Remove lwp -> pid conversion in linux_nat_xfer_partial

The linux_nat_xfer_partial does a conversion of inferior_ptid: if it's
an LWP (ptid::lwp != 0), it builds a new ptid with the lwp as
the pid and assigns that temporarily to inferior_ptid.  For example, if
inferior_ptid is:

  { .pid = 1234, .lwp = 1235 }

it will assign this to inferior_ptid for the duration of the call:

  { .pid = 1235, .lwp = 0 }

Instead of doing this, this patch teaches the inf-ptrace implementation
of xfer_partial to deal with ptids representing lwps by using
get_ptrace_pid.

Also, in linux_proc_xfer_spu and linux_proc_xfer_partial, we use ptid_get_lwp
instead of ptid_get_pid.  While not strictly necessary, since the content of
/proc/<pid> and /proc/<lwp> should be the same, it's a bit safer, because:

- some files under /proc/<pid>/ may not work if the <pid> thread is
  running, just like ptrace requires a stopped thread.  The current
  thread's lwp id is more likely to be in the necessary state (stopped).

- if the leader (<pid>) had exited and is thus now zombie, then several
  files under "/proc/<pid>" won't work, while they will if you use
  "/proc/<lwp>".

The testsuite found no regression on native amd64 linux.

gdb/ChangeLog:

	* inf-ptrace.c (inf_ptrace_xfer_partial): Get pid from ptid
	using get_ptrace_pid.
	* linux-nat.c (linux_nat_xfer_partial): Don't set/restore
	inferior_ptid.
	(linux_proc_xfer_partial, linux_proc_xfer_spu): Use lwp of
	inferior_ptid instead of pid.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a6210484dc62eac58862f525abc9ce3120735cac..8bb9e21258c2f3c3039042d1701086b5fa1a2ca6 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2017-03-22  Simon Marchi  <simon.marchi@polymtl.ca>
+
+       * inf-ptrace.c (inf_ptrace_xfer_partial): Get pid from ptid
+       using get_ptrace_pid.
+       * linux-nat.c (linux_nat_xfer_partial): Don't set/restore
+       inferior_ptid.
+       (linux_proc_xfer_partial, linux_proc_xfer_spu): Use lwp of
+       inferior_ptid instead of pid.
+
 2017-03-22  Yao Qi  <yao.qi@linaro.org>
 
        * aarch64-tdep.c: Wrap locally used classes in anonymous

diff --git a/gdb/inf-ptrace.c b/gdb/inf-ptrace.c
index 61d24269a81fdcdaedee3e1f9a08d09bb0eb9f3f..f912d28088e2253079d57ea9ddce324008b9c20e 100644 (file)
--- a/gdb/inf-ptrace.c
+++ b/gdb/inf-ptrace.c
@@ -520,7 +520,7 @@ inf_ptrace_xfer_partial (struct target_ops *ops, enum target_object object,
                         const gdb_byte *writebuf,
                         ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
 {
-  pid_t pid = ptid_get_pid (inferior_ptid);
+  pid_t pid = get_ptrace_pid (inferior_ptid);
 
   switch (object)
     {

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 73ef2d49473e9d1761e8391bd7acfeeb1a15cc02..dff0da568a778e0d3033d867fccd7b3e9aff0073 100644 (file)
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -3890,7 +3890,6 @@ linux_nat_xfer_partial (struct target_ops *ops, enum target_object object,
                        const gdb_byte *writebuf,
                        ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
 {
-  struct cleanup *old_chain;
   enum target_xfer_status xfer;
 
   if (object == TARGET_OBJECT_SIGNAL_INFO)
@@ -3903,15 +3902,9 @@ linux_nat_xfer_partial (struct target_ops *ops, enum target_object object,
   if (object == TARGET_OBJECT_MEMORY && ptid_equal (inferior_ptid, null_ptid))
     return TARGET_XFER_EOF;
 
-  old_chain = save_inferior_ptid ();
-
-  if (ptid_lwp_p (inferior_ptid))
-    inferior_ptid = pid_to_ptid (ptid_get_lwp (inferior_ptid));
-
   xfer = linux_ops->to_xfer_partial (ops, object, annex, readbuf, writebuf,
                                     offset, len, xfered_len);
 
-  do_cleanups (old_chain);
   return xfer;
 }
 
@@ -4001,8 +3994,8 @@ linux_proc_xfer_partial (struct target_ops *ops, enum target_object object,
 
   /* We could keep this file open and cache it - possibly one per
      thread.  That requires some juggling, but is even faster.  */
-  xsnprintf (filename, sizeof filename, "/proc/%d/mem",
-            ptid_get_pid (inferior_ptid));
+  xsnprintf (filename, sizeof filename, "/proc/%ld/mem",
+            ptid_get_lwp (inferior_ptid));
   fd = gdb_open_cloexec (filename, ((readbuf ? O_RDONLY : O_WRONLY)
                                    | O_LARGEFILE), 0);
   if (fd == -1)
@@ -4095,7 +4088,7 @@ linux_proc_xfer_spu (struct target_ops *ops, enum target_object object,
   char buf[128];
   int fd = 0;
   int ret = -1;
-  int pid = ptid_get_pid (inferior_ptid);
+  int pid = ptid_get_lwp (inferior_ptid);
 
   if (!annex)
     {