2004-11-03 14:43:40 +00:00
|
|
|
.\" Copyright (c) 2003 by Michael Kerrisk <mtk-manpages@gmx.net>
|
2004-11-03 13:51:07 +00:00
|
|
|
.\"
|
|
|
|
.\" Permission is granted to make and distribute verbatim copies of this
|
|
|
|
.\" manual provided the copyright notice and this permission notice are
|
|
|
|
.\" preserved on all copies.
|
|
|
|
.\"
|
|
|
|
.\" Permission is granted to copy and distribute modified versions of this
|
|
|
|
.\" manual under the conditions for verbatim copying, provided that the
|
|
|
|
.\" entire resulting derived work is distributed under the terms of a
|
|
|
|
.\" permission notice identical to this one
|
|
|
|
.\"
|
|
|
|
.\" Since the Linux kernel and libraries are constantly changing, this
|
|
|
|
.\" manual page may be incorrect or out-of-date. The author(s) assume no
|
|
|
|
.\" responsibility for errors or omissions, or for damages resulting from
|
|
|
|
.\" the use of the information contained herein.
|
|
|
|
.\"
|
|
|
|
.\" Formatted or processed versions of this manual, if unaccompanied by
|
|
|
|
.\" the source, must acknowledge the copyright and authors of this work.
|
|
|
|
.\" License.
|
|
|
|
.\"
|
|
|
|
.TH DL_ITERATE_PHDR 3 "Linux 2.4.21" "Linux Programmer's Manual"
|
|
|
|
.SH NAME
|
|
|
|
dl_iterate_phdr \- walk through list of shared objects
|
|
|
|
.SH SYNOPSIS
|
|
|
|
.nf
|
|
|
|
#define _GNU_SOURCE
|
|
|
|
.B #include <link.h>
|
|
|
|
|
|
|
|
\fBint dl_iterate_phdr(\fP
|
|
|
|
\fBint (*\fPcallback\fB) \
|
|
|
|
(struct dl_phdr_info *\fPinfo\fB,\fP
|
|
|
|
\fBsize_t\fP size\fB, void *\fPdata\fB),\fP
|
|
|
|
\fBvoid *\fPdata\fB);\fP
|
|
|
|
.fi
|
|
|
|
.SH DESCRIPTION
|
|
|
|
The
|
2005-07-19 16:23:19 +00:00
|
|
|
.BR dl_iterate_phdr ()
|
2004-11-03 13:51:07 +00:00
|
|
|
function allows an application to inquire at run-time to find
|
|
|
|
out which shared objects it has loaded.
|
|
|
|
|
|
|
|
The
|
2005-07-19 16:23:19 +00:00
|
|
|
.BR dl_iterate_phdr ()
|
2004-11-03 13:51:07 +00:00
|
|
|
function walks through the list of an
|
|
|
|
application's shared objects and calls the function
|
|
|
|
.I callback
|
|
|
|
once for each object,
|
|
|
|
until either all shared objects have been processed or
|
|
|
|
.I callback
|
|
|
|
returns a non-zero value.
|
|
|
|
|
|
|
|
Each call to
|
|
|
|
.I callback
|
|
|
|
receives three arguments:
|
|
|
|
.IR info ,
|
|
|
|
which is a pointer to a structure containing information
|
|
|
|
about the shared object;
|
|
|
|
.IR size ,
|
|
|
|
which is the size of the structure pointed to by
|
|
|
|
.IR info ;
|
|
|
|
and
|
|
|
|
.IR data ,
|
|
|
|
which is a copy of whatever value was passed by the calling
|
|
|
|
program as the second argument (also named
|
|
|
|
.IR data )
|
|
|
|
in the call to
|
2005-07-19 16:23:19 +00:00
|
|
|
.BR dl_iterate_phdr ().
|
2004-11-03 13:51:07 +00:00
|
|
|
|
|
|
|
The
|
|
|
|
.I info
|
|
|
|
argument is a structure of the following type:
|
|
|
|
|
|
|
|
.nf
|
|
|
|
struct dl_phdr_info {
|
|
|
|
ElfW(Addr) dlpi_addr; /* Base address of object */
|
|
|
|
const char *dlpi_name; /* (Null-terminated) name of
|
|
|
|
object
|
|
|
|
const ElfW(Phdr) *dlpi_phdr; /* Pointer to array of
|
|
|
|
ELF program headers
|
|
|
|
for this object */
|
|
|
|
ElfW(Half) dlpi_phnum; /* # of items in 'dlpi_phdr' */
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
|
|
|
|
(The
|
2005-10-19 07:07:02 +00:00
|
|
|
.IR ElfW ()
|
2004-11-03 13:51:07 +00:00
|
|
|
macro definition turns its argument into the name of an ELF data
|
|
|
|
type suitable for the hardware architecture.
|
|
|
|
For example, on a 32-bit platform,
|
|
|
|
ElfW(Addr) yields the data type name Elf32_Addr.
|
|
|
|
Further information on these types can be found in the
|
|
|
|
.IR <elf.h> " and " <link.h>
|
|
|
|
header files.)
|
|
|
|
|
|
|
|
The
|
|
|
|
.I dlpi_addr
|
|
|
|
field indicates the base address of the shared object
|
|
|
|
(i.e., the difference between the virtual memory address of
|
|
|
|
the shared object and the offset of that object in the file
|
|
|
|
from which it was loaded).
|
|
|
|
The
|
|
|
|
.I dlpi_name
|
|
|
|
field is a null-terminated string giving the pathname
|
|
|
|
from which the shared object was loaded.
|
|
|
|
|
|
|
|
To understand the meaning of the
|
|
|
|
.I dlpi_phdr
|
|
|
|
and
|
|
|
|
.I dlpi_phnum
|
|
|
|
fields, we need to be aware that an ELF shared object consists
|
|
|
|
of a number of segments, each of which has a corresponding
|
|
|
|
program header describing the segment.
|
|
|
|
The
|
|
|
|
.I dlpi_phdr
|
|
|
|
field is a pointer to an array of the program headers for this
|
|
|
|
shared object.
|
|
|
|
The
|
|
|
|
.I dlpi_phnum
|
|
|
|
field indicates the size of this array.
|
|
|
|
|
|
|
|
These program headers are structures of the following form:
|
|
|
|
.nf
|
|
|
|
|
|
|
|
typedef struct
|
|
|
|
{
|
|
|
|
Elf32_Word p_type; /* Segment type */
|
|
|
|
Elf32_Off p_offset; /* Segment file offset */
|
|
|
|
Elf32_Addr p_vaddr; /* Segment virtual address */
|
|
|
|
Elf32_Addr p_paddr; /* Segment physical address */
|
|
|
|
Elf32_Word p_filesz; /* Segment size in file */
|
|
|
|
Elf32_Word p_memsz; /* Segment size in memory */
|
|
|
|
Elf32_Word p_flags; /* Segment flags */
|
|
|
|
Elf32_Word p_align; /* Segment alignment */
|
|
|
|
} Elf32_Phdr;
|
|
|
|
.fi
|
|
|
|
|
|
|
|
Note that we can calculate the location of a particular program header,
|
|
|
|
.IR x ,
|
2005-07-06 11:21:27 +00:00
|
|
|
in virtual memory using the formula:
|
2004-11-03 13:51:07 +00:00
|
|
|
|
|
|
|
.nf
|
|
|
|
addr == info->dlpi_addr + info->dlpi_phdr[x].p_vaddr;
|
|
|
|
.fi
|
2006-05-22 19:44:47 +00:00
|
|
|
.SH EXAMPLE
|
2004-11-03 13:51:07 +00:00
|
|
|
The following program displays a list of pathnames of the
|
|
|
|
shared objects it has loaded.
|
|
|
|
For each shared object, the program lists the virtual addresses
|
|
|
|
at which the object's ELF segments are loaded.
|
|
|
|
|
|
|
|
.nf
|
|
|
|
#define _GNU_SOURCE
|
|
|
|
#include <link.h>
|
|
|
|
#include <stdlib.h>
|
|
|
|
#include <stdio.h>
|
|
|
|
|
|
|
|
static int
|
|
|
|
callback(struct dl_phdr_info *info, size_t size, void *data)
|
|
|
|
{
|
|
|
|
int j;
|
|
|
|
|
|
|
|
printf("name=%s (%d segments)\\n", info->dlpi_name,
|
|
|
|
info->dlpi_phnum);
|
|
|
|
|
|
|
|
for (j = 0; j < info->dlpi_phnum; j++)
|
|
|
|
printf("\\t\\t header %2d: address=%10p\\n", j,
|
|
|
|
(void *) (info->dlpi_addr + info->dlpi_phdr[j].p_vaddr));
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
int
|
|
|
|
main(int argc, char *argv[])
|
|
|
|
{
|
|
|
|
dl_iterate_phdr(callback, NULL);
|
|
|
|
|
|
|
|
exit(EXIT_SUCCESS);
|
|
|
|
}
|
|
|
|
.fi
|
|
|
|
.SH RETURN VALUE
|
|
|
|
The
|
2005-07-19 16:23:19 +00:00
|
|
|
.BR dl_iterate_phdr ()
|
2004-11-03 13:51:07 +00:00
|
|
|
function returns whatever value was returned by the last call to
|
|
|
|
.IR callback .
|
|
|
|
.SH "CONFORMING TO"
|
|
|
|
The
|
2005-07-19 16:23:19 +00:00
|
|
|
.BR dl_iterate_phdr ()
|
2004-11-03 13:51:07 +00:00
|
|
|
function is Linux specific and should be avoided in portable applications.
|
|
|
|
.SH "SEE ALSO"
|
|
|
|
.BR ldd (1),
|
|
|
|
.BR objdump (1),
|
|
|
|
.BR readelf (1),
|
|
|
|
.BR dlopen (3),
|
|
|
|
.BR ld.so (8),
|
|
|
|
and the
|
|
|
|
.I "Executable and Linking Format Specification"
|
|
|
|
available at various locations online.
|