ksyms(7D)							      Devices								 ksyms(7D)

NAME

       ksyms - kernel symbols

SYNOPSIS

       /dev/ksyms

DESCRIPTION

       The file  /dev/ksyms is a character special file that allows read-only access to an  ELF format image containing two sections: a symbol ta-
       ble and a corresponding string table. The contents of the symbol table reflect the symbol state of the currently running  kernel.  You  can
       determine  the  size   of the image with the fstat() system call. The recommended method for accessing the  /dev/ksyms file is by using the
       ELF access library.  See elf(3ELF) for details.	If you are not familiar with  ELF format, see a.out(4).

       /dev/ksyms is an executable for the processor on which you are accessing it. It contains  ELF program headers which describe the  text  and
       data  segment(s)  in kernel memory.  Since  /dev/ksyms has no text or data, the fields specific to file attributes are initialized to NULL.
       The remaining fields describe the text or data segment(s) in kernel memory.

       Symbol table	       The  SYMTAB section contains the symbol table entries present in the currently  running	kernel.  This  section	is
			       ordered	as defined by the ELF definition with locally-defined symbols first, followed by globally-defined symbols.
			       Within symbol type, the symbols are ordered by kernel module load time. For example, the kernel	file  symbols  are
			       first, followed by the first module's symbols, and so on, ending with the symbols from the last module loaded.

			       The  section header index (st_shndx) field of each symbol entry in the symbol table is set to  SHN_ABS, because any
			       necessary symbol relocations are performed by the kernel link editor at module load time.

       String table	       The  STRTAB section contains the symbol name strings that the symbol table entries reference.

SEE ALSO

       kernel(1M), stat(2), elf(3ELF), kvm_open(3KVM), a.out(4),  mem(7D)

WARNINGS

       The kernel is dynamically configured. It loads kernel modules when necessary.  Because of this aspect of the system, the symbol information
       present in the running system can vary from time to time, as kernel modules are loaded and unloaded.

       When you open the  /dev/ksyms file, you have access to an  ELF image which represents a snapshot of the state of the kernel symbol informa-
       tion at that instant in time. While the /dev/ksyms file remains open, kernel module autounloading is disabled, so that  you  are  protected
       from  the  possibility  of  acquiring  stale symbol data.  Note that new modules can still be loaded, however. If kernel modules are loaded
       while you have the  /dev/ksyms file open, the snapshot held by you will not be updated. In order to have access to the  symbol  information
       of  the newly loaded modules, you must first close and then reopen the  /dev/ksyms file. Be aware that the size of the /dev/ksyms file will
       have changed. You will need to use the fstat() function (see stat(2)) to determine the new size of the file.

       Avoid keeping the  /dev/ksyms file open for extended periods of time, either by using kvm_open(3KVM) of the default namelist file or with a
       direct open. There are two reasons why you should not hold  /dev/ksyms open. First, the system's ability to dynamically configure itself is
       partially disabled by the locking down of loaded modules. Second, the snapshot of symbol information held by you will not reflect the  sym-
       bol information of modules loaded after your initial open of  /dev/ksyms.

       Note  that  the	ksyms driver is a loadable module, and that the kernel driver modules are only loaded during an open system call.  Thus it
       is possible to run stat(2) on the  /dev/ksyms file without causing the  ksyms driver to be loaded. In this case, the file size returned	is
       UNKNOWN_SIZE.   A  solution  for this behavior is to first open the /dev/ksyms file, causing the  ksyms driver to be loaded (if necessary).
       You can then use the file descriptor from this open in a fstat() system call to get the file's size.

NOTES

       The kernel virtual memory access library (libkvm) routines use /dev/ksyms as the default namelist file. See kvm_open(3KVM) for details.

SunOS 5.10							    11 Dec 2000 							 ksyms(7D)