Add support for calling to and returning from signal handlers in in user-mode threads

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5750 42af7a65-404d-4744-a932-0658087f49c3

2 files changed, 34 insertions, 0 deletions

diff --git a/nuttx/arch/arm/include/armv7-m/irq.h b/nuttx/arch/arm/include/armv7-m/irq.h
index 7556d0747..afeebdb4f 100644
--- a/nuttx/arch/arm/include/armv7-m/irq.h
+++ b/nuttx/arch/arm/include/armv7-m/irq.h
@@ -124,6 +124,14 @@ struct xcptcontext
   uint32_t saved_primask;
 #endif
   uint32_t saved_xpsr;
+
+# ifdef CONFIG_NUTTX_KERNEL
+  /* This is the saved address to use when returning from a user-space
+   * signal handler.
+   */
+
+  uint32_t sigreturn;
+# endif
 #endif
 
 #ifdef CONFIG_NUTTX_KERNEL
diff --git a/nuttx/arch/arm/include/armv7-m/syscall.h b/nuttx/arch/arm/include/armv7-m/syscall.h
index 4278c3a36..91220f359 100644
--- a/nuttx/arch/arm/include/armv7-m/syscall.h
+++ b/nuttx/arch/arm/include/armv7-m/syscall.h
@@ -54,8 +54,22 @@
  * Pro-processor Definitions
  ****************************************************************************/
 
+/* This is the value used as the argument to the SVC instruction.  It is not
+ * used.
+ */
+
 #define SYS_syscall 0x00
 
+/* The SYS_signal_handler_return is executed here... its value is not always
+ * available in this context and so is assumed to be 7.
+ */
+
+#ifndef SYS_signal_handler_return
+#  define SYS_signal_handler_return (7)
+#elif SYS_signal_handler_return != 7
+#  error "SYS_signal_handler_return was assumed to be 7"
+#endif
+
 /****************************************************************************
  * Public Types
  ****************************************************************************/
@@ -218,6 +232,18 @@ static inline uintptr_t sys_call6(unsigned int nbr, uintptr_t parm1,
   return reg0;
 }
 
+/* This inline function is used by user-space code in order to return from
+ * a signal handler.
+ */
+
+#if defined(CONFIG_NUTTX_KERNEL) && !defined(__KERNEL__)
+static inline void signal_handler_return(void) noreturn_function;
+static inline void signal_handler_return(void)
+{
+  sys_call0(SYS_signal_handler_return);
+}
+#endif
+
 /****************************************************************************
  * Public Variables
  ****************************************************************************/