linux-kernel - Re: Intel PT: Address filtering not working. (cc me)

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Date:   Mon, 17 Oct 2016 19:12:53 -0400
From:   Muhammad Usman Nadeem <usmanone@...il.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: Re: Intel PT: Address filtering not working. (cc me)

I was providing it the Virtual Memory Address instead of offset in the
file. It is working now.

Thanks.


On Mon, Oct 17, 2016 at 2:50 AM, Adrian Hunter <adrian.hunter@...el.com> wrote:
> On 13/10/16 04:11, Muhammad Usman Nadeem wrote:
>> Usage: sudo perf record -e intel_pt//u --filter='filter 0x400000 /
>> 0x1000 @./a.out' ./a.out 123
>>
>> a.out is my program (for loop, call using function pointer and use of
>> longjump) and 123 is the argument.
>>
>> Output: [ perf record: Woken up 1 times to write data ]
>> [ perf record: Captured and wrote 1.171 MB perf.data ]
>>
>>
>> Output contains mostly MTC packets and no TNT or TIP packets.
>>
>> I am on the latest mainline version of kernel (b67be92) and perf
>> version perf version 4.8.gb67be9.
>>
>> What could be the problem?
>> I am using it wrong?
>
> Yes.  The perf-record documentation says: "<file name> is the name of the
> object file, <start> is the offset to the code to trace in that file"
>
> So 0x400000 is well off the end of the file.  Try:
>
>          --filter='filter 0 / 0x1000 @./a.out'
>
> Also note:
>
> "The kernel may not be able to configure a trace region if it is not
> within a single mapping.  MMAP events (or /proc/<pid>/maps) can be
> examined to determine if that is a possibility."
>
> You can see mmap events in using perf script with the --show-mmap-events option.
>
>>
>> Thanks
>>
>>
>> test.c
>>
>>
>> #include <iostream>
>> #include <setjmp.h>
>> jmp_buf go;
>> int foo()
>> {
>>     return 5;
>> }
>> int bar()
>> {
>>       longjmp(go,1);
>>     return 6;
>> }
>>
>> int main(int argc, char* argv[])
>> {
>>       bool jumped = false;
>>       int (*ptr) ();
>>       // if arg then long jump
>>     if (argc != 2)
>>     {
>>       ptr = foo;
>>     } else {
>>           ptr = bar;
>>     }
>>
>>     for (int i = 0; i < 50000000; ++i)
>>     {
>>         ++i;
>>         --i;
>>     }
>>     setjmp(go);
>>
>>     if (!jumped)
>>     {
>>       jumped = true;
>>           ptr();
>>     } else {
>>           std::cout <<  "AFTER long jump." << std::endl;
>>     }
>>     return 0;
>> }
>>
>