[SPCA] Finish unorthodox control flow

semester3/spca/code-examples/01_asm/08_unorthodox-controlflow.c

@@ -0,0 +1,22 @@
+#include <setjmp.h>
+#include <stdio.h>
+
+static jmp_buf buf;
+
+void second( void ) {
+    printf( "second\n" );
+    longjmp( buf, 1 );
+}
+
+void first( void ) {
+    second();
+    printf( "first\n" ); // Never executed
+}
+
+int main() {
+    if ( !setjmp( buf ) ) // returns 0 initially
+        first();
+    else
+        printf( "main\n" ); // 1 is returned when longjmp is executed
+    return 0;
+}

semester3/spca/code-examples/01_asm/09_setjmp-longjmp.s

@@ -0,0 +1,27 @@
+# Copyright 2011-2012 Nicholas J. Kain, licensed under standard MIT license
+setjmp:
+	mov %rbx, (%rdi)
+	mov %rbp, 8(%rdi)
+	mov %r12, 16(%rdi)
+	mov %r13, 24(%rdi)
+	mov %r14, 32(%rdi)
+	mov %r15, 40(%rdi)
+	lea 8(%rsp), %rdx
+	mov %rdx, 48(%rdi)
+	mov (%rsp), %rdx
+	mov %rdx, 56(%rdi)
+	xor %eax, %eax
+	ret
+
+longjmp:
+	xor %eax, %eax
+	cmp $1, %esi       # CF = val ? 0 : 1
+	adc %esi, %eax     # eax = val + !val
+	mov (%rdi), %rbx   # rdi is the jmp_buf, restore regs from it
+	mov 8(%rdi), %rbp
+	mov 16(%rdi), %r12
+	mov 24(%rdi), %r13
+	mov 32(%rdi), %r14
+	mov 40(%rdi), %r15
+	mov 48(%rdi), %rsp
+	jmp *56(%rdi)      # goto saved address without altering rsp

semester3/spca/code-examples/01_asm/10_coroutine.c

@@ -0,0 +1,40 @@
+#include "10_coroutine.h"
+#include <setjmp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#define CORO_STACK_SIZE 128
+static struct coroutine *cur_co;
+static struct coroutine *main_co;
+
+void co_init() {
+    main_co = (struct coroutine *) calloc( 1, sizeof( struct coroutine ) );
+    cur_co = main_co;
+    co_switchto( main_co );
+}
+
+void *co_switchto( struct coroutine *next, void *arg ) {
+    if ( setjmp( cur_co->env ) == 0 ) {
+        cur_co = next;
+        cur_co->arg = arg;
+        longjmp( cur_co->env, 1 );
+    }
+    return cur_co->arg;
+}
+
+static void start_cl( void ) {
+    ( cur_co->start )( cur_co->arg );
+    co_switchto( main_co );
+
+    printf( "Error: returned from coroutine start closure.\n" );
+    exit( -1 );
+}
+
+struct coroutine *co_new( co_start_fn *start, void *ctxt ) {
+    struct coroutine *co = (struct coroutine *) calloc( 1, sizeof( struct coroutine ) );
+    co->stack = calloc( 1, CORO_STACK_SIZE + 16 );
+    co->start = start;
+    co->arg = ctxt;
+    setjmp( co->env );
+    co->env[ 0 ].__jmpbuf[ 6 ] = ( (uint64_t) ( co->stack ) + CORO_STACK_SIZE ); // Machine specific
+    co->env[ 0 ].__jmpbuf[ 7 ] = ( (uint64_t) ( start_cl ) );                    // Machine specific
+}

semester3/spca/code-examples/01_asm/10_coroutine.h

@@ -0,0 +1,13 @@
+#include <setjmp.h>
+typedef void( co_start_fn )( void * );
+
+struct coroutine {
+        void *stack;        // The call stack
+        jmp_buf env;        // The saved context
+        co_start_fn *start; // Function to call
+        void *arg;          // Argument to the function
+};
+struct coroutine *co_new( co_start_fn *start, void *ctxt );
+void co_free( struct coroutine *self );
+void *co_switchto( struct coroutine *next );
+void co_init( void );