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Re: [PATCH v2] Partially revert "build: -no-pie is no functional linker


From: Paolo Bonzini
Subject: Re: [PATCH v2] Partially revert "build: -no-pie is no functional linker flag"
Date: Fri, 15 Oct 2021 12:28:15 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0

On 05/08/21 21:25, Jessica Clarke wrote:
This partially reverts commit bbd2d5a8120771ec59b86a80a1f51884e0a26e53.

This commit was misguided and broke using --disable-pie on any distro
that enables PIE by default in their compiler driver, including Debian
and its derivatives. Whilst -no-pie is not a linker flag, it is a
compiler driver flag that ensures -pie is not automatically passed by it
to the linker. Without it, all compile_prog checks will fail as any code
built with the explicit -fno-pie will fail to link with the implicit
default -pie due to trying to use position-dependent relocations. The
only bug that needed fixing was LDFLAGS_NOPIE being used as a flag for
the linker itself in pc-bios/optionrom/Makefile.

Note this does not reinstate exporting LDFLAGS_NOPIE, as it is unused,
since the only previous use was the one that should not have existed. I
have also updated the comment for the -fno-pie and -no-pie checks to
reflect what they're actually needed for.

Fixes: bbd2d5a8120771ec59b86a80a1f51884e0a26e53
Cc: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com>
---
Changes in v2:
   * Actually include the comment change; didn't add the hunk when
     amending...

  configure | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 9a79a004d7..8aecd277ed 100755
--- a/configure
+++ b/configure
@@ -2246,9 +2246,11 @@ static THREAD int tls_var;
  int main(void) { return tls_var; }
  EOF
-# Check we support --no-pie first; we will need this for building ROMs.
+# Check we support -fno-pie and -no-pie first; we will need the former for
+# building ROMs, and both for everything if --disable-pie is passed.
  if compile_prog "-Werror -fno-pie" "-no-pie"; then
    CFLAGS_NOPIE="-fno-pie"
+  LDFLAGS_NOPIE="-no-pie"
  fi
if test "$static" = "yes"; then
@@ -2264,6 +2266,7 @@ if test "$static" = "yes"; then
    fi
  elif test "$pie" = "no"; then
    CONFIGURE_CFLAGS="$CFLAGS_NOPIE $CONFIGURE_CFLAGS"
+  CONFIGURE_LDFLAGS="$LDFLAGS_NOPIE $CONFIGURE_LDFLAGS"
  elif compile_prog "-Werror -fPIE -DPIE" "-pie"; then
    CONFIGURE_CFLAGS="-fPIE -DPIE $CONFIGURE_CFLAGS"
    CONFIGURE_LDFLAGS="-pie $CONFIGURE_LDFLAGS"


Queued, thanks.

Paolo




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