xtensa: userspace: Add syscall for user exception

Trigger exception on Xtensa requires kernel privileges. Add
a new syscall that is used when ARCH_EXCEPT is invoked from userspace.

Signed-off-by: Flavio Ceolin <[email protected]>

Author: Flavio Ceolin

arch/xtensa/CMakeLists.txt

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
 
+zephyr_syscall_header(${ZEPHYR_BASE}/include/zephyr/arch/xtensa/arch.h)
 set_property(GLOBAL PROPERTY PROPERTY_OUTPUT_FORMAT elf32-xtensa-le)
 add_subdirectory(core)

arch/xtensa/core/fatal.c

@@ -149,3 +149,24 @@ FUNC_NORETURN void arch_syscall_oops(void *ssf)
 	z_xtensa_fatal_error(K_ERR_KERNEL_OOPS, esf);
 	CODE_UNREACHABLE;
 }
+
+#ifdef CONFIG_USERSPACE
+void z_impl_xtensa_user_fault(unsigned int reason)
+{
+	if ((_current->base.user_options & K_USER) != 0) {
+		if ((reason != K_ERR_KERNEL_OOPS) &&
+				(reason != K_ERR_STACK_CHK_FAIL)) {
+			reason = K_ERR_KERNEL_OOPS;
+		}
+	}
+	xtensa_arch_except(reason);
+}
+
+static void z_vrfy_xtensa_user_fault(unsigned int reason)
+{
+	z_impl_xtensa_user_fault(reason);
+}
+
+#include <syscalls/xtensa_user_fault_mrsh.c>
+
+#endif /* CONFIG_USERSPACE */

include/zephyr/arch/xtensa/arch.h

@@ -23,6 +23,7 @@
 #include <zephyr/arch/common/sys_io.h>
 #include <zephyr/arch/common/ffs.h>
 #include <zephyr/sw_isr_table.h>
+#include <zephyr/arch/xtensa/syscall.h>
 #include <zephyr/arch/xtensa/thread.h>
 #include <zephyr/arch/xtensa/irq.h>
 #include <xtensa/config/core.h>
@@ -54,11 +55,31 @@ struct arch_mem_domain {
 
 extern void xtensa_arch_except(int reason_p);
 
+#ifdef CONFIG_USERSPACE
+
+#define ARCH_EXCEPT(reason_p) do { \
+	if (k_is_user_context()) { \
+		arch_syscall_invoke1(reason_p, \
+			K_SYSCALL_XTENSA_USER_FAULT); \
+	} else { \
+		xtensa_arch_except(reason_p); \
+	} \
+	CODE_UNREACHABLE; \
+} while (false)
+
+#else
+
 #define ARCH_EXCEPT(reason_p) do { \
 	xtensa_arch_except(reason_p); \
 	CODE_UNREACHABLE; \
 } while (false)
 
+#endif
+
+__syscall void xtensa_user_fault(unsigned int reason);
+
+#include <syscalls/arch.h>
+
 /* internal routine documented in C file, needed by IRQ_CONNECT() macro */
 extern void z_irq_priority_set(uint32_t irq, uint32_t prio, uint32_t flags);