/* $Id$
 * UNIX signal handling for processor emulation for support of ntoskrnl of libcaptive
 * Copyright (C) 2002 Jan Kratochvil <project-captive@jankratochvil.net>
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; exactly version 2 of June 1991 is required
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */


#define _GNU_SOURCE 1	/* for sys/ucontext.h for REG_* */

#include "config.h"

#include "captive/signal.h"	/* self */
#include <glib/gtypes.h>
#include <glib/gmessages.h>
#include <signal.h>
#include "captive/macros.h"
#include <sys/ucontext.h>	/* for struct ucontext */
#include "captive/mm.h"	/* for captive_mmap_map_get() */
#include <sys/mman.h>
#include "reactos/internal/mm.h"  /* for PAGE_SIZE */
#include "captive/ldr.h"	/* for captive_ModuleList_patchpoint_find() */
#include "captive/ldr_exports.h"	/* for struct captive_ModuleList_patchpoint */


int _abnormal_termination_orig(void);
extern greg_t fs_KPCR_ExceptionList;

/**
 * _abnormal_termination_wrap:
 *
 * This call can be also accessed as AbnormalTermination() or _abnormal_termination().
 * It is a captive wrapper around _abnormal_termination() function.
 *
 * Returns whether some exception occured in the current #try block we are currently
 * #finish -ing. Any functions called from current #finish block will be considered
 * for returning zero back again. It is forbidden to call this function outside
 * of #finish block, result of such call is undefined.
 *
 * Exception handlers are registered from W32 binary in stack frames stored in "fs:[0x00000000]"
 * value which gets mapped by libcaptive/ps/signal.c to #fs_KPCR_ExceptionList
 * variable.
 *
 * If no exception handler was registered yet this function returns zero.
 *
 * See also RtlpDispatchException().
 *
 * Returns: non-zero if some exception is now being handled as pending.
 */
int _abnormal_termination_wrap(void)
{
	/* No handler registered yet? ntoskrnl _abnormal_termination() does not handle it
	 * and I do not want to bother with registering toplevel handler.
	 */
	if (fs_KPCR_ExceptionList==(greg_t)-1)
		return 0;

	return _abnormal_termination_orig();
}


#if 0

/**
 * RtlpDispatchException:
 * @ExceptionRecord: Ignored by libcaptive.
 * @Context: Ignored by libcaptive.
 *
 * Function definition to prevent inclusion of real RtlpDispatchException() implementation.
 * Currently libcaptive never raises any exception - fix _abnormal_termination() if it changes.
 *
 * Returns: Never returns. Value %0 if it returns although it is impossible.
 */
ULONG RtlpDispatchException(IN PEXCEPTION_RECORD ExceptionRecord,IN PCONTEXT Context)
{
	g_assert_not_reached();
	g_return_val_if_reached(0);
}

#endif


/* =='KeGetCurrentKPCR()->ExceptionList';
 * libcaptive has reduced KPCR (named 'captive_KPCR') which
 * does not contain this field
 */
greg_t fs_KPCR_ExceptionList=(greg_t)-1;

/* FIXME */
static greg_t fs_KPCR_Unknown638=0;


static gboolean instr_mov_greg_to_fsmem(int greg,const void *fsmem,struct ucontext *ucontext)
{
	if (fsmem==(const void *)0x00000000) {	/* exception stack top pointer */
		/* moving from %esp is required to pass! */
		fs_KPCR_ExceptionList=ucontext->uc_mcontext.gregs[greg];
		return TRUE;
		}
	g_return_val_if_reached(FALSE);
}

static gboolean instr_mov_immed_to_fsmem(greg_t immed,const void *fsmem,struct ucontext *ucontext)
{
	if (fsmem==(const void *)0x00000000) {	/* exception stack top pointer */
		fs_KPCR_ExceptionList=immed;
		return TRUE;
		}
	g_return_val_if_reached(FALSE);
}

static gboolean instr_mov_fsmem_to_greg(const void *fsmem,int greg,struct ucontext *ucontext)
{
	if (fsmem==(const void *)0x00000000) {	/* exception stack top pointer */
		/* moving to %esp is required to pass! */
		ucontext->uc_mcontext.gregs[greg]=fs_KPCR_ExceptionList;
		return TRUE;
		}
	if (fsmem==(const void *)0x00000051) {	/* =='KeGetCurrentKPCR()->Number' */
		g_return_val_if_fail(greg!=REG_ESP,FALSE);
		ucontext->uc_mcontext.gregs[greg]=(greg_t)0;	/* ==libcaptive version of KeGetCurrentProcessorNumber() */
		return TRUE;
		}
	if (fsmem==(const void *)0x00000124) {	/* =='KeGetCurrentKPCR()->CurrentThread' */
		g_return_val_if_fail(greg!=REG_ESP,FALSE);
		ucontext->uc_mcontext.gregs[greg]=(greg_t)captive_KeGetCurrentKPCR()->CurrentThread;
		return TRUE;
		}
	g_return_val_if_reached(FALSE);
}

static gboolean instr_push_fsmem(const void *fsmem,struct ucontext *ucontext)
{
	if (fsmem==(const void *)0x00000000) {	/* exception stack top pointer */
		ucontext->uc_mcontext.gregs[REG_ESP]-=4;
		*(greg_t *)ucontext->uc_mcontext.gregs[REG_ESP]=fs_KPCR_ExceptionList;
		return TRUE;
		}
	g_return_val_if_reached(FALSE);
}

static gboolean instr_pop_fsmem(const void *fsmem,struct ucontext *ucontext)
{
	if (fsmem==(const void *)0x00000000) {	/* exception stack top pointer */
		fs_KPCR_ExceptionList=*(greg_t *)ucontext->uc_mcontext.gregs[REG_ESP];
		ucontext->uc_mcontext.gregs[REG_ESP]+=4;
		return TRUE;
		}
	g_return_val_if_reached(FALSE);
}

static gboolean instr_incl_fsmem(const void *fsmem,struct ucontext *ucontext)
{
	if (fsmem==(const void *)0x00000638) {	/* Unknown638 */
		fs_KPCR_Unknown638++;
		return TRUE;
		}
	g_return_val_if_reached(FALSE);
}

static int op_regcode_to_greg(guint8 regcode)
{
	switch (regcode) {
		case 0x00: return REG_EAX;
		case 0x01: return REG_ECX;
		case 0x02: return REG_EDX;
		case 0x03: return REG_EBX;
		case 0x04: return REG_ESP;
		case 0x05: return REG_EBP;
		case 0x06: return REG_ESI;
		case 0x07: return REG_EDI;
		}
	g_return_val_if_reached(REG_EAX);
}

static void sigaction_SIGSEGV(int signo,siginfo_t *siginfo,struct ucontext *ucontext)
{
guint8 *reg_eip;
const void *reg_eip_aligned;
static const void *reg_eip_aligned_last_valid=NULL;	/* performance cache */

	g_return_if_fail(signo==SIGSEGV);
	g_return_if_fail(siginfo->si_signo==SIGSEGV);
	/* siginfo->si_code is weird, seen to have value 128 */

	reg_eip=(void *)ucontext->uc_mcontext.gregs[REG_EIP];

	/* 'reg_eip' is not yet PAGE_SIZE-aligned but we need the aligned ptr for captive_mmap_map_get().
	 * glib NOTE: YOU MAY NOT STORE POINTERS IN INTEGERS.
	 */
	reg_eip_aligned=(const void *)(((char *)reg_eip)-(GPOINTER_TO_UINT(reg_eip)&(PAGE_SIZE-1)));
	g_assert(reg_eip_aligned!=NULL);

	/* We do not expect any pages can get un-PROT_EXEC-ed
	 * and therefore we never invalidate our cache 'reg_eip_aligned_last_valid'.
	 */
	if (reg_eip_aligned_last_valid!=reg_eip_aligned) {
		g_return_if_fail(!(captive_mmap_map_get(reg_eip_aligned)&PROT_EXEC));
		reg_eip_aligned_last_valid=reg_eip_aligned;
		}
	
	/* all instruction notation comments are written in AT&T 'instr src,dest' syntax! */
	if (*reg_eip==0x64) {	/* prefix '%fs:' */
		reg_eip++;
		/* TODO:thread; %fs: is CPU-dependent */
		if (*reg_eip==0x0F) {	/* two-byte opcode */
			reg_eip++;
			if (*reg_eip==0xB6) {	/* ??? */
				reg_eip++;
				if (*reg_eip==0x05) {	/* movzbl %fs:{reg_eip[1..4]},%eax */
					reg_eip++;
					if (instr_mov_fsmem_to_greg(*(const void **)reg_eip,REG_EAX,ucontext)) {
						reg_eip+=4;
						goto ok;
						}
					g_assert_not_reached();
					}
				g_assert_not_reached();
				}
			g_assert_not_reached();
			}
		if (*reg_eip==0xA3) {	/* 'mov %eax,%fs:{reg_eip[1..4]}' */
			reg_eip++;
			if (instr_mov_greg_to_fsmem(REG_EAX,*(const void **)reg_eip,ucontext)) {
				reg_eip+=4;
				goto ok;
				}
			g_assert_not_reached();
			}
		if (*reg_eip==0x89) {	/* prefix 0x89 */
			reg_eip++;
			if ((*reg_eip & ~0x38)==0x05)	{ /* 'mov %{op_regcode_to_greg(*reg_eip[b3..b5])},%fs:{reg_eip[1..4]} */
				reg_eip++;
				if (instr_mov_greg_to_fsmem(op_regcode_to_greg(reg_eip[-1]>>3U),*(const void **)reg_eip,ucontext)) {
					reg_eip+=4;
					goto ok;
					}
				g_assert_not_reached();
				}
			g_assert_not_reached();
			}
		if (*reg_eip==0xA1) {	/* 'mov %fs:{reg_eip[1..4]},%eax' */
			reg_eip++;
			if (instr_mov_fsmem_to_greg(*(const void **)reg_eip,REG_EAX,ucontext)) {
				reg_eip+=4;
				goto ok;
				}
			g_assert_not_reached();
			}
		if (*reg_eip==0x8B) {	/* prefix 0x8B */
			reg_eip++;
			if ((*reg_eip & ~0x38)==0x05) {	/* 'mov %fs:{reg_eip[1..4]},%{op_regcode_to_greg(*reg_eip[b3..b5])}' */
				reg_eip++;
				if (instr_mov_fsmem_to_greg(*(const void **)reg_eip,op_regcode_to_greg(reg_eip[-1]>>3U),ucontext)) {
					reg_eip+=4;
					goto ok;
					}
				g_assert_not_reached();
				}
			g_assert_not_reached();
			}
		if (*reg_eip==0xFF) {	/* prefix 0xFF */
			reg_eip++;
			if (*reg_eip==0x05) {	/* 'incl %fs:{reg_eip[1..4]}' */
				reg_eip++;
				if (instr_incl_fsmem(*(const void **)reg_eip,ucontext)) {
					reg_eip+=4;
					goto ok;
					}
				g_assert_not_reached();
				}
			if (*reg_eip==0x35) {	/* 'pushl %fs:{reg_eip[1..4]}' */
				reg_eip++;
				if (instr_push_fsmem(*(const void **)reg_eip,ucontext)) {
					reg_eip+=4;
					goto ok;
					}
				g_assert_not_reached();
				}
			g_assert_not_reached();
			}
		if (*reg_eip==0x8F) {	/* prefix 0x0F */
			reg_eip++;
			if (*reg_eip==0x05) {	/* 'popl %fs:{reg_eip[1..4]}' */
				reg_eip++;
				if (instr_pop_fsmem(*(const void **)reg_eip,ucontext)) {
					reg_eip+=4;
					goto ok;
					}
				g_assert_not_reached();
				}
			g_assert_not_reached();
			}
		if (*reg_eip==0xC7) {	/* prefix 0xC7 */
			reg_eip++;
			if (*reg_eip==0x05) {	/* 'movl ${reg_eip[5..8]},%fs:{reg_eip[1..4]}' */
				reg_eip++;
				if (instr_mov_immed_to_fsmem(((greg_t *)reg_eip)[1],*(const void **)reg_eip,ucontext)) {
					reg_eip+=4+4;
					goto ok;
					}
				g_assert_not_reached();
				}
			g_assert_not_reached();
			}
		g_assert_not_reached();
		}

	/* all instruction notation comments are written in AT&T 'instr src,dest' syntax! */
	if (*reg_eip==0x66) {	/* prefix '%fs:' */
		reg_eip++;
		/* TODO:thread; %fs: is CPU-dependent */
		if (*reg_eip==0x8E) {	/* two-byte opcode */
			reg_eip++;
			if (*reg_eip==0xE3) {	/* 'mov %bx,%fs' */
				reg_eip++;
				g_assert(0x30==(0xFFFF&ucontext->uc_mcontext.gregs[REG_EBX]));
				/* 'reload' of %fs can be ignored */
				goto ok;
				}
			g_assert_not_reached();
			}
		g_assert_not_reached();
		}

	if (*reg_eip==0xF4) {	/* hlt; from captive_ModuleList_patch() */
struct captive_ModuleList_patchpoint *patchpoint;
const gchar *funcname_disabled;

		g_log(G_LOG_DOMAIN,G_LOG_LEVEL_DEBUG,"%s: reg_eip=%p; 0xF4 hit",G_STRLOC,reg_eip);

		if ((funcname_disabled=captive_ModuleList_function_disable_find(
						reg_eip)))	{ /* ExportAddress */
			g_error("%s: Reached disabled W32 function: %s",G_STRLOC,funcname_disabled);
			g_assert_not_reached();
			}
		patchpoint=captive_ModuleList_patchpoint_find(
				reg_eip);	/* ExportAddress */
		g_assert(patchpoint!=NULL);
		if (reg_eip==patchpoint->orig_w32_func) {
			g_assert(0xF4 /* hlt */ ==*patchpoint->orig_w32_func);
			g_assert(patchpoint->orig_w32_2ndinstr_byte ==*patchpoint->orig_w32_2ndinstr);
			if (patchpoint->through_w32_func) {
				*patchpoint->orig_w32_func=patchpoint->orig_w32_func_byte;
				*patchpoint->orig_w32_2ndinstr=0xF4;	/* hlt */
				}
			else {	/* !patchpoint->through_w32_func */
				reg_eip=(guint8 *)patchpoint->wrap_wrap_func;
				}
			goto ok;
			}
		if (reg_eip==patchpoint->orig_w32_2ndinstr) {
			g_assert(patchpoint->orig_w32_func_byte ==*patchpoint->orig_w32_func);
			g_assert(0xF4 /* hlt */ ==*patchpoint->orig_w32_2ndinstr);
			g_assert(patchpoint->through_w32_func==TRUE);
			*patchpoint->orig_w32_func=0xF4;	/* hlt */
			*patchpoint->orig_w32_2ndinstr=patchpoint->orig_w32_2ndinstr_byte;
			patchpoint->through_w32_func=FALSE;
			goto ok;
			}
		g_assert_not_reached();
		}

	if (*reg_eip==0xFA) {	/* cli */
		g_log(G_LOG_DOMAIN,G_LOG_LEVEL_DEBUG,"%s: reg_eip=%p; CLI neutralized",G_STRLOC,reg_eip);
		*reg_eip=0x90;	/* nop */
		goto ok;
		}

	if (*reg_eip==0xFB) {	/* sti */
		g_log(G_LOG_DOMAIN,G_LOG_LEVEL_DEBUG,"%s: reg_eip=%p; STI neutralized",G_STRLOC,reg_eip);
		*reg_eip=0x90;	/* nop */
		goto ok;
		}

	g_assert_not_reached();

ok:
	ucontext->uc_mcontext.gregs[REG_EIP]=(greg_t)reg_eip;
	/* success */
}

/**
 * captive_signal_init:
 *
 * Initialize UNIX signal handling to be able to emulate foreign W32
 * instructions. These instructions must be located inside address
 * space of foreign W32 binary code which is identified by successful
 * call to captive_mmap_map_get() returning #PROT_EXEC bit set.
 * This bit should be set from MmAllocateSection() called from
 * ntoskrnl/ldr/loader.c/LdrPEProcessModule().
 *
 * Currently emulated set is the access to %fs register offset %0
 * where the exception stack top pointer is located.
 *
 * Returns: %TRUE if successful.
 */
gboolean captive_signal_init(void)
{
gint errint;
struct sigaction sigaction_struct;
sigset_t sigset;

	CAPTIVE_MEMZERO(&sigaction_struct);	/* this structure may have unpredictable fields */

	/* Init 'sigaction_struct.sa_mask'. */
	errint=sigemptyset(&sigaction_struct.sa_mask);
	g_return_val_if_fail(errint==0,FALSE);
	errint=sigaddset(&sigaction_struct.sa_mask,SIGSEGV);
	g_return_val_if_fail(errint==0,FALSE);

	/* Set the signal sigaction handler. */
	sigaction_struct.sa_sigaction=(void (*)(int,siginfo_t *,void *))sigaction_SIGSEGV;
	sigaction_struct.sa_flags=0
			|SA_SIGINFO;	/* Use 'sa_sigaction' (not 'sa_handler') */
	errint=sigaction(SIGSEGV,
			&sigaction_struct,	/* act */
			NULL);	/* oldact */
	g_return_val_if_fail(errint==0,FALSE);

	/* Enable SIGSEGV signal (should be default). */
	errint=sigemptyset(&sigset);
	g_return_val_if_fail(errint==0,FALSE);
	errint=sigaddset(&sigset,SIGSEGV);
	g_return_val_if_fail(errint==0,FALSE);
	errint=sigprocmask(SIG_UNBLOCK,
			&sigset,	/* set */
			NULL);	/* oldset */
	g_return_val_if_fail(errint==0,FALSE);

	return TRUE;
}