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.
+2018-09-25 Adam J. Richte <adam_richter2004@yahoo.com>
+ Adhemerval Zanella <adhemerval.zanella@linaro.org>
+ Fangrui Song <maskray@google.com>
+
+ [BZ #20480]
+ * config.make.in (have-textrel_ifunc): New define.
+ * configure.ac: Add check if linker supports textrel relocation with
+ ifunc.
+ * elf/Makefile [have-textrel_ifunc == yes] (ifunc-pie-tests): Add
+ tst-ifunc-textrel.
+ (CFLAGS-tst-ifunc-textrel.c): New rule.
+ * elf/dl-reloc.c (_dl_relocate_object): Use all required flags on
+ DT_TEXTREL segments, not only PROT_READ and PROT_WRITE.
+ * elf/tst-ifunc-textrel.c: New file.
+
2018-09-25 Joseph Myers <joseph@codesourcery.com>
* sysdeps/unix/sysv/linux/sys/procfs.h: Include
output-format = @libc_cv_output_format@
have-cxx-thread_local = @libc_cv_cxx_thread_local@
have-loop-to-function = @libc_cv_cc_loop_to_function@
+have-textrel_ifunc = @libc_cv_textrel_ifunc@
multi-arch = @multi_arch@
sysnames
submachine
multi_arch
+libc_cv_textrel_ifunc
no_stack_protector
stack_protector
libc_cv_ssp
{ $as_echo "$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; }
+
+
# 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; }
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 $no_ssp -pie -o conftest conftest.S); then
+ libc_cv_textrel_ifunc=yes
+ fi
+fi
+rm -f conftest*])
+AC_SUBST(libc_cv_textrel_ifunc)
+
# Check if gcc warns about alias for function with incompatible types.
AC_CACHE_CHECK([if compiler warns about alias for function with incompatible types],
libc_cv_gcc_incompatible_alias, [dnl
ifeq (yes,$(have-fpie))
ifunc-pie-tests = ifuncmain1pie ifuncmain1vispie ifuncmain1staticpie \
ifuncmain5pie ifuncmain6pie ifuncmain7pie
+ifeq (yes,$(have-textrel_ifunc))
+ifunc-pie-tests += tst-ifunc-textrel
+endif
tests-internal += $(ifunc-pie-tests)
tests-pie += $(ifunc-pie-tests)
endif
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
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;
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;
}
--- /dev/null
+/* 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>
+
+/* 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");
+
+static int
+do_test (void)
+{
+ return (uintptr_t) foo () != 0 ? 0 : 1;
+}
+
+#include <support/test-driver.c>
projects / thirdparty / glibc.git / commitdiff
