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It can be convenient to put a string value into a ptwrite payload as
a quick and easy way to identify what is being printed.
To make that useful, if the Intel ptwrite payload value contains only
printable ASCII characters padded with NULLs, then print it also as a
string.
Using the example program from the "Emulated PTWRITE" section of
tools/perf/Documentation/perf-intel-pt.txt:
$ echo -n "Hello" | od -t x8
0000000 0000006f6c6c6548
0000005
$ perf record -e intel_pt//u ./eg_ptw 0x0000006f6c6c6548
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.016 MB perf.data ]
$ perf script --itrace=ew
eg_ptw 35563 [005] 18256.087338: ptwrite: IP: 0 payload: 0x6f6c6c6548 Hello 55e764db5196 perf_emulate_ptwrite+0x16 (/home/user/eg_ptw)
$
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20220509152400.376613-3-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.