From cb7364414157c42de5ea618d98e2be9eff1894ba Mon Sep 17 00:00:00 2001
From: George Barrett <bob@bob131.so>
Date: Sun, 15 Dec 2019 11:12:09 +1100
Subject: [PATCH] Fix disabling of solib probes when LD_AUDITing
The SVR4 solib event handler determines whether an event is related to a
non-base link namespace by comparing the event's debug struct address
to the debug struct address of the initial program image. However, this
can fail when using LD_AUDIT as audit libraries are loaded before the
loader has initialised the initial program image's debug struct. When
the event handler fails to find the debug struct, the probe-based
debugger interface is disabled and a warning is flagged to the user.
This commit adds a fallback test to help determine whether an event is
for a foreign link namespace when the debug struct isn't available.
gdb/ChangeLog:
2019-12-15 George Barrett <bob@bob131.so>
* solib-svr4.c (svr4_handle_solib_event): Add fallback link
namespace test for when the debug struct isn't available.
---
gdb/ChangeLog | 5 +++++
gdb/solib-svr4.c | 22 +++++++++++++++++++++-
2 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0ba175a4315..acf9106e844 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-21 George Barrett <bob@bob131.so>
+
+ * solib-svr4.c (svr4_handle_solib_event): Add fallback link
+ namespace test for when the debug struct isn't available.
+
2019-12-21 Eli Zaretskii <eliz@gnu.org>
* top.c (print_gdb_configuration): Print "--with-xxhash" or
diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index de765576d0b..f0c7769ac2c 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -1942,7 +1942,27 @@ svr4_handle_solib_event (void)
/* Always locate the debug struct, in case it moved. */
info->debug_base = 0;
if (locate_base (info) == 0)
- return;
+ {
+ /* It's possible for the reloc_complete probe to be triggered before
+ the linker has set the DT_DEBUG pointer (for example, when the
+ linker has finished relocating an LD_AUDIT library or its
+ dependencies). Since we can't yet handle libraries from other link
+ namespaces, we don't lose anything by ignoring them here. */
+ struct value *link_map_id_val;
+ try
+ {
+ link_map_id_val = pa->prob->evaluate_argument (0, frame);
+ }
+ catch (const gdb_exception_error)
+ {
+ link_map_id_val = NULL;
+ }
+ /* glibc and illumos' libc both define LM_ID_BASE as zero. */
+ if (link_map_id_val != NULL && value_as_long (link_map_id_val) != 0)
+ action = DO_NOTHING;
+ else
+ return;
+ }
/* GDB does not currently support libraries loaded via dlmopen
into namespaces other than the initial one. We must ignore
--
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