x86/build: Don't convert boot/{cmdline,head}.bin back to .S

There's no point wasting time converting binaries back to asm source.  Just
use .incbin directly.  Explain in head.S what these binaries are.

Also, explicitly align the blobs.  They contain 4-byte objects, and happen to
be 4-byte aligned currently because of the position of `lret` and the size of
cmdline.S but this is incredibly fragile.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/boot/Makefile

@@ -7,10 +7,8 @@ targets += $(head-srcs:.S=.o)
 
 head-srcs := $(addprefix $(obj)/, $(head-srcs))
 
-ifdef building_out_of_srctree
-$(obj)/head.o: CFLAGS-y += -iquote $(obj)
-endif
-$(obj)/head.o: $(head-srcs)
+$(obj)/head.o: AFLAGS-y += -Wa$(comma)-I$(obj)
+$(obj)/head.o: $(head-srcs:.S=.bin)
 
 CFLAGS_x86_32 := $(subst -m64,-m32 -march=i686,$(XEN_TREEWIDE_CFLAGS))
 $(call cc-options-add,CFLAGS_x86_32,CC,$(EMBEDDED_EXTRA_CFLAGS))
@@ -27,14 +25,10 @@ $(head-srcs:.S=.o): XEN_CFLAGS := $(CFLAGS_x86_32) -fpic
 LDFLAGS_DIRECT-$(call ld-option,--warn-rwx-segments) := --no-warn-rwx-segments
 LDFLAGS_DIRECT += $(LDFLAGS_DIRECT-y)
 
-$(head-srcs): %.S: %.bin
-	(od -v -t x $< | tr -s ' ' | awk 'NR > 1 {print s} {s=$$0}' | \
-	sed 's/ /,0x/g' | sed 's/,0x$$//' | sed 's/^[0-9]*,/ .long /') >$@
-
 %.bin: %.lnk
 	$(OBJCOPY) -j .text -O binary $< $@
 
 %.lnk: %.o $(src)/build32.lds
 	$(LD) $(subst x86_64,i386,$(LDFLAGS_DIRECT)) -N -T $(filter %.lds,$^) -o $@ $<
 
-clean-files := cmdline.S reloc.S *.lnk *.bin
+clean-files := *.lnk *.bin

xen/arch/x86/boot/head.S

@@ -777,11 +777,17 @@ trampoline_setup:
         /* Jump into the relocated trampoline. */
         lret
 
+        /*
+         * cmdline and reloc are written in C, and linked to be 32bit PIC with
+         * entrypoints at 0 and using the stdcall convention.
+         */
+        ALIGN
 cmdline_parse_early:
-#include "cmdline.S"
+        .incbin "cmdline.bin"
 
+        ALIGN
 reloc:
-#include "reloc.S"
+        .incbin "reloc.bin"
 
 ENTRY(trampoline_start)
 #include "trampoline.S"