Don't use -fomit-frame-pointer when building VGA bios.

The real-mode emulator that Windows 7 uses to execute the vga bios rom
becomes very confused when the code tries to dereference the stack
pointer instead of using the frame pointer, leading to corruption of
parameters passed on the stack from one function to another.

Signed-off-by: Julian Pidancet <julian.pidancet@gmail.com>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

Makefile

@@ -32,21 +32,20 @@ COMMONCFLAGS = -I$(OUT) -Os -MD \
     $(call cc-option,$(CC),-Wtype-limits,) \
     -m32 -march=i386 -mregparm=3 -mpreferred-stack-boundary=2 \
     -mrtd -minline-all-stringops \
-    -freg-struct-return -ffreestanding -fomit-frame-pointer \
-    -fno-delete-null-pointer-checks \
+    -freg-struct-return -ffreestanding -fno-delete-null-pointer-checks \
     -ffunction-sections -fdata-sections -fno-common
 COMMONCFLAGS += $(call cc-option,$(CC),-nopie,)
 COMMONCFLAGS += $(call cc-option,$(CC),-fno-stack-protector,)
 COMMONCFLAGS += $(call cc-option,$(CC),-fno-stack-protector-all,)
 
-CFLAGS32FLAT = $(COMMONCFLAGS) -g -DMODE16=0 -DMODESEGMENT=0
+CFLAGS32FLAT = $(COMMONCFLAGS) -DMODE16=0 -DMODESEGMENT=0 -g -fomit-frame-pointer
 CFLAGSSEG = $(COMMONCFLAGS) -DMODESEGMENT=1 -fno-defer-pop \
     $(call cc-option,$(CC),-fno-jump-tables,-DMANUAL_NO_JUMP_TABLE) \
     $(call cc-option,$(CC),-fno-tree-switch-conversion,)
-CFLAGS32SEG = $(CFLAGSSEG) -DMODE16=0 -g
+CFLAGS32SEG = $(CFLAGSSEG) -DMODE16=0 -g -fomit-frame-pointer
 CFLAGS16INC = $(CFLAGSSEG) -DMODE16=1 \
     $(call cc-option,$(CC),--param large-stack-frame=4,-fno-inline)
-CFLAGS16 = $(CFLAGS16INC) -g
+CFLAGS16 = $(CFLAGS16INC) -g -fomit-frame-pointer
 
 all: $(OUT) $(OUT)bios.bin
 
@@ -173,7 +172,9 @@ $(OUT)bios.bin.elf $(OUT)bios.bin: $(OUT)rom.o tools/checkrom.py
 SRCVGA=src/output.c src/util.c vgasrc/vga.c vgasrc/vgafb.c vgasrc/vgaio.c \
        vgasrc/vgatables.c vgasrc/vgafonts.c vgasrc/clext.c
 
-$(OUT)vgaccode.16.s: $(OUT)autoconf.h ; $(call whole-compile, $(CFLAGS16) -S -Isrc, $(SRCVGA),$@)
+CFLAGS16VGA = $(CFLAGS16INC) -g -Isrc
+
+$(OUT)vgaccode.16.s: $(OUT)autoconf.h ; $(call whole-compile, $(CFLAGS16VGA) -S, $(SRCVGA),$@)
 
 $(OUT)vgalayout16.o: vgaentry.S $(OUT)vgaccode.16.s $(OUT)asm-offsets.h
 	@echo "  Compiling (16bit) $@"