/*
	File:		MoreAddrToSym.c

	Contains:	Code for mapping addresses to their symbolic names.

	Written by:	DTS

	Copyright:	Copyright (c) 2006 by Apple Computer, Inc., All Rights Reserved.

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	Change History (most recent first):

$Log: MoreAddrToSym.c,v $
Revision 1.2  2006/01/22 22:47:13  eskimo1
Significant rewrite to account for changes in MoreBacktrace.  Still not as functional as I'd like.

Revision 1.1  2003/04/04 15:02:57  eskimo1
First checked in.  This code still has bugs, but I've written enough code that checking in is a good idea.


*/

/////////////////////////////////////////////////////////////////

// Our Prototypes

#include "MoreAddrToSym.h"

// Mac OS Interfaces

#include <assert.h>
#include <string.h>
#include <stdbool.h>
#include <errno.h>
#include <stdlib.h>
#include <mach-o/dyld.h>
#include <mach-o/loader.h>
#include <mach-o/nlist.h>
#include <mach-o/stab.h>

// MIB Prototypes

/////////////////////////////////////////////////////////////////

extern int  MoreAToSCreate(size_t count, MoreAToSSymInfo *symbols[])
	// See comments in header.
{
	int err;
	
	assert(symbols != NULL);
	assert(*symbols == NULL);
	
	err = 0;
	*symbols = calloc(count, sizeof(MoreAToSSymInfo));
	if (*symbols == NULL) {
		err = ENOMEM;
	}
	
	assert( (err == 0) == (*symbols != NULL) );
	
	return err;
}

extern void MoreAToSDestroy(size_t count, MoreAToSSymInfo symbols[])
	// See comments in header.
{
	size_t index;

	if (symbols != NULL) {
		for (index = 0; index < count; index++) {
			free( (void *) symbols[index].symbolName );
		}
		free(symbols);
	}
}

static int ReplaceSymbolIfBetter(
	MoreAToSSymInfo *	existingSymbol, 
	MoreAToSSymbolType	symbolType, 
	const char *		symbolName, 
	MoreAToSOffset		symbolOffset
)
	// Check to see whether the symbolic information defined by symbolType, 
	// symbolName, and symbolOffset is 'better' than the symbolic information 
	// in existingSymbol.  If so, replace the old information with the new. 
	// In this case, 'better' is defined as being having a smaller 
	// symbolOffset, that is, we've found a symbol that's closer to the 
	// requested address.
	//
	// The idea behind this code is that one day I'll come up with multiple 
	// ways to get at symbolic information, and then I'll only keep the best 
	// result.  However, I don't really use this functionality yet.
{
	int		err;
	bool	replace;
	
	assert(existingSymbol != NULL);
	assert(symbolType     != kMoreAToSNoSymbol);
	assert(symbolName     != NULL);
	assert( (existingSymbol->symbolType == kMoreAToSNoSymbol) == (existingSymbol->symbolName == NULL) );
	
	err = 0;
	
	if (existingSymbol->symbolType == kMoreAToSNoSymbol) {
		replace = true;
	} else {
		replace = (symbolOffset < existingSymbol->symbolOffset);
	}
	
	if (replace) {
		char *	tmp;
		
		tmp = strdup(symbolName);
		if (tmp == NULL) {
			err = ENOMEM;
		} else {
			free( (void *) existingSymbol->symbolName );
			
			existingSymbol->symbolType   = symbolType;
			existingSymbol->symbolName   = tmp;
			existingSymbol->symbolOffset = symbolOffset;
		}
	}
	
	return err;
}

// FindOwnerOfPC and GetFunctionName countesy of Ed Wynne.  Don't ask me 
// how it works, or I'll start to whimper.  Actually, I have a fairly good idea 
// how it works, and a fairly good idea how to fix its more serious problems, 
// but I just don't have time at the moment.

static const struct mach_header *FindOwnerOfPC(unsigned int pc)
{
	unsigned int				count,index,offset,cmdex;
	struct segment_command *	seg;
	struct load_command	*		cmd;
	const struct mach_header *	header;
	
	count = _dyld_image_count();
	for (index = 0;index < count;index += 1)
	{
		header = _dyld_get_image_header(index);
		offset = _dyld_get_image_vmaddr_slide(index);
		cmd = (struct load_command*)((char*)header + sizeof(struct mach_header));
		for (cmdex = 0;cmdex < header->ncmds;cmdex += 1,cmd = (struct load_command*)((char*)cmd + cmd->cmdsize))
		{
			switch(cmd->cmd)
			{
				case LC_SEGMENT:
					seg = (struct segment_command*)cmd;
					if ((pc >= (seg->vmaddr + offset)) && (pc < (seg->vmaddr + offset + seg->vmsize)))
						return header;
					break;
			}
		}
	}
	
	return NULL;
}

static const char *GetFunctionName(unsigned int pc,unsigned int *offset, bool *publicSymbol)
{
	struct segment_command	*seg_linkedit = NULL;
	struct segment_command	*seg_text = NULL;
	struct symtab_command	*symtab = NULL;
	struct load_command		*cmd;
	const struct mach_header*header;
	unsigned int			vm_slide,file_slide;
	struct nlist			*sym,*symbase;
	char					*strings,*name;
	unsigned int			base,index;
	
	header = FindOwnerOfPC(pc);
	if (header != NULL)
	{
		cmd = (struct load_command*)((char*)header + sizeof(struct mach_header));
		for (index = 0;index < header->ncmds;index += 1,cmd = (struct load_command*)((char*)cmd + cmd->cmdsize))
		{
			switch(cmd->cmd)
			{
				case LC_SEGMENT:
					if (!strcmp(((struct segment_command*)cmd)->segname,SEG_TEXT))
						seg_text = (struct segment_command*)cmd;
					else if (!strcmp(((struct segment_command*)cmd)->segname,SEG_LINKEDIT))
						seg_linkedit = (struct segment_command*)cmd;
					break;
				
				case LC_SYMTAB:
					symtab = (struct symtab_command*)cmd;
					break;
			}
		}
		
		if ((seg_text == NULL) || (seg_linkedit == NULL) || (symtab == NULL))
		{
			*offset = 0;
			return NULL;
		}
		
		vm_slide = (unsigned long)header - (unsigned long)seg_text->vmaddr;
		file_slide = ((unsigned long)seg_linkedit->vmaddr - (unsigned long)seg_text->vmaddr) - seg_linkedit->fileoff;
		symbase = (struct nlist*)((unsigned long)header + (symtab->symoff + file_slide));
		strings = (char*)((unsigned long)header + (symtab->stroff + file_slide));
		
		// Look for a global symbol.
		for (index = 0,sym = symbase;index < symtab->nsyms;index += 1,sym += 1)
		{
			if (sym->n_type != N_FUN)
				continue;
			
			name = sym->n_un.n_strx ? (strings + sym->n_un.n_strx) : NULL;
			base = sym->n_value + vm_slide;
			
			for (index += 1,sym += 1;index < symtab->nsyms;index += 1,sym += 1)
				if (sym->n_type == N_FUN)
					break;
			
			if ((pc >= base) && (pc <= (base + sym->n_value)) && (name != NULL) && (strlen(name) > 0))
			{
				*offset = pc - base;
				*publicSymbol = true;
				return strdup(name);
			}
		}
		
		// Look for a reasonably close private symbol.
		for (name = NULL,base = 0xFFFFFFFF,index = 0,sym = symbase;index < symtab->nsyms;index += 1,sym += 1)
		{
			if ((sym->n_type & 0x0E) != 0x0E)
				continue;
			
			if ((sym->n_value + vm_slide) > pc)
				continue;
			
			if ((base != 0xFFFFFFFF) && ((pc - (sym->n_value + vm_slide)) >= (pc - base)))
				continue;
			
			name = sym->n_un.n_strx ? (strings + sym->n_un.n_strx) : NULL;
			base = sym->n_value + vm_slide;
		}
		
		*offset = pc - base;
		*publicSymbol = false;
		return (name != NULL) ? strdup(name) : NULL;
	}
	
	*offset = 0;
	return NULL;
}

extern int MoreAToSCopySymbolNamesUsingDyld(
	size_t			count, 
	MoreAToSAddr 	addresses[],
	MoreAToSSymInfo symbols[]
)
	// See comments in header.
{
	int 	err;
	size_t 	index;
	
	assert(addresses != NULL);
	assert(symbols != NULL);
	
	err = 0;
	for (index = 0; index < count; index++) {
		const char * 		thisSymbol;
		const char * 		cleanSymbol;
		unsigned int 		thisSymbolOffset;
		bool				thisSymbolPublic;
		MoreAToSSymbolType	thisSymbolType;
		
		thisSymbol = NULL;
		if (addresses[index] != 0) {		// NULL is never a useful symbol
			thisSymbol = GetFunctionName( (unsigned int) addresses[index], &thisSymbolOffset, &thisSymbolPublic);
		}
		if (thisSymbol != NULL) {
		
			// Mach-O symbols virtually always start with '_'.  If there's one there, 
			// let's strip it.
			
			if (thisSymbol[0] == '_') {
				cleanSymbol = &thisSymbol[1];
			} else {
				cleanSymbol = thisSymbol;
			}
			
			if (thisSymbolPublic) {
				thisSymbolType = kMoreAToSDyldPubliSymbol;
			} else {
				thisSymbolType = kMoreAToSDyldPrivateSymbol;
			}
			
			err = ReplaceSymbolIfBetter(&symbols[index], thisSymbolType, cleanSymbol, thisSymbolOffset);
		}
		
		free( (void *) thisSymbol);
		
		if (err != 0) {
			break;
		}
	}
	
	return err;
}