Re: perf script intel_pt decoding reading instructions from wrong shared lib

[Adrian Hunter <adrian.hunter@intel.com>]

On 24/06/2026 23:23, Namhyung Kim wrote:
> Hello,
> 
> On Tue, Jun 02, 2026 at 10:32:02PM +0300, Adrian Hunter wrote:
>> On 15/04/2025 00:59, Todd Lipcon wrote:
>>> Hi folks,
>>>
>>> It seems there may be a bug in perf-script when processing intel_pt.
>>> Specifically, in order to reconstruct the instructions, it maps
>>> instruction pointers back to DSO-relative addresses, and then reads
>>> from the associated ELF files to find the actual instructions that
>>> were traced.
>>>
>>> In the case that the ELF file has an associated separate-debug ELF
>>> file linked via `.gnu-debuglink` (common in some Linux distros), it
>>> appears to be reading the debuginfo file instead of the shared library
>>> that actually contains the code.
>>>
>>> I've posted a simple repro here:
>>> https://github.com/toddlipcon/perf-debuglink-bug/blob/main/repro.sh
>>>
>>> I haven't dug into the code yet enough to see where it's going wrong,
>>> but figured I would report to the users list first.
>>
>> Seems to be caused by commit 5363c306787c8 - see further below.
>> Reverting that makes the issue go away.
> 
> Sorry for the trouble.
> 
>>
>> With that commit, dso__load() sets the binary_type to the first symbol
>> source file type, which is DSO_BINARY_TYPE__DEBUGLINK in this case.
>> That causes dso__get_filename() to get the file name of the debug file,
>> not the file actually executed.
>>
>> Leaving the binary_type as DSO_BINARY_TYPE__NOT_FOUND will result in
>> try_to_open_dso() using either DSO_BINARY_TYPE__BUILD_ID_CACHE or
>> DSO_BINARY_TYPE__SYSTEM_PATH_DSO.
> 
> Ok, I feel like we should split the dso access for the binary file (for
> annotate or intel-pt) and debug symbols (symbol table or DWARF).
> Probably we can use the binary_type and symtab_type respectively.
> 
> I'll take a look.

Would it make sense to apply the workaround in the meantime?

> 
> Thanks,
> Namhyung
> 
>>
>> A quick workaround hack:
>>
>> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
>> index dd30f17cb1ca..09fd79ca1d48 100644
>> --- a/tools/perf/util/symbol.c
>> +++ b/tools/perf/util/symbol.c
>> @@ -1825,7 +1825,10 @@ int dso__load(struct dso *dso, struct map *map)
>>  		if (next_slot) {
>>  			ss_pos++;
>>  
>> -			if (dso__binary_type(dso) == DSO_BINARY_TYPE__NOT_FOUND)
>> +			if (dso__binary_type(dso) == DSO_BINARY_TYPE__NOT_FOUND ||
>> +			    symtab_type == DSO_BINARY_TYPE__BUILD_ID_CACHE ||
>> +			    (symtab_type == DSO_BINARY_TYPE__SYSTEM_PATH_DSO &&
>> +			     dso__binary_type(dso) != DSO_BINARY_TYPE__BUILD_ID_CACHE))
>>  				dso__set_binary_type(dso, symtab_type);
>>  
>>  			if (syms_ss && runtime_ss)