[PATCH v4 14/44] gdbserver: adjust pid after the target attaches

[Markus Metzger <markus.t.metzger@intel.com>]

From: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>

The PID argument of the attach operation may be interpreted in a
target specific way, and may not necessarily mean that the process we
attached to has PID as its process id.  This is for example the case
for Intel GT targets, where the PID refers to the process id of the
host application that is using the devices.  The target in that case
creates a new process for each device where the PID of the process is
the device id/ordinal.  Therefore, once the target completes the
attach, we want adjust the PID value.  For this, revise the meaning
of the return value of the 'attach' target op in case of success:
return the PID of the process that was attached to.

The PID argument to the 'attach' target op is of type 'int' in caller
sites.  Also, the type of the PID field in ptid_t is of type 'int'.
Hence, update the parameter of 'attach' to 'int', too.
---
 gdbserver/linux-low.cc  |  6 +++---
 gdbserver/linux-low.h   |  2 +-
 gdbserver/netbsd-low.cc |  2 +-
 gdbserver/netbsd-low.h  |  2 +-
 gdbserver/server.cc     | 18 ++++++++++++++----
 gdbserver/target.h      | 11 ++++++++---
 gdbserver/win32-low.cc  |  4 ++--
 gdbserver/win32-low.h   |  2 +-
 8 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
index f14e5b1dc32..8f8bcfb72ea 100644
--- a/gdbserver/linux-low.cc
+++ b/gdbserver/linux-low.cc
@@ -1191,7 +1191,7 @@ static void async_file_mark (void);
    of its threads.  */
 
 int
-linux_process_target::attach (unsigned long pid)
+linux_process_target::attach (int pid)
 {
   struct process_info *proc;
   thread_info *initial_thread;
@@ -1210,7 +1210,7 @@ linux_process_target::attach (unsigned long pid)
       this->remove_linux_process (proc);
 
       std::string reason = linux_ptrace_attach_fail_reason_string (ptid, err);
-      error (_("Cannot attach to process %ld: %s"), pid, reason.c_str ());
+      error (_("Cannot attach to process %d: %s"), pid, reason.c_str ());
     }
 
   /* Don't report shared library events after attaching, even if some
@@ -1279,7 +1279,7 @@ linux_process_target::attach (unsigned long pid)
       gdb_assert (proc->tdesc != NULL);
     }
 
-  return 0;
+  return pid;
 }
 
 static int
diff --git a/gdbserver/linux-low.h b/gdbserver/linux-low.h
index 60154240ddd..f8cddef7236 100644
--- a/gdbserver/linux-low.h
+++ b/gdbserver/linux-low.h
@@ -150,7 +150,7 @@ class linux_process_target : public process_stratum_target
 
   void post_create_inferior () override;
 
-  int attach (unsigned long pid) override;
+  int attach (int pid) override;
 
   int kill (process_info *proc) override;
 
diff --git a/gdbserver/netbsd-low.cc b/gdbserver/netbsd-low.cc
index 326b4d55860..c74c1da6fed 100644
--- a/gdbserver/netbsd-low.cc
+++ b/gdbserver/netbsd-low.cc
@@ -105,7 +105,7 @@ netbsd_process_target::post_create_inferior ()
 /* Implement the attach target_ops method.  */
 
 int
-netbsd_process_target::attach (unsigned long pid)
+netbsd_process_target::attach (int pid)
 {
   /* Unimplemented.  */
   return -1;
diff --git a/gdbserver/netbsd-low.h b/gdbserver/netbsd-low.h
index 265009739a9..65866308902 100644
--- a/gdbserver/netbsd-low.h
+++ b/gdbserver/netbsd-low.h
@@ -46,7 +46,7 @@ class netbsd_process_target : public process_stratum_target
 
   void post_create_inferior () override;
 
-  int attach (unsigned long pid) override;
+  int attach (int pid) override;
 
   int kill (process_info *proc) override;
 
diff --git a/gdbserver/server.cc b/gdbserver/server.cc
index 471d6782091..13a806421a0 100644
--- a/gdbserver/server.cc
+++ b/gdbserver/server.cc
@@ -301,16 +301,26 @@ static int
 attach_inferior (int pid)
 {
   client_state &cs = get_client_state ();
-  /* myattach should return -1 if attaching is unsupported,
-     0 if it succeeded, and call error() otherwise.  */
 
   if (find_process_pid (pid) != nullptr)
     error (_("Already attached to process %d\n"), pid);
 
-  if (myattach (pid) != 0)
+  /* If attaching is unsupported, myattach returns -1.  If successful,
+     it returns the PID of the process that was attached to.  In other
+     cases, it calls error().  */
+  int new_pid = myattach (pid);
+  if (new_pid == -1)
     return -1;
 
-  fprintf (stderr, "Attached; pid = %d\n", pid);
+  if (new_pid == pid)
+    fprintf (stderr, "Attached; pid = %d\n", pid);
+  else
+    {
+      fprintf (stderr, "Attached; given pid = %d, updated to %d\n",
+	       pid, new_pid);
+      pid = new_pid;
+    }
+
   fflush (stderr);
 
   /* FIXME - It may be that we should get the SIGNAL_PID from the
diff --git a/gdbserver/target.h b/gdbserver/target.h
index 82eab9d1243..e38570dabb2 100644
--- a/gdbserver/target.h
+++ b/gdbserver/target.h
@@ -95,9 +95,14 @@ class process_stratum_target
      PID is the process ID to attach to, specified by the user
      or a higher layer.
 
-     Returns -1 if attaching is unsupported, 0 on success, and calls
-     error() otherwise.  */
-  virtual int attach (unsigned long pid) = 0;
+     If attaching is unsupported, returns -1.
+
+     If successful, returns the ID of the process that was attached to.
+     This return value may be different from the argument PID, depending
+     on how the target interpreted the argument.
+
+     Calls error() in other cases.  */
+  virtual int attach (int pid) = 0;
 
   /* Kill process PROC.  Return -1 on failure, and 0 on success.  */
   virtual int kill (process_info *proc) = 0;
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 935ac6657f7..ecfdd030d8b 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -604,7 +604,7 @@ win32_process_target::create_inferior (const char *program,
    PID is the process ID to attach to, specified by the user
    or a higher layer.  */
 int
-win32_process_target::attach (unsigned long pid)
+win32_process_target::attach (int pid)
 {
   HANDLE h;
   DWORD err;
@@ -619,7 +619,7 @@ win32_process_target::attach (unsigned long pid)
 	  /* win32_wait needs to know we're attaching.  */
 	  windows_process.attaching = 1;
 	  do_initial_child_stuff (h, pid, 1);
-	  return 0;
+	  return pid;
 	}
 
       CloseHandle (h);
diff --git a/gdbserver/win32-low.h b/gdbserver/win32-low.h
index 439adb84bc2..03bd625e23d 100644
--- a/gdbserver/win32-low.h
+++ b/gdbserver/win32-low.h
@@ -100,7 +100,7 @@ class win32_process_target : public process_stratum_target
   int create_inferior (const char *program,
 		       const std::string &program_args) override;
 
-  int attach (unsigned long pid) override;
+  int attach (int pid) override;
 
   int kill (process_info *proc) override;
 
-- 
2.43.0

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