8..c794cea4359b3da3 100755
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--- a/configure
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+++ b/configure
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@@ -3339,7 +3339,7 @@ fi
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if test "${with_default_link+set}" = set; then :
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withval=$with_default_link; use_default_link=$withval
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else
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- use_default_link=default
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+ use_default_link=no
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fi
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@@ -5965,69 +5965,6 @@ fi
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$as_echo "$libc_cv_hashstyle" >&6; }
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-# The linker's default -shared behavior is good enough if it
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-# does these things that our custom linker scripts ensure that
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-# all allocated NOTE sections come first.
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-if test "$use_default_link" = default; then
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- { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sufficient default -shared layout" >&5
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-$as_echo_n "checking for sufficient default -shared layout... " >&6; }
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-if ${libc_cv_use_default_link+:} false; then :
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- $as_echo_n "(cached) " >&6
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-else
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- libc_cv_use_default_link=no
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- cat > conftest.s <<\EOF
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- .section .note.a,"a",%note
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- .balign 4
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- .long 4,4,9
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- .string "GNU"
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- .string "foo"
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- .section .note.b,"a",%note
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- .balign 4
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- .long 4,4,9
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- .string "GNU"
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- .string "bar"
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-EOF
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- if { ac_try=' ${CC-cc} $ASFLAGS -shared -o conftest.so conftest.s 1>&5'
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- { { eval echo "\"\$as_me\":${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 $ac_status = 0; }; } &&
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- ac_try=`$READELF -S conftest.so | sed -n \
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- '${x;p;}
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- s/^ *\[ *[1-9][0-9]*\] *\([^ ][^ ]*\) *\([^ ][^ ]*\) .*$/\2 \1/
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- t a
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- b
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- : a
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- H'`
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- then
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- libc_seen_a=no libc_seen_b=no
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- set -- $ac_try
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- while test $# -ge 2 -a "$1" = NOTE; do
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- case "$2" in
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- .note.a) libc_seen_a=yes ;;
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- .note.b) libc_seen_b=yes ;;
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- esac
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- shift 2
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- done
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- case "$libc_seen_a$libc_seen_b" in
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- yesyes)
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- libc_cv_use_default_link=yes
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- ;;
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- *)
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- echo >&5 "\
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-$libc_seen_a$libc_seen_b from:
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-$ac_try"
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- ;;
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- esac
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- fi
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- rm -f conftest*
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-fi
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-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_use_default_link" >&5
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-$as_echo "$libc_cv_use_default_link" >&6; }
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- use_default_link=$libc_cv_use_default_link
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-fi
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-
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for GLOB_DAT reloc" >&5
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$as_echo_n "checking for GLOB_DAT reloc... " >&6; }
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if ${libc_cv_has_glob_dat+:} false; then :
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diff --git a/configure.ac b/configure.ac
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index 82d9ab2fb67145bb..52429d82344954b3 100644
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--- a/configure.ac
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+++ b/configure.ac
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@@ -152,7 +152,7 @@ AC_ARG_WITH([default-link],
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AC_HELP_STRING([--with-default-link],
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[do not use explicit linker scripts]),
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[use_default_link=$withval],
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- [use_default_link=default])
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+ [use_default_link=no])
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dnl Additional build flags injection.
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AC_ARG_WITH([nonshared-cflags],
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@@ -1352,59 +1352,6 @@ fi
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rm -f conftest*])
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AC_SUBST(libc_cv_hashstyle)
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-# The linker's default -shared behavior is good enough if it
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-# does these things that our custom linker scripts ensure that
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-# all allocated NOTE sections come first.
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-if test "$use_default_link" = default; then
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- AC_CACHE_CHECK([for sufficient default -shared layout],
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- libc_cv_use_default_link, [dnl
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- libc_cv_use_default_link=no
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- cat > conftest.s <<\EOF
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- .section .note.a,"a",%note
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- .balign 4
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- .long 4,4,9
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- .string "GNU"
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- .string "foo"
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- .section .note.b,"a",%note
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- .balign 4
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- .long 4,4,9
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- .string "GNU"
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- .string "bar"
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-EOF
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- if AC_TRY_COMMAND([dnl
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- ${CC-cc} $ASFLAGS -shared -o conftest.so conftest.s 1>&AS_MESSAGE_LOG_FD]) &&
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- ac_try=`$READELF -S conftest.so | sed -n \
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- ['${x;p;}
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- s/^ *\[ *[1-9][0-9]*\] *\([^ ][^ ]*\) *\([^ ][^ ]*\) .*$/\2 \1/
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- t a
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- b
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- : a
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- H']`
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- then
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- libc_seen_a=no libc_seen_b=no
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- set -- $ac_try
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- while test $# -ge 2 -a "$1" = NOTE; do
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- case "$2" in
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- .note.a) libc_seen_a=yes ;;
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- .note.b) libc_seen_b=yes ;;
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- esac
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- shift 2
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- done
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- case "$libc_seen_a$libc_seen_b" in
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- yesyes)
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- libc_cv_use_default_link=yes
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- ;;
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- *)
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- echo >&AS_MESSAGE_LOG_FD "\
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-$libc_seen_a$libc_seen_b from:
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-$ac_try"
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- ;;
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- esac
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- fi
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- rm -f conftest*])
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- use_default_link=$libc_cv_use_default_link
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-fi
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-
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AC_CACHE_CHECK(for GLOB_DAT reloc,
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libc_cv_has_glob_dat, [dnl
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cat > conftest.c <<EOF
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diff --git a/elf/Makefile b/elf/Makefile
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index 89ce4f5196e5eb39..1fdf40cbd49e233e 100644
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--- a/elf/Makefile
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+++ b/elf/Makefile
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@@ -477,6 +477,40 @@ tests-execstack-yes = \
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# tests-execstack-yes
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endif
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endif
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+
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+tests-special += $(objpfx)tst-relro-ldso.out $(objpfx)tst-relro-libc.out
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+$(objpfx)tst-relro-ldso.out: tst-relro-symbols.py $(..)/scripts/glibcelf.py \
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+ $(objpfx)ld.so
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+ $(PYTHON) tst-relro-symbols.py $(objpfx)ld.so \
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+ --required=_rtld_global_ro \
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+ > $@ 2>&1; $(evaluate-test)
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+# The optional symbols are present in libc only if the architecture has
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+# the GLIBC_2.0 symbol set in libc.
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+$(objpfx)tst-relro-libc.out: tst-relro-symbols.py $(..)/scripts/glibcelf.py \
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+ $(common-objpfx)libc.so
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+ $(PYTHON) tst-relro-symbols.py $(common-objpfx)libc.so \
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+ --required=_IO_cookie_jumps \
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+ --required=_IO_file_jumps \
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+ --required=_IO_file_jumps_maybe_mmap \
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+ --required=_IO_file_jumps_mmap \
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+ --required=_IO_helper_jumps \
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+ --required=_IO_mem_jumps \
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+ --required=_IO_obstack_jumps \
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+ --required=_IO_proc_jumps \
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+ --required=_IO_str_chk_jumps \
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+ --required=_IO_str_jumps \
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+ --required=_IO_strn_jumps \
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+ --required=_IO_wfile_jumps \
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+ --required=_IO_wfile_jumps_maybe_mmap \
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+ --required=_IO_wfile_jumps_mmap \
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+ --required=_IO_wmem_jumps \
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+ --required=_IO_wstr_jumps \
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+ --required=_IO_wstrn_jumps \
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+ --optional=_IO_old_cookie_jumps \
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+ --optional=_IO_old_file_jumps \
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+ --optional=_IO_old_proc_jumps \
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+ > $@ 2>&1; $(evaluate-test)
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+
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tests += $(tests-execstack-$(have-z-execstack))
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ifeq ($(run-built-tests),yes)
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tests-special += \
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diff --git a/elf/tst-relro-symbols.py b/elf/tst-relro-symbols.py
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new file mode 100644
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index 0000000000000000..368ea3349f86bd81
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--- /dev/null
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+++ b/elf/tst-relro-symbols.py
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@@ -0,0 +1,137 @@
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+#!/usr/bin/python3
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+# Verify that certain symbols are covered by RELRO.
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+# Copyright (C) 2022 Free Software Foundation, Inc.
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+# This file is part of the GNU C Library.
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+#
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+# The GNU C Library is free software; you can redistribute it and/or
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+# modify it under the terms of the GNU Lesser General Public
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+# License as published by the Free Software Foundation; either
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+# version 2.1 of the License, or (at your option) any later version.
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+#
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+# The GNU C Library is distributed in the hope that it will be useful,
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+# but WITHOUT ANY WARRANTY; without even the implied warranty of
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+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+# Lesser General Public License for more details.
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+#
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+# You should have received a copy of the GNU Lesser General Public
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+# License along with the GNU C Library; if not, see
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+# <https://www.gnu.org/licenses/>.
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+
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+"""Analyze a (shared) object to verify that certain symbols are
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+present and covered by the PT_GNU_RELRO segment.
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+
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+"""
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+
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+import argparse
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+import os.path
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+import sys
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+
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+# Make available glibc Python modules.
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+sys.path.append(os.path.join(
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+ os.path.dirname(os.path.realpath(__file__)), os.path.pardir, 'scripts'))
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+
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+import glibcelf
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+
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+def find_relro(path: str, img: glibcelf.Image) -> (int, int):
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+ """Discover the address range of the PT_GNU_RELRO segment."""
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+ for phdr in img.phdrs():
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+ if phdr.p_type == glibcelf.Pt.PT_GNU_RELRO:
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+ # The computation is not entirely accurate because
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+ # _dl_protect_relro in elf/dl-reloc.c rounds both the
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+ # start end and downwards using the run-time page size.
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+ return phdr.p_vaddr, phdr.p_vaddr + phdr.p_memsz
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+ sys.stdout.write('{}: error: no PT_GNU_RELRO segment\n'.format(path))
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+ sys.exit(1)
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+
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+def check_in_relro(kind, relro_begin, relro_end, name, start, size, error):
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+ """Check if a section or symbol falls within in the RELRO segment."""
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+ end = start + size - 1
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+ if not (relro_begin <= start < end < relro_end):
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+ error(
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+ '{} {!r} of size {} at 0x{:x} is not in RELRO range [0x{:x}, 0x{:x})'.format(
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+ kind, name.decode('UTF-8'), start, size,
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+ relro_begin, relro_end))
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+
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+def get_parser():
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+ """Return an argument parser for this script."""
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+ parser = argparse.ArgumentParser(description=__doc__)
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+ parser.add_argument('object', help='path to object file to check')
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+ parser.add_argument('--required', metavar='NAME', default=(),
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+ help='required symbol names', nargs='*')
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+ parser.add_argument('--optional', metavar='NAME', default=(),
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+ help='required symbol names', nargs='*')
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+ return parser
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+
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+def main(argv):
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+ """The main entry point."""
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+ parser = get_parser()
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+ opts = parser.parse_args(argv)
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+ img = glibcelf.Image.readfile(opts.object)
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+
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+ required_symbols = frozenset([sym.encode('UTF-8')
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+ for sym in opts.required])
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+ optional_symbols = frozenset([sym.encode('UTF-8')
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+ for sym in opts.optional])
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+ check_symbols = required_symbols | optional_symbols
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+
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+ # Tracks the symbols in check_symbols that have been found.
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+ symbols_found = set()
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+
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+ # Discover the extent of the RELRO segment.
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+ relro_begin, relro_end = find_relro(opts.object, img)
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+ symbol_table_found = False
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+
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+ errors = False
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+ def error(msg: str) -> None:
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+ """Record an error condition and write a message to standard output."""
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+ nonlocal errors
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+ errors = True
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+ sys.stdout.write('{}: error: {}\n'.format(opts.object, msg))
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+
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+ # Iterate over section headers to find the symbol table.
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+ for shdr in img.shdrs():
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+ if shdr.sh_type == glibcelf.Sht.SHT_SYMTAB:
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+ symbol_table_found = True
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+ for sym in img.syms(shdr):
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+ if sym.st_name in check_symbols:
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+ symbols_found.add(sym.st_name)
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+
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+ # Validate symbol type, section, and size.
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+ if sym.st_info.type != glibcelf.Stt.STT_OBJECT:
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+ error('symbol {!r} has wrong type {}'.format(
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+ sym.st_name.decode('UTF-8'), sym.st_info.type))
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+ if sym.st_shndx in glibcelf.Shn:
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+ error('symbol {!r} has reserved section {}'.format(
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+ sym.st_name.decode('UTF-8'), sym.st_shndx))
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+ continue
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+ if sym.st_size == 0:
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+ error('symbol {!r} has size zero'.format(
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+ sym.st_name.decode('UTF-8')))
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+ continue
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+
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+ check_in_relro('symbol', relro_begin, relro_end,
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+ sym.st_name, sym.st_value, sym.st_size,
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+ error)
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+ continue # SHT_SYMTAB
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+ if shdr.sh_name == b'.data.rel.ro' \
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+ or shdr.sh_name.startswith(b'.data.rel.ro.'):
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+ check_in_relro('section', relro_begin, relro_end,
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+ shdr.sh_name, shdr.sh_addr, shdr.sh_size,
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+ error)
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+ continue
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+
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+ if required_symbols - symbols_found:
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+ for sym in sorted(required_symbols - symbols_found):
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+ error('symbol {!r} not found'.format(sym.decode('UTF-8')))
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+
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+ if errors:
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+ sys.exit(1)
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+
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+ if not symbol_table_found:
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+ sys.stdout.write(
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+ '{}: warning: no symbol table found (stripped object)\n'.format(
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+ opts.object))
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+ sys.exit(77)
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+
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+if __name__ == '__main__':
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+ main(sys.argv[1:])
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diff --git a/manual/install.texi b/manual/install.texi
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index c262fd56d0cef67b..a2c43bd692de7825 100644
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--- a/manual/install.texi
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+++ b/manual/install.texi
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@@ -117,6 +117,12 @@ problem and suppress these constructs, so that the library will still be
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usable, but functionality may be lost---for example, you can't build a
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shared libc with old binutils.
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+@item --with-default-link=@var{FLAG}
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+With @code{--with-default-link=yes}, the build system does not use a
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+custom linker script for linking shared objects. The default for
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+@var{FLAG} is the opposite, @samp{no}, because the custom linker script
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+is needed for full RELRO protection.
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+
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@item --with-nonshared-cflags=@var{cflags}
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Use additional compiler flags @var{cflags} to build the parts of the
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library which are always statically linked into applications and
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diff --git a/sysdeps/unix/sysv/linux/ia64/Makefile b/sysdeps/unix/sysv/linux/ia64/Makefile
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index 97fc7df0b122d6a0..b1ad1ab7b1efa34c 100644
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--- a/sysdeps/unix/sysv/linux/ia64/Makefile
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+++ b/sysdeps/unix/sysv/linux/ia64/Makefile
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@@ -1,3 +1,9 @@
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+ifeq ($(subdir),elf)
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+# ia64 does not support PT_GNU_RELRO.
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+test-xfail-tst-relro-ldso = yes
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+test-xfail-tst-relro-libc = yes
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+endif
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+
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ifeq ($(subdir),misc)
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sysdep_headers += sys/rse.h
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endif
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