[Xen-changelog] [xen-unstable] x86: check for data and BSS in reloc code at compile time.

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Tim Deegan <tim@xxxxxxx>
# Date 1347550893 -3600
# Node ID 4aa37a8fb32ae77beafb5ae9d6abd3878a2d4901
# Parent  b3e6de36c91e9466498946cbb9a9e71c4efd5eae
x86: check for data and BSS in reloc code at compile time.

This is a more useful failure mode than hanging at boot time, and
incidentally fixes the clang/LLVM build by removing a .subsection rune.

Signed-off-by: Tim Deegan <tim@xxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Committed-by: Tim Deegan <tim@xxxxxxx>
---


diff -r b3e6de36c91e -r 4aa37a8fb32a xen/arch/x86/boot/build32.mk
--- a/xen/arch/x86/boot/build32.mk      Thu Sep 13 16:41:33 2012 +0100
+++ b/xen/arch/x86/boot/build32.mk      Thu Sep 13 16:41:33 2012 +0100
@@ -20,6 +20,15 @@ CFLAGS := $(filter-out -flto,$(CFLAGS))
 
 %.o: %.c
        $(CC) $(CFLAGS) -c -fpic $< -o $@
+       $(OBJDUMP) -h $@ | sed -n '/[0-9]/{s,00*,0,g;p}' |\
+               while read idx name sz rest; do \
+                       case "$$name" in \
+                       .data|.data.*|.rodata|.rodata.*|.bss|.bss.*) \
+                               test $$sz != 0 || continue; \
+                               echo "Error: non-empty $$name: 0x$$sz" >&2; \
+                               exit $$(expr $$idx + 1);; \
+                       esac; \
+               done
 
 reloc.o: $(BASEDIR)/include/asm-x86/config.h
 .PRECIOUS: %.bin %.lnk
diff -r b3e6de36c91e -r 4aa37a8fb32a xen/arch/x86/boot/reloc.c
--- a/xen/arch/x86/boot/reloc.c Thu Sep 13 16:41:33 2012 +0100
+++ b/xen/arch/x86/boot/reloc.c Thu Sep 13 16:41:33 2012 +0100
@@ -18,10 +18,7 @@ asm (
     "    call 1f                       \n"
     "1:  pop  %ebx                     \n"
     "    mov  %eax,alloc-1b(%ebx)      \n"
-    "    mov  $_end,%ecx               \n"  /* check that BSS is empty! */
-    "    sub  $__bss_start,%ecx        \n"
-    "    jz reloc                      \n"
-    "1:  jmp 1b                        \n"
+    "    jmp  reloc                    \n"
     );
 
 /* This is our data.  Because the code must be relocatable, no BSS is
@@ -30,9 +27,6 @@ asm (
 asm (
     "alloc:                            \n"
     "    .long 0                       \n"
-    "    .subsection 1                 \n"
-    "    .p2align 4, 0xcc              \n"
-    "    .subsection 0                 \n"
     );
 
 typedef unsigned int u32;

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