path: root/unix/tclLoadAout.c

/* 
 * tclLoadAout.c --
 *
 *	This procedure provides a version of the TclLoadFile that
 *	provides pseudo-static linking using version-7 compatible
 *	a.out files described in either sys/exec.h or sys/a.out.h.
 *
 * Copyright (c) 1995, by General Electric Company. All rights reserved.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * This work was supported in part by the ARPA Manufacturing Automation
 * and Design Engineering (MADE) Initiative through ARPA contract
 * F33615-94-C-4400.
 *
 * RCS: @(#) $Id: tclLoadAout.c,v 1.14 2002/10/10 12:25:53 vincentdarley Exp $
 */

#include "tclInt.h"
#include <fcntl.h>
#ifdef HAVE_EXEC_AOUT_H
#   include <sys/exec_aout.h>
#endif
#ifdef HAVE_UNISTD_H
#   include <unistd.h>
#else
#   include "../compat/unistd.h"
#endif

/*
 * Some systems describe the a.out header in sys/exec.h, and some in
 * a.out.h.
 */

#ifdef USE_SYS_EXEC_H
#include <sys/exec.h>
#endif
#ifdef USE_A_OUT_H
#include <a.out.h>
#endif
#ifdef USE_SYS_EXEC_AOUT_H
#include <sys/exec_aout.h>
#define a_magic a_midmag
#endif

/*
 * TCL_LOADSHIM is the amount by which to shim the break when loading
 */

#ifndef TCL_LOADSHIM
#define TCL_LOADSHIM 0x4000L
#endif

/*
 * TCL_LOADALIGN must be a power of 2, and is the alignment to which
 * to force the origin of load modules
 */

#ifndef TCL_LOADALIGN
#define TCL_LOADALIGN 0x4000L
#endif

/*
 * TCL_LOADMAX is the maximum size of a load module, and is used as
 * a sanity check when loading
 */

#ifndef TCL_LOADMAX
#define TCL_LOADMAX 2000000L
#endif

/*
 * Kernel calls that appear to be missing from the system .h files:
 */

extern char * brk _ANSI_ARGS_((char *));
extern char * sbrk _ANSI_ARGS_((size_t));

/*
 * The static variable SymbolTableFile contains the file name where the
 * result of the last link was stored.  The file is kept because doing so
 * allows one load module to use the symbols defined in another.
 */

static char * SymbolTableFile = NULL;

/*
 * Type of the dictionary function that begins each load module.
 */

typedef Tcl_PackageInitProc * (* DictFn) _ANSI_ARGS_ ((CONST char * symbol));

/*
 * Prototypes for procedures referenced only in this file:
 */

static int FindLibraries _ANSI_ARGS_((Tcl_Interp * interp, Tcl_Obj * pathPtr,
				      Tcl_DString * buf));
static void UnlinkSymbolTable _ANSI_ARGS_((void));

/*
 *----------------------------------------------------------------------
 *
 * TclpDlopen --
 *
 *	Dynamically loads a binary code file into memory and returns
 *	a handle to the new code.
 *
 * Results:
 *	A standard Tcl completion code.  If an error occurs, an error
 *	message is left in the interp's result. 
 *
 * Side effects:
 *	New code suddenly appears in memory.
 *
 *
 * Bugs:
 *	This function does not attempt to handle the case where the
 *	BSS segment is not executable.  It will therefore fail on
 *	Encore Multimax, Pyramid 90x, and similar machines.  The
 *	reason is that the mprotect() kernel call, which would
 *	otherwise be employed to mark the newly-loaded text segment
 *	executable, results in a system crash on BSD/386.
 *
 *	In an effort to make it fast, this function eschews the
 *	technique of linking the load module once, reading its header
 *	to determine its size, allocating memory for it, and linking
 *	it again.  Instead, it `shims out' memory allocation by
 *	placing the module TCL_LOADSHIM bytes beyond the break,
 *	and assuming that any malloc() calls required to run the
 *	linker will not advance the break beyond that point.  If
 *	the break is advanced beyonnd that point, the load will
 *	fail with an `inconsistent memory allocation' error.
 *	It perhaps ought to retry the link, but the failure has
 *	not been observed in two years of daily use of this function.
 *----------------------------------------------------------------------
 */

int
TclpDlopen(interp, pathPtr, loadHandle, unloadProcPtr)
    Tcl_Interp *interp;		/* Used for error reporting. */
    Tcl_Obj *pathPtr;		/* Name of the file containing the desired
				 * code (UTF-8). */
    Tcl_LoadHandle *loadHandle;	/* Filled with token for dynamically loaded
				 * file which will be passed back to 
				 * (*unloadProcPtr)() to unload the file. */
    Tcl_FSUnloadFileProc **unloadProcPtr;	
				/* Filled with address of Tcl_FSUnloadFileProc
				 * function which should be used for
				 * this file. */
{
    char * inputSymbolTable;	/* Name of the file containing the 
				 * symbol table from the last link. */
    Tcl_DString linkCommandBuf;	/* Command to do the run-time relocation
				 * of the module.*/
    char * linkCommand;
    char relocatedFileName [L_tmpnam];
				/* Name of the file holding the relocated */
				/* text of the module */
    int relocatedFd;		/* File descriptor of the file holding
				 * relocated text */
    struct exec relocatedHead;	/* Header of the relocated text */
    unsigned long relocatedSize;/* Size of the relocated text */
    char * startAddress;	/* Starting address of the module */
    int status;			/* Status return from Tcl_ calls */
    char * p;

    /* Find the file that contains the symbols for the run-time link. */
    
    if (SymbolTableFile != NULL) {
	inputSymbolTable = SymbolTableFile;
    } else if (tclExecutableName == NULL) {
	Tcl_SetResult (interp, "can't find the tclsh executable", TCL_STATIC);
	return TCL_ERROR;
    } else {
	inputSymbolTable = tclExecutableName;
    }
    
    /* Construct the `ld' command that builds the relocated module */
    
    tmpnam (relocatedFileName);
    Tcl_DStringInit (&linkCommandBuf);
    Tcl_DStringAppend (&linkCommandBuf, "exec ld -o ", -1);
    Tcl_DStringAppend (&linkCommandBuf, relocatedFileName, -1);
#if defined(__mips) || defined(mips)
    Tcl_DStringAppend (&linkCommandBuf, " -G 0 ", -1);
#endif
    Tcl_DStringAppend (&linkCommandBuf, " -u TclLoadDictionary_", -1);
    TclGuessPackageName(Tcl_GetString(pathPtr), &linkCommandBuf);
    Tcl_DStringAppend (&linkCommandBuf, " -A ", -1);
    Tcl_DStringAppend (&linkCommandBuf, inputSymbolTable, -1);
    Tcl_DStringAppend (&linkCommandBuf, " -N -T XXXXXXXX ", -1);
    Tcl_DStringAppend (&linkCommandBuf, Tcl_GetString(pathPtr), -1);
    Tcl_DStringAppend (&linkCommandBuf, " ", -1);
    
    if (FindLibraries (interp, pathPtr, &linkCommandBuf) != TCL_OK) {
	Tcl_DStringFree (&linkCommandBuf);
	return TCL_ERROR;
    }
    
    linkCommand = Tcl_DStringValue (&linkCommandBuf);
    
    /* Determine the starting address, and plug it into the command */
    
    startAddress = (char *) (((unsigned long) sbrk (0)
			      + TCL_LOADSHIM + TCL_LOADALIGN - 1)
			     & (- TCL_LOADALIGN));
    p = strstr (linkCommand, "-T") + 3;
    sprintf (p, "%08lx", (long) startAddress);
    p [8] = ' ';
    
    /* Run the linker */
    
    status = Tcl_Eval (interp, linkCommand);
    Tcl_DStringFree (&linkCommandBuf);
    if (status != 0) {
	return TCL_ERROR;
    }
    
    /* Open the linker's result file and read the header */
    
    relocatedFd = open (relocatedFileName, O_RDONLY);
    if (relocatedFd < 0) {
	goto ioError;
    }
    status= read (relocatedFd, (char *) & relocatedHead, sizeof relocatedHead);
    if (status < sizeof relocatedHead) {
	goto ioError;
    }
    
    /* Check the magic number */
    
    if (relocatedHead.a_magic != OMAGIC) {
	Tcl_AppendResult (interp, "bad magic number in intermediate file \"",
			  relocatedFileName, "\"", (char *) NULL);
	goto failure;
    }
    
    /* Make sure that memory allocation is still consistent */
    
    if ((unsigned long) sbrk (0) > (unsigned long) startAddress) {
	Tcl_SetResult (interp, "can't load, memory allocation is inconsistent.",
		       TCL_STATIC);
	goto failure;
    }
    
    /* Make sure that the relocated module's size is reasonable */
    
    relocatedSize = relocatedHead.a_text + relocatedHead.a_data
      + relocatedHead.a_bss;
    if (relocatedSize > TCL_LOADMAX) {
	Tcl_SetResult (interp, "module too big to load", TCL_STATIC);
	goto failure;
    }
    
    /* Advance the break to protect the loaded module */
    
    (void) brk (startAddress + relocatedSize);
    
    /*
     * Seek to the start of the module's text.
     *
     * Note that this does not really work with large files (i.e. where
     * lseek64 exists and is different to lseek), but anyone trying to
     * dynamically load a binary that is larger than what can fit in
     * addressable memory is in trouble anyway...
     */
    
#if defined(__mips) || defined(mips)
    status = lseek (relocatedFd,
		    (off_t) N_TXTOFF (relocatedHead.ex_f, relocatedHead.ex_o),
		    SEEK_SET);
#else
    status = lseek (relocatedFd, (off_t) N_TXTOFF (relocatedHead), SEEK_SET);
#endif
    if (status < 0) {
	goto ioError;
    }
    
    /* Read in the module's text and data */
    
    relocatedSize = relocatedHead.a_text + relocatedHead.a_data;
    if (read (relocatedFd, startAddress, relocatedSize) < relocatedSize) {
	brk (startAddress);
      ioError:
	Tcl_AppendResult (interp, "error on intermediate file \"",
			  relocatedFileName, "\": ", Tcl_PosixError (interp),
			  (char *) NULL);
      failure:
	(void) unlink (relocatedFileName);
	return TCL_ERROR;
    }
    
    /* Close the intermediate file. */
    
    (void) close (relocatedFd);
    
    /* Arrange things so that intermediate symbol tables eventually get
    * deleted. */
    
    if (SymbolTableFile != NULL) {
	UnlinkSymbolTable ();
    } else {
	atexit (UnlinkSymbolTable);
    }
    SymbolTableFile = ckalloc (strlen (relocatedFileName) + 1);
    strcpy (SymbolTableFile, relocatedFileName);
    
    *loadHandle = startAddress;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpFindSymbol --
 *
 *	Looks up a symbol, by name, through a handle associated with
 *	a previously loaded piece of code (shared library).
 *
 * Results:
 *	Returns a pointer to the function associated with 'symbol' if
 *	it is found.  Otherwise returns NULL and may leave an error
 *	message in the interp's result.
 *
 *----------------------------------------------------------------------
 */
Tcl_PackageInitProc*
TclpFindSymbol(interp, loadHandle, symbol) 
    Tcl_Interp *interp;
    Tcl_LoadHandle loadHandle;
    CONST char *symbol;
{
    /* Look up the entry point in the load module's dictionary. */
    DictFn dictionary = (DictFn) loadHandle;
    return (Tcl_PackageInitProc*) dictionary(sym1);
}


/*
 *------------------------------------------------------------------------
 *
 * FindLibraries --
 *
 *	Find the libraries needed to link a load module at run time.
 *
 * Results:
 *	A standard Tcl completion code.  If an error occurs,
 *	an error message is left in the interp's result.  The -l and -L
 *	flags are concatenated onto the dynamic string `buf'.
 *
 *------------------------------------------------------------------------
 */

static int
FindLibraries (interp, pathPtr, buf)
    Tcl_Interp * interp;	/* Used for error reporting */
    Tcl_Obj * pathPtr;		/* Name of the load module */
    Tcl_DString * buf;		/* Buffer where the -l an -L flags */
{
    FILE * f;			/* The load module */
    int c = 0;			/* Byte from the load module */
    char * p;
    CONST char *native;

    char *fileName = Tcl_GetString(pathPtr);
  
    /* Open the load module */
    
    native = Tcl_FSGetNativePath(pathPtr);
    f = fopen(native, "rb");				/* INTL: Native. */
    
    if (f == NULL) {
	Tcl_AppendResult (interp, "couldn't open \"", fileName, "\": ",
			  Tcl_PosixError (interp), (char *) NULL);
	return TCL_ERROR;
    }
    
    /* Search for the library list in the load module */
    
    p = "@LIBS: ";
    while (*p != '\0' && (c = getc (f)) != EOF) {
	if (c == *p) {
	    ++p;
	}
	else {
	    p = "@LIBS: ";
	    if (c == *p) {
		++p;
	    }
	}
    }
    
    /* No library list -- this must be an ill-formed module */
    
    if (c == EOF) {
	Tcl_AppendResult (interp, "File \"", fileName,
			  "\" is not a Tcl load module.", (char *) NULL);
	(void) fclose (f);
	return TCL_ERROR;
    }
    
    /* Accumulate the library list */
    
    while ((c = getc (f)) != '\0' && c != EOF) {
	char cc = c;
	Tcl_DStringAppend (buf, &cc, 1);
    }
    (void) fclose (f);
    
    if (c == EOF) {
	Tcl_AppendResult (interp, "Library directory in \"", fileName,
			  "\" ends prematurely.", (char *) NULL);
	return TCL_ERROR;
    }

    return TCL_OK;
}

/*
 *------------------------------------------------------------------------
 *
 * UnlinkSymbolTable --
 *
 *	Remove the symbol table file from the last dynamic link.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The symbol table file from the last dynamic link is removed.
 *	This function is called when (a) a new symbol table is present
 *	because another dynamic link is complete, or (b) the process
 *	is exiting.
 *------------------------------------------------------------------------
 */

static void
UnlinkSymbolTable ()
{
    (void) unlink (SymbolTableFile);
    ckfree (SymbolTableFile);
    SymbolTableFile = NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpUnloadFile --
 *
 *	Unloads a dynamically loaded binary code file from memory.
 *	Code pointers in the formerly loaded file are no longer valid
 *	after calling this function.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Does nothing.  Can anything be done?
 *
 *----------------------------------------------------------------------
 */

void
TclpUnloadFile(loadHandle)
    Tcl_LoadHandle loadHandle;	/* loadHandle returned by a previous call
				 * to TclpDlopen().  The loadHandle is 
				 * a token that represents the loaded 
				 * file. */
{
}

/*
 *----------------------------------------------------------------------
 *
 * TclGuessPackageName --
 *
 *	If the "load" command is invoked without providing a package
 *	name, this procedure is invoked to try to figure it out.
 *
 * Results:
 *	Always returns 0 to indicate that we couldn't figure out a
 *	package name;  generic code will then try to guess the package
 *	from the file name.  A return value of 1 would have meant that
 *	we figured out the package name and put it in bufPtr.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
TclGuessPackageName(fileName, bufPtr)
    CONST char *fileName;	/* Name of file containing package (already
				 * translated to local form if needed). */
    Tcl_DString *bufPtr;	/* Initialized empty dstring.  Append
				 * package name to this if possible. */
{
    CONST char *p, *q;
    char *r;

    if ((q = strrchr(fileName,'/'))) {
	q++;
    } else {
	q = fileName;
    }
    if (!strncmp(q,"lib",3)) {
	q+=3;
    }
    p = q;
    while ((*p) && (*p != '.') && ((*p<'0') || (*p>'9'))) {
	p++;
    }
    if ((p>q+2) && !strncmp(p-2,"_G0.",4)) {
	p-=2;
    }
    if (p<q) {
	return 0;
    }

    Tcl_DStringAppend(bufPtr,q, p-q);

    r = Tcl_DStringValue(bufPtr);
    r += strlen(r) - (p-q);

    /*
     * Capitalize the string and then recompute the length.
     */

    Tcl_UtfToTitle(r);
    Tcl_DStringSetLength(bufPtr, strlen(Tcl_DStringValue(bufPtr)));

    return 1;
}