[Bug dynamic-link/28130] New: DT_DEBUG doesn't work with COPY relocation

[Bug dynamic-link/28130] New: DT_DEBUG doesn't work with COPY relocation

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28130

            Bug ID: 28130
           Summary: DT_DEBUG doesn't work with COPY relocation
           Product: glibc
           Version: 2.34
            Status: NEW
          Severity: normal
          Priority: P2
         Component: dynamic-link
          Assignee: unassigned at sourceware dot org
          Reporter: hjl.tools at gmail dot com
  Target Milestone: ---

rtld.c has

  /* Initialize _r_debug.  */
  struct r_debug *r = _dl_debug_initialize (GL(dl_rtld_map).l_addr,
                                            LM_ID_BASE);

  if (main_map->l_info[DT_DEBUG] != NULL)
    /* There is a DT_DEBUG entry in the dynamic section.  Fill it in
       with the run-time address of the r_debug structure  */
    main_map->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;

With COPY relocation, the real address of _r_debug may be in the executable
if it references _r_debug.  If debugger uses DT_DEBUG, it will reference the
staled original definition of _r_debug in ld.so.

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[Bug dynamic-link/28130] DT_DEBUG doesn't work with COPY relocation

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28130

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
We can hide _r_debug and add

extern struct r_debug * __r_debug_location (void) __attribute_const__;
#define _r_debug (*__r_debug_location (())

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[Bug dynamic-link/28130] DT_DEBUG doesn't work with COPY relocation

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28130

--- Comment #2 from Andreas Schwab <schwab@linux-m68k.org> ---
Nothing should be using _r_debug.

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[Bug dynamic-link/28130] DT_DEBUG doesn't work with COPY relocation

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28130

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Andreas Schwab from comment #2)
> Nothing should be using _r_debug.

_r_debug is exported and used by glibc tests.

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[Bug dynamic-link/28130] DT_DEBUG doesn't work with COPY relocation

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28130

--- Comment #4 from Andreas Schwab <schwab@linux-m68k.org> ---
That doesn't matter.

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