/*
 * @(#)dlfcn.c	1.7 revision of 95/08/14  19:08:38
 * This is an unpublished work copyright (c) 1992 HELIOS Software GmbH
 * 30159 Hannover, Germany
 */

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ldr.h>
#include <a.out.h>
#include <ldfcn.h>
#include "postgres.h"
#include "dynloader.h"

/*
 * We simulate dlopen() et al. through a call to load. Because AIX has
 * no call to find an exported symbol we read the loader section of the
 * loaded module and build a list of exported symbols and their virtual
 * address.
 */

typedef struct
{
	char	   *name;			/* the symbols's name */
	void	   *addr;			/* its relocated virtual address */
}			Export, *ExportPtr;

/*
 * xlC uses the following structure to list its constructors and
 * destructors. This is gleaned from the output of munch.
 */
typedef struct
{
	void		(*init) (void); /* call static constructors */
	void		(*term) (void); /* call static destructors */
}			Cdtor, *CdtorPtr;

/*
 * The void * handle returned from dlopen is actually a ModulePtr.
 */
typedef struct Module
{
	struct Module *next;
	char	   *name;			/* module name for refcounting */
	int			refCnt;			/* the number of references */
	void	   *entry;			/* entry point from load */
	struct dl_info *info;		/* optional init/terminate functions */
	CdtorPtr	cdtors;			/* optional C++ constructors */
	int			nExports;		/* the number of exports found */
	ExportPtr	exports;		/* the array of exports */
}			Module, *ModulePtr;

/*
 * We keep a list of all loaded modules to be able to call the fini
 * handlers and destructors at atexit() time.
 */
static ModulePtr modList;

/*
 * The last error from one of the dl* routines is kept in static
 * variables here. Each error is returned only once to the caller.
 */
static char errbuf[BUFSIZ];
static int	errvalid;

extern char *strdup(const char *);
static void caterr(char *);
static int	readExports(ModulePtr);
static void terminate(void);
static void *findMain(void);

void *
dlopen(const char *path, int mode)
{
	ModulePtr	mp;
	static void *mainModule;

	/*
	 * Upon the first call register a terminate handler that will close
	 * all libraries. Also get a reference to the main module for use with
	 * loadbind.
	 */
	if (!mainModule)
	{
		if ((mainModule = findMain()) == NULL)
			return NULL;
		atexit(terminate);
	}

	/*
	 * Scan the list of modules if we have the module already loaded.
	 */
	for (mp = modList; mp; mp = mp->next)
		if (strcmp(mp->name, path) == 0)
		{
			mp->refCnt++;
			return mp;
		}
	if ((mp = (ModulePtr) calloc(1, sizeof(*mp))) == NULL)
	{
		errvalid++;
		strcpy(errbuf, "calloc: ");
		strcat(errbuf, strerror(errno));
		return NULL;
	}
	if ((mp->name = strdup(path)) == NULL)
	{
		errvalid++;
		strcpy(errbuf, "strdup: ");
		strcat(errbuf, strerror(errno));
		free(mp);
		return NULL;
	}

	/*
	 * load should be declared load(const char *...). Thus we cast the
	 * path to a normal char *. Ugly.
	 */
	if ((mp->entry = (void *) load((char *) path, L_NOAUTODEFER, NULL)) == NULL)
	{
		free(mp->name);
		free(mp);
		errvalid++;
		strcpy(errbuf, "dlopen: ");
		strcat(errbuf, path);
		strcat(errbuf, ": ");

		/*
		 * If AIX says the file is not executable, the error can be
		 * further described by querying the loader about the last error.
		 */
		if (errno == ENOEXEC)
		{
			char	   *tmp[BUFSIZ / sizeof(char *)];

			if (loadquery(L_GETMESSAGES, tmp, sizeof(tmp)) == -1)
				strcpy(errbuf, strerror(errno));
			else
			{
				char	  **p;

				for (p = tmp; *p; p++)
					caterr(*p);
			}
		}
		else
			strcat(errbuf, strerror(errno));
		return NULL;
	}
	mp->refCnt = 1;
	mp->next = modList;
	modList = mp;
	if (loadbind(0, mainModule, mp->entry) == -1)
	{
		dlclose(mp);
		errvalid++;
		strcpy(errbuf, "loadbind: ");
		strcat(errbuf, strerror(errno));
		return NULL;
	}

	/*
	 * If the user wants global binding, loadbind against all other loaded
	 * modules.
	 */
	if (mode & RTLD_GLOBAL)
	{
		ModulePtr	mp1;

		for (mp1 = mp->next; mp1; mp1 = mp1->next)
			if (loadbind(0, mp1->entry, mp->entry) == -1)
			{
				dlclose(mp);
				errvalid++;
				strcpy(errbuf, "loadbind: ");
				strcat(errbuf, strerror(errno));
				return NULL;
			}
	}
	if (readExports(mp) == -1)
	{
		dlclose(mp);
		return NULL;
	}

	/*
	 * If there is a dl_info structure, call the init function.
	 */
	if (mp->info = (struct dl_info *) dlsym(mp, "dl_info"))
	{
		if (mp->info->init)
			(*mp->info->init) ();
	}
	else
		errvalid = 0;

	/*
	 * If the shared object was compiled using xlC we will need to call
	 * static constructors (and later on dlclose destructors).
	 */
	if (mp->cdtors = (CdtorPtr) dlsym(mp, "__cdtors"))
	{
		while (mp->cdtors->init)
		{
			(*mp->cdtors->init) ();
			mp->cdtors++;
		}
	}
	else
		errvalid = 0;
	return mp;
}

/*
 * Attempt to decipher an AIX loader error message and append it
 * to our static error message buffer.
 */
static void
caterr(char *s)
{
	char	   *p = s;

	while (*p >= '0' && *p <= '9')
		p++;
	switch (atoi(s))
	{
		case L_ERROR_TOOMANY:
			strcat(errbuf, "to many errors");
			break;
		case L_ERROR_NOLIB:
			strcat(errbuf, "can't load library");
			strcat(errbuf, p);
			break;
		case L_ERROR_UNDEF:
			strcat(errbuf, "can't find symbol");
			strcat(errbuf, p);
			break;
		case L_ERROR_RLDBAD:
			strcat(errbuf, "bad RLD");
			strcat(errbuf, p);
			break;
		case L_ERROR_FORMAT:
			strcat(errbuf, "bad exec format in");
			strcat(errbuf, p);
			break;
		case L_ERROR_ERRNO:
			strcat(errbuf, strerror(atoi(++p)));
			break;
		default:
			strcat(errbuf, s);
			break;
	}
}

void *
dlsym(void *handle, const char *symbol)
{
	ModulePtr	mp = (ModulePtr) handle;
	ExportPtr	ep;
	int			i;

	/*
	 * Could speed up the search, but I assume that one assigns the result
	 * to function pointers anyways.
	 */
	for (ep = mp->exports, i = mp->nExports; i; i--, ep++)
		if (strcmp(ep->name, symbol) == 0)
			return ep->addr;
	errvalid++;
	strcpy(errbuf, "dlsym: undefined symbol ");
	strcat(errbuf, symbol);
	return NULL;
}

char *
dlerror(void)
{
	if (errvalid)
	{
		errvalid = 0;
		return errbuf;
	}
	return NULL;
}

int
dlclose(void *handle)
{
	ModulePtr	mp = (ModulePtr) handle;
	int			result;
	ModulePtr	mp1;

	if (--mp->refCnt > 0)
		return 0;
	if (mp->info && mp->info->fini)
		(*mp->info->fini) ();
	if (mp->cdtors)
		while (mp->cdtors->term)
		{
			(*mp->cdtors->term) ();
			mp->cdtors++;
		}
	result = unload(mp->entry);
	if (result == -1)
	{
		errvalid++;
		strcpy(errbuf, strerror(errno));
	}
	if (mp->exports)
	{
		ExportPtr	ep;
		int			i;

		for (ep = mp->exports, i = mp->nExports; i; i--, ep++)
			if (ep->name)
				free(ep->name);
		free(mp->exports);
	}
	if (mp == modList)
		modList = mp->next;
	else
	{
		for (mp1 = modList; mp1; mp1 = mp1->next)
			if (mp1->next == mp)
			{
				mp1->next = mp->next;
				break;
			}
	}
	free(mp->name);
	free(mp);
	return result;
}

static void
terminate(void)
{
	while (modList)
		dlclose(modList);
}

/*
 * Build the export table from the XCOFF .loader section.
 */
static int
readExports(ModulePtr mp)
{
	LDFILE	   *ldp = NULL;
	SCNHDR		sh,
				shdata;
	LDHDR	   *lhp;
	char	   *ldbuf;
	LDSYM	   *ls;
	int			i;
	ExportPtr	ep;

	if ((ldp = ldopen(mp->name, ldp)) == NULL)
	{
		struct ld_info *lp;
		char	   *buf;
		int			size = 4 * 1024;

		if (errno != ENOENT)
		{
			errvalid++;
			strcpy(errbuf, "readExports: ");
			strcat(errbuf, strerror(errno));
			return -1;
		}

		/*
		 * The module might be loaded due to the LIBPATH environment
		 * variable. Search for the loaded module using L_GETINFO.
		 */
		if ((buf = malloc(size)) == NULL)
		{
			errvalid++;
			strcpy(errbuf, "readExports: ");
			strcat(errbuf, strerror(errno));
			return -1;
		}
		while ((i = loadquery(L_GETINFO, buf, size)) == -1 && errno == ENOMEM)
		{
			free(buf);
			size += 4 * 1024;
			if ((buf = malloc(size)) == NULL)
			{
				errvalid++;
				strcpy(errbuf, "readExports: ");
				strcat(errbuf, strerror(errno));
				return -1;
			}
		}
		if (i == -1)
		{
			errvalid++;
			strcpy(errbuf, "readExports: ");
			strcat(errbuf, strerror(errno));
			free(buf);
			return -1;
		}

		/*
		 * Traverse the list of loaded modules. The entry point returned
		 * by load() does actually point to the data segment origin.
		 */
		lp = (struct ld_info *) buf;
		while (lp)
		{
			if (lp->ldinfo_dataorg == mp->entry)
			{
				ldp = ldopen(lp->ldinfo_filename, ldp);
				break;
			}
			if (lp->ldinfo_next == 0)
				lp = NULL;
			else
				lp = (struct ld_info *) ((char *) lp + lp->ldinfo_next);
		}
		free(buf);
		if (!ldp)
		{
			errvalid++;
			strcpy(errbuf, "readExports: ");
			strcat(errbuf, strerror(errno));
			return -1;
		}
	}
	if (TYPE(ldp) != U802TOCMAGIC)
	{
		errvalid++;
		strcpy(errbuf, "readExports: bad magic");
		while (ldclose(ldp) == FAILURE)
			;
		return -1;
	}

	/*
	 * Get the padding for the data section. This is needed for AIX 4.1
	 * compilers. This is used when building the final function pointer to
	 * the exported symbol.
	 */
	if (ldnshread(ldp, _DATA, &shdata) != SUCCESS)
	{
		errvalid++;
		strcpy(errbuf, "readExports: cannot read data section header");
		while (ldclose(ldp) == FAILURE)
			;
		return -1;
	}
	if (ldnshread(ldp, _LOADER, &sh) != SUCCESS)
	{
		errvalid++;
		strcpy(errbuf, "readExports: cannot read loader section header");
		while (ldclose(ldp) == FAILURE)
			;
		return -1;
	}

	/*
	 * We read the complete loader section in one chunk, this makes
	 * finding long symbol names residing in the string table easier.
	 */
	if ((ldbuf = (char *) malloc(sh.s_size)) == NULL)
	{
		errvalid++;
		strcpy(errbuf, "readExports: ");
		strcat(errbuf, strerror(errno));
		while (ldclose(ldp) == FAILURE)
			;
		return -1;
	}
	if (FSEEK(ldp, sh.s_scnptr, BEGINNING) != OKFSEEK)
	{
		errvalid++;
		strcpy(errbuf, "readExports: cannot seek to loader section");
		free(ldbuf);
		while (ldclose(ldp) == FAILURE)
			;
		return -1;
	}
	if (FREAD(ldbuf, sh.s_size, 1, ldp) != 1)
	{
		errvalid++;
		strcpy(errbuf, "readExports: cannot read loader section");
		free(ldbuf);
		while (ldclose(ldp) == FAILURE)
			;
		return -1;
	}
	lhp = (LDHDR *) ldbuf;
	ls = (LDSYM *) (ldbuf + LDHDRSZ);

	/*
	 * Count the number of exports to include in our export table.
	 */
	for (i = lhp->l_nsyms; i; i--, ls++)
	{
		if (!LDR_EXPORT(*ls))
			continue;
		mp->nExports++;
	}
	if ((mp->exports = (ExportPtr) calloc(mp->nExports, sizeof(*mp->exports))) == NULL)
	{
		errvalid++;
		strcpy(errbuf, "readExports: ");
		strcat(errbuf, strerror(errno));
		free(ldbuf);
		while (ldclose(ldp) == FAILURE)
			;
		return -1;
	}

	/*
	 * Fill in the export table. All entries are relative to the entry
	 * point we got from load.
	 */
	ep = mp->exports;
	ls = (LDSYM *) (ldbuf + LDHDRSZ);
	for (i = lhp->l_nsyms; i; i--, ls++)
	{
		char	   *symname;
		char		tmpsym[SYMNMLEN + 1];

		if (!LDR_EXPORT(*ls))
			continue;
		if (ls->l_zeroes == 0)
			symname = ls->l_offset + lhp->l_stoff + ldbuf;
		else
		{

			/*
			 * The l_name member is not zero terminated, we must copy the
			 * first SYMNMLEN chars and make sure we have a zero byte at
			 * the end.
			 */
			StrNCpy(tmpsym, ls->l_name, SYMNMLEN + 1);
			symname = tmpsym;
		}
		ep->name = strdup(symname);
		ep->addr = (void *) ((unsigned long) mp->entry +
							 ls->l_value - shdata.s_vaddr);
		ep++;
	}
	free(ldbuf);
	while (ldclose(ldp) == FAILURE)
		;
	return 0;
}

/*
 * Find the main modules entry point. This is used as export pointer
 * for loadbind() to be able to resolve references to the main part.
 */
static void *
findMain(void)
{
	struct ld_info *lp;
	char	   *buf;
	int			size = 4 * 1024;
	int			i;
	void	   *ret;

	if ((buf = malloc(size)) == NULL)
	{
		errvalid++;
		strcpy(errbuf, "findMain: ");
		strcat(errbuf, strerror(errno));
		return NULL;
	}
	while ((i = loadquery(L_GETINFO, buf, size)) == -1 && errno == ENOMEM)
	{
		free(buf);
		size += 4 * 1024;
		if ((buf = malloc(size)) == NULL)
		{
			errvalid++;
			strcpy(errbuf, "findMain: ");
			strcat(errbuf, strerror(errno));
			return NULL;
		}
	}
	if (i == -1)
	{
		errvalid++;
		strcpy(errbuf, "findMain: ");
		strcat(errbuf, strerror(errno));
		free(buf);
		return NULL;
	}

	/*
	 * The first entry is the main module. The entry point returned by
	 * load() does actually point to the data segment origin.
	 */
	lp = (struct ld_info *) buf;
	ret = lp->ldinfo_dataorg;
	free(buf);
	return ret;
}
