//
// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// invoke.c --
//
// Author           : Thierry Delisle
// Created On       : Tue Jan 17 12:27:26 2016
// Last Modified By : Peter A. Buhr
// Last Modified On : Fri Feb  9 16:37:42 2018
// Update Count     : 5
//

#define __cforall_thread__

#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <unwind.h>

#include "invoke.h"

#define __CFA_INVOKE_PRIVATE__
#include "invoke.h"

// magically invoke the "main" of the most derived class
// Called from the kernel when starting a coroutine or task so must switch back to user mode.

extern void __leave_coroutine ( struct coroutine_desc * );
extern struct coroutine_desc * __finish_coroutine(void);
extern void __leave_thread_monitor();
extern void disable_interrupts() OPTIONAL_THREAD;
extern void enable_interrupts( __cfaabi_dbg_ctx_param );

void CtxInvokeCoroutine(
	void (*main)(void *),
	void *this
) {
	// Finish setting up the coroutine by setting its state
	struct coroutine_desc * cor = __finish_coroutine();

	// Call the main of the coroutine
	main( this );

	//Final suspend, should never return
	__leave_coroutine( cor );
	__cabi_abort( "Resumed dead coroutine" );
}

static _Unwind_Reason_Code _CtxCoroutine_UnwindStop(
	__attribute((__unused__)) int version,
	_Unwind_Action actions,
	__attribute((__unused__)) _Unwind_Exception_Class exceptionClass,
	__attribute((__unused__)) struct _Unwind_Exception * unwind_exception,
	__attribute((__unused__)) struct _Unwind_Context * context,
	void * param
) {
	if( actions & _UA_END_OF_STACK  ) {
		// We finished unwinding the coroutine,
		// leave it
		__leave_coroutine( param );
		__cabi_abort( "Resumed dead coroutine" );
	}
	if( actions & _UA_CLEANUP_PHASE ) return _URC_NO_REASON;

	return _URC_FATAL_PHASE2_ERROR;
}

void _CtxCoroutine_Unwind(struct _Unwind_Exception * storage, struct coroutine_desc * cor) __attribute__ ((__noreturn__));
void _CtxCoroutine_Unwind(struct _Unwind_Exception * storage, struct coroutine_desc * cor) {
	_Unwind_Reason_Code ret = _Unwind_ForcedUnwind( storage, _CtxCoroutine_UnwindStop, cor );
	printf("UNWIND ERROR %d after force unwind\n", ret);
	abort();
}

void CtxInvokeThread(
	void (*main)(void *),
	void *this
) {
	// Officially start the thread by enabling preemption
	enable_interrupts( __cfaabi_dbg_ctx );

	// Call the main of the thread
	main( this );

	// To exit a thread we must :
	// 1 - Mark it as halted
	// 2 - Leave its monitor
	// 3 - Disable the interupts
	// 4 - Final suspend
	// The order of these 4 operations is very important
	//Final suspend, should never return
	__leave_thread_monitor();
	__cabi_abort( "Resumed dead thread" );
}

void CtxStart(
	void (*main)(void *),
	struct coroutine_desc * cor,
	void *this,
	void (*invoke)(void *)
) {
	struct __stack_t * stack = cor->stack.storage;

#if defined( __i386 )

	struct FakeStack {
	    void *fixedRegisters[3];              // fixed registers ebx, edi, esi (popped on 1st uSwitch, values unimportant)
	    void *rturn;                          // where to go on return from uSwitch
	    void *dummyReturn;                    // fake return compiler would have pushed on call to uInvoke
	    void *argument[3];                    // for 16-byte ABI, 16-byte alignment starts here
	    void *padding;                        // padding to force 16-byte alignment, as "base" is 16-byte aligned
	};

	cor->context.SP = (char *)stack->base - sizeof( struct FakeStack );
	cor->context.FP = NULL;		// terminate stack with NULL fp

	struct FakeStack *fs = (struct FakeStack *)cor->context.SP;

	fs->dummyReturn = NULL;
	fs->argument[0] = main;     // argument to invoke
	fs->argument[1] = this;     // argument to invoke
	fs->rturn = invoke;

#elif defined( __x86_64 )

	struct FakeStack {
		void *fixedRegisters[5];            // fixed registers rbx, r12, r13, r14, r15
		void *rturn;                        // where to go on return from uSwitch
		void *dummyReturn;                  // NULL return address to provide proper alignment
	};

	cor->context.SP = (char *)stack->base - sizeof( struct FakeStack );
	cor->context.FP = NULL;		// terminate stack with NULL fp

	struct FakeStack *fs = (struct FakeStack *)cor->context.SP;

	fs->dummyReturn = NULL;
	fs->rturn = CtxInvokeStub;
	fs->fixedRegisters[0] = main;
	fs->fixedRegisters[1] = this;
	fs->fixedRegisters[2] = invoke;

#elif defined( __ARM_ARCH )
#error ARM needs to be upgrade to use to parameters like X86/X64 (A.K.A. : I broke this and do not know how to fix it)
	struct FakeStack {
		float fpRegs[16];			// floating point registers
		void *intRegs[9];			// integer/pointer registers
		void *arg[2];				// placeholder for this pointer
	};

	cor->context.SP = (char *)stack->base - sizeof( struct FakeStack );
	cor->context.FP = NULL;

	struct FakeStack *fs = (struct FakeStack *)cor->context.SP;

	fs->intRegs[8] = CtxInvokeStub;
	fs->arg[0] = this;
	fs->arg[1] = invoke;

#else
	#error uknown hardware architecture
#endif
}

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