[Qemu-devel] [RFC PATCH 1/2] target/arm: Add stubs to build with CONFIG_SEMIHOSTING disabled

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

If a distribution wants to build QEMU without semihosting support,
it currently gets this build failure:

  $ ./configure --target-list=aarch64-softmmu --without-default-devices
  $ sed -i s/CONFIG_SEMIHOSTING=y/CONFIG_SEMIHOSTING=n/ default-configs/arm-softmmu.mak
  $ make subdir-aarch64-softmmu
  [...]
    LINK    aarch64-softmmu/qemu-system-aarch64
  /usr/bin/ld: target/arm/arm-semi.o: in function `do_arm_semihosting':
  ./target/arm/arm-semi.c:321: undefined reference to `qemu_semihosting_console_out'
  /usr/bin/ld: ./target/arm/arm-semi.c:318: undefined reference to `qemu_semihosting_console_out'
  collect2: error: ld returned 1 exit status
  make[1]: *** [Makefile:204: qemu-system-aarch64] Error 1
  make: *** [Makefile:472: subdir-aarch64-softmmu] Error 2

Fix it by providing a stub when semihosting is disabled.

Reported-by: Miroslav Rezanina <mrezanin@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 target/arm/Makefile.objs    |  3 ++-
 target/arm/arm-semi-stubs.c | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 target/arm/arm-semi-stubs.c

diff --git a/target/arm/Makefile.objs b/target/arm/Makefile.objs
index 6bdcc65c2c..39b02b1fa4 100644
--- a/target/arm/Makefile.objs
+++ b/target/arm/Makefile.objs
@@ -1,4 +1,5 @@
-obj-y += arm-semi.o
+obj-$(CONFIG_SEMIHOSTING) += arm-semi.o
+obj-$(call lnot,$(CONFIG_SEMIHOSTING)) += arm-semi-stubs.o
 obj-$(CONFIG_SOFTMMU) += machine.o psci.o arch_dump.o monitor.o
 obj-$(CONFIG_KVM) += kvm.o
 obj-$(call land,$(CONFIG_KVM),$(call lnot,$(TARGET_AARCH64))) += kvm32.o
diff --git a/target/arm/arm-semi-stubs.c b/target/arm/arm-semi-stubs.c
new file mode 100644
index 0000000000..a91ecbd9d5
--- /dev/null
+++ b/target/arm/arm-semi-stubs.c
@@ -0,0 +1,21 @@
+/*
+ *  Arm "Angel" semihosting stubs
+ *
+ * Copyright (c) 2019 Red Hat, Inc.
+ *
+ * Author:
+ *   Philippe Mathieu-Daudé <philmd@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+
+target_ulong do_arm_semihosting(CPUARMState *env)
+{
+    g_assert_not_reached();
+}
-- 
2.20.1