[PATCH 2/4] Check -z single-global-definition and -fsingle-global-definition
H.J. Lu
hjl.tools@gmail.com
Sun Jun 20 23:36:18 GMT 2021
1. Check linker support for -z single-global-definition. If
GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION is set on any input
relocatable files:
a. Don't generate copy relocations.
b. Turn off extern_protected_data.
c. Treate reference to protected symbols with single global definition
as local.
d. Set GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION on output.
e. Add -z [no]single-global-definition to control single global
definition.
2. Check compiler support for -fsingle-global-definition:
a. Generate a single global definition marker in relocatable objects.
i. Always use GOT to access undefined data and function symbols,
including in PIE and non-PIE. These will avoid copy relocations in
executables.
ii. This is compatible with existing executables and shared libraries.
b. In executable and shared library, bind symbols with the STV_PROTECTED
visibility locally:
i. The address of data symbol is the address of data body.
ii. For systems without function descriptor, the function pointer is
the address of function body.
iii. The resulting shared libraries may not be incompatible with
executables which have copy relocations on protected symbols.
Size comparison of non-PIE builds with GCC 12 -O2:
1. On x86-64:
text data bss dec hex filename
190218 9672 416 200306 30e72 ld.so (original)
190258 9336 416 200010 30d4a ld.so (-fsingle-global-definition)
1917384 20232 52424 1990040 1e5d98 libc.so (original)
1919946 20240 52432 1992618 1e67aa libc.so (-fsingle-global-definition)
261734 10339 744 272817 429b1 localedef (original)
233084 41734 648 275466 4340a localedef (-fsingle-global-definition)
2. On i686:
text data bss dec hex filename
199369 6796 212 206377 32629 ld.so (original)
199381 6796 212 206389 32635 ld.so (-fsingle-global-definition)
2058080 11136 38856 2108072 202aa8 libc.so (original)
2058092 11136 38856 2108084 202ab4 libc.so (-fsingle-global-definition)
276207 9559 552 286318 45e6e localedef (original)
254249 33734 520 288503 466f7 localedef (-fsingle-global-definition)
---
configure | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++-
configure.ac | 37 ++++++++++++++++++++++++++
2 files changed, 109 insertions(+), 1 deletion(-)
diff --git a/configure b/configure
index 9619c10991..5844dad68f 100755
--- a/configure
+++ b/configure
@@ -732,6 +732,7 @@ infodir
docdir
oldincludedir
includedir
+runstatedir
localstatedir
sharedstatedir
sysconfdir
@@ -844,6 +845,7 @@ datadir='${datarootdir}'
sysconfdir='${prefix}/etc'
sharedstatedir='${prefix}/com'
localstatedir='${prefix}/var'
+runstatedir='${localstatedir}/run'
includedir='${prefix}/include'
oldincludedir='/usr/include'
docdir='${datarootdir}/doc/${PACKAGE_TARNAME}'
@@ -1096,6 +1098,15 @@ do
| -silent | --silent | --silen | --sile | --sil)
silent=yes ;;
+ -runstatedir | --runstatedir | --runstatedi | --runstated \
+ | --runstate | --runstat | --runsta | --runst | --runs \
+ | --run | --ru | --r)
+ ac_prev=runstatedir ;;
+ -runstatedir=* | --runstatedir=* | --runstatedi=* | --runstated=* \
+ | --runstate=* | --runstat=* | --runsta=* | --runst=* | --runs=* \
+ | --run=* | --ru=* | --r=*)
+ runstatedir=$ac_optarg ;;
+
-sbindir | --sbindir | --sbindi | --sbind | --sbin | --sbi | --sb)
ac_prev=sbindir ;;
-sbindir=* | --sbindir=* | --sbindi=* | --sbind=* | --sbin=* \
@@ -1233,7 +1244,7 @@ fi
for ac_var in exec_prefix prefix bindir sbindir libexecdir datarootdir \
datadir sysconfdir sharedstatedir localstatedir includedir \
oldincludedir docdir infodir htmldir dvidir pdfdir psdir \
- libdir localedir mandir
+ libdir localedir mandir runstatedir
do
eval ac_val=\$$ac_var
# Remove trailing slashes.
@@ -1386,6 +1397,7 @@ Fine tuning of the installation directories:
--sysconfdir=DIR read-only single-machine data [PREFIX/etc]
--sharedstatedir=DIR modifiable architecture-independent data [PREFIX/com]
--localstatedir=DIR modifiable single-machine data [PREFIX/var]
+ --runstatedir=DIR modifiable per-process data [LOCALSTATEDIR/run]
--libdir=DIR object code libraries [EPREFIX/lib]
--includedir=DIR C header files [PREFIX/include]
--oldincludedir=DIR C header files for non-gcc [/usr/include]
@@ -5746,6 +5758,65 @@ fi
$as_echo "$libc_cv_insert" >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking -z single-global-definition" >&5
+$as_echo_n "checking -z single-global-definition... " >&6; }
+if ${libc_cv_z_single_global_definition+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ cat > conftest.c <<EOF
+ __attribute__ ((visibility ("protected")))
+ void bar (void) {}
+ void *bar_p (void) { return &bar; }
+EOF
+ libc_cv_z_single_global_definition=no
+ if { ac_try='${CC-cc} -Wl,-z,single-global-definition
+ -nostdlib -nostartfiles $CFLAGS $CPPFLAGS $LDFLAGS
+ -fPIC -shared $no_ssp -o conftest.so conftest.c
+ 1>&5'
+ { { eval echo "\"\$as_me\":${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
+ libc_cv_z_single_global_definition=yes
+ else
+ libc_cv_z_single_global_definition=no
+ fi
+ rm -f conftest.*
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_z_single_global_definition" >&5
+$as_echo "$libc_cv_z_single_global_definition" >&6; }
+config_vars="$config_vars
+have-z-single-global-definition = $libc_cv_z_single_global_definition"
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for -fsingle-global-definition" >&5
+$as_echo_n "checking for -fsingle-global-definition... " >&6; }
+if ${libc_cv_fsingle_global_definition+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ cat > conftest.c <<EOF
+int foo;
+EOF
+ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -S
+ -fsingle-global-definition
+ conftest.c 1>&5'
+ { { eval echo "\"\$as_me\":${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
+ libc_cv_fsingle_global_definition=yes
+ else
+ libc_cv_fsingle_global_definition=no
+ fi
+ rm -f conftest*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_fsingle_global_definition" >&5
+$as_echo "$libc_cv_fsingle_global_definition" >&6; }
+config_vars="$config_vars
+have-fsingle-global-definition = $libc_cv_fsingle_global_definition"
+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for broken __attribute__((alias()))" >&5
$as_echo_n "checking for broken __attribute__((alias()))... " >&6; }
if ${libc_cv_broken_alias_attribute+:} false; then :
diff --git a/configure.ac b/configure.ac
index 34ecbba540..26932812da 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1222,6 +1222,43 @@ EOF
])
AC_SUBST(libc_cv_insert)
+AC_CACHE_CHECK(-z single-global-definition,
+ libc_cv_z_single_global_definition,
+ [cat > conftest.c <<EOF
+ __attribute__ ((visibility ("protected")))
+ void bar (void) {}
+ void *bar_p (void) { return &bar; }
+EOF
+ libc_cv_z_single_global_definition=no
+ if AC_TRY_COMMAND([${CC-cc} -Wl,-z,single-global-definition
+ -nostdlib -nostartfiles $CFLAGS $CPPFLAGS $LDFLAGS
+ -fPIC -shared $no_ssp -o conftest.so conftest.c
+ 1>&AS_MESSAGE_LOG_FD]); then
+ libc_cv_z_single_global_definition=yes
+ else
+ libc_cv_z_single_global_definition=no
+ fi
+ rm -f conftest.*
+ ])
+LIBC_CONFIG_VAR([have-z-single-global-definition],
+ [$libc_cv_z_single_global_definition])
+
+AC_CACHE_CHECK(for -fsingle-global-definition,
+ libc_cv_fsingle_global_definition,
+ [cat > conftest.c <<EOF
+int foo;
+EOF
+ if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS -S
+ -fsingle-global-definition
+ conftest.c 1>&AS_MESSAGE_LOG_FD]); then
+ libc_cv_fsingle_global_definition=yes
+ else
+ libc_cv_fsingle_global_definition=no
+ fi
+ rm -f conftest*])
+LIBC_CONFIG_VAR([have-fsingle-global-definition],
+ [$libc_cv_fsingle_global_definition])
+
AC_CACHE_CHECK(for broken __attribute__((alias())),
libc_cv_broken_alias_attribute,
[cat > conftest.c <<EOF
--
2.31.1
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