-.\" Copyright (c) 2003 by Michael Kerrisk <mtk.manpages@gmail.com>
+.\" Copyright (c) 2003, 2017 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" 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.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
-.\" License.
+.\" %%%LICENSE_END
.\"
-.TH DL_ITERATE_PHDR 3 2007-05-18 "GNU" "Linux Programmer's Manual"
+.TH DL_ITERATE_PHDR 3 2017-07-13 "GNU" "Linux Programmer's Manual"
.SH NAME
dl_iterate_phdr \- walk through list of shared objects
.SH SYNOPSIS
.BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */"
.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
+.BI "int dl_iterate_phdr("
+.BI " int (*" callback ") (struct dl_phdr_info *" info ,
+.BI " size_t " size ", void *" data "),"
+.BI " void *" data ");"
.fi
.SH DESCRIPTION
The
.BR dl_iterate_phdr ()
function allows an application to inquire at run time to find
-out which shared objects it has loaded.
+out which shared objects it has loaded,
+and the order in which they were loaded.
The
.BR dl_iterate_phdr ()
ELF program headers
for this object */
ElfW(Half) dlpi_phnum; /* # of items in \fIdlpi_phdr\fP */
+
+ /* The following fields were added in glibc 2.4, after the first
+ version of this structure was available. Check the \fIsize\fP
+ argument passed to the dl_iterate_phdr callback to determine
+ whether or not each later member is available. */
+
+ unsigned long long int dlpi_adds;
+ /* Incremented when a new object may
+ have been added */
+ unsigned long long int dlpi_subs;
+ /* Incremented when an object may
+ have been removed */
+ size_t dlpi_tls_modid;
+ /* If there is a PT_TLS segment, its module
+ ID as used in TLS relocations, else zero */
+ void *dlpi_tls_data;
+ /* The address of the calling thread's instance
+ of this module's PT_TLS segment, if it has
+ one and it has been allocated in the calling
+ thread, otherwise a null pointer */
};
.fi
.in
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.
+.I ElfW(Addr)
+yields the data type name
+.IR Elf32_Addr .
Further information on these types can be found in the
.IR <elf.h> " and " <link.h>
header files.)
.nf
addr == info\->dlpi_addr + info\->dlpi_phdr[x].p_vaddr;
.fi
+
+Possible values for
+.I p_type
+include the following (see
+.IR <elf.h>
+for further details):
+
+.nf
+.in +4n
+#define PT_LOAD 1 /* Loadable program segment */
+#define PT_DYNAMIC 2 /* Dynamic linking information */
+#define PT_INTERP 3 /* Program interpreter */
+#define PT_NOTE 4 /* Auxiliary information */
+#define PT_SHLIB 5 /* Reserved */
+#define PT_PHDR 6 /* Entry for header table itself */
+#define PT_TLS 7 /* Thread-local storage segment */
+#define PT_GNU_EH_FRAME 0x6474e550 /* GCC .eh_frame_hdr segment */
+#define PT_GNU_STACK 0x6474e551 /* Indicates stack executability */
+.\" For PT_GNU_STACK, see http://www.airs.com/blog/archives/518
+#define PT_GNU_RELRO 0x6474e552 /* Read-only after relocation */
+.in
+.fi
.SH RETURN VALUE
The
.BR dl_iterate_phdr ()
.SH VERSIONS
.BR dl_iterate_phdr ()
has been supported in glibc since version 2.2.4.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lb lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR dl_iterate_phdr ()
+T} Thread safety MT-Safe
+.TE
+
.SH CONFORMING TO
The
.BR dl_iterate_phdr ()
-function is Linux-specific and should be avoided in portable applications.
+function is not specified in any standard.
+Various other systems provide a version of this function,
+although details of the returned
+.I dl_phdr_info
+structure differ.
+On the BSDs and Solaris, the structure includes the fields
+.IR dlpi_addr ,
+.IR dlpi_name ,
+.IR dlpi_phdr ,
+and
+.IR dlpi_phnum
+in addition to other implementation-specific fields.
+.SH NOTES
+Future versions of the C library may add further fields to the
+.IR dl_phdr_info
+structure; in that event, the
+.I size
+argument provides a mechanism for the callback function to discover
+whether it is running on a system with added fields.
+
+The first object visited by
+.IR callback
+is the main program.
+For the main program, the
+.I dlpi_name
+field will be an empty string.
.SH EXAMPLE
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.
+For each shared object, the program lists some information
+(virtual address, size, flags, and type)
+for each of the objects ELF segments.
+The following shell session demonstrates the output
+produced by the program on an x86-64 system.
+The first shared object for which output is displayed
+(where the name is an empty string)
+is the main program.
+.nf
+.in +4n
+$ \fB./a.out\fP
+Name: "" (9 segments)
+ 0: [ 0x400040; memsz: 1f8] flags: 0x5; PT_PHDR
+ 1: [ 0x400238; memsz: 1c] flags: 0x4; PT_INTERP
+ 2: [ 0x400000; memsz: ac4] flags: 0x5; PT_LOAD
+ 3: [ 0x600e10; memsz: 240] flags: 0x6; PT_LOAD
+ 4: [ 0x600e28; memsz: 1d0] flags: 0x6; PT_DYNAMIC
+ 5: [ 0x400254; memsz: 44] flags: 0x4; PT_NOTE
+ 6: [ 0x400970; memsz: 3c] flags: 0x4; PT_GNU_EH_FRAME
+ 7: [ (nil); memsz: 0] flags: 0x6; PT_GNU_STACK
+ 8: [ 0x600e10; memsz: 1f0] flags: 0x4; PT_GNU_RELRO
+Name: "linux-vdso.so.1" (4 segments)
+ 0: [0x7ffc6edd1000; memsz: e89] flags: 0x5; PT_LOAD
+ 1: [0x7ffc6edd1360; memsz: 110] flags: 0x4; PT_DYNAMIC
+ 2: [0x7ffc6edd17b0; memsz: 3c] flags: 0x4; PT_NOTE
+ 3: [0x7ffc6edd17ec; memsz: 3c] flags: 0x4; PT_GNU_EH_FRAME
+Name: "/lib64/libc.so.6" (10 segments)
+ 0: [0x7f55712ce040; memsz: 230] flags: 0x5; PT_PHDR
+ 1: [0x7f557145b980; memsz: 1c] flags: 0x4; PT_INTERP
+ 2: [0x7f55712ce000; memsz: 1b6a5c] flags: 0x5; PT_LOAD
+ 3: [0x7f55716857a0; memsz: 9240] flags: 0x6; PT_LOAD
+ 4: [0x7f5571688b80; memsz: 1f0] flags: 0x6; PT_DYNAMIC
+ 5: [0x7f55712ce270; memsz: 44] flags: 0x4; PT_NOTE
+ 6: [0x7f55716857a0; memsz: 78] flags: 0x4; PT_TLS
+ 7: [0x7f557145b99c; memsz: 544c] flags: 0x4; PT_GNU_EH_FRAME
+ 8: [0x7f55712ce000; memsz: 0] flags: 0x6; PT_GNU_STACK
+ 9: [0x7f55716857a0; memsz: 3860] flags: 0x4; PT_GNU_RELRO
+Name: "/lib64/ld-linux-x86-64.so.2" (7 segments)
+ 0: [0x7f557168f000; memsz: 20828] flags: 0x5; PT_LOAD
+ 1: [0x7f55718afba0; memsz: 15a8] flags: 0x6; PT_LOAD
+ 2: [0x7f55718afe10; memsz: 190] flags: 0x6; PT_DYNAMIC
+ 3: [0x7f557168f1c8; memsz: 24] flags: 0x4; PT_NOTE
+ 4: [0x7f55716acec4; memsz: 604] flags: 0x4; PT_GNU_EH_FRAME
+ 5: [0x7f557168f000; memsz: 0] flags: 0x6; PT_GNU_STACK
+ 6: [0x7f55718afba0; memsz: 460] flags: 0x4; PT_GNU_RELRO
+.in
+.fi
+
+.SS Program source
+\&
.nf
#define _GNU_SOURCE
#include <link.h>
static int
callback(struct dl_phdr_info *info, size_t size, void *data)
{
- int j;
+ char *type;
+ int p_type, j;
+
+ printf("Name: \\"%s\\" (%d segments)\\n", info\->dlpi_name,
+ info\->dlpi_phnum);
- printf("name=%s (%d segments)\\n", info\->dlpi_name,
- info\->dlpi_phnum);
+ for (j = 0; j < info\->dlpi_phnum; j++) {
+ p_type = info\->dlpi_phdr[j].p_type;
+ type = (p_type == PT_LOAD) ? "PT_LOAD" :
+ (p_type == PT_DYNAMIC) ? "PT_DYNAMIC" :
+ (p_type == PT_INTERP) ? "PT_INTERP" :
+ (p_type == PT_NOTE) ? "PT_NOTE" :
+ (p_type == PT_INTERP) ? "PT_INTERP" :
+ (p_type == PT_PHDR) ? "PT_PHDR" :
+ (p_type == PT_TLS) ? "PT_TLS" :
+ (p_type == PT_GNU_EH_FRAME) ? "PT_GNU_EH_FRAME" :
+ (p_type == PT_GNU_STACK) ? "PT_GNU_STACK" :
+ (p_type == PT_GNU_RELRO) ? "PT_GNU_RELRO" : NULL;
+
+ printf(" %2d: [%14p; memsz:%7lx] flags: 0x%x; ", j,
+ (void *) (info\->dlpi_addr + info\->dlpi_phdr[j].p_vaddr),
+ info\->dlpi_phdr[j].p_memsz,
+ info\->dlpi_phdr[j].p_flags);
+ if (type != NULL)
+ printf("%s\\n", type);
+ else
+ printf("[other (0x%x)]\\n", p_type);
+ }
- 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;
}
.BR ldd (1),
.BR objdump (1),
.BR readelf (1),
+.BR dladdr (3),
.BR dlopen (3),
.BR elf (5),
.BR ld.so (8)
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