Re: [PATCHSET 0/9] perf tools: More updates on data type profiling (v4)

[Ian Rogers]

On Tue, Jan 16, 2024 at 10:27 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> Hello,
>
> This is a continuation of the data type profiling series.  Now the basic
> part (v3) which uses pointer variables is merged to the perf-tools-next
> tree.  And this part is for memory accesses without pointers as well as
> small updates to handle some corner cases.  Still mores to come to
> complete the original series.
>
> There's no change from the previous version.  For background and usages,
> pleaes refer the posting of previous version [1] and a LWN article [2].
>
> Basically most memory accesses happen with pointers, but there are cases
> don't use pointers - direct accesses to global and local variables.
>
> Global variables are located in a static memory at a specific address.
> So the DWARF location expression for the global vairable would also have
> the static address.  And it's common to access them using PC-relative
> addressing mode.  Thus it needs a special handling for global variables.
>
> On the other hand, local variables are located in the stack which varies
> as program executes.  So the local variables are accessed either by the
> (stack) frame pointer or (current) stack pointer.  But sometimes DWARF
> location expression uses a frame base address (CFA) to specify location
> of local variables.  So it may need to convert or normalize the location
> extracted from the instruction to match DWARF expression.
>
> Lastly, there are some cases DWARF location expressions end up having
> complex (or not straight-forward) location.  In that case, it cannot
> simply match just the first expression with the instruction location.
> It'd be safer to reject them.
>
> The code is available at 'perf/data-profile-update-v4' branch in the tree
> below.  The full version of the code is in 'perf/data-profile-v4' branch.
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
>
> Thanks,
> Namhyung
>
>
> Cc: Ben Woodard <woodard@xxxxxxxxxx>
> Cc: Joe Mario <jmario@xxxxxxxxxx>
> CC: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: David Blaikie <blaikie@xxxxxxxxxx>
> Cc: Xu Liu <xliuprof@xxxxxxxxxx>
> Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> Cc: Ravi Bangoria <ravi.bangoria@xxxxxxx>
> Cc: Mark Wielaard <mark@xxxxxxxxx>
> Cc: Jason Merrill <jason@xxxxxxxxxx>
> Cc: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx>
> Cc: William Huang <williamjhuang@xxxxxxxxxx>
>
> [1] https://lore.kernel.org/linux-perf-users/20231213001323.718046-1-namhyung@xxxxxxxxxx/
> [2] https://lwn.net/Articles/955709/
>
>
> Namhyung Kim (9):
>   perf annotate-data: Parse 'lock' prefix from llvm-objdump
>   perf annotate-data: Handle macro fusion on x86
>   perf annotate-data: Handle array style accesses
>   perf annotate-data: Add stack operation pseudo type
>   perf annotate-data: Handle PC-relative addressing
>   perf annotate-data: Support global variables
>   perf dwarf-aux: Add die_get_cfa()
>   perf annotate-data: Support stack variables
>   perf dwarf-aux: Check allowed DWARF Ops

Series:
Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

>  tools/perf/util/annotate-data.c | 119 ++++++++++++++++----
>  tools/perf/util/annotate-data.h |   8 +-
>  tools/perf/util/annotate.c      | 153 ++++++++++++++++++++++++--
>  tools/perf/util/annotate.h      |  12 +-
>  tools/perf/util/dwarf-aux.c     | 187 ++++++++++++++++++++++++++++----
>  tools/perf/util/dwarf-aux.h     |  18 +++
>  6 files changed, 439 insertions(+), 58 deletions(-)
>
>
> base-commit: d988c9f511af71a3445b6a4f3a2c67208ff8e480
> --
> 2.43.0.381.gb435a96ce8-goog
>