getksym(2)

NAME

getksym() — get information for local and global kernel symbols

SYNOPSIS

#include <sys/types.h>
#include <sys/ksym.h>
#include <elf.h>
#include <elf_parisc.h>  /* For STT_PARISC_MILLI on PA-RISC */

int getksym(char * symname, char * modname, uint64_t *value,
            uint64_t *info);

DESCRIPTION

There are two ways that getksym() can be used to retrieve kernel symbol information. As detailed below, if symname is provided and value is set to zero, getksym() attempts to retrieve the value of the symbol; if a non-zero value is provided, the associated symbol name is retrieved.

getksym(), given a symname, looks for global (STB_GLOBAL or STB_WEAK) and local (STB_LOCAL) symbols of that name in the symbol table of the static kernel and all currently loaded kernel modules. If it finds a match, getksym() returns the value associated with that symbol (typically its address) in the space pointed to by value, and the type of that symbol in the space pointed to by info.

NOTE: If there are two symbols (a local and a global symbol) with the same name, getksym() returns the first symbol that it finds with that name, which will be the local symbol.

The types returned are:

STT_NOTYPE: unknown type
STT_FUNC: text symbol (typically function)
STT_PARISC_MILLI: PA-RISC millicode function (PA-RISC only)
STT_OBJECT: data symbol
STT_SECTION: section symbol

The symbol name can be no more than MAXSYMNMLEN characters. If modname is set to the name (basename only) of a dynamically loaded module, then the search for the symbol name will only be in that module. If modname is NULL, then the search order for the symbol name will be the static kernel followed by each of the currently loaded modules in the order in which they were loaded. The module name can be no more than MODMAXNAMELEN characters.

If both a non-zero value and a symname are provided, the behavior of getksym() is undefined. If a zero value and an empty or NULL symname is provided, the behavior of getksym() is undefined.

If getksym() is given a valid non-zero address in the statically configured kernel or one of the currently loaded modules in the space pointed to by value, it will return, in the space pointed to by symname, the name of the symbol whose value is the closest one less than or equal to the given value and, in space pointed to by info, the difference between the address given and the value of the symbol found.

NOTE: If two symbols (an STT_SECTION symbol and an STT_FUNC/STT_OBJECT symbol) have the same address, getksym() returns the STT_FUNC/STT_OBJECT symbol.

The space pointed to by symname must be at least MAXSYMNMLEN characters long.

RETURN VALUE

getksym() returns 0 upon successful completion. If an error occurs, a value of -1 is returned and errno is set to indicate the error.

ERRORS

getksym() fails if one or more of the following are true:

EINVAL: modname does not represent a currently loaded module.
ENAMETOOLONG: modname is greater than MODMAXNAMELEN characters long, or symname is greater than MAXSYMNMLEN characters long.
ENOMATCH: The symbol name given is not found, or the value given is not a currently valid address.

EXAMPLES

The following code sequence and call to getksym() obtains a symbol name (and an offset) given an address.

#include <sys/types.h> 
#include <sys/ksym.h> 
#include <elf.h> 
uint64_t value=0x12345678, info=0; 
char symname[MAXSYMNMLEN]; 
/* name will be placed in symname, and offset in info */ 
if (getksym(symname, NULL, &value, &info) != 0) { 
    perror("getksym"); 
    return(-1); 
} 

The following code sequence and call to getksym() obtains an address given a symbol name.

#include <sys/types.h> 
#include <sys/ksym.h> 
#include <elf.h> 
uint64_t value=0, info=0; 
/* The address will be placed in value */ 
if (getksym("bzero",NULL, &value, &info) != 0) {  
    perror("getksym"); 
    return(-1); 
} 

getksym(2)

Technical documentation

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