getksym(2)

NAME

getksym — get information for a global kernel symbol

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);

Remarks

getksym is currently implemented as a macro.

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 a global (STB_GLOBAL or STB_WEAK) symbol 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.

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

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. 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:

[ENOMATCH]: The symbol name given is not found, or the value given is not a currently valid address.
[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.

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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