[Buildroot] [PATCH 1/1] qemu: explicitly disable SSP support

[Rodrigo Rebello <rprebello@gmail.com>]

Even though the QEMU configure script does a full compile and link test
to detect SSP support, it does so by using the compiler option
-fstack-protector-strong (and then -fstack-protector-all if that fails).

The problem with this method is that the test program passes the check
with -fstack-protector-strong even when SSP support is not available in
the toolchain, since that option restricts stack protection to only a
subset of all the functions in a program and (in the case of the test
program) no "canary" code gets inserted, producing a false-positive.
This causes a subsequent failure when the probe for pthreads is
performed.

To avoid patching the configure script, fix that by simply disabling the
use of stack protector when SSP is known to be unavailable in the
toolchain.

Fixes:

  http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
  http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
  http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
  ...and many others.

Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
---
 package/qemu/qemu.mk | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
index 94e1bcf..0161b10 100644
--- a/package/qemu/qemu.mk
+++ b/package/qemu/qemu.mk
@@ -133,6 +133,12 @@ QEMU_VARS = \
 	PYTHON=$(HOST_DIR)/usr/bin/python2 \
 	PYTHONPATH=$(TARGET_DIR)/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages
 
+# Force disable stack protector when SSP isn't available in toolchain as
+# QEMU configure script fails to properly detect that.
+ifeq ($(BR2_TOOLCHAIN_HAS_SSP),)
+QEMU_OPTS += --disable-stack-protector
+endif
+
 # If we want to specify only a subset of targets, we must still enable all
 # of them, so that QEMU properly builds its list of default targets, from
 # which it then checks if the specified sub-set is valid. That's what we
-- 
2.1.4