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authorSandra Loosemore <sandra@codesourcery.com>2019-11-20 19:10:40 -0700
committerFlorian Weimer <fweimer@redhat.com>2019-11-26 19:18:23 +0100
commitc72e5cd87dcb075782f9b6beea024b984f2e1130 (patch)
tree5775f299eaf17d56b80ff23f1a92e6f45925265a
parentcc0e0b097c3e2176b51c32c09a76766e890cd2d4 (diff)
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Compile elf/rtld.c with -fno-tree-loop-distribute-patterns.
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.
-rw-r--r--elf/Makefile6
1 files changed, 6 insertions, 0 deletions
diff --git a/elf/Makefile b/elf/Makefile
index 06688181e3..b05af5ce3a 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -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.