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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2018-08-27 16:16:43 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2018-09-25 16:27:50 -0300
commitb5c45e83753b27dc538dff2d55d4410c385cf3a4 (patch)
tree7c88e09f3bcf2edbdf2a1196b50c54ab7459b0c5 /configure
parentd62f9ec0cce26a275ec68f4564814041a33395b1 (diff)
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Fix ifunc support with DT_TEXTREL segments (BZ#20480)
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.
Diffstat (limited to 'configure')
-rwxr-xr-xconfigure47
1 files changed, 47 insertions, 0 deletions
diff --git a/configure b/configure
index 285a6537f0..f30c31afdc 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 +4053,52 @@ 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; }
+
+
# 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; }