Re: [PATCH] perf probe: Fix add event failed when 32-bit perf running in 64-bit kernel

[Yang Jihong]

Hello Hiramatsu,

On 2021/7/15 12:58, Masami Hiramatsu wrote:
> On Thu, 15 Jul 2021 09:20:01 +0800
> Yang Jihong <yangjihong1@xxxxxxxxxx> wrote:
>
> > Hello Hiramatsu,
> >
> > On 2021/7/14 16:35, Masami Hiramatsu wrote:
> > > Hi Yang,
> > >
> > > On Wed, 14 Jul 2021 14:54:32 +0800
> > > Yang Jihong <yangjihong1@xxxxxxxxxx> wrote:
> > >
> > > > The "address" member  of "struct probe_trace_point" uses long data type.
> > > > If kernel is 64-bit and perf program is 32-bit, size of "address" variable is
> > > > 32 bits. As a result, upper 32 bits of address read from kernel are truncated,
> > > > An error occurs during address comparison in kprobe_warn_out_range function.
> > >
> > > Good catch!
> > > I didn't imagine that such a use case. But that is important because perf
> > > probe can be used for cross-arch probe definition too.
> > >
> > > > Before:
> > > >
> > > >     # perf probe -a schedule
> > > >     schedule is out of .text, skip it.
> > > >       Error: Failed to add events.
> > > >
> > > > Solution:
> > > >     Change data type of "address" variable to u64 and change corresponding
> > > > address printing and value assignment.
> > >
> > > OK, as far as I can see, the other parts of the perf also uses u64 for
> > > "address" storing variables. (e.g. symbols, maps etc.)
> > >
> > > > After:
> > > >
> > > >     # perf.new.new probe -a schedule
> > > >     Added new event:
> > > >       probe:schedule       (on schedule)
> > > >
> > > >     You can now use it in all perf tools, such as:
> > > >
> > > >             perf record -e probe:schedule -aR sleep 1
> > > >
> > > >     # perf probe -l
> > > >       probe:schedule       (on schedule)
> > >
> > > I think you missed one thing here.
> > > Usually, this shows the filename and line number of schedule().
> > Yes,  I tried the following diff and now it can show the filename (as is
> > function entry, relative line number is 0), thank you very much :)
> >
> > The test result in my environment is as follows:
> >
> > # perf probe -a schedule
> > Added new event:
> >     probe:schedule       (on schedule)
> >
> > You can now use it in all perf tools, such as:
> >
> >           perf record -e probe:schedule -aR sleep 1
> >
> > # perf probe -l schedule -k vmlinux.debug
> >     probe:schedule       (on schedule@kernel/sched/core.c)
>
> OK, good!
>
> > Can I put the following diff together and submit a v2 patch?
>
> Yes, please include this fix in your patch, because it is what your patch
> has to do :)
OK，I have submitted the v2 patch:
https://lore.kernel.org/patchwork/patch/1460154/

Thanks very much for your patient review.:)

Jihong
> Thank you!
>
> > > Could you try below diff?
> > >
> > > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> > > index 7d2ba8419b0c..609ca1671501 100644
> > > --- a/tools/perf/util/dwarf-aux.c
> > > +++ b/tools/perf/util/dwarf-aux.c
> > > @@ -113,14 +113,14 @@ static Dwarf_Line *cu_getsrc_die(Dwarf_Die *cu_die, Dwarf_Addr addr)
> > >     *
> > >     * Find a line number and file name for @addr in @cu_die.
> > >     */
> > > -int cu_find_lineinfo(Dwarf_Die *cu_die, unsigned long addr,
> > > -		    const char **fname, int *lineno)
> > > +int cu_find_lineinfo(Dwarf_Die *cu_die, Dwarf_Addr addr,
> > > +		     const char **fname, int *lineno)
> > >    {
> > >    	Dwarf_Line *line;
> > >    	Dwarf_Die die_mem;
> > >    	Dwarf_Addr faddr;
> > >    
> > > -	if (die_find_realfunc(cu_die, (Dwarf_Addr)addr, &die_mem)
> > > +	if (die_find_realfunc(cu_die, addr, &die_mem)
> > >    	    && die_entrypc(&die_mem, &faddr) == 0 &&
> > >    	    faddr == addr) {
> > >    		*fname = dwarf_decl_file(&die_mem);
> > > @@ -128,7 +128,7 @@ int cu_find_lineinfo(Dwarf_Die *cu_die, unsigned long addr,
> > >    		goto out;
> > >    	}
> > >    
> > > -	line = cu_getsrc_die(cu_die, (Dwarf_Addr)addr);
> > > +	line = cu_getsrc_die(cu_die, addr);
> > >    	if (line && dwarf_lineno(line, lineno) == 0) {
> > >    		*fname = dwarf_linesrc(line, NULL, NULL);
> > >    		if (!*fname)
> > > diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
> > > index cb99646843a9..7ee0fa19b5c4 100644
> > > --- a/tools/perf/util/dwarf-aux.h
> > > +++ b/tools/perf/util/dwarf-aux.h
> > > @@ -19,7 +19,7 @@ const char *cu_find_realpath(Dwarf_Die *cu_die, const char *fname);
> > >    const char *cu_get_comp_dir(Dwarf_Die *cu_die);
> > >    
> > >    /* Get a line number and file name for given address */
> > > -int cu_find_lineinfo(Dwarf_Die *cudie, unsigned long addr,
> > > +int cu_find_lineinfo(Dwarf_Die *cudie, Dwarf_Addr addr,
> > >    		     const char **fname, int *lineno);
> > >    
> > >    /* Walk on functions at given address */
> > > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > > index 8ba01bbdf05c..50d861a80f57 100644
> > > --- a/tools/perf/util/probe-finder.c
> > > +++ b/tools/perf/util/probe-finder.c
> > > @@ -1727,7 +1727,7 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, u64 addr,
> > >    	}
> > >    
> > >    	/* Find a corresponding line (filename and lineno) */
> > > -	cu_find_lineinfo(&cudie, addr, &fname, &lineno);
> > > +	cu_find_lineinfo(&cudie, (Dwarf_Addr)addr, &fname, &lineno);
> > >    	/* Don't care whether it failed or not */
> > >    
> > >    	/* Find a corresponding function (name, baseline and baseaddr) */
> > > @@ -1828,8 +1828,7 @@ static int line_range_add_line(const char *src, unsigned int lineno,
> > >    }
> > >    
> > >    static int line_range_walk_cb(const char *fname, int lineno,
> > > -			      Dwarf_Addr addr __maybe_unused,
> > > -			      void *data)
> > > +			      Dwarf_Addr addr, void *data)
> > >    {
> > >    	struct line_finder *lf = data;
> > >    	const char *__fname;