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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.
This commit is contained in:
Adhemerval Zanella
parent
d62f9ec0cc
commit
b5c45e8375
15
ChangeLog
15
ChangeLog
@ -1,3 +1,18 @@
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2018-09-25 Adam J. Richte <adam_richter2004@yahoo.com>
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Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Fangrui Song <maskray@google.com>
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[BZ #20480]
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* config.make.in (have-textrel_ifunc): New define.
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* configure.ac: Add check if linker supports textrel relocation with
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ifunc.
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* elf/Makefile [have-textrel_ifunc == yes] (ifunc-pie-tests): Add
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tst-ifunc-textrel.
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(CFLAGS-tst-ifunc-textrel.c): New rule.
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* elf/dl-reloc.c (_dl_relocate_object): Use all required flags on
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DT_TEXTREL segments, not only PROT_READ and PROT_WRITE.
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* elf/tst-ifunc-textrel.c: New file.
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2018-09-25 Joseph Myers <joseph@codesourcery.com>
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* sysdeps/unix/sysv/linux/sys/procfs.h: Include
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@ -75,6 +75,7 @@ use-default-link = @use_default_link@
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output-format = @libc_cv_output_format@
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have-cxx-thread_local = @libc_cv_cxx_thread_local@
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have-loop-to-function = @libc_cv_cc_loop_to_function@
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have-textrel_ifunc = @libc_cv_textrel_ifunc@
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multi-arch = @multi_arch@
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47
configure
vendored
47
configure
vendored
@ -664,6 +664,7 @@ INSTALL_PROGRAM
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sysnames
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submachine
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multi_arch
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libc_cv_textrel_ifunc
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no_stack_protector
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stack_protector
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libc_cv_ssp
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@ -4052,6 +4053,52 @@ fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gcc_indirect_function" >&5
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$as_echo "$libc_cv_gcc_indirect_function" >&6; }
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# Check if linker supports textrel relocation with ifunc (used on elf/tests).
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# Note that it relies on libc_cv_ld_gnu_indirect_function test above.
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the linker supports textrels along with ifunc" >&5
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$as_echo_n "checking whether the linker supports textrels along with ifunc... " >&6; }
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if ${libc_cv_textrel_ifunc+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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cat > conftest.S <<EOF
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.type foo,%gnu_indirect_function
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foo:
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.globl _start
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_start:
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.globl __start
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__start:
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.data
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#ifdef _LP64
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.quad foo
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#else
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.long foo
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#endif
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.text
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.globl address
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address:
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#ifdef _LP64
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.quad address
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#else
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.long address
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#endif
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EOF
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libc_cv_textrel_ifunc=no
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if test $libc_cv_ld_gnu_indirect_function = yes; then
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if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -nostartfiles -nostdlib $no_ssp -pie -o conftest conftest.S'
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{ { eval echo "\"\$as_me\":${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; }; }; then
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libc_cv_textrel_ifunc=yes
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fi
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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: $libc_cv_textrel_ifunc" >&5
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$as_echo "$libc_cv_textrel_ifunc" >&6; }
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# Check if gcc warns about alias for function with incompatible types.
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler warns about alias for function with incompatible types" >&5
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$as_echo_n "checking if compiler warns about alias for function with incompatible types... " >&6; }
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35
configure.ac
35
configure.ac
@ -671,6 +671,41 @@ if ${CC-cc} -c conftest.c -o conftest.o 1>&AS_MESSAGE_LOG_FD \
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fi
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rm -f conftest*])
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# Check if linker supports textrel relocation with ifunc (used on elf/tests).
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# Note that it relies on libc_cv_ld_gnu_indirect_function test above.
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AC_CACHE_CHECK([whether the linker supports textrels along with ifunc],
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libc_cv_textrel_ifunc, [dnl
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cat > conftest.S <<EOF
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.type foo,%gnu_indirect_function
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foo:
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.globl _start
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_start:
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.globl __start
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__start:
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.data
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#ifdef _LP64
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.quad foo
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#else
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.long foo
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#endif
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.text
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.globl address
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address:
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#ifdef _LP64
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.quad address
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#else
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.long address
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#endif
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EOF
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libc_cv_textrel_ifunc=no
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if test $libc_cv_ld_gnu_indirect_function = yes; then
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if AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -nostartfiles -nostdlib $no_ssp -pie -o conftest conftest.S); then
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libc_cv_textrel_ifunc=yes
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fi
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fi
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rm -f conftest*])
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AC_SUBST(libc_cv_textrel_ifunc)
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# Check if gcc warns about alias for function with incompatible types.
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AC_CACHE_CHECK([if compiler warns about alias for function with incompatible types],
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libc_cv_gcc_incompatible_alias, [dnl
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@ -340,6 +340,9 @@ test-internal-extras += $(ifunc-test-modules)
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ifeq (yes,$(have-fpie))
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ifunc-pie-tests = ifuncmain1pie ifuncmain1vispie ifuncmain1staticpie \
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ifuncmain5pie ifuncmain6pie ifuncmain7pie
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ifeq (yes,$(have-textrel_ifunc))
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ifunc-pie-tests += tst-ifunc-textrel
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endif
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tests-internal += $(ifunc-pie-tests)
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tests-pie += $(ifunc-pie-tests)
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endif
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@ -1269,6 +1272,7 @@ CFLAGS-ifuncmain1staticpie.c += $(pie-ccflag)
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CFLAGS-ifuncmain5pie.c += $(pie-ccflag)
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CFLAGS-ifuncmain6pie.c += $(pie-ccflag)
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CFLAGS-ifuncmain7pie.c += $(pie-ccflag)
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CFLAGS-tst-ifunc-textrel.c += $(pic-ccflag)
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$(objpfx)ifuncmain1pie: $(objpfx)ifuncmod1.so
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$(objpfx)ifuncmain1staticpie: $(objpfx)ifuncdep1pic.o
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@ -200,17 +200,6 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
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newp->start = PTR_ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize))
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+ (caddr_t) l->l_addr;
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if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
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{
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errstring = N_("cannot make segment writable for relocation");
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call_error:
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_dl_signal_error (errno, l->l_name, NULL, errstring);
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}
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#if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
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newp->prot = (PF_TO_PROT
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>> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
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#else
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newp->prot = 0;
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if (ph->p_flags & PF_R)
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newp->prot |= PROT_READ;
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@ -218,7 +207,14 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
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newp->prot |= PROT_WRITE;
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if (ph->p_flags & PF_X)
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newp->prot |= PROT_EXEC;
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#endif
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if (__mprotect (newp->start, newp->len, newp->prot|PROT_WRITE) < 0)
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{
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errstring = N_("cannot make segment writable for relocation");
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call_error:
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_dl_signal_error (errno, l->l_name, NULL, errstring);
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}
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newp->next = textrels;
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textrels = newp;
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}
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45
elf/tst-ifunc-textrel.c
Normal file
45
elf/tst-ifunc-textrel.c
Normal file
@ -0,0 +1,45 @@
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/* Check DT_TEXTREL/DF_TEXTREL support with ifunc.
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Copyright (C) 2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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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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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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<http://www.gnu.org/licenses/>. */
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#include <stdint.h>
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/* Force a text relocation in the object. */
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static const uintptr_t
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address __attribute__((section(".text"))) = (uintptr_t) &address;
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static uintptr_t
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foo_impl (void)
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{
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return address;
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}
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void *
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__attribute__((noinline))
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foo (void)
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{
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return (void*) foo_impl;
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}
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__asm__ (".type foo, %gnu_indirect_function");
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static int
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do_test (void)
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{
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return (uintptr_t) foo () != 0 ? 0 : 1;
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}
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#include <support/test-driver.c>
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