[PATCH v3 30/44] gdbserver: adjust pid after the target attaches

[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 39642705b0d8bc614e7da84f0d0e1c34cd045b12..073289af7c94cd486908863ed91d4e1ead1920f4 100644
--- a/gdbserver/linux-low.cc
+++ b/gdbserver/linux-low.cc
@@ -1155,7 +1155,7 @@ 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;
@@ -1174,7 +1174,7 @@ 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 ());
     }
 
   open_proc_mem_file (proc);
@@ -1238,7 +1238,7 @@ 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 e1c88ee0bb2cb64f7f1400f926e45e901d977333..d02f6745cea5c05eb35c78fed1ebae912667e703 100644
--- a/gdbserver/linux-low.h
+++ b/gdbserver/linux-low.h
@@ -145,7 +145,7 @@ 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 2984b5b6e5649d01ce686fc5cdd96660a21b5fb6..14f87c1004f80522414fe0a300fb4416dd891eb9 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 a503afd870a898e6279549e22796c7aa5a69cbaa..232ada9b9f53017ebb444138b083119cc4749b5d 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 6707e27a788fb6e9de9854e9d025a2bbda38a474..119d87cc21ca95563cf89356b2fa4fce614b5e17 100644
--- a/gdbserver/server.cc
+++ b/gdbserver/server.cc
@@ -303,16 +303,26 @@ 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 a98dd33676dc2156f94a08f93177ace3a0d5153d..9fa405d8538a535522cd05853f190357a0919b7e 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 89831de9d4301ae906d765cccccd4135d858ff42..cf4341f7817359b4ccd09da2ebfe4fb67c3ca11d 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -581,7 +581,7 @@ 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;
@@ -596,7 +596,7 @@ 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 a76ed9fad3f8e6a9d7b752b83dd77b3448d21076..fdf23c94095ea9a1896c9cd0c70e06771ab39f1c 100644
--- a/gdbserver/win32-low.h
+++ b/gdbserver/win32-low.h
@@ -103,7 +103,7 @@ 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;
 

-- 
2.34.1

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