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

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Message-ID: <d7b31967-0820-4eef-8746-db0299af154f@intel.com>
Date: Tue, 26 Mar 2024 18:52:12 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Ian Rogers <irogers@...gle.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 26/03/24 18:13, Ian Rogers wrote:
> 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")

Yes, I should have put a fixes tag, cc stable.  I think the issue
has always been there, so:

Fixes: 90e457f7be087 ("perf tools: Add Intel PT support")
Cc: stable@...r.kernel.org

> 
> 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
>>