mmap() on 64 bit m/c Post: 302319767

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Operating Systems Solaris mmap() on 64 bit m/c Post 302319767 by vin_pll on Tuesday 26th of May 2009 07:13:11 AM

05-26-2009

Registered User

Sigbus with mmap.

sorry for the delayed reply,
please help me i am trying like this, though this is one sample test,
iam opening the two files one for reading and one for writing, and i am checking like this

Code:

if((input = open(argv[1], O_RDONLY)) == -1)
  fprintf(stderr, "%s: Error: opening file: %s\n", PACKAGE, argv[1]), exit(1);

 if((output = open(argv[2], O_RDWR|O_CREAT|O_TRUNC, 0666)) == -1)
  fprintf(stderr, "%s: Error: opening file: %s\n", PACKAGE, argv[2]), exit(1);

   source = (char *)mmap((char *)0, filesize, PROT_READ, MAP_SHARED,   input, 0);
printf("\n address of source==%p",source);
 if(source[0] ==-1)
  fprintf(stderr, "Error mapping input file: %s\n", argv[1]), exit(1);

target =(char *) mmap((char  *)0, filesize, PROT_WRITE, MAP_SHARED, output, 0);

printf("\n address of target==%d",target);
 if(target[0]==-1) //problem here
  fprintf(stderr, "Error mapping ouput file: %s\n", argv[2]), exit(1);

as i am opening both of them and checking instead of MAP_FAILED for the failure to target[0]==-1 ,
my question is what exactly is the data structure that mmap returns when i test for read it is successfull and for write it is not and also
if i change that to
if(target==(void*)-1 ) it returns successfull,
because in my code they have used
target[0]==-1 which is failing and results in sigbus if i replace it with
if(target==MAP_FAILED)
it is not even going for failure nor the sucess,
and fails some where in the reading. so what is the reason of sigbus
please solve my problem

vin_pll

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explain_mmap_or_die

explain_mmap_or_die(3)					     Library Functions Manual					    explain_mmap_or_die(3)

NAME

       explain_mmap_or_die - map file or device into memory and report errors

SYNOPSIS

       #include <libexplain/mmap.h>
       void *explain_mmap_or_die(void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);
       void *explain_mmap_on_error(void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);

DESCRIPTION

       The  explain_mmap_or_die  function  is  used to call the mmap(2) system call. On failure an explanation will be printed to stderr, obtained
       from the explain_mmap(3) function, and then the process terminates by calling exit(EXIT_FAILURE).

       The explain_mmap_on_error function is used to call the mmap(2) system call. On failure an explanation will be printed to  stderr,  obtained
       from the explain_mmap(3) function, but still returns to the caller.

       data    The data, exactly as to be passed to the mmap(2) system call.

       data_size
	       The data_size, exactly as to be passed to the mmap(2) system call.

       prot    The prot, exactly as to be passed to the mmap(2) system call.

       flags   The flags, exactly as to be passed to the mmap(2) system call.

       fildes  The fildes, exactly as to be passed to the mmap(2) system call.

       offset  The offset, exactly as to be passed to the mmap(2) system call.

RETURN VALUE

       The explain_mmap_or_die function only returns on success, see mmap(2) for more information. On failure, prints an explanation and exits, it
       does not return.

       The explain_mmap_on_error function always returns the value return by the wrapped mmap(2) system call.

EXAMPLE

       The explain_mmap_or_die function is intended to be used in a fashion similar to the following example:
	      explain_mmap_or_die(data, data_size, prot, flags, fildes, offset);

SEE ALSO

       mmap(2) map file or device into memory

       explain_mmap(3)
	       explain mmap(2) errors

       exit(2) terminate the calling process

COPYRIGHT

       libexplain version 0.52
       Copyright (C) 2010 Peter Miller

															    explain_mmap_or_die(3)