os_dep.c

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#       if defined(SUNOS5SIGS) || defined(IRIX5) \
	   || defined(OSF1) || defined(HURD) || defined(NETBSD)
	  (void) sigaction(SIGSEGV, &old_segv_act, 0);
#	  if defined(IRIX5) && defined(_sigargs) /* Irix 5.x, not 6.x */ \
	     || defined(HPUX) || defined(HURD) || defined(NETBSD)
	      (void) sigaction(SIGBUS, &old_bus_act, 0);
#	  endif
#       else
  	  (void) signal(SIGSEGV, old_segv_handler);
#	  ifdef SIGBUS
	    (void) signal(SIGBUS, old_bus_handler);
#	  endif
#       endif
    }

    /* Return the first nonaddressible location > p (up) or 	*/
    /* the smallest location q s.t. [q,p) is addressable (!up).	*/
    /* We assume that p (up) or p-1 (!up) is addressable.	*/
    /* Requires allocation lock.				*/
    ptr_t GC_find_limit_with_bound(ptr_t p, GC_bool up, ptr_t bound)
    {
        static volatile ptr_t result;
    		/* Safer if static, since otherwise it may not be	*/
    		/* preserved across the longjmp.  Can safely be 	*/
    		/* static since it's only called with the		*/
    		/* allocation lock held.				*/

	GC_ASSERT(I_HOLD_LOCK());
	GC_setup_temporary_fault_handler();
	if (SETJMP(GC_jmp_buf) == 0) {
	    result = (ptr_t)(((word)(p))
			      & ~(MIN_PAGE_SIZE-1));
	    for (;;) {
 	        if (up) {
		    result += MIN_PAGE_SIZE;
		    if (result >= bound) return bound;
 	        } else {
		    result -= MIN_PAGE_SIZE;
		    if (result <= bound) return bound;
 	        }
		GC_noop1((word)(*result));
	    }
	}
	GC_reset_fault_handler();
 	if (!up) {
	    result += MIN_PAGE_SIZE;
 	}
	return(result);
    }

    ptr_t GC_find_limit(ptr_t p, GC_bool up)
    {
      if (up) {
	return GC_find_limit_with_bound(p, up, (ptr_t)(word)(-1));
      } else {
	return GC_find_limit_with_bound(p, up, 0);
      }
    }
# endif

#if defined(ECOS) || defined(NOSYS)
  ptr_t GC_get_main_stack_base(void)
  {
    return STACKBOTTOM;
  }
#endif

#ifdef HPUX_STACKBOTTOM

#include <sys/param.h>
#include <sys/pstat.h>

  ptr_t GC_get_register_stack_base(void)
  {
    struct pst_vm_status vm_status;

    int i = 0;
    while (pstat_getprocvm(&vm_status, sizeof(vm_status), 0, i++) == 1) {
      if (vm_status.pst_type == PS_RSESTACK) {
        return (ptr_t) vm_status.pst_vaddr;
      }
    }

    /* old way to get the register stackbottom */
    return (ptr_t)(((word)GC_stackbottom - BACKING_STORE_DISPLACEMENT - 1)
                   & ~(BACKING_STORE_ALIGNMENT - 1));
  }

#endif /* HPUX_STACK_BOTTOM */

#ifdef LINUX_STACKBOTTOM

#include <sys/types.h>
#include <sys/stat.h>

# define STAT_SKIP 27   /* Number of fields preceding startstack	*/
			/* field in /proc/self/stat			*/

#ifdef USE_LIBC_PRIVATES
# pragma weak __libc_stack_end
  extern ptr_t __libc_stack_end;
#endif

# ifdef IA64
#   ifdef USE_LIBC_PRIVATES
#     pragma weak __libc_ia64_register_backing_store_base
      extern ptr_t __libc_ia64_register_backing_store_base;
#   endif

    ptr_t GC_get_register_stack_base(void)
    {
      ptr_t result;

#     ifdef USE_LIBC_PRIVATES
        if (0 != &__libc_ia64_register_backing_store_base
	    && 0 != __libc_ia64_register_backing_store_base) {
	  /* Glibc 2.2.4 has a bug such that for dynamically linked	*/
	  /* executables __libc_ia64_register_backing_store_base is 	*/
	  /* defined but uninitialized during constructor calls.  	*/
	  /* Hence we check for both nonzero address and value.		*/
	  return __libc_ia64_register_backing_store_base;
        }
#     endif
      result = backing_store_base_from_proc();
      if (0 == result) {
	  result = GC_find_limit(GC_save_regs_in_stack(), FALSE);
	  /* Now seems to work better than constant displacement	*/
	  /* heuristic used in 6.X versions.  The latter seems to	*/
	  /* fail for 2.6 kernels.					*/
      }
      return result;
    }
# endif

  ptr_t GC_linux_stack_base(void)
  {
    /* We read the stack base value from /proc/self/stat.  We do this	*/
    /* using direct I/O system calls in order to avoid calling malloc   */
    /* in case REDIRECT_MALLOC is defined.				*/ 
#   define STAT_BUF_SIZE 4096
#   define STAT_READ read
	  /* Should probably call the real read, if read is wrapped.	*/
    char stat_buf[STAT_BUF_SIZE];
    int f;
    char c;
    word result = 0;
    size_t i, buf_offset = 0;

    /* First try the easy way.  This should work for glibc 2.2	*/
    /* This fails in a prelinked ("prelink" command) executable */
    /* since the correct value of __libc_stack_end never	*/
    /* becomes visible to us.  The second test works around 	*/
    /* this.							*/  
#   ifdef USE_LIBC_PRIVATES
      if (0 != &__libc_stack_end && 0 != __libc_stack_end ) {
#       if defined(IA64)
	  /* Some versions of glibc set the address 16 bytes too	*/
	  /* low while the initialization code is running.		*/
	  if (((word)__libc_stack_end & 0xfff) + 0x10 < 0x1000) {
	    return __libc_stack_end + 0x10;
	  } /* Otherwise it's not safe to add 16 bytes and we fall	*/
	    /* back to using /proc.					*/
#	elif defined(SPARC)
	  /* Older versions of glibc for 64-bit Sparc do not set
	   * this variable correctly, it gets set to either zero
	   * or one.
	   */
	  if (__libc_stack_end != (ptr_t) (unsigned long)0x1)
	    return __libc_stack_end;
#	else
	  return __libc_stack_end;
#	endif
      }
#   endif
    f = open("/proc/self/stat", O_RDONLY);
    if (f < 0 || STAT_READ(f, stat_buf, STAT_BUF_SIZE) < 2 * STAT_SKIP) {
	ABORT("Couldn't read /proc/self/stat");
    }
    c = stat_buf[buf_offset++];
    /* Skip the required number of fields.  This number is hopefully	*/
    /* constant across all Linux implementations.			*/
      for (i = 0; i < STAT_SKIP; ++i) {
	while (isspace(c)) c = stat_buf[buf_offset++];
	while (!isspace(c)) c = stat_buf[buf_offset++];
      }
    while (isspace(c)) c = stat_buf[buf_offset++];
    while (isdigit(c)) {
      result *= 10;
      result += c - '0';
      c = stat_buf[buf_offset++];
    }
    close(f);
    if (result < 0x10000000) ABORT("Absurd stack bottom value");
    return (ptr_t)result;
  }

#endif /* LINUX_STACKBOTTOM */

#ifdef FREEBSD_STACKBOTTOM

/* This uses an undocumented sysctl call, but at least one expert 	*/
/* believes it will stay.						*/

#include <unistd.h>
#include <sys/types.h>
#include <sys/sysctl.h>

  ptr_t GC_freebsd_stack_base(void)
  {
    int nm[2] = {CTL_KERN, KERN_USRSTACK};
    ptr_t base;
    size_t len = sizeof(ptr_t);
    int r = sysctl(nm, 2, &base, &len, NULL, 0);
    
    if (r) ABORT("Error getting stack base");

    return base;
  }

#endif /* FREEBSD_STACKBOTTOM */

#if !defined(BEOS) && !defined(AMIGA) && !defined(MSWIN32) \
    && !defined(MSWINCE) && !defined(OS2) && !defined(NOSYS) && !defined(ECOS) \
    && !defined(CYGWIN32)

ptr_t GC_get_main_stack_base(void)
{
#   if defined(HEURISTIC1) || defined(HEURISTIC2)
      word dummy;
#   endif
    ptr_t result;

#   define STACKBOTTOM_ALIGNMENT_M1 ((word)STACK_GRAN - 1)

#   ifdef STACKBOTTOM
	return(STACKBOTTOM);
#   else
#	ifdef HEURISTIC1
#	   ifdef STACK_GROWS_DOWN
	     result = (ptr_t)((((word)(&dummy))
	     		       + STACKBOTTOM_ALIGNMENT_M1)
			      & ~STACKBOTTOM_ALIGNMENT_M1);
#	   else
	     result = (ptr_t)(((word)(&dummy))
			      & ~STACKBOTTOM_ALIGNMENT_M1);
#	   endif
#	endif /* HEURISTIC1 */
#	ifdef LINUX_STACKBOTTOM
	   result = GC_linux_stack_base();
#	endif
#	ifdef FREEBSD_STACKBOTTOM
	   result = GC_freebsd_stack_base();
#	endif
#	ifdef HEURISTIC2
#	    ifdef STACK_GROWS_DOWN
		result = GC_find_limit((ptr_t)(&dummy), TRUE);
#           	ifdef HEURISTIC2_LIMIT
		    if (result > HEURISTIC2_LIMIT
		        && (ptr_t)(&dummy) < HEURISTIC2_LIMIT) {
		            result = HEURISTIC2_LIMIT;
		    }
#	        endif
#	    else
		result = GC_find_limit((ptr_t)(&dummy), FALSE);
#           	ifdef HEURISTIC2_LIMIT
		    if (result < HEURISTIC2_LIMIT
		        && (ptr_t)(&dummy) > HEURISTIC2_LIMIT) {
		            result = HEURISTIC2_LIMIT;
		    }
#	        endif
#	    endif

#	endif /* HEURISTIC2 */
#	ifdef STACK_GROWS_DOWN
	    if (result == 0) result = (ptr_t)(signed_word)(-sizeof(ptr_t));
#	endif
    	return(result);
#   endif /* STACKBOTTOM */
}

# endif /* ! AMIGA, !OS 2, ! MS Windows, !BEOS, !NOSYS, !ECOS */

#if defined(GC_LINUX_THREADS) && !defined(HAVE_GET_STACK_BASE)

#include <pthread.h>

#ifdef IA64
  ptr_t GC_greatest_stack_base_below(ptr_t bound);
  	/* From pthread_support.c */
#endif

int GC_get_stack_base(struct GC_stack_base *b)
{
    pthread_attr_t attr;
    size_t size;

    if (pthread_getattr_np(pthread_self(), &attr) != 0) {
	WARN("pthread_getattr_np failed\n", 0);
	return GC_UNIMPLEMENTED;
    }
    if (pthread_attr_getstack(&attr, &(b -> mem_base), &size) != 0) {
	ABORT("pthread_attr_getstack failed");
    }
#   ifdef STACK_GROWS_DOWN
        b -> mem_base = (char *)(b -> mem_base) + size;
#   endif
#   ifdef IA64
      /* We could try backing_store_base_from_proc, but that's safe	*/
      /* only if no mappings are being asynchronously created.		*/
      /* Subtracting the size from the stack base doesn't work for at	*/
      /* least the main thread.						*/
      LOCK();
      {
	ptr_t bsp = GC_save_regs_in_stack();
	ptr_t next_stack = GC_greatest_stack_base_below(bsp);
	if (0 == next_stack) {
          b -> reg_base = GC_find_limit(bsp, FALSE);
	} else {
	  /* Avoid walking backwards into preceding memory stack and	*/
	  /* growing it.						*/
          b -> reg_base = GC_find_limit_with_bound(bsp, FALSE, next_stack);
	}
      }
      UNLOCK();
#   endif
    return GC_SUCCESS;
}

#define HAVE_GET_STACK_BASE

#endif /* GC_LINUX_THREADS */

#ifndef HAVE_GET_STACK_BASE
/* Retrieve stack base.						*/
/* Using the GC_find_limit version is risky.			*/
/* On IA64, for example, there is no guard page between the	*/
/* stack of one thread and the register backing store of the 	*/
/* next.  Thus this is likely to identify way too large a	*/
/* "stack" and thus at least result in disastrous performance.	*/
/* FIXME - Implement better strategies here.			*/
int GC_get_stack_base(struct GC_stack_base *b)
{
    int dummy;

#   ifdef NEED_FIND_LIMIT
#     ifdef STACK_GROWS_DOWN
    	b -> mem_base = GC_find_limit((ptr_t)(&dummy), TRUE);
#       ifdef IA64
	  b -> reg_base = GC_find_limit(GC_save_regs_in_stack(), FALSE);
#       endif
#     else
	b -> mem_base = GC_find_limit(&dummy, FALSE);
#     endif
      return GC_SUCCESS;
#   else
      return GC_UNIMPLEMENTED;
#   endif
}
#endif

/*
 * Register static data segment(s) as roots.
 * If more data segments are added later then they need to be registered
 * add that point (as we do with SunOS dynamic loading),
 * or GC_mark_roots needs to check for them (as we do with PCR).
 * Called with allocator lock held.
 */

# ifdef OS2

void GC_register_data_segments(void)
{
    PTIB ptib;
    PPIB ppib;
    HMODULE module_handle;
#   define PBUFSIZ 512
    UCHAR path[PBUFSIZ];
    FILE * myexefile;
    struct exe_hdr hdrdos;	/* MSDOS header.	*/
    struct e32_exe hdr386;	/* Real header for my executable */
    struct o32_obj seg;	/* Currrent segment */
    int nsegs;
    
    
    if (DosGetInfoBlocks(&ptib, &ppib) != NO_ERROR) {
    	GC_err_printf("DosGetInfoBlocks failed\n");
    	ABORT("DosGetInfoBlocks failed\n");
    }
    module_handle = ppib -> pib_hmte;
    if (DosQueryModuleName(module_handle, PBUFSIZ, path) != NO_ERROR) {
    	GC_err_printf("DosQueryModuleName failed\n");
    	ABORT("DosGetInfoBlocks failed\n");
    }
    myexefile = fopen(path, "rb");
    if (myexefile == 0) {
        GC_err_puts("Couldn't open executable ");
        GC_err_puts(path); GC_err_puts("\n");
        ABORT("Failed to open executable\n");
    }
    if (fread((char *)(&hdrdos), 1, sizeof hdrdos, myexefile) < sizeof hdrdos) {
        GC_err_puts("Couldn't read MSDOS header from ");
        GC_err_puts(path); GC_err_puts("\n");
        ABORT("Couldn't read MSDOS header");
    }
    if (E_MAGIC(hdrdos) != EMAGIC) {
        GC_err_puts("Executable has wrong DOS magic number: ");
        GC_err_puts(path); GC_err_puts("\n");
        ABORT("Bad DOS magic number");
    }
    if (fseek(myexefile, E_LFANEW(hdrdos), SEEK_SET) != 0) {
        GC_err_puts("Seek to new header failed in ");
        GC_err_puts(path); GC_err_puts("\n");
        ABORT("Bad DOS magic number");
    }
    if (fread((char *)(&hdr386), 1, sizeof hdr386, myexefile) < sizeof hdr386) {
        GC_err_puts("Couldn't read MSDOS header from ");
        GC_err_puts(path); GC_err_puts("\n");
        ABORT("Couldn't read OS/2 header");
    }
    if (E32_MAGIC1(hdr386) != E32MAGIC1 || E32_MAGIC2(hdr386) != E32MAGIC2) {
        GC_err_puts("Executable has wrong OS/2 magic number:");
        GC_err_puts(path); GC_err_puts("\n");
        ABORT("Bad OS/2 magic number");
    }
    if ( E32_BORDER(hdr386) != E32LEBO || E32_WORDER(hdr386) != E32LEWO) {
        GC_err_puts("Executable %s has wrong byte order: ");
        GC_err_puts(path); GC_err_puts("\n");
        ABORT("Bad byte order");
    }
    if ( E32_CPU(hdr386) == E32CPU286) {
        GC_err_puts("GC can't handle 80286 executables: ");
        GC_err_puts(path); GC_err_puts("\n");
        EXIT();
    }
    if (fseek(myexefile, E_LFANEW(hdrdos) + E32_OBJTAB(hdr386),
    	      SEEK_SET) != 0) {
        GC_err_puts("Seek to object table failed: ");
        GC_err_puts(path); GC_err_puts("\n");