xen: fix build with _FORTIFY_SOURCE, gcc 8.2 and glibc 2.28

Apply upstream-reviewed patch to fix compilation.
Patch reorders header includes to issue a pragma to disable SSE before
including any potentially always_inline functions that would use SSE.

Also modify the recipe to supply compiler flags via the tools variables where
they will get used, necessary as _FORTIFY_SOURCE requires optimization flags to
be supplied.

Signed-off-by: Christopher Clark <christopher.clark6@baesystems.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>

recipes-extended/xen/files/xen-disable-sse-before-inlines.patch

@@ -0,0 +1,140 @@
+From 6d50ae155c0f736aa6239eabf1bc8c8e3704742d Mon Sep 17 00:00:00 2001
+From: Christopher Clark <christopher.w.clark@gmail.com>
+Date: Fri, 21 Sep 2018 08:28:02 -0700
+Subject: [PATCH v2] fuzz, test x86_emulator: disable sse before including
+ always_inline fns
+To: xen-devel@lists.xenproject.org,
+    jbeulich@suse.com
+Cc: ian.jackson@eu.citrix.com,
+    wei.liu2@citrix.com,
+    andrew.cooper3@citrix.com
+
+Workaround for compiler rejection of SSE-using always_inlines defined before
+SSE is disabled.
+
+Compiling with _FORTIFY_SOURCE or higher levels of optimization enabled
+will always_inline several library fns (memset, memcpy, ...)
+(with gcc 8.2.0 and glibc 2.28).
+
+In fuzz and x86_emulator test, the compiler is instructed not
+to generate SSE instructions via: #pragma GCC target("no-sse")
+because those registers are needed for use by the workload.
+
+The combination above causes compilation failure as the inline functions
+use those instructions. This is resolved by reordering the inclusion of
+<stdio.h> and <string.h> to after the pragma disabling SSE generation.
+
+It would be preferable to locate the no-sse pragma within x86-emulate.h at the
+top of the file, prior to including any other headers; unfortunately doing so
+before <stdlib.h> causes compilation failure due to declaration of 'atof' with:
+  "SSE register return with SSE disabled".
+Fortunately there is no (known) current dependency on any always_inline
+SSE-inclined function declared in <stdlib.h> or any of its dependencies, so the
+pragma is therefore issued immediately after inclusion of <stdlib.h> with a
+comment introduced to explain its location there.
+
+Add compile-time checks for unwanted prior inclusion of <string.h> and
+<stdio.h>, which are the two headers that provide the library functions that
+are handled with wrappers and listed within "x86-emulate.h" as ones "we think
+might access any of the FPU state".
+* Use standard-defined "EOF" macro to detect prior <stdio.h> inclusion.
+* Use "_STRING_H" (non-standardized guard macro) as best-effort
+  for detection of prior <string.h> inclusion. This is non-universally
+  viable but will provide error output on common GLIBC systems, so
+  provides some defensive coverage.
+
+Adds conditional #include <stdio.h> to x86-emulate.h because fwrite, printf,
+etc. are referenced when WRAP has been defined.
+
+Signed-off-by: Christopher Clark <christopher.clark6@baesystems.com>
+Reviewed-by: Jan Beulich <jbeulich@suse.com>
+---
+ tools/fuzz/x86_instruction_emulator/fuzz-emul.c | 10 +++++++--
+ tools/tests/x86_emulator/wrappers.c             |  1 -
+ tools/tests/x86_emulator/x86-emulate.h          | 28 +++++++++++++++++++++++--
+ 3 files changed, 34 insertions(+), 5 deletions(-)
+
+diff --git a/tools/fuzz/x86_instruction_emulator/fuzz-emul.c b/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
+index 03a2473..0ffd0fb 100644
+--- a/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
++++ b/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
+@@ -6,9 +6,7 @@
+ #include <stdbool.h>
+ #include <stddef.h>
+ #include <stdint.h>
+-#include <stdio.h>
+ #include <stdlib.h>
+-#include <string.h>
+ #include <sys/types.h>
+ #include <sys/stat.h>
+ #include <sys/mman.h>
+@@ -16,6 +14,14 @@
+ #include <xen/xen.h>
+ 
+ #include "x86-emulate.h"
++/*
++ * include "x86-emulate.h" prior to <stdio.h> and <string.h>:
++ * x86-emulate.h disables use of SSE registers, while <stdio.h> and <string.h>
++ * declare functions that may be always_inline and use those registers
++ * unless they have been disabled earlier, which can fail to compile.
++ */
++#include <stdio.h>
++#include <string.h>
+ #include "fuzz-emul.h"
+ 
+ #define MSR_INDEX_MAX 16
+diff --git a/tools/tests/x86_emulator/wrappers.c b/tools/tests/x86_emulator/wrappers.c
+index d02013c..eba7cc9 100644
+--- a/tools/tests/x86_emulator/wrappers.c
++++ b/tools/tests/x86_emulator/wrappers.c
+@@ -1,5 +1,4 @@
+ #include <stdarg.h>
+-#include <stdio.h>
+ 
+ #define WRAP(x) typeof(x) emul_##x
+ #include "x86-emulate.h"
+diff --git a/tools/tests/x86_emulator/x86-emulate.h b/tools/tests/x86_emulator/x86-emulate.h
+index b249e46..07ea1e8 100644
+--- a/tools/tests/x86_emulator/x86-emulate.h
++++ b/tools/tests/x86_emulator/x86-emulate.h
+@@ -3,11 +3,35 @@
+ #include <stddef.h>
+ #include <stdint.h>
+ #include <stdlib.h>
+-#include <string.h>
+-
++/*
++ * Use of sse registers must be disabled prior to the definition of
++ * always_inline functions that would use them (memcpy, memset, etc),
++ * so do this as early as possible, aiming to be before any always_inline
++ * functions that are used are declared.
++ * Unfortunately, this cannot be done prior to inclusion of <stdlib.h>
++ * due to functions such as 'atof' that have SSE register return declared,
++ * so do so here, immediately after that.
++ */
+ #if __GNUC__ >= 6
+ #pragma GCC target("no-sse")
+ #endif
++ /*
++ * Attempt detection of unwanted prior inclusion of some headers known to use
++ * always_inline with SSE registers in some library / compiler / optimization
++ * combinations.
++ */
++#ifdef _STRING_H
++#error "Must not include <string.h> before x86-emulate.h"
++#endif
++#include <string.h>
++
++/* EOF is a standard macro defined in <stdio.h> so use it for detection */
++#ifdef EOF
++#error "Must not include <stdio.h> before x86-emulate.h"
++#endif
++#ifdef WRAP
++#include <stdio.h>
++#endif
+ 
+ #include <xen/xen.h>
+ 
+-- 
+2.1.4
+

recipes-extended/xen/xen.inc

@@ -842,6 +842,12 @@ export LDFLAGS=""
 # patching the build to be ok with this
 TUNE_CCARGS := "${@oe.utils.str_filter_out('-mfpmath=sse', '${TUNE_CCARGS}', d)}"
 
+# Supply the full set of compiler flags via the tool variables
+# Yocto supplys _FORTIFY_SOURCE via CC/CPP/CXX but optimization -O via C*FLAGS
+CC_append = " ${CFLAGS}"
+CPP_append = " ${CPPFLAGS}"
+CXX_append = " ${CXXFLAGS}"
+
 EXTRA_OECONF += " \
     --exec-prefix=/usr \
     --prefix=/usr \

recipes-extended/xen/xen_4.11.0.bb

@@ -6,6 +6,7 @@ SRC_URI = " \
     file://tools-xentop-vwprintw.patch \
     file://xen-4.11-arm-acpi-fix-string-lengths.patch \
     file://xen-tools-xenpmd-snprintf.patch \
+    file://xen-disable-sse-before-inlines.patch \
     "
 
 SRC_URI[md5sum] = "cbec0600284921744bc14119f4ed3fff"

recipes-extended/xen/xen_git.bb

@@ -12,6 +12,7 @@ S = "${WORKDIR}/git"
 
 SRC_URI = " \
     git://xenbits.xen.org/xen.git;branch=${XEN_BRANCH} \
+    file://xen-disable-sse-before-inlines.patch \
     "
 
 DEFAULT_PREFERENCE = "-1"