From 963beb216d886a0eb8ad30a77570aff8a755c355 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>
Date: Mon, 11 Mar 2019 16:45:56 -0400
Subject: [PATCH] configure: Disable W^X on OpenBSD

Since OpenBSD 6.0 [1], W^X is enforced by default [2].
TCG requires WX access. Disable W^X if it is available.
This fixes:

\# lm32-softmmu/qemu-system-lm32
Could not allocate dynamic translator buffer

\# sysctl kern.wxabort=1
kern.wxabort: 0 -> 1
\# lm32-softmmu/qemu-system-lm32
mmap: Not supported
Abort trap (core dumped)
\# gdb -q lm32-softmmu/qemu-system-lm32 qemu-system-lm32.core
(gdb) bt
\#0 0x000017e3c156c50a in _thread_sys___syscall () at {standard input}:5
\#1 0x000017e3c15e5d7a in *_libc_mmap (addr=Variable "addr" is not available.) at /usr/src/lib/libc/sys/mmap.c:47
\#2 0x000017e17d9abc8b in alloc_code_gen_buffer () at /usr/src/qemu/accel/tcg/translate-all.c:1064
\#3 0x000017e17d9abd04 in code_gen_alloc (tb_size=0) at /usr/src/qemu/accel/tcg/translate-all.c:1112
\#4 0x000017e17d9abe81 in tcg_exec_init (tb_size=0) at /usr/src/qemu/accel/tcg/translate-all.c:1149
\#5 0x000017e17d9897e9 in tcg_init (ms=0x17e45e456800) at /usr/src/qemu/accel/tcg/tcg-all.c:66
\#6 0x000017e17d9891b8 in accel_init_machine (acc=0x17e3c3f50800, ms=0x17e45e456800) at /usr/src/qemu/accel/accel.c:63
\#7 0x000017e17d989312 in configure_accelerator (ms=0x17e45e456800, progname=0x7f7fffff07b0 "lm32-softmmu/qemu-system-lm32") at /usr/src/qemu/accel/accel.c:111
\#8 0x000017e17d9d8616 in main (argc=1, argv=0x7f7fffff06b8, envp=0x7f7fffff06c8) at vl.c:4325

[1] https://www.openbsd.org/faq/upgrade60.html
[2] https://undeadly.org/cgi?action=article&sid=20160527203200

Backports commit 7776ea6b49873ed18a2111e25ed8a6d94bd73db8 from qemu
---
 qemu/configure | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/qemu/configure b/qemu/configure
index 8306d09f..d03a493a 100755
--- a/qemu/configure
+++ b/qemu/configure
@@ -1385,6 +1385,17 @@ if test "$mingw32" = "yes" ; then
     done
 fi
 
+# Disable OpenBSD W^X if available
+if test "$tcg" = "yes" && test "$targetos" = "OpenBSD"; then
+    cat > $TMPC <<EOF
+    int main(void) { return 0; }
+EOF
+    wx_ldflags="-Wl,-z,wxneeded"
+    if compile_prog "" "$wx_ldflags"; then
+        QEMU_LDFLAGS="$QEMU_LDFLAGS $wx_ldflags"
+    fi
+fi
+
 echo "Source path       $source_path"
 echo "C compiler        $cc"
 echo "Host C compiler   $host_cc"