cpu/native: unify ucontext manipulation

cpu/native/include/native_internal.h

@@ -237,7 +237,29 @@ extern ucontext_t *_native_isr_context;
  */
 extern void _native_isr_leave(void);
 
+/**
+ * @brief Makes ISR context so that execution continues at `func` when the context is applied
+ *
+ * @param func Function executed when `_native_isr_context` is applied
+ */
+static inline void _native_isr_context_make(void (*func)(void)) {
+    _native_isr_context->uc_stack.ss_sp = _isr_stack;
+    _native_isr_context->uc_stack.ss_size = sizeof(_isr_stack);
+    _native_isr_context->uc_stack.ss_flags = 0;
 
+    /* Create the ISR context, will execute _isr_schedule_and_switch */
+    makecontext(_native_isr_context, func, 0);
+}
+
+/**
+ * @brief Retrieves user context
+ * @returns `ucontext_t`
+ */
+static inline ucontext_t* _native_user_context(void) {
+    /* Use intermediate cast to uintptr_t to silence -Wcast-align.
+     * stacks are manually word aligned in thread_static_init() */
+    return (ucontext_t *)(uintptr_t)thread_get_active()->sp;
+}
 /** @} */
 
 /* MARK: - Native Process State */

cpu/native/include/util/ucontext.h

@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2013 - 2016 Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>
+ * Copyright (C) 2025 carl-tud
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+#ifndef UTIL_UCONTEXT_H
+#define UTIL_UCONTEXT_H
+
+#if USE_LIBUCONTEXT
+# include <libucontext/libucontext.h>
+#else
+# include <ucontext.h>
+#endif /* USE_LIBUCONTEXT */
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @addtogroup cpu_native
+ * @{
+ */
+
+/* MARK: - Context accessors */
+/**
+ * @name Context accessors
+ * @{
+ */
+
+/**
+ * @brief Retrieves function pointer generated during calls to `makecontext`/`setcontext`/`swapcontext`
+ * @param context `ucontext_t`
+ * @returns Function pointer (does not need to be start of a function, points to instruction)
+ */
+static inline uintptr_t _context_get_fptr(ucontext_t *context) {
+# if defined(__FreeBSD__) /* FreeBSD */
+    return (uintptr_t)((struct sigcontext *)context)->sc_eip;
+# elif defined(__linux__) /* Linux */
+#  if defined(__arm__)
+    return (uintptr_t)((ucontext_t *)context)->uc_mcontext.arm_pc;
+#  elif defined(__x86_64__)
+    return (uintptr_t)((ucontext_t *)context)->uc_mcontext.gregs[REG_RIP];
+#  elif defined(__i386__)
+    return (uintptr_t)((ucontext_t *)context)->uc_mcontext.gregs[REG_EIP];
+#  else
+#   error "Unsupported Linux architecture"
+#  endif
+# else
+#  error "Operating system unsupported"
+# endif
+}
+
+/**
+ * @brief Retrieves function pointer generated during calls to `makecontext`/`setcontext`/`swapcontext`
+ * @param context `ucontext_t`
+ * @param func Function pointer
+ */
+static inline void _context_set_fptr(ucontext_t *context, uintptr_t func) {
+# if defined(__FreeBSD__) /* FreeBSD */
+    ((struct sigcontext *)context)->sc_eip = (unsigned int)func;
+# elif defined(__linux__) /* Linux */
+#  if defined(__arm__)
+    ((ucontext_t *)context)->uc_mcontext.arm_lr = func;
+    ((ucontext_t *)context)->uc_mcontext.arm_pc = func;
+#  elif defined(__x86_64__)
+    ((ucontext_t *)context)->uc_mcontext.gregs[REG_RIP] = (greg_t)func;
+#  elif defined(__i386__)
+    ((ucontext_t *)context)->uc_mcontext.gregs[REG_EIP] = func;
+#  else
+#   error "Unsupported Linux architecture"
+#  endif
+# else
+#  error "Operating system unsupported"
+# endif
+}
+/** @} */
+
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* UTIL_UCONTEXT_H */

cpu/native/irq_cpu.c

@@ -323,36 +323,22 @@ void native_signal_action(int sig, siginfo_t *info, void *context)
         return;
     }
 
-    native_isr_context.uc_stack.ss_sp = __isr_stack;
-    native_isr_context.uc_stack.ss_size = sizeof(__isr_stack);
-    native_isr_context.uc_stack.ss_flags = 0;
-    makecontext(&native_isr_context, native_irq_handler, 0);
-    /* Use intermediate cast to uintptr_t to silence -Wcast-align.
-     * stacks are manually word aligned in thread_stack_init() */
-    _native_cur_ctx = (ucontext_t *)(uintptr_t)thread_get_active()->sp;
+    /* We will switch to the ISR context with ISR stack */
+    _native_isr_context_make(_native_call_sig_handlers_and_switch);
+
+    /* Current user thread context */
+    _native_current_context = _native_user_context();
 
     DEBUG_IRQ("\n\n\t\tnative_signal_action: return to _native_sig_leave_tramp\n\n");
     /* disable interrupts in context */
-    isr_set_sigmask((ucontext_t *)context);
+    _set_sigmask((ucontext_t *)context);
     _native_in_isr = 1;
-#if defined(__FreeBSD__)
-    _native_saved_eip = ((struct sigcontext *)context)->sc_eip;
-    ((struct sigcontext *)context)->sc_eip = (unsigned int)&_native_sig_leave_tramp;
-#else /* Linux */
-#if defined(__arm__)
-    _native_saved_eip = ((ucontext_t *)context)->uc_mcontext.arm_pc;
-    ((ucontext_t *)context)->uc_mcontext.arm_pc = (unsigned int)&_native_sig_leave_tramp;
-#else /* Linux/x86 */
-  #ifdef __x86_64__
-    _native_saved_eip = ((ucontext_t *)context)->uc_mcontext.gregs[REG_RIP];
-    ((ucontext_t *)context)->uc_mcontext.gregs[REG_RIP] = (uintptr_t)&_native_sig_leave_tramp;
-  #else
-    //printf("\n\033[31mEIP:\t%p\ngo switching\n\n\033[0m", (void*)((ucontext_t *)context)->uc_mcontext.gregs[REG_EIP]);
-    _native_saved_eip = ((ucontext_t *)context)->uc_mcontext.gregs[REG_EIP];
-    ((ucontext_t *)context)->uc_mcontext.gregs[REG_EIP] = (unsigned int)&_native_sig_leave_tramp;
-  #endif
-#endif
-#endif
+
+    /* Get PC/LR. This is where we will resume execution on the userspace thread. */
+    _native_user_fptr = (uintptr_t)_context_get_fptr((ucontext_t *)context);
+
+    /* Now we want to go to _native_sig_leave_tramp before resuming execution at _native_user_fptr. */
+    _context_set_fptr(context, (uintptr_t)_native_sig_leave_tramp);
 }
 
 static void _set_signal_handler(int sig, bool add)
@@ -487,10 +473,7 @@ void native_interrupt_init(void)
         err(EXIT_FAILURE, "native_interrupt_init: getcontext");
     }
 
-    native_isr_context.uc_stack.ss_sp = __isr_stack;
-    native_isr_context.uc_stack.ss_size = sizeof(__isr_stack);
-    native_isr_context.uc_stack.ss_flags = 0;
-    _native_isr_ctx = &native_isr_context;
+    _native_isr_context_make(_native_call_sig_handlers_and_switch);
 
     static stack_t sigstk;
     sigstk.ss_sp = malloc(SIGSTKSZ);

cpu/native/native_cpu.c

@@ -55,30 +55,6 @@ extern netdev_tap_t netdev_tap;
 
 static ucontext_t _end_context;
 
-/**
- * make the new context assign `_native_in_isr = 0` before resuming
- */
-static void _native_mod_ctx_leave_sigh(ucontext_t *ctx)
-{
-#if defined(__FreeBSD__)
-    _native_saved_eip = ((struct sigcontext *)ctx)->sc_eip;
-    ((struct sigcontext *)ctx)->sc_eip = (unsigned int)&_native_sig_leave_handler;
-#else /* Linux */
-#if defined(__arm__)
-    _native_saved_eip = ((ucontext_t *)ctx)->uc_mcontext.arm_pc;
-    ((ucontext_t *)ctx)->uc_mcontext.arm_pc = (unsigned int)&_native_sig_leave_handler;
-#else /* Linux/x86 */
-  #ifdef __x86_64__
-    _native_saved_eip = ctx->uc_mcontext.gregs[REG_RIP];
-    ctx->uc_mcontext.gregs[REG_RIP] = (unsigned long)&_native_sig_leave_handler;
-  #else
-    _native_saved_eip = ctx->uc_mcontext.gregs[REG_EIP];
-    ctx->uc_mcontext.gregs[REG_EIP] = (unsigned int)&_native_sig_leave_handler;
-  #endif
-#endif
-#endif
-}
-
 /**
  * TODO: implement
  */

cpu/native/syscalls.c

@@ -39,6 +39,7 @@
 # include "time_units.h"
 # include "ztimer64.h"
 #endif
+
 #include "stdio_base.h"
 
 #include "kernel_defines.h"
@@ -80,15 +81,10 @@ void _native_syscall_leave(void)
        )
     {
         _native_in_isr = 1;
-        /* Use intermediate cast to uintptr_t to silence -Wcast-align.
-         * stacks are manually word aligned in thread_static_init() */
-        _native_cur_ctx = (ucontext_t *)(uintptr_t)thread_get_active()->sp;
-        native_isr_context.uc_stack.ss_sp = __isr_stack;
-        native_isr_context.uc_stack.ss_size = __isr_stack_size;
-        native_isr_context.uc_stack.ss_flags = 0;
-        native_interrupts_enabled = 0;
-        makecontext(&native_isr_context, native_irq_handler, 0);
-        if (swapcontext(_native_cur_ctx, &native_isr_context) == -1) {
+        _native_interrupts_enabled = false;
+
+        _native_isr_context_make(_native_call_sig_handlers_and_switch);
+        if (swapcontext(_native_user_context(), _native_isr_context) == -1) {
             err(EXIT_FAILURE, "_native_syscall_leave: swapcontext");
         }
     }