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Ignore __stack_chk_fail* in the rtld mapfile computation [BZ #7065]

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The previous commit prevented rtld itself from being built with
-fstack-protector, but this is not quite enough.  We identify which
objects belong in rtld via a test link and analysis of the resulting
mapfile.  That link is necessarily done against objects that are
stack-protected, so drags in __stack_chk_fail_local, __stack_chk_fail,
and all the libc and libio code they use.

To stop this happening, use --defsym in the test librtld.map-production
link to force the linker to predefine these two symbols (to 0, but it
could be to anything).  (In a real link, this would of course be
catastrophic, but these object files are never used for anything else.)
This commit is contained in:
Nick Alcock 2016-12-26 10:08:51 +01:00 committed by Florian Weimer
parent 995635f95b
commit bc174f20b8
2 changed files with 20 additions and 1 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2016-12-26 Nick Alcock <nick.alcock@oracle.com>
[BZ #7065]
* elf/Makefile (dummy-stack-chk-fail): New.
(librtld.map): Use it.
2016-12-26 Nick Alcock <nick.alcock@oracle.com>
[BZ #7065]

15
elf/Makefile
View File

@ -386,9 +386,22 @@ $(objpfx)dl-allobjs.os: $(all-rtld-routines:%=$(objpfx)%.os)
# are compiled with special flags, and puts these modules into rtld-libc.a
# for us. Then we do the real link using rtld-libc.a instead of libc_pic.a.
# If the compiler can do SSP, build the mapfile with dummy __stack_chk_fail
# and __stack_chk_fail_local symbols defined, to prevent the real things
# being dragged into rtld even though rtld is never built with stack-
# protection.
ifeq ($(have-ssp),yes)
dummy-stack-chk-fail := -Wl,--defsym='__stack_chk_fail=0' \
-Wl,--defsym='__stack_chk_fail_local=0'
else
dummy-stack-chk-fail :=
endif
$(objpfx)librtld.map: $(objpfx)dl-allobjs.os $(common-objpfx)libc_pic.a
@-rm -f $@T
$(reloc-link) -o $@.o '-Wl,-(' $^ -lgcc '-Wl,-)' -Wl,-Map,$@T
$(reloc-link) -o $@.o $(dummy-stack-chk-fail) \
'-Wl,-(' $^ -lgcc '-Wl,-)' -Wl,-Map,$@T
rm -f $@.o
mv -f $@T $@