KSYMS(4)

NAME
ksyms - kernel symbol table interface

SYNOPSIS
pseudo-device ksyms

DESCRIPTION
The /dev/ksyms character device provides a read-only interface to the current kernel symbol table. It can be accessed either as a sequential file, where it looks like an executable file but with zero-sized text and data segments, or via ioctl(2).

/dev/ksyms represents the symbol table at the time when the device is opened, and may not change until it is closed.

The in-kernel symbol manager is designed to be able to handle any type of symbol table. However, only elf(5) symbol tables are currently dealt with.

IOCTLS
The ioctl(2) command codes below are defined in <sys/ksyms.h>.

The (third) argument to the ioctl(2) should be a pointer to the type indicated.

KIOCGSIZE (int)
    Returns the total size of the current symbol table. This should be used when allocating a buffer to read in the whole symbol table to memory.

KIOCGVALUE (struct ksyms_gsymbol)
    Returns the value for the given symbol name in a symtab-independent fashion.

        struct ksyms_gsymbol {
        	const char *kg_name;
        	unsigned long *kg_value;
        };

    The struct element kg_name should be set to the name of the requested value, and the address that kg_value points to will receive the symbol value.

KIOCGSYMBOL (struct ksyms_gsymbol)
    Returns the complete symbol for the given symbol name.

        struct ksyms_gsymbol {
        	const char *kg_name;
                void *kg_sym;
        };

    The struct element kg_name should be set to the name of the requested symbol, and the found symbol will be written to the kg_sym address. It is the callers responsibility to ensure that enough space for the symbol is allocated.

FILES

/dev/ksyms

SEE ALSO
ioctl(2), nlist(3), elf(5)

HISTORY
A ksyms device exists in many different operating systems. This implementation is modelled in function after Solaris ksyms. This ksyms driver was written by Anders Magnusson for NetBSD.

The ksyms driver first appeared in NetBSD 2.0.

BUGS
No LKM modules can be loaded or unloaded while /dev/ksyms is open.