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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2018-08-27 16:16:43 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2018-08-30 16:19:09 -0300
commit1823a9665c2d842db70c732eb3fe8a13c98f5319 (patch)
treee0fca2e0658483b80dc76f78dbe69bc077c2ce83
parentc3ab211099d304542a0ccfd8f5b743c12ac5bad9 (diff)
downloadglibc-azanella/bz20480.tar.gz
Fix ifunc support with DT_TEXTREL segments (BZ#20480)azanella/bz20480
Currently, DT_TEXTREL is incompatible with IFUNC. When DT_TEXTREL or DF_TEXTREL is seen, the dynamic linker calls __mprotect on the segments with PROT_READ|PROT_WRITE before applying dynamic relocations. It leads to segfault when performing IFUNC resolution (which requires PROT_EXEC as well for the IFUNC resolver). This patch makes it call __mprotect with extra PROT_WRITE bit, which will keep the PROT_EXEC bit if exists, and thus fixes the segfault. FreeBSD rtld libexec/rtld-elf/rtld.c (reloc_textrel_prot) does the same. Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu, sparc64-linux-gnu, sparcv9-linux-gnu, and armv8-linux-gnueabihf. Adam J. Richte <adam_richter2004@yahoo.com> Adhemerval Zanella <adhemerval.zanella@linaro.org> Fangrui Song <maskray@google.com> [BZ #20480] * config.h.in (CAN_TEXTREL_IFUNC): New define. * configure.ac: Add check if linker supports textrel relocation with ifunc. * elf/dl-reloc.c (_dl_relocate_object): Use all required flags on DT_TEXTREL segments, not only PROT_READ and PROT_WRITE. * elf/Makefile (ifunc-pie-tests): Add tst-ifunc-textrel. (CFLAGS-tst-ifunc-textrel.c): New rule. * elf/tst-ifunc-textrel.c: New file.
-rw-r--r--ChangeLog14
-rw-r--r--config.h.in3
-rwxr-xr-xconfigure51
-rw-r--r--configure.ac38
-rw-r--r--elf/Makefile4
-rw-r--r--elf/dl-reloc.c20
-rw-r--r--elf/tst-ifunc-textrel.c53
7 files changed, 170 insertions, 13 deletions
diff --git a/ChangeLog b/ChangeLog
index 157689fe45..3c29add3c3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2018-08-27 Adam J. Richte <adam_richter2004@yahoo.com>
+ Adhemerval Zanella <adhemerval.zanella@linaro.org>
+ Fangrui Song <maskray@google.com>
+
+ [BZ #20480]
+ * config.h.in (CAN_TEXTREL_IFUNC): New define.
+ * configure.ac: Add check if linker supports textrel relocation with
+ ifunc.
+ * elf/dl-reloc.c (_dl_relocate_object): Use all required flags on
+ DT_TEXTREL segments, not only PROT_READ and PROT_WRITE.
+ * elf/Makefile (ifunc-pie-tests): Add tst-ifunc-textrel.
+ (CFLAGS-tst-ifunc-textrel.c): New rule.
+ * elf/tst-ifunc-textrel.c: New file.
+
2018-08-27 Joseph Myers <joseph@codesourcery.com>
* sysdeps/generic/math-tests-trap-force.h: New file.
diff --git a/config.h.in b/config.h.in
index 141db213a9..d6fcbbac78 100644
--- a/config.h.in
+++ b/config.h.in
@@ -247,4 +247,7 @@
in i386 6 argument syscall issue). */
#define CAN_USE_REGISTER_ASM_EBP 0
+/* Linker supports ifunc with text relocation (used in tests). */
+#define CAN_TEXTREL_IFUNC 0
+
#endif
diff --git a/configure b/configure
index 285a6537f0..ab4c12c5ba 100755
--- a/configure
+++ b/configure
@@ -664,6 +664,7 @@ INSTALL_PROGRAM
sysnames
submachine
multi_arch
+libc_cv_textrel_ifunc
no_stack_protector
stack_protector
libc_cv_ssp
@@ -4052,6 +4053,56 @@ fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gcc_indirect_function" >&5
$as_echo "$libc_cv_gcc_indirect_function" >&6; }
+# Check if linker supports textrel relocation with ifunc (used on elf/tests).
+# Note that it relies on libc_cv_ld_gnu_indirect_function test above.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the linker supports textrels along with ifunc" >&5
+$as_echo_n "checking whether the linker supports textrels along with ifunc... " >&6; }
+if ${libc_cv_textrel_ifunc+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ cat > conftest.S <<EOF
+.type foo,%gnu_indirect_function
+foo:
+.globl _start
+_start:
+.globl __start
+__start:
+.data
+#ifdef _LP64
+.quad foo
+#else
+.long foo
+#endif
+.text
+.globl address
+address:
+#ifdef _LP64
+.quad address
+#else
+.long address
+#endif
+EOF
+libc_cv_textrel_ifunc=no
+if test $libc_cv_ld_gnu_indirect_function = yes; then
+ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -nostartfiles -nostdlib $no_ssp -pie -o conftest conftest.S'
+ { { eval echo "\"\$as_me\":${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_textrel_ifunc=yes
+ fi
+fi
+rm -f conftest*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_textrel_ifunc" >&5
+$as_echo "$libc_cv_textrel_ifunc" >&6; }
+if test $libc_cv_textrel_ifunc = yes; then
+ $as_echo "#define CAN_TEXTREL_IFUNC 1" >>confdefs.h
+
+fi
+
+
# Check if gcc warns about alias for function with incompatible types.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler warns about alias for function with incompatible types" >&5
$as_echo_n "checking if compiler warns about alias for function with incompatible types... " >&6; }
diff --git a/configure.ac b/configure.ac
index 8045d44dd0..e3d5c0598b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -671,6 +671,44 @@ if ${CC-cc} -c conftest.c -o conftest.o 1>&AS_MESSAGE_LOG_FD \
fi
rm -f conftest*])
+# Check if linker supports textrel relocation with ifunc (used on elf/tests).
+# Note that it relies on libc_cv_ld_gnu_indirect_function test above.
+AC_CACHE_CHECK([whether the linker supports textrels along with ifunc],
+ libc_cv_textrel_ifunc, [dnl
+cat > conftest.S <<EOF
+.type foo,%gnu_indirect_function
+foo:
+.globl _start
+_start:
+.globl __start
+__start:
+.data
+#ifdef _LP64
+.quad foo
+#else
+.long foo
+#endif
+.text
+.globl address
+address:
+#ifdef _LP64
+.quad address
+#else
+.long address
+#endif
+EOF
+libc_cv_textrel_ifunc=no
+if test $libc_cv_ld_gnu_indirect_function = yes; then
+ if AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -nostartfiles -nostdlib $no_ssp -pie -o conftest conftest.S); then
+ libc_cv_textrel_ifunc=yes
+ fi
+fi
+rm -f conftest*])
+if test $libc_cv_textrel_ifunc = yes; then
+ AC_DEFINE(CAN_TEXTREL_IFUNC)
+fi
+AC_SUBST(libc_cv_textrel_ifunc)
+
# Check if gcc warns about alias for function with incompatible types.
AC_CACHE_CHECK([if compiler warns about alias for function with incompatible types],
libc_cv_gcc_incompatible_alias, [dnl
diff --git a/elf/Makefile b/elf/Makefile
index cd0771307f..77eb6ef104 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -335,7 +335,8 @@ extra-test-objs += $(ifunc-test-modules:=.o)
test-internal-extras += $(ifunc-test-modules)
ifeq (yes,$(have-fpie))
ifunc-pie-tests = ifuncmain1pie ifuncmain1vispie ifuncmain1staticpie \
- ifuncmain5pie ifuncmain6pie ifuncmain7pie
+ ifuncmain5pie ifuncmain6pie ifuncmain7pie \
+ tst-ifunc-textrel
tests-internal += $(ifunc-pie-tests)
tests-pie += $(ifunc-pie-tests)
endif
@@ -1265,6 +1266,7 @@ CFLAGS-ifuncmain1staticpie.c += $(pie-ccflag)
CFLAGS-ifuncmain5pie.c += $(pie-ccflag)
CFLAGS-ifuncmain6pie.c += $(pie-ccflag)
CFLAGS-ifuncmain7pie.c += $(pie-ccflag)
+CFLAGS-tst-ifunc-textrel.c += $(pic-ccflag)
$(objpfx)ifuncmain1pie: $(objpfx)ifuncmod1.so
$(objpfx)ifuncmain1staticpie: $(objpfx)ifuncdep1pic.o
diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
index 053916eeae..164f4efa10 100644
--- a/elf/dl-reloc.c
+++ b/elf/dl-reloc.c
@@ -200,17 +200,6 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
newp->start = PTR_ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize))
+ (caddr_t) l->l_addr;
- if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
- {
- errstring = N_("cannot make segment writable for relocation");
- call_error:
- _dl_signal_error (errno, l->l_name, NULL, errstring);
- }
-
-#if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
- newp->prot = (PF_TO_PROT
- >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
-#else
newp->prot = 0;
if (ph->p_flags & PF_R)
newp->prot |= PROT_READ;
@@ -218,7 +207,14 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
newp->prot |= PROT_WRITE;
if (ph->p_flags & PF_X)
newp->prot |= PROT_EXEC;
-#endif
+
+ if (__mprotect (newp->start, newp->len, newp->prot|PROT_WRITE) < 0)
+ {
+ errstring = N_("cannot make segment writable for relocation");
+ call_error:
+ _dl_signal_error (errno, l->l_name, NULL, errstring);
+ }
+
newp->next = textrels;
textrels = newp;
}
diff --git a/elf/tst-ifunc-textrel.c b/elf/tst-ifunc-textrel.c
new file mode 100644
index 0000000000..60e5ac3bf8
--- /dev/null
+++ b/elf/tst-ifunc-textrel.c
@@ -0,0 +1,53 @@
+/* Check DT_TEXTREL/DF_TEXTREL support with ifunc.
+ Copyright (C) 2018 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
+ <http://www.gnu.org/licenses/>. */
+
+#include <stdint.h>
+
+/* Some linkers may fail to produce a shared object with ifunc and text
+ relocations. */
+#if CAN_TEXTREL_IFUNC
+/* Force a text relocation in the object. */
+static const uintptr_t
+address __attribute__((section(".text"))) = (uintptr_t) &address;
+
+static uintptr_t
+foo_impl (void)
+{
+ return address;
+}
+
+void *
+__attribute__((noinline))
+foo (void)
+{
+ return (void*) foo_impl;
+}
+__asm__ (".type foo, %gnu_indirect_function");
+#endif
+
+static int
+do_test (void)
+{
+#if CAN_TEXTREL_IFUNC
+ return (uintptr_t) foo () != 0 ? 0 : 1;
+#else
+ return 0;
+#endif
+}
+
+#include <support/test-driver.c>