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authorH.J. Lu <hjl.tools@gmail.com>2021-08-17 19:35:48 -0700
committerH.J. Lu <hjl.tools@gmail.com>2021-09-19 13:51:35 -0700
commita93d9e03a31ec14405cb3a09aa95413b67067380 (patch)
tree532f865c7241b3cf363433272e5923c468ea2969 /csu
parent885762aa31d75de8b9fea4c0e2e372b582d4c548 (diff)
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Extend struct r_debug to support multiple namespaces [BZ #15971]
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>
Diffstat (limited to 'csu')
-rw-r--r--csu/Makefile3
-rw-r--r--csu/rtld-sizes.sym6
2 files changed, 9 insertions, 0 deletions
diff --git a/csu/Makefile b/csu/Makefile
index 3054329cea..e2390e4a7d 100644
--- a/csu/Makefile
+++ b/csu/Makefile
@@ -88,6 +88,9 @@ endif
 before-compile += $(objpfx)abi-tag.h
 generated += abi-tag.h
 
+# Put it here to generate it earlier.
+gen-as-const-headers += rtld-sizes.sym
+
 # These are the special initializer/finalizer files.  They are always the
 # first and last file in the link.  crti.o ... crtn.o define the global
 # "functions" _init and _fini to run the .init and .fini sections.
diff --git a/csu/rtld-sizes.sym b/csu/rtld-sizes.sym
new file mode 100644
index 0000000000..13924d5efd
--- /dev/null
+++ b/csu/rtld-sizes.sym
@@ -0,0 +1,6 @@
+#include <link.h>
+
+--
+R_DEBUG_SIZE		sizeof (struct r_debug)
+R_DEBUG_EXTENDED_SIZE	sizeof (struct r_debug_extended)
+R_DEBUG_EXTENDED_ALIGN	__alignof (struct r_debug_extended)