[Qemu-devel] [PATCH v3] Fix QEMU build on OpenBSD on x86 archs

[Brad Smith <brad@comstyle.com>]

This resolves the build issue with building the ROMs on OpenBSD on x86 archs.
As of OpenBSD 5.3 the compiler builds PIE binaries by default and thus the
whole OS/packages and so forth. The ROMs need to have PIE disabled. This
is my initial attempt at trying to get somehting upstream so that QEMU
both builds out of the box and to resolve the build issue with the
buildbots that has been around for awhile. We have a patch in our ports
tree but it is just the flags hardcoded into the Makefile which obviously
is not appropriate for upstream.

>From the OpenBSD buildbots..
  Building optionrom/multiboot.img
ld: multiboot.o: relocation R_X86_64_16 can not be used when making a shared object; recompile with -fPIC

Signed-off by: Brad Smith <brad@comstyle.com>
---

Change in v2:
    * Fix '==' is not portable syntax.

Change in v3:
    * Rename variables and use compile_prog to detect the presence of the compiler/linker
      flags, as suggested by Stefan Weil.

diff --git a/configure b/configure
index 5d82283..89ae89d 100755
--- a/configure
+++ b/configure
@@ -1365,6 +1365,11 @@ EOF
       pie="no"
     fi
   fi
+
+  if compile_prog "-fno-pie" "-nopie"; then
+    CFLAGS_NOPIE="-fno-pie"
+    LDFLAGS_NOPIE="-nopie"
+  fi
 fi
 
 ##########################################
@@ -4320,6 +4325,7 @@ echo "LD=$ld" >> $config_host_mak
 echo "WINDRES=$windres" >> $config_host_mak
 echo "LIBTOOL=$libtool" >> $config_host_mak
 echo "CFLAGS=$CFLAGS" >> $config_host_mak
+echo "CFLAGS_NOPIE=$CFLAGS_NOPIE" >> $config_host_mak
 echo "QEMU_CFLAGS=$QEMU_CFLAGS" >> $config_host_mak
 echo "QEMU_INCLUDES=$QEMU_INCLUDES" >> $config_host_mak
 if test "$sparse" = "yes" ; then
@@ -4333,6 +4339,7 @@ else
   echo "AUTOCONF_HOST := "                             >> $config_host_mak
 fi
 echo "LDFLAGS=$LDFLAGS" >> $config_host_mak
+echo "LDFLAGS_NOPIE=$LDFLAGS_NOPIE" >> $config_host_mak
 echo "LIBTOOLFLAGS=$LIBTOOLFLAGS" >> $config_host_mak
 echo "LIBS+=$LIBS" >> $config_host_mak
 echo "LIBS_TOOLS+=$libs_tools" >> $config_host_mak
diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
index 57d8bd0..ce4852a 100644
--- a/pc-bios/optionrom/Makefile
+++ b/pc-bios/optionrom/Makefile
@@ -12,6 +12,7 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/optionrom)
 CFLAGS := -Wall -Wstrict-prototypes -Werror -fomit-frame-pointer -fno-builtin
 CFLAGS += -I$(SRC_PATH)
 CFLAGS += $(call cc-option, $(CFLAGS), -fno-stack-protector)
+CFLAGS += $(CFLAGS_NOPIE)
 QEMU_CFLAGS = $(CFLAGS)
 
 build-all: multiboot.bin linuxboot.bin kvmvapic.bin
@@ -20,7 +21,7 @@ build-all: multiboot.bin linuxboot.bin kvmvapic.bin
 .SECONDARY:
 
 %.img: %.o
-	$(call quiet-command,$(LD) -Ttext 0 -e _start -s -o $@ $<,"  Building $(TARGET_DIR)$@")
+	$(call quiet-command,$(LD) $(LDFLAGS_NOPIE) -Ttext 0 -e _start -s -o $@ $<,"  Building $(TARGET_DIR)$@")
 
 %.raw: %.img
 	$(call quiet-command,$(OBJCOPY) -O binary -j .text $< $@,"  Building $(TARGET_DIR)$@")

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