configure: Simplify alternate .text segment

For bsd-user and linux-user emulation modes QEMU needs to be linked at an
alternate .text segment address, so that it's out of the way of the guest
executable.  Instead of including modified linker scripts for each arch,
just set the address with -Ttext-segment if supported, or by using sed to
edit the default linker script.

Cc: Ed Maste <emaste@freebsd.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Acked-by: Ed Maste <emaste@freebsd.org>
Signed-off-by: Ed Maste <emaste@freebsd.org>
Message-id: 1371867016-7660-1-git-send-email-rth@twiddle.net
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

configure

@@ -3445,6 +3445,36 @@ if test "$cpu" = "s390x" ; then
   roms="$roms s390-ccw"
 fi
 
+# Probe for the need for relocating the user-only binary.
+if test "$pie" = "no" ; then
+  textseg_addr=
+  case "$cpu" in
+    arm | hppa | i386 | m68k | ppc | ppc64 | s390* | sparc | sparc64 | x86_64)
+      textseg_addr=0x60000000
+      ;;
+    mips)
+      textseg_addr=0x400000
+      ;;
+  esac
+  if [ -n "$textseg_addr" ]; then
+    cat > $TMPC <<EOF
+    int main(void) { return 0; }
+EOF
+    textseg_ldflags="-Wl,-Ttext-segment=$textseg_addr"
+    if ! compile_prog "" "$textseg_ldflags"; then
+      # In case ld does not support -Ttext-segment, edit the default linker
+      # script via sed to set the .text start addr.  This is needed on FreeBSD
+      # at least.
+      $ld --verbose | sed \
+        -e '1,/==================================================/d' \
+        -e '/==================================================/,$d' \
+        -e "s/[.] = [0-9a-fx]* [+] SIZEOF_HEADERS/. = $textseg_addr + SIZEOF_HEADERS/" \
+        -e "s/__executable_start = [0-9a-fx]*/__executable_start = $textseg_addr/" > config-host.ld
+      textseg_ldflags="-Wl,-T../config-host.ld"
+    fi
+  fi
+fi
+
 # add pixman flags after all config tests are done
 QEMU_CFLAGS="$QEMU_CFLAGS $pixman_cflags $fdt_cflags"
 libs_softmmu="$libs_softmmu $pixman_libs"
@@ -4073,9 +4103,6 @@ if test "$gcov" = "yes" ; then
   echo "GCOV=$gcov_tool" >> $config_host_mak
 fi
 
-# generate list of library paths for linker script
-$ld --verbose -v 2> /dev/null | grep SEARCH_DIR > config-host.ld
-
 # use included Linux headers
 if test "$linux" = "yes" ; then
   mkdir -p linux-headers
@@ -4438,21 +4465,8 @@ if test "$gprof" = "yes" ; then
   fi
 fi
 
-if test "$ARCH" = "tci"; then
-  linker_script=""
-else
-  linker_script="-Wl,-T../config-host.ld -Wl,-T,\$(SRC_PATH)/ldscripts/\$(ARCH).ld"
-fi
-
 if test "$target_linux_user" = "yes" -o "$target_bsd_user" = "yes" ; then
-  case "$ARCH" in
-  alpha | s390x | aarch64)
-    # The default placement of the application is fine.
-    ;;
-  *)
-    ldflags="$linker_script $ldflags"
-    ;;
-  esac
+  ldflags="$ldflags $textseg_ldflags"
 fi
 
 echo "LDFLAGS+=$ldflags" >> $config_target_mak