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Re: [Xen-devel] [Qemu-devel] [Bug 1257099] [NEW] QEMU fails to build on CentOS 5.10 with relocation R_X86_64_PC32 error



On 12/05/13 10:18, Paolo Bonzini wrote:
Il 04/12/2013 02:32, Don Slutz ha scritto:
Any hints or pointers about the bug in RHEL5 binutils?  I can try and
make a patch to auto detect this.
Actually it's RHEL5 GCC:

$ cat f.c
void *
f(unsigned char *buf, int len)
{
     return (void*)0L;
}


void *
g(unsigned char *buf, int len)
{
     return f(buf, len);
}
$ gcc -shared -o f.so f.c -fPIE -fPIC
/usr/bin/ld: /tmp/ccQc9els.o: relocation R_X86_64_PC32 against `f' can not be 
used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: ld returned 1 exit status


The bug is simply that "-fPIE -fPIC" counts as -fPIE rather than -fPIC:

$ gcc -S -o - f.c -fPIE |grep call
        call    f                      # PC32 relocation
$ gcc -S -o - f.c -fPIC |grep call
        call    f@PLT                  # PLT32 relocation

On RHEL5:
$ gcc -S -o - f.c -fPIE -fPIC |grep call
        call    f

On RHEL6:
$ gcc -S -o - f.c -fPIE -fPIC |grep call
        call    f@PLT

Paolo
How about this as a patch:

From 282fba086186ff3b8e2b2b15e647df2b58d082dd Mon Sep 17 00:00:00 2001
From: Don Slutz <dslutz@xxxxxxxxxxx>
Date: Thu, 5 Dec 2013 18:50:18 +0000
Subject: [PATCH] configure: Auto disabling of PIE due to broken toolchain
 support (bug #1257099)

See https://bugs.launchpad.net/bugs/1257099

On RHEL5 GCC, you can get 'relocation R_X86_64_PC32' errors from ld.
So disable PIE is this is true.

Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
---
 configure | 43 +++++++++++++++++++++++++++++++++++--------
 1 file changed, 35 insertions(+), 8 deletions(-)

diff --git a/configure b/configure
index cf8123b..a51a9dd 100755
--- a/configure
+++ b/configure
@@ -1339,23 +1339,50 @@ if test "$pie" != "no" ; then
 #  define THREAD
 #endif

+void *f(unsigned char *buf, int len);
+void *g(unsigned char *buf, int len);
+
+void *
+f(unsigned char *buf, int len)
+{
+    return (void*)0L;
+}
+
+
+void *
+g(unsigned char *buf, int len)
+{
+    return f(buf, len);
+}
+
+#ifdef PIE
 static THREAD int tls_var;

 int main(void) { return tls_var; }
+#endif

 EOF
-  if compile_prog "-fPIE -DPIE" "-pie"; then
-    QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
-    LDFLAGS="-pie $LDFLAGS"
-    pie="yes"
-    if compile_prog "" "-Wl,-z,relro -Wl,-z,now" ; then
-      LDFLAGS="-Wl,-z,relro -Wl,-z,now $LDFLAGS"
+  if compile_prog "-shared -fPIE -fPIC" ""; then
+    if compile_prog "-fPIE -DPIE" "-pie"; then
+      QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
+      LDFLAGS="-pie $LDFLAGS"
+      pie="yes"
+      if compile_prog "" "-Wl,-z,relro -Wl,-z,now" ; then
+        LDFLAGS="-Wl,-z,relro -Wl,-z,now $LDFLAGS"
+      fi
+    else
+      if test "$pie" = "yes"; then
+        error_exit "PIE not available due to missing toolchain support"
+      else
+        echo "Disabling PIE due to missing toolchain support"
+        pie="no"
+      fi
     fi
   else
     if test "$pie" = "yes"; then
-      error_exit "PIE not available due to missing toolchain support"
+      error_exit "PIE not available due to broken toolchain support"
     else
-      echo "Disabling PIE due to missing toolchain support"
+      echo "Disabling PIE due to broken toolchain support"
       pie="no"
     fi
   fi
--
1.8.2.1


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