On 07/13/2012 01:06 PM, Geert Uytterhoeven wrote:
> Hi Michael,
>
> On Fri, Jul 13, 2012 at 9:14 PM, Michael Eager <eager@eagercon.com> wrote:
>> I've tracked down a problem in gdb/gdbserver to ptrace() not
>> clearing the i/d cache after modifying memory.
>>
>> To reproduce:
>>    m68k-gcc -g -o cf-gdb-test-no-io cf-gdb-test-no-io.c
>>    scp cf-gdb-test-no-io <target>:/
>>    on target:   gdbserver :1234 cf-gdb-test-no-io
>>    m68k-gcc cf-gdb-test-no-io
>>    (gdb) b 8
>>    (gdb) b 10
>>    (gdb) tar rem <target>:1234
>>    (gdb) c
>>    (gdb) c
>>
>> Program will hit first breakpoint, but not second breakpoint.
>>
>> It appears that the instruction at the last breakpoint location
>> is in the icache and does not get flushed when the bp is written.
>>
>> After applying the attached patch, gdb/gdbserver behavior is correct.
>
> Thanks for your report and patch!

I attached the test program, which I previously forgot.

> Does this happen only in 2.6.29, or also in current kernels?
> The first hunk of your patch no longer applies, as the affected code is
> gone and those cases are now handled purely by the generic code.

I'm working with a client's environment using 2.6.29, so I can't verify
that the same failure occurs in recent kernels.  But I don't see anything
in ptrace.c in the latest kernel which would clear the i/d caches when
writing to memory.

>
> If yes, feel free to take this to linux-m68k@lists.linux-m68k.org.

Done.


-- 
Michael Eager	 eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077