Handle DW_OP_form_tls_address

Currently gdb supports DW_OP_GNU_push_tls_address, but not
DW_OP_form_tls_address.  I think it would be better if the toolchain
as a whole moved to using the standard opcode, and the prerequisite to
this is getting gdb to recognize it.

GCC can sometimes emit DW_OP_form_tls_address for emultls targets.  As
far as I know, nobody has ever tried this with gdb (since it wouldn't
work at all).

I don't think there's a major drawback to using a single opcode for
all targets, because computing the location of a thread-local is
already target specific.

This is PR gdb/11616.

I don't know how to write a test case for this; though it's worth
noting that there aren't explicit tests for DW_OP_GNU_push_tls_address
either -- and if I change GCC, these paths will be tested to the same
extent they are now.

2016-09-02  Tom Tromey  <tom@tromey.com>

	PR gdb/11616:
	* dwarf2read.c (decode_locdesc): Handle DW_OP_form_tls_address.
	* dwarf2loc.c (dwarf2_compile_expr_to_ax): Handle
	DW_OP_form_tls_address.
	(locexpr_describe_location_piece): Likewise.
	* dwarf2expr.h (struct dwarf_expr_context_funcs): Update comment.
	* dwarf2expr.c (execute_stack_op): Handle DW_OP_form_tls_address.
	(ctx_no_get_tls_address): Mention DW_OP_form_tls_address.
	* compile/compile-loc2c.c (struct insn_info): Update comment.
	(compute_stack_depth_worker): Handle DW_OP_form_tls_address.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 08509fbdc1c4f2480fd29600addc1703fbb5d665..222f78700dac8c73afb627a12fca5b99a104a0c6 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,16 @@
+2016-09-02  Tom Tromey  <tom@tromey.com>
+
+       PR gdb/11616:
+       * dwarf2read.c (decode_locdesc): Handle DW_OP_form_tls_address.
+       * dwarf2loc.c (dwarf2_compile_expr_to_ax): Handle
+       DW_OP_form_tls_address.
+       (locexpr_describe_location_piece): Likewise.
+       * dwarf2expr.h (struct dwarf_expr_context_funcs): Update comment.
+       * dwarf2expr.c (execute_stack_op): Handle DW_OP_form_tls_address.
+       (ctx_no_get_tls_address): Mention DW_OP_form_tls_address.
+       * compile/compile-loc2c.c (struct insn_info): Update comment.
+       (compute_stack_depth_worker): Handle DW_OP_form_tls_address.
+
 2016-09-01  Sergio Durigan Junior  <sergiodj@redhat.com>
 
        * target.c (target_wait): Mention that the function's prototype

diff --git a/gdb/compile/compile-loc2c.c b/gdb/compile/compile-loc2c.c
index 1a267b852374b42cdeb7fac9d425da80023cb759..e8bef55e0481bfc9dfa7bb778e963e42301fc33a 100644 (file)
--- a/gdb/compile/compile-loc2c.c
+++ b/gdb/compile/compile-loc2c.c
@@ -48,9 +48,9 @@ struct insn_info
 
   unsigned int label : 1;
 
-  /* Whether this instruction is DW_OP_GNU_push_tls_address.  This is
-     a hack until we can add a feature to glibc to let us properly
-     generate code for TLS.  */
+  /* Whether this instruction is DW_OP_GNU_push_tls_address or
+     DW_OP_form_tls_address.  This is a hack until we can add a
+     feature to glibc to let us properly generate code for TLS.  */
 
   unsigned int is_tls : 1;
 };
@@ -323,6 +323,7 @@ compute_stack_depth_worker (int start, int *need_tempvar,
          break;
 
        case DW_OP_GNU_push_tls_address:
+       case DW_OP_form_tls_address:
          info[ndx].is_tls = 1;
          break;
 

diff --git a/gdb/dwarf2expr.c b/gdb/dwarf2expr.c
index 7bf3c78d86370cf1458c398deedaea9f483f1357..7eb1982e5a580759bd11473d613b36b9d615e555 100644 (file)
--- a/gdb/dwarf2expr.c
+++ b/gdb/dwarf2expr.c
@@ -1257,6 +1257,7 @@ execute_stack_op (struct dwarf_expr_context *ctx,
          break;
 
        case DW_OP_GNU_push_tls_address:
+       case DW_OP_form_tls_address:
          /* Variable is at a constant offset in the thread-local
          storage block into the objfile for the current thread and
          the dynamic linker module containing this expression.  Here
@@ -1533,7 +1534,7 @@ ctx_no_get_frame_pc (void *baton)
 CORE_ADDR
 ctx_no_get_tls_address (void *baton, CORE_ADDR offset)
 {
-  error (_("%s is invalid in this context"), "DW_OP_GNU_push_tls_address");
+  error (_("%s is invalid in this context"), "DW_OP_form_tls_address");
 }
 
 /* Stub dwarf_expr_context_funcs.dwarf_call implementation.  */

diff --git a/gdb/dwarf2expr.h b/gdb/dwarf2expr.h
index 3d7ca002c5e7c6e9a2f1a67d7deeaacba245e269..cbab45b4bb6dea433213ecc1fa03f664533c8a40 100644 (file)
--- a/gdb/dwarf2expr.h
+++ b/gdb/dwarf2expr.h
@@ -56,7 +56,7 @@ struct dwarf_expr_context_funcs
   CORE_ADDR (*get_frame_pc) (void *baton);
 
   /* Return the thread-local storage address for
-     DW_OP_GNU_push_tls_address.  */
+     DW_OP_GNU_push_tls_address or DW_OP_form_tls_address.  */
   CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset);
 
   /* Execute DW_AT_location expression for the DWARF expression subroutine in

diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c
index e60475fecc499a555c5f756d479eece9d805e4c7..946ddf8b6e94d8a4908d237ec8cf12ead2d8ff41 100644 (file)
--- a/gdb/dwarf2loc.c
+++ b/gdb/dwarf2loc.c
@@ -3571,6 +3571,7 @@ dwarf2_compile_expr_to_ax (struct agent_expr *expr, struct axs_value *loc,
          break;
 
        case DW_OP_GNU_push_tls_address:
+       case DW_OP_form_tls_address:
          unimplemented (op);
          break;
 
@@ -3907,7 +3908,8 @@ locexpr_describe_location_piece (struct symbol *symbol, struct ui_file *stream,
           && (data[0] == DW_OP_addr
               || (addr_size == 4 && data[0] == DW_OP_const4u)
               || (addr_size == 8 && data[0] == DW_OP_const8u))
-          && data[1 + addr_size] == DW_OP_GNU_push_tls_address
+          && (data[1 + addr_size] == DW_OP_GNU_push_tls_address
+              || data[1 + addr_size] == DW_OP_form_tls_address)
           && piece_end_p (data + 2 + addr_size, end))
     {
       ULONGEST offset;
@@ -3930,7 +3932,8 @@ locexpr_describe_location_piece (struct symbol *symbol, struct ui_file *stream,
           && data + 1 + (leb128_size = skip_leb128 (data + 1, end)) < end
           && data[0] == DW_OP_GNU_const_index
           && leb128_size > 0
-          && data[1 + leb128_size] == DW_OP_GNU_push_tls_address
+          && (data[1 + leb128_size] == DW_OP_GNU_push_tls_address
+              || data[1 + leb128_size] == DW_OP_form_tls_address)
           && piece_end_p (data + 2 + leb128_size, end))
     {
       uint64_t offset;

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 924b417f339e40364fcb08a1bdf66f9d1371cca8..9ad2caa821878baf6794c31d314d8be43dffb943 100644 (file)
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -20817,6 +20817,7 @@ decode_locdesc (struct dwarf_block *blk, struct dwarf2_cu *cu)
          break;
 
         case DW_OP_GNU_push_tls_address:
+       case DW_OP_form_tls_address:
          /* The top of the stack has the offset from the beginning
             of the thread control block at which the variable is located.  */
          /* Nothing should follow this operator, so the top of stack would