Do not cast away const in agent_run_command

While investigating something else, I noticed some weird code in
agent_run_command (use of memcpy rather than strcpy).  Then I noticed
that 'cmd' is used as both an in and out parameter, despite being
const.

Casting away const like this is bad.  This patch removes the const and
fixes the memcpy.  I also added a static assert to assure myself that
the code in gdbserver is correct -- gdbserver is passing its own
buffer directly to agent_run_command.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

5 files changed, 17 insertions, 13 deletions

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 2b206a4..d6e69e6 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -4114,9 +4114,7 @@ linux_nat_target::static_tracepoint_markers_by_strid (const char *strid)
   /* Pause all */
   target_stop (ptid);
 
-  memcpy (s, "qTfSTM", sizeof ("qTfSTM"));
-  s[sizeof ("qTfSTM")] = 0;
-
+  strcpy (s, "qTfSTM");
   agent_run_command (pid, s, strlen (s) + 1);
 
   /* Unpause all.  */
@@ -4133,8 +4131,7 @@ linux_nat_target::static_tracepoint_markers_by_strid (const char *strid)
 	}
       while (*p++ == ',');	/* comma-separated list */
 
-      memcpy (s, "qTsSTM", sizeof ("qTsSTM"));
-      s[sizeof ("qTsSTM")] = 0;
+      strcpy (s, "qTsSTM");
       agent_run_command (pid, s, strlen (s) + 1);
       p = s;
     }
diff --git a/gdbserver/server.cc b/gdbserver/server.cc
index 21fb51a..46dfe70 100644
--- a/gdbserver/server.cc
+++ b/gdbserver/server.cc
@@ -51,6 +51,11 @@
 #include "gdbsupport/scoped_restore.h"
 #include "gdbsupport/search.h"
 
+/* PBUFSIZ must also be at least as big as IPA_CMD_BUF_SIZE, because
+   the client state data is passed directly to some agent
+   functions.  */
+gdb_static_assert (PBUFSIZ >= IPA_CMD_BUF_SIZE);
+
 #define require_running_or_return(BUF)		\
   if (!target_running ())			\
     {						\
diff --git a/gdbserver/tracepoint.cc b/gdbserver/tracepoint.cc
index 37a9a8c..b59077a 100644
--- a/gdbserver/tracepoint.cc
+++ b/gdbserver/tracepoint.cc
@@ -6820,7 +6820,7 @@ run_inferior_command (char *cmd, int len)
   target_pause_all (false);
   uninsert_all_breakpoints ();
 
-  err = agent_run_command (pid, (const char *) cmd, len);
+  err = agent_run_command (pid, cmd, len);
 
   reinsert_all_breakpoints ();
   target_unpause_all (false);
diff --git a/gdbsupport/agent.cc b/gdbsupport/agent.cc
index 531807b..81c925d 100644
--- a/gdbsupport/agent.cc
+++ b/gdbsupport/agent.cc
@@ -179,14 +179,16 @@ gdb_connect_sync_socket (int pid)
 #endif
 }
 
-/* Execute an agent command in the inferior.  PID is the value of pid of the
-   inferior.  CMD is the buffer for command.  GDB or GDBserver will store the
-   command into it and fetch the return result from CMD.  The interaction
-   between GDB/GDBserver and the agent is synchronized by a synchronization
-   socket.  Return zero if success, otherwise return non-zero.  */
+/* Execute an agent command in the inferior.  PID is the value of pid
+   of the inferior.  CMD is the buffer for command.  It is assumed to
+   be at least IPA_CMD_BUF_SIZE bytes long.  GDB or GDBserver will
+   store the command into it and fetch the return result from CMD.
+   The interaction between GDB/GDBserver and the agent is synchronized
+   by a synchronization socket.  Return zero if success, otherwise
+   return non-zero.  */
 
 int
-agent_run_command (int pid, const char *cmd, int len)
+agent_run_command (int pid, char *cmd, int len)
 {
   int fd;
   int tid = agent_get_helper_thread_id ();
diff --git a/gdbsupport/agent.h b/gdbsupport/agent.h
index dceb33f..7a258e2 100644
--- a/gdbsupport/agent.h
+++ b/gdbsupport/agent.h
@@ -22,7 +22,7 @@
 
 #include "gdbsupport/preprocessor.h"
 
-int agent_run_command (int pid, const char *cmd, int len);
+int agent_run_command (int pid, char *cmd, int len);
 
 int agent_look_up_symbols (void *);