[PATCH 17/21] lto, workaround: Disable LTO for BPF

Andi Kleen
2017-11-27T21:34:33Z

Disable LTO for the BPF interpreter. This works around a gcc bug in the LTO
partitioner that partitions the jumptable used the BPF interpreter
into a different LTO unit. This in term causes assembler
errors because the jump table contains references to the
code labels in the original file.

gcc problem tracked in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50676

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
kernel/bpf/Makefile | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index e691da0b3bab..409d4b6762ee 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -16,3 +16,8 @@ ifeq ($(CONFIG_PERF_EVENTS),y)
obj-$(CONFIG_BPF_SYSCALL) += stackmap.o
endif
obj-$(CONFIG_CGROUP_BPF) += cgroup.o
+
+# various version of gcc have a LTO bug where the &&labels used in the
+# BPF interpreter can cause linker errors when spread incorrectly over
+# partitions. Disable LTO for BPF for now
+CFLAGS_core.o = $(DISABLE_LTO)
--
2.13.6