[Qemu-devel] [RFC PATCH-for-4.1? v2 5/5] target/mips: 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=mips64el-softmmu --without-default-devices
  $ sed -i s/CONFIG_SEMIHOSTING=y/CONFIG_SEMIHOSTING=n/ default-configs/mips-softmmu-common.mak
  $ make subdir-mips64el-softmmu
  [...]
    LINK    mips64el-softmmu/qemu-system-mips64el
  /usr/bin/ld: target/mips/mips-semi.o: in function `helper_do_semihosting':
  ./target/mips/mips-semi.c:335: undefined reference to `qemu_semihosting_log_out'
  /usr/bin/ld: ./target/mips/mips-semi.c:338: undefined reference to `qemu_semihosting_log_out'
  collect2: error: ld returned 1 exit status
  make[1]: *** [Makefile:204: qemu-system-mips64el] Error 1
  make: *** [Makefile:472: subdir-mips64el-softmmu] Error 2

Fix it by providing a stub when semihosting is disabled.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 default-configs/mips-softmmu-common.mak |  2 +-
 target/mips/Makefile.objs               |  3 ++-
 target/mips/mips-semi-stubs.c           | 22 ++++++++++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 target/mips/mips-semi-stubs.c

diff --git a/default-configs/mips-softmmu-common.mak b/default-configs/mips-softmmu-common.mak
index da29c6c0b2..08fa16191f 100644
--- a/default-configs/mips-softmmu-common.mak
+++ b/default-configs/mips-softmmu-common.mak
@@ -1,6 +1,6 @@
 # Common mips*-softmmu CONFIG defines
 
-# CONFIG_SEMIHOSTING is always required on this architecture
+# CONFIG_SEMIHOSTING is probably not required on KVM only builds
 CONFIG_SEMIHOSTING=y
 
 CONFIG_ISA_BUS=y
diff --git a/target/mips/Makefile.objs b/target/mips/Makefile.objs
index 3448ad5e19..3f4d566a35 100644
--- a/target/mips/Makefile.objs
+++ b/target/mips/Makefile.objs
@@ -1,5 +1,6 @@
 obj-y += translate.o dsp_helper.o op_helper.o lmi_helper.o helper.o cpu.o
 obj-y += gdbstub.o msa_helper.o
-obj-$(CONFIG_SOFTMMU) += mips-semi.o
+obj-$(CONFIG_SEMIHOSTING) += mips-semi.o
+obj-$(call lnot,$(CONFIG_SEMIHOSTING)) += mips-semi-stubs.o
 obj-$(CONFIG_SOFTMMU) += machine.o cp0_timer.o
 obj-$(CONFIG_KVM) += kvm.o
diff --git a/target/mips/mips-semi-stubs.c b/target/mips/mips-semi-stubs.c
new file mode 100644
index 0000000000..b1d3f88edc
--- /dev/null
+++ b/target/mips/mips-semi-stubs.c
@@ -0,0 +1,22 @@
+/*
+ * Unified Hosting Interface syscalls 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"
+#include "exec/helper-proto.h"
+
+void helper_do_semihosting(CPUMIPSState *env)
+{
+    g_assert_not_reached();
+}
-- 
2.20.1