arch/posix.h: implement ARCH_EXCEPT() with abort() for debug convenience

Flush all messages and invoke `abort()` when a k_panic() or k_oops() is
hit in native_posix mode.

One of the main purposes of `native_posix` is to provide debug
convenience. When running in a debugger, `abort()` stops execution which
provides a backtrace and the ability to inspect all variables.

A practical use case is fuzzing failures in SOF, see an example in:
thesofproject/sof#8632

Signed-off-by: Marc Herbert <[email protected]>

include/zephyr/arch/posix/arch.h

@@ -17,6 +17,8 @@
 #ifndef ZEPHYR_INCLUDE_ARCH_POSIX_ARCH_H_
 #define ZEPHYR_INCLUDE_ARCH_POSIX_ARCH_H_
 
+#include <stdlib.h>
+
 /* Add include for DTS generated information */
 #include <zephyr/devicetree.h>
 
@@ -38,6 +40,41 @@ extern "C" {
 #define ARCH_STACK_PTR_ALIGN 4
 #endif
 
+/* "native_posix" should really use CONFIG_LOG_MODE_IMMEDIATE=y but better safe
+ * than sorry: debugging crashes is painful enough already, so try to be nice
+ * and flush all messages. The deferred logging code may also want to enjoy
+ * native_posix too.
+ *
+ * Other archs use Zephyr's elaborate "Fatal Errors" framework which takes care
+ * of flushing logs but native_posix is simpler so we have to do it ourselves.
+ */
+static inline void posix_arch_log_immediate(void)
+{
+#ifdef CONFIG_LOG
+	/* We can't #include the higher-level "log_ctrl.h" in this low-level
+	 * file here because this descends into .h dependency hell.  So let's
+	 * use a one-line forward declaration instead. This void->void
+	 * prototype does not look like it's going to change much in the
+	 * future.
+	 *
+	 * We can't declare "void log_panic(void);" because it is not what it
+	 * seems but a complicated static inline + macro override in
+	 * generated/syscalls/log_ctrl.h. In native_posix mode log_panic()
+	 * boils down to just z_impl_log_panic() so exceptionally invoke that
+	 * directly.
+	 */
+	void z_impl_log_panic(void);
+	z_impl_log_panic();
+#endif
+}
+/* Invoked by k_panic() and k_oops() */
+#define ARCH_EXCEPT(reason_p) do { \
+	posix_arch_log_immediate(); \
+	printk("ARCH_EXCEPT reason: %u\n", reason_p);  \
+	abort(); CODE_UNREACHABLE; \
+} while (false)
+
+/* Exception context */
 struct __esf {
 	uint32_t dummy; /*maybe we will want to add something someday*/
 };