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Compile elf/rtld.c with -fno-tree-loop-distribute-patterns.

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In GCC 10, the default at -O2 is now -ftree-loop-distribute-patterns.
This optimization causes GCC to "helpfully" convert the hand-written
loop in _dl_start into a call to memset, which is not available that
early in program startup.  Similar problems in other places in GLIBC
have been addressed by explicitly building with
-fno-tree-loop-distribute-patterns, but this one may have been
overlooked previously because it only affects targets where
HAVE_BUILTIN_MEMSET is not defined.

This patch fixes a bug observed on nios2-linux-gnu target that caused
all programs to segv on startup.
This commit is contained in:
Sandra Loosemore 2019-11-20 19:10:40 -07:00 committed by Florian Weimer
parent cc0e0b097c
commit c72e5cd87d
1 changed files with 6 additions and 0 deletions
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6
elf/Makefile
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@ -65,6 +65,12 @@ CFLAGS-dl-runtime.c += -fexceptions -fasynchronous-unwind-tables
CFLAGS-dl-lookup.c += -fexceptions -fasynchronous-unwind-tables
CFLAGS-dl-iterate-phdr.c += $(uses-callbacks)
# On targets without __builtin_memset, rtld.c uses a hand-coded loop
# in _dl_start. Make sure this isn't turned into a call to regular memset.
ifeq (yes,$(have-loop-to-function))
CFLAGS-rtld.c += -fno-tree-loop-distribute-patterns
endif
# Compile rtld itself without stack protection.
# Also compile all routines in the static library that are elided from
# the shared libc because they are in libc.a in the same way.