NAME

dl_iterate_phdr — iterate over program headers

LIBRARY

For the dynamically linked binaries, the service is provided by ld-elf.so.1(1) dynamic linker. Statically linked programs use an implementation of dl_iterate_phdr() from libc.

SYNOPSIS

#include < link.h>

int
dl_iterate_phdr( int (*callback)(struct dl_phdr_info *, size_t, void *), void *data);

DESCRIPTION

The dl_iterate_phdr() function iterates over all ELF objects loaded into a process's address space, calling callback for each object, passing it information about the object's program headers and the data argument. The iteration is aborted when all objects are passed, or when the next callback call returns non-zero value. The information about the program headers is passed in a structure that is defined as:

struct dl_phdr_info { 
 Elf_Addr dlpi_addr; 
 const char *dlpi_name; 
 const Elf_Phdr *dlpi_phdr; 
 Elf_Half dlpi_phnum; 
 unsigned long long int dlpi_adds; 
 unsigned long long int dlpi_subs; 
 size_t  dlpi_tls_modid; 
 void  *dlpi_tls_data; 
};

The members of struct dl_phdr_info have the following meaning:

dlpi_addr

The base address at which the object is mapped into the address space of the calling process.

dlpi_name

The name of the ELF object.

dlpi_phdr

A pointer to the object's program headers.

dlpi_phnum

The number of program headers in the object.

dlpi_adds

The counter of the object loads performed by the dynamic linker.

dlpi_subs

The counter of the object unloads performed by the dynamic linker.

dlpi_tls_modid

The TLS index of the object.

dlpi_tls_data

A pointer to the initialization data for the object TLS segment.

Future versions of FreeBSD might add more members to this structure. To make it possible for programs to check whether any new members have been added, the size of the structure is passed as an second argument to callback.

The third argument to callback is the data value passed to the call to dl_iterate_phdr(), allowing the callback to have a context.

RETURN VALUES

The dl_iterate_phdr() returns the value returned by the last callback call executed.

SEE ALSO

ld(1), ld-elf.so.1(1), dlopen(3), elf(5)

HISTORY

The dl_iterate_phdr function first appeared in FreeBSD 7.0.