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Fix write endianness/size problem for fast tracepoint enabled flag

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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.
This commit is contained in:
Par Olsson 2016-04-28 12:54:07 -04:00 • committed by Simon Marchi
parent 952ebca583
commit 35fd2deb69
2 changed files with 14 additions and 1 deletions
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7
gdb/gdbserver/ChangeLog
View file

@ -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.

8
gdb/gdbserver/tracepoint.c
View file

@ -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)