[Qemu-devel] [PATCH] optionrom: fix compilation with mingw docker target

[Paolo Bonzini <pbonzini@redhat.com>]

Two fixes are needed.  First, mingw does not have -D_FORTIFY_SOURCE,
hence --enable-debug disables optimization.  This is not acceptable
for ROMs, which should override CFLAGS to force inclusion of -O2.

Second, PE stores global constructors and destructors using the
following linker script snippet:

     ___CTOR_LIST__ = .; __CTOR_LIST__ = . ;
			LONG (-1);*(.ctors); *(.ctor); *(SORT(.ctors.*));  LONG (0);
     ___DTOR_LIST__ = .; __DTOR_LIST__ = . ;
			LONG (-1); *(.dtors); *(.dtor); *(SORT(.dtors.*));  LONG (0);

The LONG directives cause the .img files to be 16 bytes too large;
the recently added check to signrom.py catches this.  To fix this,
replace -T and -e options with a linker script.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 pc-bios/optionrom/Makefile | 10 +++++++++-
 pc-bios/optionrom/flat.lds |  6 ++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 pc-bios/optionrom/flat.lds

diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
index 9c018ea..8aef152 100644
--- a/pc-bios/optionrom/Makefile
+++ b/pc-bios/optionrom/Makefile
@@ -9,6 +9,14 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/optionrom)
 
 .PHONY : all clean build-all
 
+# Compiling with no optimization creates ROMs that are too large
+ifeq ($(filter -O%, $(CFLAGS)),)
+override CFLAGS += -O2
+endif
+ifeq ($(filter -O%, $(CFLAGS)),-O0)
+override CFLAGS += -O2
+endif
+
 # Drop -fstack-protector and the like
 QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS)) $(CFLAGS_NOPIE) -ffreestanding
 QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
@@ -51,7 +59,7 @@ endif
 endif
 
 %.img: %.o
-	$(call quiet-command,$(LD) $(LDFLAGS_NOPIE) -m $(LD_EMULATION) -Ttext 0 -e _start -s -o $@ $<,"  Building $(TARGET_DIR)$@")
+	$(call quiet-command,$(LD) $(LDFLAGS_NOPIE) -m $(LD_EMULATION) -T $(SRC_PATH)/pc-bios/optionrom/flat.lds -s -o $@ $<,"  Building $(TARGET_DIR)$@")
 
 %.raw: %.img
 	$(call quiet-command,$(OBJCOPY) -O binary -j .text $< $@,"  Building $(TARGET_DIR)$@")
diff --git a/pc-bios/optionrom/flat.lds b/pc-bios/optionrom/flat.lds
new file mode 100644
index 0000000..cee2eda
--- /dev/null
+++ b/pc-bios/optionrom/flat.lds
@@ -0,0 +1,6 @@
+SECTIONS
+{
+  . = 0;
+  .text : { *(.text) *(.text.$) }
+}
+ENTRY(_start)
-- 
1.8.3.1