[PATCH v2] gdb/remote: Remove negative tid/pid handling in wite_ptid

[PATCH v2] gdb/remote: Remove negative tid/pid handling in wite_ptid

[Evgeniy Didin]

Actually thread and process ID's are positive values. Accorting to
http://man7.org/linux/man-pages/man7/pthreads.7.html
threads are creating using "clone" syscall, so the ID generation mechanism
is similar for threads and processes. According to Linux source code
there is a function call tree, which allocates  PID[TID]:
clone
 |->_do_fork
    |->copy_process
      |->alloc_pid
        |->idr_alloc_cyclic
          |->idr_alloc_u32(idr, ptr, &id, max, gfp);
And in idr_alloc_u32() "id" is u32 value, which means positiveness.
Also according to:
https://elixir.bootlin.com/linux/latest/source/kernel/pid.c#L177
PID cannot be less than 1.

In Zephyr RTOS the k_thread_create function returns
thread ID which is actually pointer to k_thread structure.
If the memory addressing starts from 0x80000000, passing such
big values to write_ptid() leads to overflow of "int tid" variable
and thread ID becomes negative.
So lets remove the code, which handles negative tid/pid values.

gdb/ChangeLog:

2019-11-06  Evgeniy Didin <didin@synopsys.com>

        * remote.c (remote_target::write_ptid):  Remove handling
         negative tid,pid. Change "int" to "unsigned int" for pid/tid.

Signed-off-by: Evgeniy Didin <didin@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Claudiu Zissulescu <claziss@synopsys.com>
Cc: Cupertino Miranda <cmiranda@synopsys.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Shahab Vahedi <shahab@synopsys.com>
Cc: linux-snps-arc@lists.infradead.org

Signed-off-by: Evgeniy Didin <didin@synopsys.com>
---
Changes v1-v2:
-make no change of tid/pid bitness, 
 use generic "unsigned int" instead of "uint32_t"	

 gdb/ChangeLog |  6 ++++++
 gdb/remote.c  | 12 +++---------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index e886480d62..cd55d65ced 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2019-11-06  Evgeniy Didin <didin@synopsys.com>
+
+	* remote.c (remote_target::write_ptid):  Remove handling
+	negative tid,pid. Change "int" to "unsigned int" for pid/tid.
+
+
 2019-11-05  Tom Tromey  <tom@tromey.com>
 
 	* tui/tui-disasm.c (struct tui_asm_line) <addr_size>: New member.
diff --git a/gdb/remote.c b/gdb/remote.c
index 8ea52d355a..ea12d738c8 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -2909,22 +2909,16 @@ static int remote_newthread_step (threadref *ref, void *context);
 char *
 remote_target::write_ptid (char *buf, const char *endbuf, ptid_t ptid)
 {
-  int pid, tid;
+  unsigned int pid, tid;
   struct remote_state *rs = get_remote_state ();
 
   if (remote_multi_process_p (rs))
     {
       pid = ptid.pid ();
-      if (pid < 0)
-	buf += xsnprintf (buf, endbuf - buf, "p-%x.", -pid);
-      else
-	buf += xsnprintf (buf, endbuf - buf, "p%x.", pid);
+      buf += xsnprintf (buf, endbuf - buf, "p%x.", pid);
     }
   tid = ptid.lwp ();
-  if (tid < 0)
-    buf += xsnprintf (buf, endbuf - buf, "-%x", -tid);
-  else
-    buf += xsnprintf (buf, endbuf - buf, "%x", tid);
+  buf += xsnprintf (buf, endbuf - buf, "%x", tid);
 
   return buf;
 }
-- 
2.17.2


_______________________________________________
linux-snps-arc mailing list
linux-snps-arc@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-snps-arc

Re: [PATCH v2] gdb/remote: Remove negative tid/pid handling in wite_ptid

[Pedro Alves]

On 11/6/19 1:27 PM, Evgeniy Didin wrote:
> Actually thread and process ID's are positive values. Accorting to
> http://man7.org/linux/man-pages/man7/pthreads.7.html
> threads are creating using "clone" syscall, so the ID generation mechanism
> is similar for threads and processes. According to Linux source code
> there is a function call tree, which allocates  PID[TID]:
> clone
>  |->_do_fork
>     |->copy_process
>       |->alloc_pid
>         |->idr_alloc_cyclic
>           |->idr_alloc_u32(idr, ptr, &id, max, gfp);
> And in idr_alloc_u32() "id" is u32 value, which means positiveness.
> Also according to:
> https://elixir.bootlin.com/linux/latest/source/kernel/pid.c#L177
> PID cannot be less than 1.

Sure for Linux.  But negative numbers have meaning in the remote protocol:

 https://sourceware.org/gdb/current/onlinedocs/gdb/Packets.html#thread_002did-syntax

Thanks,
Pedro Alves


_______________________________________________
linux-snps-arc mailing list
linux-snps-arc@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-snps-arc