Re: [Qemu-devel] [PATCH v3] configure: Simplify alternate .text segment

[Richard Henderson <rth@twiddle.net>]

Ping.

On 06/21/2013 07:10 PM, Richard Henderson wrote:
> 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>
> ---
>  configure | 48 +++++++++++++++++++++++++++++++-----------------
>  2 files changed, 31 insertions(+), 18 deletions(-)
> --
> 
> Changes v2-v3:
>   * Move the check for textseg_ldflags much earlier in the configure file,
>     so that we've not got cflags invalid for configure time.  Plus, the
>     check (and generated ld script) only gets done once, not once per
>     target directory.
>   * Remove ia64 from the hosts that get relocation
>   * Handle s390x like s390.
> 
> Tested on x86_64, arm, hppa (old binutils needing config-host.ld),
> sparc64, and ia64.  All various versions of linux.
> 
> 
> r~
> 
> 
> 
> diff --git a/configure b/configure
> index ad32f87..63da418 100755
> --- a/configure
> +++ b/configure
> @@ -3444,6 +3444,36 @@ 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 $pixman_libs"
> @@ -4072,9 +4102,6 @@ if test "$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 "$linux" = "yes" ; then
>    mkdir -p linux-headers
> @@ -4437,21 +4464,8 @@ if test "$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
>