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Extend struct r_debug to support multiple namespaces [BZ #15971]

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Glibc does not provide an interface for debugger to access libraries
loaded in multiple namespaces via dlmopen.

The current rtld-debugger interface is described in the file:

elf/rtld-debugger-interface.txt

under the "Standard debugger interface" heading.  This interface only
provides access to the first link-map (LM_ID_BASE).

1. Bump r_version to 2 when multiple namespaces are used.  This triggers
the GDB bug:

https://sourceware.org/bugzilla/show_bug.cgi?id=28236

2. Add struct r_debug_extended to extend struct r_debug into a linked-list,
where each element correlates to an unique namespace.
3. Initialize the r_debug_extended structure.  Bump r_version to 2 for
the new namespace and add the new namespace to the namespace linked list.
4. Add _dl_debug_update to return the address of struct r_debug' of a
namespace.
5. Add a hidden symbol, _r_debug_extended, for struct r_debug_extended.
6. Provide the symbol, _r_debug, with size of struct r_debug, as an alias
of _r_debug_extended, for programs which reference _r_debug.

This fixes BZ #15971.

Reviewed-by: Florian Weimer <fweimer@redhat.com>
This commit is contained in:
H.J. Lu
2021-08-17 19:35:48 -07:00
parent 885762aa31
commit a93d9e03a3
16 changed files with 258 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
elf/dl-open.c
View File

@@ -574,7 +574,7 @@ dl_open_worker (void *a)
if ((mode & RTLD_GLOBAL) && new->l_global == 0)
add_to_global_update (new);
assert (_dl_debug_initialize (0, args->nsid)->r_state == RT_CONSISTENT);
assert (_dl_debug_update (args->nsid)->r_state == RT_CONSISTENT);
return;
}
@@ -630,7 +630,7 @@ dl_open_worker (void *a)
#endif
/* Notify the debugger all new objects are now ready to go. */
struct r_debug *r = _dl_debug_initialize (0, args->nsid);
struct r_debug *r = _dl_debug_update (args->nsid);
r->r_state = RT_CONSISTENT;
_dl_debug_state ();
LIBC_PROBE (map_complete, 3, args->nsid, r, new);
@@ -830,7 +830,7 @@ no more namespaces available for dlmopen()"));
++GL(dl_nns);
}
_dl_debug_initialize (0, nsid)->r_state = RT_CONSISTENT;
_dl_debug_update (nsid)->r_state = RT_CONSISTENT;
}
/* Never allow loading a DSO in a namespace which is empty. Such
direct placements is only causing problems. Also don't allow
@@ -899,7 +899,7 @@ no more namespaces available for dlmopen()"));
the flag here. */
}
assert (_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT);
assert (_dl_debug_update (args.nsid)->r_state == RT_CONSISTENT);
/* Release the lock. */
__rtld_lock_unlock_recursive (GL(dl_load_lock));
@@ -908,7 +908,7 @@ no more namespaces available for dlmopen()"));
_dl_signal_exception (errcode, &exception, NULL);
}
assert (_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT);
assert (_dl_debug_update (args.nsid)->r_state == RT_CONSISTENT);
/* Release the lock. */
__rtld_lock_unlock_recursive (GL(dl_load_lock));