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commit abcc039d2e26b3c9c723d6419e086753a791b3d5
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Fri Feb 7 20:06:32 2020 +0100
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elf: Introduce the rtld-stubbed-symbols makefile variable
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This generalizes a mechanism used for stack-protector support, so
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that it can be applied to other symbols if required.
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Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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diff --git a/elf/Makefile b/elf/Makefile
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index 4ab73dc48d9ac126..a1ea44f231d8cec5 100644
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--- a/elf/Makefile
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+++ b/elf/Makefile
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@@ -474,21 +474,25 @@ $(objpfx)dl-allobjs.os: $(all-rtld-routines:%=$(objpfx)%.os)
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# are compiled with special flags, and puts these modules into rtld-libc.a
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# for us. Then we do the real link using rtld-libc.a instead of libc_pic.a.
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-# If the compiler can do SSP, build the mapfile with dummy __stack_chk_fail
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-# and __stack_chk_fail_local symbols defined, to prevent the real things
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-# being dragged into rtld even though rtld is never built with stack-
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-# protection.
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+# These symbols need to be stubbed out during symbol discovery because
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+# their implementation is provided differently in rtld, and the symbol
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+# discovery mechanism is not compatible with the libc implementation
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+# when compiled for libc.
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+rtld-stubbed-symbols =
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+
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+# The GCC arguments that implement $(rtld-stubbed-symbols).
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+rtld-stubbed-symbols-args = \
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+ $(patsubst %,-Wl$(comma)--defsym=%=0, $(rtld-stubbed-symbols))
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ifeq ($(have-ssp),yes)
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-dummy-stack-chk-fail := -Wl,--defsym='__stack_chk_fail=0' \
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- -Wl,--defsym='__stack_chk_fail_local=0'
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-else
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-dummy-stack-chk-fail :=
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+# rtld is not built with the stack protector, so these references will
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+# go away in the rebuilds.
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+rtld-stubbed-symbols += __stack_chk_fail __stack_chk_fail_local
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endif
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$(objpfx)librtld.map: $(objpfx)dl-allobjs.os $(common-objpfx)libc_pic.a
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@-rm -f $@T
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- $(reloc-link) -o $@.o $(dummy-stack-chk-fail) \
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+ $(reloc-link) -o $@.o $(rtld-stubbed-symbols-args) \
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'-Wl,-(' $^ -lgcc '-Wl,-)' -Wl,-Map,$@T
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rm -f $@.o
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mv -f $@T $@
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