From bc174f20b83d19167ecac14ce0762eddbe47cc64 Mon Sep 17 00:00:00 2001 From: Nick Alcock Date: Mon, 26 Dec 2016 10:08:51 +0100 Subject: Ignore __stack_chk_fail* in the rtld mapfile computation [BZ #7065] 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.) --- elf/Makefile | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'elf/Makefile') diff --git a/elf/Makefile b/elf/Makefile index 1e7d724..04d5f07 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -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 $@ -- cgit v1.1