linux-kernel - Re: [PATCH] perf intel-pt: Fix unassigned instruction op

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Date: Tue, 26 Mar 2024 09:13:40 -0700
From: Ian Rogers <irogers@...gle.com>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	Namhyung Kim <namhyung@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf intel-pt: Fix unassigned instruction op

On Tue, Mar 26, 2024 at 1:32 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> MemorySanitizer discovered instances where the instruction op value was
> not assigned.:
>
>   WARNING: MemorySanitizer: use-of-uninitialized-value
>     #0 0x5581c00a76b3 in intel_pt_sample_flags tools/perf/util/intel-pt.c:1527:17
>   Uninitialized value was stored to memory at
>     #0 0x5581c005ddf8 in intel_pt_walk_insn tools/perf/util/intel-pt-decoder/intel-pt-decoder.c:1256:25
>
> The op value is used to set branch flags for branch instructions
> encountered when walking the code, so fix by setting op to
> INTEL_PT_OP_OTHER in other cases.
>
> Reported-by: Ian Rogers <irogers@...gle.com>
> Closes: https://lore.kernel.org/linux-perf-users/20240320162619.1272015-1-irogers@google.com/
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

Great, thanks! Should it have a Fixes tag like:

Fixes: 4c761d805bb2 ("perf intel-pt: Fix intel_pt_fup_event()
assumptions about setting state type")

Tested-by: Ian Rogers <irogers@...gle.com>

Ian

> ---
>  tools/perf/util/intel-pt-decoder/intel-pt-decoder.c | 2 ++
>  tools/perf/util/intel-pt.c                          | 2 ++
>  2 files changed, 4 insertions(+)
>
> diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
> index b450178e3420..e733f6b1f7ac 100644
> --- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
> +++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
> @@ -1319,6 +1319,8 @@ static bool intel_pt_fup_event(struct intel_pt_decoder *decoder, bool no_tip)
>         bool ret = false;
>
>         decoder->state.type &= ~INTEL_PT_BRANCH;
> +       decoder->state.insn_op = INTEL_PT_OP_OTHER;
> +       decoder->state.insn_len = 0;
>
>         if (decoder->set_fup_cfe_ip || decoder->set_fup_cfe) {
>                 bool ip = decoder->set_fup_cfe_ip;
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index f38893e0b036..4db9a098f592 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -764,6 +764,7 @@ static int intel_pt_walk_next_insn(struct intel_pt_insn *intel_pt_insn,
>
>         addr_location__init(&al);
>         intel_pt_insn->length = 0;
> +       intel_pt_insn->op = INTEL_PT_OP_OTHER;
>
>         if (to_ip && *ip == to_ip)
>                 goto out_no_cache;
> @@ -898,6 +899,7 @@ static int intel_pt_walk_next_insn(struct intel_pt_insn *intel_pt_insn,
>
>                         if (to_ip && *ip == to_ip) {
>                                 intel_pt_insn->length = 0;
> +                               intel_pt_insn->op = INTEL_PT_OP_OTHER;
>                                 goto out_no_cache;
>                         }
>
> --
> 2.34.1
>