dlinfo(3) - NetBSD Manual Pages

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DLINFO(3)               NetBSD Library Functions Manual              DLINFO(3)


NAME
dlinfo -- information about a dynamically loaded object
LIBRARY
(These functions are not in a library. They are included in every dynam- ically linked program automatically.)
SYNOPSIS
#include <link.h> #include <dlfcn.h> int dlinfo(void *handle, int request, void *p);
DESCRIPTION
The dlinfo() function provides information about a dynamically loaded object. The action taken by dlinfo() and exact meaning and type of p argument depend on value of the request argument provided by caller. The handle argument is either the value returned from the dlopen(3) func- tion call or special handle RTLD_SELF. If handle is the value returned from dlopen(3), the information returned by the dlinfo() function per- tains to the specified object. If handle is the special handle RTLD_SELF, the information returned pertains to the caller itself. Possible values for the request argument are: RTLD_DI_LINKMAP Retrieve the pointer to the Link_map for the specified handle. On successful return, the p argument is filled with the pointer to the Link_map structure (Link_map **p) describing a shared object specified by the handle argument. The Link_map struc- tures are maintained as a doubly linked list by ld.so(1), in the same order as dlopen(3) and dlclose(3) are called. The Link_map structure is defined in <link.h> and has the fol- lowing members: caddr_t l_addr; /* Base Address of library */ #ifdef __mips__ caddr_t l_offs; /* Load Offset of library */ #endif const char *l_name; /* Absolute Path to Library */ void *l_ld; /* Pointer to .dynamic in memory */ struct link_map *l_next, /* linked list of mapped libs */ *l_prev; l_addr The base address of the object loaded into mem- ory. l_name The absolute pathname of the loaded shared object. l_ld The address of the dynamic linking information segment (PT_DYNAMIC) loaded into memory. l_next The next Link_map structure on the link-map list. l_prev The previous Link_map structure on the link-map list.
RETURN VALUES
The dlinfo() function returns 0 on success, or -1 if an error occurred. Whenever an error has been detected, a message detailing it can be retrieved via a call to dlerror(3).
EXAMPLES
Using dlinfo() to retrieve Link_map structure. The following example shows how dynamic library can detect the list of shared libraries loaded after caller's one. For simplicity, error check- ing has been omitted. Link_map *map; dlinfo(RTLD_SELF, RTLD_DI_LINKMAP, &map); while (map != NULL) { printf("%p: %s\n", map->l_addr, map->l_name); map = map->l_next; }
SEE ALSO
rtld(1), dladdr(3), dlopen(3), dlsym(3)
HISTORY
The dlinfo() function first appeared in the Solaris operating system. In NetBSD, it first appeared in NetBSD 5.1.
AUTHORS
The NetBSD implementation of the dlinfo() function was written by Antti Kantee <pooka@NetBSD.org>. The manual page for this function was written by Alexey Zelkin <phantom@FreeBSD.org> and adapted to NetBSD by Kamil Rytarowski <kamil@NetBSD.org>. NetBSD 9.99 January 13, 2020 NetBSD 9.99
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