Re: RFE: dl_iterate_phdr, r_debug.r_brk usability for introspection

[Roland McGrath <roland at hack dot frob dot com>]

> I just remembered: there's already an equivalent API from one or more
> of the BSDs (I'd have to look back to see which) that was adopted in
> musl. See:
> 
> http://git.musl-libc.org/cgit/musl/tree/include/link.h#n27
> 
> Rather than inventing something new and gratuitously incompatible it
> would be nice if glibc could adopt the same member names (and layout).
> We also have the TLS module id (for use with __tls_get_addr) and image
> pointer available there.

Your musl source link shows:

	struct dl_phdr_info {
	       ElfW(Addr) dlpi_addr;
	       const char *dlpi_name;
	       const ElfW(Phdr) *dlpi_phdr;
	       ElfW(Half) dlpi_phnum;
	       unsigned long long int dlpi_adds;
	       unsigned long long int dlpi_subs;
	       size_t dlpi_tls_modid;
	       void *dlpi_tls_data;
	};

while the glibc definition reads:

	struct dl_phdr_info
	  {
	    ElfW(Addr) dlpi_addr;
	    const char *dlpi_name;
	    const ElfW(Phdr) *dlpi_phdr;
	    ElfW(Half) dlpi_phnum;

	    /* Note: Following members were introduced after the first
	       version of this structure was available.  Check the SIZE
	       argument passed to the dl_iterate_phdr callback to determine
	       whether or not each later member is available.  */

	    /* Incremented when a new object may have been added.  */
	    __extension__ unsigned long long int dlpi_adds;
	    /* Incremented when an object may have been removed.  */
	    __extension__ unsigned long long int dlpi_subs;

	    /* If there is a PT_TLS segment, its module ID as used in
	       TLS relocations, else zero.  */
	    size_t dlpi_tls_modid;

	    /* 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.  */
	    void *dlpi_tls_data;
	  };

I think I invented dlpi_tls_{modid,data} in commit
d78efd9f369a8fc46229fc9224e10e3781eecc43 (2006-02-28 in ChangeLog.16).

dlip_{adds,subs} were added in commit bed12f78fab86b2349cab6e7f4c0e46bde5e9711
(2004-01-23 in ChangeLog.14).

I suspect all of that was before any BSD had dl_iterate_phdr.

So, I guess the answer is, "You're welcome."


Thanks,
Roland