target/arm: Factor out code for setting MTE TCF0 field

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>
Message-Id: <20240628050850.536447-7-gustavo.romero@linaro.org>
[AJB: clean-up includes, move MTE defines]
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240705084047.857176-36-alex.bennee@linaro.org>

linux-user/aarch64/meson.build

@@ -9,3 +9,5 @@ vdso_le_inc = gen_vdso.process('vdso-le.so',
                                extra_args: ['-r', '__kernel_rt_sigreturn'])
 
 linux_user_ss.add(when: 'TARGET_AARCH64', if_true: [vdso_be_inc, vdso_le_inc])
+
+linux_user_ss.add(when: 'TARGET_AARCH64', if_true: [files('mte_user_helper.c')])

linux-user/aarch64/mte_user_helper.c

@@ -0,0 +1,35 @@
+/*
+ * ARM MemTag convenience functions.
+ *
+ * This code is licensed under the GNU GPL v2 or later.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qemu.h"
+#include "mte_user_helper.h"
+
+void arm_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);
+}

linux-user/aarch64/mte_user_helper.h

@@ -0,0 +1,32 @@
+/*
+ * ARM MemTag convenience functions.
+ *
+ * This code is licensed under the GNU GPL v2 or later.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#ifndef AARCH64_MTE_USER_HELPER_H
+#define AARCH64_MTE USER_HELPER_H
+
+#ifndef PR_MTE_TCF_SHIFT
+# define PR_MTE_TCF_SHIFT       1
+# define PR_MTE_TCF_NONE        (0UL << PR_MTE_TCF_SHIFT)
+# define PR_MTE_TCF_SYNC        (1UL << PR_MTE_TCF_SHIFT)
+# define PR_MTE_TCF_ASYNC       (2UL << PR_MTE_TCF_SHIFT)
+# define PR_MTE_TCF_MASK        (3UL << PR_MTE_TCF_SHIFT)
+# define PR_MTE_TAG_SHIFT       3
+# define PR_MTE_TAG_MASK        (0xffffUL << PR_MTE_TAG_SHIFT)
+#endif
+
+/**
+ * arm_set_mte_tcf0 - Set TCF0 field in SCTLR_EL1 register
+ * @env: The CPU environment
+ * @value: The value to be set for the Tag Check Fault in EL0 field.
+ *
+ * Only SYNC and ASYNC modes can be selected. If ASYMM mode is given, the SYNC
+ * mode is selected instead. So, there is no way to set the ASYMM mode.
+ */
+void arm_set_mte_tcf0(CPUArchState *env, abi_long value);
+
+#endif /* AARCH64_MTE_USER_HELPER_H */

linux-user/aarch64/target_prctl.h

@@ -7,6 +7,7 @@
 #define AARCH64_TARGET_PRCTL_H
 
 #include "target/arm/cpu-features.h"
+#include "mte_user_helper.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);
+        arm_set_mte_tcf0(env, arg2);
 
         /*
          * Write PR_MTE_TAG to GCR_EL1[Exclude].

linux-user/syscall.c

@@ -6281,15 +6281,6 @@ abi_long do_arch_prctl(CPUX86State *env, int code, abi_ulong addr)
 # define PR_GET_TAGGED_ADDR_CTRL 56
 # define PR_TAGGED_ADDR_ENABLE  (1UL << 0)
 #endif
-#ifndef PR_MTE_TCF_SHIFT
-# define PR_MTE_TCF_SHIFT       1
-# define PR_MTE_TCF_NONE        (0UL << PR_MTE_TCF_SHIFT)
-# define PR_MTE_TCF_SYNC        (1UL << PR_MTE_TCF_SHIFT)
-# define PR_MTE_TCF_ASYNC       (2UL << PR_MTE_TCF_SHIFT)
-# define PR_MTE_TCF_MASK        (3UL << PR_MTE_TCF_SHIFT)
-# define PR_MTE_TAG_SHIFT       3
-# define PR_MTE_TAG_MASK        (0xffffUL << PR_MTE_TAG_SHIFT)
-#endif
 #ifndef PR_SET_IO_FLUSHER
 # define PR_SET_IO_FLUSHER 57
 # define PR_GET_IO_FLUSHER 58