soc/runtime: fix use of setjmp

soc/runtime/exceptions.c

@@ -1,32 +1,33 @@
-#include <setjmp.h>
-
 #include "exceptions.h"
 
-static struct exception_env *env_top;
+#define MAX_EXCEPTION_CONTEXTS 64
+
+struct exception_context {
+    void *jb[5];
+};
+
+static struct exception_context exception_contexts[MAX_EXCEPTION_CONTEXTS];
+static int ec_top;
 static int stored_id;
 
-int exception_catch(struct exception_env *ee, int *id)
+void *exception_push(void)
 {
-	ee->prev = env_top;
-	env_top = ee;
-	if(setjmp(env_top->jb)) {
-		*id = stored_id;
-		return 1;
-	} else
-		return 0;
+    if(ec_top >= MAX_EXCEPTION_CONTEXTS)
+        exception_raise(EID_NOMEM);
+    return exception_contexts[ec_top++].jb;
 }
 
 void exception_pop(void)
 {
-	env_top = env_top->prev;
+    ec_top--;
+}
+
+int exception_getid(void)
+{
+    return stored_id;
 }
 
 void exception_raise(int id)
 {
-	struct exception_env *ee;
-
-	ee = env_top;
-	env_top = env_top->prev;
-	stored_id = id; /* __builtin_longjmp needs its second argument set to 1 */
-	longjmp(ee->jb, 1);
+    __builtin_longjmp(exception_contexts[--ec_top].jb, 1);
 }

soc/runtime/exceptions.h

@@ -1,15 +1,13 @@
 #ifndef __EXCEPTIONS_H
 #define __EXCEPTIONS_H
 
-#include <setjmp.h>
-
-struct exception_env {
-	jmp_buf jb;
-	struct exception_env *prev;
+enum {
+	EID_NOMEM = 0
 };
 
-int exception_catch(struct exception_env *ee, int *id);
+void *exception_push(void);
 void exception_pop(void);
+int exception_getid(void);
 void exception_raise(int id) __attribute__((noreturn));
 
 #endif /* __EXCEPTIONS_H */

soc/runtime/main.c

@@ -68,8 +68,7 @@ typedef void (*kernel_function)(void);
 static int run_kernel(const char *kernel_name, int *eid)
 {
     kernel_function k;
-    struct exception_env ee;
-    int exception_occured;
+    void *jb;
 
     k = find_symbol(symtab, kernel_name);
     if(k == NULL) {
@@ -77,10 +76,11 @@ static int run_kernel(const char *kernel_name, int *eid)
         return KERNEL_RUN_STARTUP_FAILED;
     }
 
-    exception_occured = exception_catch(&ee, eid);
-    if(exception_occured)
+    jb = exception_push();
+    if(__builtin_setjmp(jb)) {
+        *eid = exception_getid();
         return KERNEL_RUN_EXCEPTION;
-    else {
+    } else {
         rtio_init();
         flush_cpu_icache();
         k();