//
// 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.
//
// coroutine.c --
//
// Author           : Thierry Delisle
// Created On       : Mon Nov 28 12:27:26 2016
// Last Modified By : Peter A. Buhr
// Last Modified On : Tue Dec 15 12:06:04 2020
// Update Count     : 23
//

#define __cforall_thread__
#define _GNU_SOURCE

#include "coroutine.hfa"

#include <stddef.h>
#include <malloc.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>									// mprotect
#include <unwind.h>

#include "kernel/private.hfa"
#include "exception.hfa"
#include "math.hfa"

#define CFA_COROUTINE_USE_MMAP 0

#define __CFA_INVOKE_PRIVATE__
#include "invoke.h"

extern "C" {
	void _CtxCoroutine_Unwind(struct _Unwind_Exception * storage, struct coroutine$ *) __attribute__ ((__noreturn__));
	static void _CtxCoroutine_UnwindCleanup(_Unwind_Reason_Code, struct _Unwind_Exception *) __attribute__ ((__noreturn__));
	static void _CtxCoroutine_UnwindCleanup(_Unwind_Reason_Code, struct _Unwind_Exception *) {
		abort();
	}

	extern void CtxRet( struct __stack_context_t * to ) asm ("CtxRet") __attribute__ ((__noreturn__));
}

//-----------------------------------------------------------------------------
forall(T &)
void copy(CoroutineCancelled(T) * dst, CoroutineCancelled(T) * src) libcfa_public {
	dst->virtual_table = src->virtual_table;
	dst->the_coroutine = src->the_coroutine;
	dst->the_exception = src->the_exception;
}

forall(T &)
const char * msg(CoroutineCancelled(T) *) libcfa_public {
	return "CoroutineCancelled(...)";
}

// This code should not be inlined. It is the error path on resume.
forall(T & | is_coroutine(T))
void __cfaehm_cancelled_coroutine(
		T & cor, coroutine$ * desc, EHM_DEFAULT_VTABLE(CoroutineCancelled(T)) ) libcfa_public {
	verify( desc->cancellation );
	desc->state = Cancelled;
	exception_t * except = __cfaehm_cancellation_exception( desc->cancellation );

	// TODO: Remove explitate vtable set once trac#186 is fixed.
	CoroutineCancelled(T) except;
	except.virtual_table = &_default_vtable;
	except.the_coroutine = &cor;
	except.the_exception = except;
	// Why does this need a cast?
	throwResume (CoroutineCancelled(T) &)except;

	except->virtual_table->free( except );
	free( desc->cancellation );
	desc->cancellation = 0p;
}

//-----------------------------------------------------------------------------
// Global state variables

// minimum feasible stack size in bytes
static const size_t MinStackSize = 1000;
extern size_t __page_size;				// architecture pagesize HACK, should go in proper runtime singleton
extern int __map_prot;

void __stack_prepare( __stack_info_t * this, size_t create_size );
static void __stack_clean  ( __stack_info_t * this );

//-----------------------------------------------------------------------------
// Coroutine ctors and dtors
void ?{}( __stack_info_t & this, void * storage, size_t storageSize ) {
	this.storage   = (__stack_t *)storage;

	// Did we get a piece of storage ?
	if (this.storage || storageSize != 0) {
		// We either got a piece of storage or the user asked for a specific size
		// Immediately create the stack
		// (This is slightly unintuitive that non-default sized coroutines create are eagerly created
		// but it avoids that all coroutines carry an unnecessary size)
		verify( storageSize != 0 );
		__stack_prepare( &this, storageSize );
	}
}

void ^?{}(__stack_info_t & this) {
	bool userStack = ((intptr_t)this.storage & 0x1) != 0;
	if ( ! userStack && this.storage ) {
		__stack_clean( &this );
	}
}

void ?{}( coroutine$ & this, const char name[], void * storage, size_t storageSize ) libcfa_public with( this ) {
	(this.context){0p, 0p};
	(this.stack){storage, storageSize};
	this.name = name;
	state = Start;
	starter = 0p;
	last = 0p;
	cancellation = 0p;
}

void ^?{}(coroutine$& this) libcfa_public {
	if(this.state != Halted && this.state != Start && this.state != Primed) {
		coroutine$ * src = active_coroutine();
		coroutine$ * dst = &this;

		struct _Unwind_Exception storage;
		storage.exception_class = -1;
		storage.exception_cleanup = _CtxCoroutine_UnwindCleanup;
		this.cancellation = &storage;
		this.last = src;

		// not resuming self ?
		if ( src == dst ) {
			abort( "Attempt by coroutine %.256s (%p) to terminate itself.\n", src->name, src );
		}

		$ctx_switch( src, dst );
	}
}

// Part of the Public API
// Not inline since only ever called once per coroutine
forall(T & | is_coroutine(T) | { EHM_DEFAULT_VTABLE(CoroutineCancelled(T)); })
void prime(T& cor) libcfa_public {
	coroutine$* this = get_coroutine(cor);
	assert(this->state == Start);

	this->state = Primed;
	resume(cor);
}

static [void *, size_t] __stack_alloc( size_t storageSize ) {
	const size_t stack_data_size = libCeiling( sizeof(__stack_t), 16 ); // minimum alignment
	assert(__page_size != 0l);
	size_t size = libCeiling( storageSize, 16 ) + stack_data_size;
	size = ceiling(size, __page_size);

	// If we are running debug, we also need to allocate a guardpage to catch stack overflows.
	void * storage;
	#if CFA_COROUTINE_USE_MMAP
		storage = mmap(0p, size + __page_size, PROT_EXEC | PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
		if(storage == ((void*)-1)) {
			abort( "coroutine stack creation : internal error, mmap failure, error(%d) %s.", errno, strerror( errno ) );
		}
		if ( mprotect( storage, __page_size, PROT_NONE ) == -1 ) {
			abort( "coroutine stack creation : internal error, mprotect failure, error(%d) %s.", errno, strerror( errno ) );
		} // if
		storage = (void *)(((intptr_t)storage) + __page_size);
	#else
		__cfaabi_dbg_debug_do(
			storage = memalign( __page_size, size + __page_size );
		);
		__cfaabi_dbg_no_debug_do(
			storage = (void*)malloc(size);
		);

		__cfaabi_dbg_debug_do(
			if ( mprotect( storage, __page_size, PROT_NONE ) == -1 ) {
				abort( "__stack_alloc : internal error, mprotect failure, error(%d) %s.", (int)errno, strerror( (int)errno ) );
			}
			storage = (void *)(((intptr_t)storage) + __page_size);
		);
	#endif
	__cfaabi_dbg_print_safe("Kernel : Created stack %p of size %zu\n", storage, size);

	verify( ((intptr_t)storage & (libAlign() - 1)) == 0ul );
	return [storage, size];
}

static void __stack_clean  ( __stack_info_t * this ) {
	void * storage = this->storage->limit;

	#if CFA_COROUTINE_USE_MMAP
		size_t size = ((intptr_t)this->storage->base) - ((intptr_t)this->storage->limit) + sizeof(__stack_t);
		storage = (void *)(((intptr_t)storage) - __page_size);
		if(munmap(storage, size + __page_size) == -1) {
			abort( "coroutine stack destruction : internal error, munmap failure, error(%d) %s.", errno, strerror( errno ) );
		}
	#else
		__cfaabi_dbg_debug_do(
			storage = (char*)(storage) - __page_size;
			if ( mprotect( storage, __page_size, __map_prot ) == -1 ) {
				abort( "(coStack_t *)%p.^?{}() : internal error, mprotect failure, error(%d) %s.", &this, errno, strerror( errno ) );
			}
		);

		free( storage );
	#endif
	__cfaabi_dbg_print_safe("Kernel : Deleting stack %p\n", storage);
}

void __stack_prepare( __stack_info_t * this, size_t create_size ) libcfa_public {
	const size_t stack_data_size = libCeiling( sizeof(__stack_t), 16 ); // minimum alignment
	bool userStack;
	void * storage;
	size_t size;
	if ( !this->storage ) {
		userStack = false;
		[storage, size] = __stack_alloc( create_size );
	} else {
		userStack = true;
		__cfaabi_dbg_print_safe("Kernel : stack obj %p using user stack %p(%zd bytes)\n", this, this->storage, (intptr_t)this->storage->limit - (intptr_t)this->storage->base);

		// The stack must be aligned, advance the pointer to the next align data
		storage = (void*)libCeiling( (intptr_t)this->storage, libAlign());

		// The size needs to be shrinked to fit all the extra data structure and be aligned
		ptrdiff_t diff = (intptr_t)storage - (intptr_t)this->storage;
		size = libFloor(create_size - stack_data_size - diff, libAlign());
	} // if
	assertf( size >= MinStackSize, "Stack size %zd provides less than minimum of %zd bytes for a stack.", size, MinStackSize );

	this->storage = (__stack_t *)((intptr_t)storage + size - sizeof(__stack_t));
	this->storage->limit = storage;
	this->storage->base  = (void*)((intptr_t)storage + size - sizeof(__stack_t));
	this->storage->exception_context.top_resume = 0p;
	this->storage->exception_context.current_exception = 0p;
	__attribute__((may_alias)) intptr_t * istorage = (intptr_t*)&this->storage;
	*istorage |= userStack ? 0x1 : 0x0;
}

// We need to call suspend from invoke.c, so we expose this wrapper that
// is not inline (We can't inline Cforall in C)
extern "C" {
	void __cfactx_cor_leave( struct coroutine$ * src ) {
		coroutine$ * starter = src->cancellation != 0 ? src->last : src->starter;

		src->state = Halted;

		assertf( starter != 0,
			"Attempt to suspend/leave coroutine \"%.256s\" (%p) that has never been resumed.\n"
			"Possible cause is a suspend executed in a member called by a coroutine user rather than by the coroutine main.",
			src->name, src );
		assertf( starter->state != Halted,
			"Attempt by coroutine \"%.256s\" (%p) to suspend/leave back to terminated coroutine \"%.256s\" (%p).\n"
			"Possible cause is terminated coroutine's main routine has already returned.",
			src->name, src, starter->name, starter );

		$ctx_switch( src, starter );
	}

	struct coroutine$ * __cfactx_cor_finish(void) {
		struct coroutine$ * cor = active_coroutine();

		// get the active thread once
		thread$ * athrd = active_thread();

		/* paranoid */ verify( athrd->corctx_flag );
		athrd->corctx_flag = false;

		if(cor->state == Primed) {
			__cfactx_suspend();
		}

		cor->state = Active;

		return cor;
	}
}

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