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SubjectRe: Intel PT: Address filtering not working. (cc me)
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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;
> }
>

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