gdb: testsuite: Test whether PC register is expedited in gdb.server/server-run.exp

One thing GDB always does when the inferior stops is finding out where
it's stopped at, by way of querying the value of the program counter
register.

To save a packet round trip, the remote target can send the PC
value (often alongside other frequently consulted registers such as the
stack pointer) in the stop reply packet as an "expedited register".

Test that this is actually done for the targets where gdbserver is
supposed to.

Extend the "maintenance print remote-registers" command output with an
"Expedited" column which says "yes" if the register was seen by GDB in
the last stop reply packet it received, and is left blank otherwise.

Tested for regressions on aarch64-linux-gnu native-extended-remote.

The testcase was tested on aarch64-linux-gnu, i686-linux-gnu and
x86_64-linux-gnu native-remote and native-extended-remote targets.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>

diff --git a/gdb/NEWS b/gdb/NEWS
index 5e0ac313f0a69851b694b1562fd76056d6998fa9..26dd4de82a25352eeefe3cb952d53888bddd818e 100644 (file)
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -90,6 +90,11 @@ save gdb-index
   it contains white space or quote characters.  If the argument
   contains no such special characters then quoting is not required.
 
+maintenance print remote-registers
+  Add an "Expedited" column to the output of the command.  It indicates
+  which registers were included in the last stop reply packet received by
+  GDB.
+
 * New remote packets
 
 vFile:stat

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 891344b1bf3670444bbae255139f15e6b6f60d1a..143e498b742b6195b16304583327ad6cc8e2b3e0 100644 (file)
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -42082,7 +42082,11 @@ including registers which aren't available on the target nor visible
 to user; the command @code{maint print register-groups} includes the
 groups that each register is a member of; and the command @code{maint
 print remote-registers} includes the remote target's register numbers
-and offsets in the `G' packets.
+and offsets in the `G' packets, as well as an indication of which
+registers were included in the last stop reply packet received by
+@value{GDBN} (@pxref{Stop Reply Packets}).  Please note that the list
+of registers included in a stop reply can change from one stop to the
+next.
 
 These commands take an optional parameter, a file name to which to
 write the information.

diff --git a/gdb/regcache-dump.c b/gdb/regcache-dump.c
index bc665dc08a67379afb691c20f4deae31922902d4..6b711bf6c2a01e21b89b952e9926a7acfb27540b 100644 (file)
--- a/gdb/regcache-dump.c
+++ b/gdb/regcache-dump.c
@@ -162,7 +162,7 @@ protected:
   {
     if (regnum < 0)
       {
-       gdb_printf (file, "Rmt Nr  g/G Offset");
+       gdb_printf (file, "Rmt Nr  g/G Offset  Expedited");
       }
     else if (regnum < gdbarch_num_regs (m_gdbarch))
       {
@@ -170,7 +170,12 @@ protected:
 
        if (remote_register_number_and_offset (m_gdbarch, regnum,
                                               &pnum, &poffset))
-         gdb_printf (file, "%7d %11d", pnum, poffset);
+         {
+           if (remote_register_is_expedited (regnum))
+             gdb_printf (file, "%7d %11d  yes", pnum, poffset);
+           else
+             gdb_printf (file, "%7d %11d", pnum, poffset);
+         }
       }
   }
 };
@@ -324,9 +329,11 @@ _initialize_regcache_dump ()
             "Takes an optional file parameter."),
           &maintenanceprintlist);
   add_cmd ("remote-registers", class_maintenance,
-          maintenance_print_remote_registers, _("\
-Print the internal register configuration including remote register number "
-"and g/G packets offset.\n\
-Takes an optional file parameter."),
+          maintenance_print_remote_registers,
+          _("Print the internal register configuration including remote "
+            "register number and g/G packets offset.\n"
+            "Also prints which registers were sent in the last stop reply "
+            "packet (i.e. expedited).\n"
+            "Takes an optional file parameter."),
           &maintenanceprintlist);
 }

diff --git a/gdb/remote.c b/gdb/remote.c
index 8e704a770ce18d4cb2d57c8d370b80e41b132974..4ec25ee23428364891eb05a899b8142848e0760e 100644 (file)
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -696,6 +696,10 @@ public: /* data */
      qSupported.  */
   gdb_thread_options supported_thread_options = 0;
 
+  /* Contains the regnums of the expedited registers in the last stop
+     reply packet.  */
+  std::set<int> last_seen_expedited_registers;
+
 private:
   /* Asynchronous signal handle registered as event loop source for
      when we have pending events ready to be passed to the core.  */
@@ -1493,6 +1497,20 @@ is_remote_target (process_stratum_target *target)
   return as_remote_target (target) != nullptr;
 }
 
+/* See remote.h.  */
+
+bool
+remote_register_is_expedited (int regnum)
+{
+  remote_target *rt = as_remote_target (current_inferior ()->process_target ());
+
+  if (rt == nullptr)
+    return false;
+
+  remote_state *rs = rt->get_remote_state ();
+  return rs->last_seen_expedited_registers.count (regnum) > 0;
+}
+
 /* Per-program-space data key.  */
 static const registry<program_space>::key<char, gdb::xfree_deleter<char>>
   remote_pspace_data;
@@ -8523,6 +8541,10 @@ remote_target::process_stop_reply (stop_reply_up stop_reply,
 {
   *status = stop_reply->ws;
   ptid_t ptid = stop_reply->ptid;
+  struct remote_state *rs = get_remote_state ();
+
+  /* Forget about last reply's expedited registers.  */
+  rs->last_seen_expedited_registers.clear ();
 
   /* If no thread/process was reported by the stub then select a suitable
      thread/process.  */
@@ -8549,7 +8571,10 @@ remote_target::process_stop_reply (stop_reply_up stop_reply,
                                        stop_reply->arch);
 
          for (cached_reg_t &reg : stop_reply->regcache)
-           regcache->raw_supply (reg.num, reg.data.get ());
+           {
+             regcache->raw_supply (reg.num, reg.data.get ());
+             rs->last_seen_expedited_registers.insert (reg.num);
+           }
        }
 
       remote_thread_info *remote_thr = get_remote_thread_info (this, ptid);

diff --git a/gdb/remote.h b/gdb/remote.h
index cb0a66da66e57de3d3d3902e601d6ec3be27ace8..bfe3c65b4637bfcb59d86b9c4d611ebdd1301181 100644 (file)
--- a/gdb/remote.h
+++ b/gdb/remote.h
@@ -121,4 +121,9 @@ extern void send_remote_packet (gdb::array_view<const char> &buf,
 
 extern bool is_remote_target (process_stratum_target *target);
 
+/* Return true if REGNUM was returned as an expedited register in the last
+   stop reply we received.  */
+
+extern bool remote_register_is_expedited (int regnum);
+
 #endif

diff --git a/gdb/testsuite/gdb.server/server-run.exp b/gdb/testsuite/gdb.server/server-run.exp
index 92eb38bd9db055afe109b817b7ab702167c59108..af5a5f53ca03f1bd9507f8b7284d70ddb7f12915 100644 (file)
--- a/gdb/testsuite/gdb.server/server-run.exp
+++ b/gdb/testsuite/gdb.server/server-run.exp
@@ -52,3 +52,36 @@ if { [istarget *-*-linux*] } {
 
 gdb_breakpoint main
 gdb_test "continue" "Breakpoint.* main .*" "continue to main"
+
+if { [istarget "aarch64*-*-*"]
+     || [istarget "arm*-*-*"]
+     || [istarget "csky*-*-*"]
+     || [istarget "loongarch*-*-*"]
+     || [istarget "riscv*-*-*"] } {
+    set pc_regname "pc"
+} elseif { [is_amd64_regs_target] } {
+    set pc_regname "rip"
+} elseif { [is_x86_like_target] } {
+    set pc_regname "eip"
+} elseif { [istarget "tic6x-*-*"] } {
+    set pc_regname "PC"
+}
+
+# Sending the PC register in advance is good practice.  Test that this is
+# actually done for the targets where gdbserver is supposed to.
+set expedited_pc_test_name "send PC as expedited register in stop reply"
+if { [info exists pc_regname] } {
+    set seen_line false
+    gdb_test_multiple "maintenance print remote-registers" \
+            $expedited_pc_test_name -lbl {
+       -re " ${pc_regname}\[\[:space:\]\]+${decimal}.*${decimal}  yes" {
+           set seen_line true
+           exp_continue
+       }
+       -re "\r\n$gdb_prompt $" {
+           gdb_assert { $seen_line } $gdb_test_name
+       }
+    }
+} else {
+    untested $expedited_pc_test_name
+}