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

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Date:   Mon, 17 Oct 2016 09:50:11 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Muhammad Usman Nadeem <usmanone@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: Re: Intel PT: Address filtering not working. (cc me)

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;
> }
>