[PATCH PR gdb/18071] TLS variables can't be resolved on aarch64-linux-gnu

Weimin Pan
2017-11-03T00:54:21Z

Running the test case with upstream gdb shows two failures:

(1) Receiving different error messages when printing TLS variable before
program runs - because the ARM compiler does not emit dwarf attribute
DW_AT_location for TLS, the result is expected and the baseline may
need to be changed for aarch64.

(2) Using "info address" command on C++ static TLS object resulted in
"symbol unresolved" error - below is a snippet from the test case:

class K {
public:
static __thread int another_thread_local;
};

__thread int K::another_thread_local;

(gdb) info address K::another_thread_local
Symbol "K::another_thread_local" is unresolved.

This patch contains fix for (2).

Function info_address_command() handles the "info address" command and
calls lookup_minimal_symbol_and_objfile() to find sym's symbol entry in
mininal symbol table if SYMBOL_COMPUTED_OPS (sym) is false. Problem is
that function lookup_minimal_symbol_and_objfile() only looked up an
objfile's minsym ordinary hash table, not its demangled hash table, which
was the reason why the C++ name was not found.

The fix is to call lookup_minimal_symbol(), which already looks up entries
in both minsym's hash tables, to find names when traversing the object file
list in lookup_minimal_symbol_and_objfile().

Tested in both aarch64-linux-gnu and amd64-linux-gnu. No regressions.
---
gdb/ChangeLog | 5 +++++
gdb/minsyms.c | 17 +++--------------
2 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4b292e0..2f630bc 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2017-11-01 Weimin Pan <weimin.pan@oracle.com>
+
+ * minsyms.c (lookup_minimal_symbol_and_objfile): Use
+ lookup_minimal_symbol() to find symbol entry.
+
2017-10-27 Keith Seitz <keiths@redhat.com>

* breakpoint.c (print_breakpoint_location): Use the symbol saved
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index 37edbd8..4edd8b1 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -881,23 +881,12 @@ lookup_minimal_symbol_and_objfile (const char *name)
{
struct bound_minimal_symbol result;
struct objfile *objfile;
- unsigned int hash = msymbol_hash (name) % MINIMAL_SYMBOL_HASH_SIZE;

ALL_OBJFILES (objfile)
{
- struct minimal_symbol *msym;
-
- for (msym = objfile->per_bfd->msymbol_hash[hash];
- msym != NULL;
- msym = msym->hash_next)
- {
- if (strcmp (MSYMBOL_LINKAGE_NAME (msym), name) == 0)
- {
- result.minsym = msym;
- result.objfile = objfile;
- return result;
- }
- }
+ result = lookup_minimal_symbol (name, NULL, objfile);
+ if (result.minsym != NULL)
+ return result;
}

memset (&result, 0, sizeof (result));
--
1.7.1