Pass -mno-red-zone to gcc to be compatible with the UEFI ABI
gcc by default outputs code using the SysV AMD64 ABI. We need to pass
-mno-red-zone to ensure compatibility with the Microsoft ABI, which is
what UEFI uses.
Matthew Garrett explains,
"The red zone is part of the AMD64 System V ABI and consists of
128 bytes at the bottom of the stack frame. This region is
guaranteed to be left untouched by any interrupt or signal
handlers, so it's available for functions to use as scratch
space. UEFI uses the Microsoft AMD64 ABI rather than the System V
one, and the Microsoft ABI doesn't define a red zone. UEFI
executables built on Linux tend to use System V because that means
we can link in static libraries built for Linux, rather than
needing an entirely separate toolchain and libraries to build UEFI
executables. The problem arises when we run one of these
executables and there's a UEFI interrupt handler still
running. Take an interrupt, Microsoft ABI interrupt handler gets
called and the red zone gets overwritten."
Signed-off-by: Steve Langasek <steve.langasek@canonical.com>
Cc: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
diff --git a/Makefile b/Makefile
index 75936c6..3b02abe 100644
--- a/Makefile
+++ b/Makefile
@@ -63,6 +63,9 @@
CFLAGS += -m32
endif
endif
+ifeq ($(ARCH),x86_64)
+ CFLAGS += -mno-red-zone
+endif
LDFLAGS=-T $(LDSCRIPT) -Bsymbolic -shared -nostdlib -znocombreloc \
-L$(LIBDIR) $(CRT0)
