Fix write endianness/size problem for fast tracepoint enabled flag

I am sending this fix on behalf of Par Olsson, as a follow-up of this
one:

https://www.sourceware.org/ml/gdb-patches/2015-10/msg00196.html

This problem is exposed when enabling/disabling fast tracepoints on big
endian machines.  The flag is defined as an int8_t, but is written from
gdbserver as an integer (usually 32 bits).  When the agent code reads it
as an int8_t, it only considers the most significant byte, which is
always 0.

Also, we were writing 32 bits in an 8 bits field, so the write would
overflow, but since the following bytes are padding (the next field is
an uint64_t), it luckily didn't cause any issue on little endian
systems.

The fix was originally tested on ARM big endian systems, but I don't
have access to such a system.  However, thanks to Marcin's PowerPC fast
tracepoint patches and gcc110 (big endian Power7) on the gcc compile
farm, I was able to reproduce the problem, test the fix and write a
test (the following patch).

gdb/gdbserver/ChangeLog:

YYYY-MM-DD  Par Olsson  <par.olsson@windriver.com>

	* tracepoint.c (write_inferior_int8): New function.
	(cmd_qtenable_disable): Write enable flag using
	write_inferior_int8.

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index c9b1e9d85655db44912309cff7985755b01b3727..a0c90ee0a7ce5f4658dbe5d0e4e160c933d9fa9a 100644 (file)
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,10 @@
+2016-04-28  Par Olsson  <par.olsson@windriver.com>
+2016-04-28  Simon Marchi  <simon.marchi@ericsson.com>
+
+       * tracepoint.c (write_inferior_int8): New function.
+       (cmd_qtenable_disable): Write enable flag using
+       write_inferior_int8.
+
 2016-04-25  Yao Qi  <yao.qi@linaro.org>
 
        * linux-low.c (lwp_signal_can_be_delivered): Adjust.

diff --git a/gdb/gdbserver/tracepoint.c b/gdb/gdbserver/tracepoint.c
index 620b94f5259fbd8abc97a836a89552ce25cc1896..c07e5256d3fe9052153941ec487ad92feffd5f56 100644 (file)
--- a/gdb/gdbserver/tracepoint.c
+++ b/gdb/gdbserver/tracepoint.c
@@ -448,6 +448,12 @@ write_inferior_integer (CORE_ADDR symaddr, int val)
   return write_inferior_memory (symaddr, (unsigned char *) &val, sizeof (val));
 }
 
+static int
+write_inferior_int8 (CORE_ADDR symaddr, int8_t val)
+{
+  return write_inferior_memory (symaddr, (unsigned char *) &val, sizeof (val));
+}
+
 static int
 write_inferior_uinteger (CORE_ADDR symaddr, unsigned int val)
 {
@@ -2784,7 +2790,7 @@ cmd_qtenable_disable (char *own_buf, int enable)
              return;
            }
 
-         ret = write_inferior_integer (obj_addr, enable);
+         ret = write_inferior_int8 (obj_addr, enable);
          done_accessing_memory ();
          
          if (ret)