[binutils-gdb] Fix write endianness/size problem for fast tracepoint enabled flag

[Simon Marchi <simark at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=35fd2deb6916e972248d52b1bc1d584fa9059f8f

commit 35fd2deb6916e972248d52b1bc1d584fa9059f8f
Author: Par Olsson <par.olsson@windriver.com>
Date:   Thu Apr 28 12:54:07 2016 -0400

    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:
---
 gdb/gdbserver/ChangeLog    | 7 +++++++
 gdb/gdbserver/tracepoint.c | 8 +++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index c9b1e9d..a0c90ee 100644
--- 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 620b94f..c07e525 100644
--- a/gdb/gdbserver/tracepoint.c
+++ b/gdb/gdbserver/tracepoint.c
@@ -449,6 +449,12 @@ write_inferior_integer (CORE_ADDR symaddr, int 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)
 {
   return write_inferior_memory (symaddr, (unsigned char *) &val, sizeof (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)