[PATCH v2 6/9] target/arm: Factor out code for setting MTE TCF0 field

[Gustavo Romero]

Factor out the code used for setting the MTE TCF0 field from the prctl
code into a convenient function. Other subsystems, like gdbstub, need to
set this field as well, so keep it as a separate function to avoid
duplication and ensure consistency in how this field is set across the
board.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
---
 linux-user/aarch64/target_prctl.h | 22 ++-----------
 target/arm/mte.h                  | 53 +++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 20 deletions(-)
 create mode 100644 target/arm/mte.h

diff --git a/linux-user/aarch64/target_prctl.h 
b/linux-user/aarch64/target_prctl.h
index aa8e203c15..8a11404222 100644
--- a/linux-user/aarch64/target_prctl.h
+++ b/linux-user/aarch64/target_prctl.h
@@ -7,6 +7,7 @@
 #define AARCH64_TARGET_PRCTL_H
 
 #include "target/arm/cpu-features.h"
+#include "target/arm/mte.h"
 
 static abi_long do_prctl_sve_get_vl(CPUArchState *env)
 {
@@ -173,26 +174,7 @@ static abi_long do_prctl_set_tagged_addr_ctrl(CPUArchState 
*env, abi_long arg2)
     env->tagged_addr_enable = arg2 & PR_TAGGED_ADDR_ENABLE;
 
     if (cpu_isar_feature(aa64_mte, cpu)) {
-        /*
-         * Write PR_MTE_TCF to SCTLR_EL1[TCF0].
-         *
-         * The kernel has a per-cpu configuration for the sysadmin,
-         * /sys/devices/system/cpu/cpu<N>/mte_tcf_preferred,
-         * which qemu does not implement.
-         *
-         * Because there is no performance difference between the modes, and
-         * because SYNC is most useful for debugging MTE errors, choose SYNC
-         * as the preferred mode.  With this preference, and the way the API
-         * uses only two bits, there is no way for the program to select
-         * ASYMM mode.
-         */
-        unsigned tcf = 0;
-        if (arg2 & PR_MTE_TCF_SYNC) {
-            tcf = 1;
-        } else if (arg2 & PR_MTE_TCF_ASYNC) {
-            tcf = 2;
-        }
-        env->cp15.sctlr_el[1] = deposit64(env->cp15.sctlr_el[1], 38, 2, tcf);
+        set_mte_tcf0(env, arg2);
 
         /*
          * Write PR_MTE_TAG to GCR_EL1[Exclude].
diff --git a/target/arm/mte.h b/target/arm/mte.h
new file mode 100644
index 0000000000..89712aad70
--- /dev/null
+++ b/target/arm/mte.h
@@ -0,0 +1,53 @@
+/*
+ * ARM MemTag convenience functions.
+ *
+ * Copyright (c) 2024 Linaro, Ltd.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef MTE_H
+#define MTE_H
+
+#ifdef CONFIG_TCG
+#ifdef CONFIG_USER_ONLY
+#include "sys/prctl.h"
+
+static void set_mte_tcf0(CPUArchState *env, abi_long value)
+{
+    /*
+     * Write PR_MTE_TCF to SCTLR_EL1[TCF0].
+     *
+     * The kernel has a per-cpu configuration for the sysadmin,
+     * /sys/devices/system/cpu/cpu<N>/mte_tcf_preferred,
+     * which qemu does not implement.
+     *
+     * Because there is no performance difference between the modes, and
+     * because SYNC is most useful for debugging MTE errors, choose SYNC
+     * as the preferred mode.  With this preference, and the way the API
+     * uses only two bits, there is no way for the program to select
+     * ASYMM mode.
+     */
+    unsigned tcf = 0;
+    if (value & PR_MTE_TCF_SYNC) {
+        tcf = 1;
+    } else if (value & PR_MTE_TCF_ASYNC) {
+        tcf = 2;
+    }
+    env->cp15.sctlr_el[1] = deposit64(env->cp15.sctlr_el[1], 38, 2, tcf);
+}
+#endif /* CONFIG_USER_ONLY */
+#endif /* CONFIG_TCG */
+
+#endif /* MTE_H */
-- 
2.34.1