Re: [PATCH] perf tools: set kernel end address properly

[Kim Phillips]

On Mon, 16 Apr 2018 12:24:07 -0500
Kim Phillips <kim.phillips@xxxxxxx> wrote:

> On Mon, 16 Apr 2018 13:58:00 -0300
> Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
> 
> > Em Mon, Apr 16, 2018 at 11:07:30AM -0500, Kim Phillips escreveu:
> > > On Mon, 16 Apr 2018 10:51:25 -0300
> > > Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
> > > 
> > > > Em Mon, Apr 16, 2018 at 11:23:45AM +0200, Jiri Olsa escreveu:
> > > > > On Mon, Apr 16, 2018 at 01:22:40PM +0900, Namhyung Kim wrote:
> > > > > > The map_groups__fixup_end() was called to set end addresses of kernel
> > > > > > map and module maps.  But now machine__create_modules() is set the end
> > > > > > address of modules properly so the only remaining piece is the kernel
> > > > > > map.  We can set it with adjacent module's address directly instead of
> > > > > > calling the map_groups__fixup_end().  If there's no module after the
> > > > > > kernel map, the end address will be ~0ULL.
> > > > 
> > > > I wonder if it wouldn't be better to have it as last symbol + PAGE_SIZE
> > > > or something like that...
> > > > 
> > > > But, anyway, Kim, does this fix things for you? Can I have your
> > > > Tested-by?
> > > 
> > > No, perf test 1 still fails:
> > > 
> > > vmlinux symtab matches kallsyms: FAILED!
> > 
> > Ok, -vv please
> 
> a perf/urgent from last week (commit 918965d4897) + this patch:
> 
> $ sudo ./perf test -vv 1 |& head 
>  1: vmlinux symtab matches kallsyms                       :
> --- start ---
> test child forked, pid 6194
> Looking at the vmlinux_path (8 entries long)
> Using /lib/modules/4.16.0+/build/vmlinux for symbols
> ERR : 0xffff200008081000: do_undefinstr not on kallsyms
> ERR : 0xffff2000080810b8: do_sysinstr not on kallsyms
> ERR : 0xffff200008081258: do_debug_exception not on kallsyms
> ERR : 0xffff200008081648: do_mem_abort not on kallsyms
> ERR : 0xffff2000080818b8: do_el0_irq_bp_hardening not on kallsyms
> $ sudo ./perf test -vv 1 |& tail
> ERR : 0xffff20000a1d37c8: tramp_exit_native not on kallsyms
> ERR : 0xffff20000a1d37e8: tramp_exit_compat not on kallsyms
> ERR : 0xffff20000a1d4000: __entry_tramp_text_end not on kallsyms
> WARN: Maps only in vmlinux:
>  ffff200008080000-ffff200008081000 10000 [kernel].head.text
>  ffff20000aec0000-ffff20000aff7548 2e50000 [kernel].init.text
>  ffff20000aff7548-ffff20000b0126d4 2f87548 [kernel].exit.text
> test child finished with -1
> ---- end ----
> vmlinux symtab matches kallsyms: FAILED!

this patch's advertised "If there's no module after the kernel map, the
end address will be ~0ULL." doesn't seem to be working: the value it
gets for 'end' is 0xffff200008080000.

I even hardcoded 'end' variable to the value for '_end' in kallsyms
prior to the machine__set_kernel_mmap() call, and test 1 still fails.

The problem is earlier on in the code, somewhere.

I've moved to working on the updated perf/urgent.  Reverting the
original patch doesn't make test 1 resume succeeding anymore.

Pointers appreciated.

Kim