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

[Namhyung Kim <namhyung@kernel.org>]

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.

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)