[PATCH v2] x86/boot: Handle better alignment for 32 bit code

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

Output file didn't have correct alignment.
Allows alignment into data or code up to 2mb.
Intermediate object files are kept in order to copy alignment
from object produced by the linker and final object (produced
by combine_two_binaries.py script).

Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
---
 xen/arch/x86/boot/Makefile        | 12 ++++++++----
 xen/tools/combine_two_binaries.py |  7 ++++++-
 2 files changed, 14 insertions(+), 5 deletions(-)

Changes since v1:
- Improve comments and description.

diff --git a/xen/arch/x86/boot/Makefile b/xen/arch/x86/boot/Makefile
index 13d4583173..a56d8a7e0f 100644
--- a/xen/arch/x86/boot/Makefile
+++ b/xen/arch/x86/boot/Makefile
@@ -40,8 +40,12 @@ LD32 := $(LD) $(subst x86_64,i386,$(LDFLAGS_DIRECT))
 # are affected by both text_diff and text_gap.  Ensure the sum of gap and diff
 # is greater than 2^16 so that any 16bit relocations if present in the object
 # file turns into a build-time error.
-text_gap := 0x010200
-text_diff := 0x408020
+# As gap will affect the output section size it should not be huge to avoid the
+# creation of huge files.
+# The sum of gap and diff will affect the possible alignment so should be a
+# multiple of the possible alignment.
+text_gap := 0x01c240
+text_diff := 0x7e3dc0
 
 $(obj)/build32.base.lds: AFLAGS-y += -DGAP=$(text_gap) -DTEXT_DIFF=$(text_diff)
 $(obj)/build32.offset.lds: AFLAGS-y += -DGAP=$(text_gap) 
-DTEXT_DIFF=$(text_diff) -DAPPLY_OFFSET
@@ -69,7 +73,6 @@ $(obj)/built-in-32.%.bin: $(obj)/build32.%.lds 
$(obj)/built-in-32.tmp.o
        $(LD32) $(orphan-handling-y) -N -T $< -o $(@:bin=o) $(filter %.o,$^)
        $(NM) -p --format=bsd $(@:bin=o) > $(@:bin=map)
        $(OBJCOPY) -j .text -O binary $(@:bin=o) $@
-       rm -f $(@:bin=o)
 
 quiet_cmd_combine = GEN     $@
 cmd_combine = \
@@ -80,6 +83,7 @@ cmd_combine = \
               --bin1      $(obj)/built-in-32.base.bin \
               --bin2      $(obj)/built-in-32.offset.bin \
               --map       $(obj)/built-in-32.base.map \
+              --align     $(shell $(OBJDUMP) -h $(obj)/built-in-32.base.o|sed 
'/text.*2\*\*/ {s/.*2\*\*//;p;}; d') \
               --exports   cmdline_parse_early,reloc,reloc_trampoline32 \
               --output    $@
 
@@ -90,4 +94,4 @@ $(obj)/built-in-32.S: $(obj)/built-in-32.base.bin 
$(obj)/built-in-32.offset.bin
                       $(srctree)/tools/combine_two_binaries.py FORCE
        $(call if_changed,combine)
 
-clean-files := built-in-32.*.bin built-in-32.*.map build32.*.lds
+clean-files := built-in-32.*.bin built-in-32.*.map built-in-32.*.o 
build32.*.lds
diff --git a/xen/tools/combine_two_binaries.py 
b/xen/tools/combine_two_binaries.py
index 581e57cbc0..8e587c24fb 100755
--- a/xen/tools/combine_two_binaries.py
+++ b/xen/tools/combine_two_binaries.py
@@ -26,6 +26,10 @@ parser.add_argument('--text-diff', dest='text_diff',
                     required=True,
                     type=auto_int,
                     help='Difference between code section start')
+parser.add_argument('--align', dest='align',
+                    default=2,
+                    type=auto_int,
+                    help='Alignment in power of 2')
 parser.add_argument('--output', dest='output',
                     help='Output file')
 parser.add_argument('--map', dest='mapfile',
@@ -93,7 +97,7 @@ if size1 > size2:
     file1, file2 = file2, file1
     size1, size2 = size2, size1
 if size2 != size1 + gap:
-    raise Exception('File sizes do not match')
+    raise Exception('File sizes do not match %d != %d + %d' % (size2, size1, 
gap))
 del size2
 
 file1.seek(0, 0)
@@ -219,6 +223,7 @@ print('''/*
  * File autogenerated by combine_two_binaries.py DO NOT EDIT
  */''', file=out)
 print('\t' + args.section_header, file=out)
+print('\t.p2align\t' + str(args.align), file=out)
 print('obj32_start:', file=out)
 output(out)
 print('\n\t.section .note.GNU-stack,"",@progbits', file=out)
-- 
2.34.1