Re: KMSAN and dtrace

On Fri, Nov 22, 2024 at 7:07 AM Mark Johnston <markj@freebsd.org> wrote:
>
> On Thu, Nov 21, 2024 at 04:06:53PM -0700, Alan Somers wrote:
> > Would it be possible to make dtrace with with KMSAN?  It would
> > certainly make my life easier.  As it is, every time I try to kldload
> > traceall, whether from the command line or in the loader, my VM
> > infinite loops printing alerts like this:
> >
> > MSan: Uninitialized stack memory from isize64+0x2e
> > #0 0xffffffff833d8f10 at __msan_warning+0x140
> > #1 0xffffffff86ec9c03 at dtrace_disp_opnd+0xd3
> > #2 0xffffffff86ebe552 at dtrace_disx86+0xc602
> > #3 0xffffffff86eca98e at dtrace_instr_size+0xee
> > #4 0xffffffff86d5ec27 at fbt_provide_module_function+0x957
> > #5 0xffffffff83303eff at link_elf_each_function_nameval+0x56f
> > #6 0xffffffff86d56cb3 at fbt_provide_module+0x423
> > #7 0xffffffff86d56871 at fbt_linker_file_cb+0x41
> > #8 0xffffffff830d9f5c at linker_file_foreach+0xdc
> > #9 0xffffffff830d63dd at linker_load_module+0x413d
> > #10 0xffffffff830e6116 at linker_load_dependencies+0x1136
> > #11 0xffffffff853b70b8 at link_elf_load_file+0x65c8
> > #12 0xffffffff830d542e at linker_load_module+0x318e
> > #13 0xffffffff830e0611 at kern_kldload+0x5d1
> > #14 0xffffffff830e0d74 at sys_kldload+0x1a4
> > #15 0xffffffff84fe56f6 at amd64_syscall+0x706
> > #16 0xffffffff84f0ef4b at fast_syscall_common+0xf8
> >
>
> Here you go:
>
> https://cgit.freebsd.org/src/commit/?id=418d8f0dc269b314bba51de63869b20da1d9a76e
> https://cgit.freebsd.org/src/commit/?id=cc3da1955c16df5eb0019e0fef810696b035b7cf
>
> This one might also be important if your test system is low on RAM,
> since the KMSAN shadow map gobbles up quite a lot of memory:
>
> https://cgit.freebsd.org/src/commit/?id=5d12db2dafece9f6a0453c4a45c4abed6b1e15ec
>
> I haven't yet tried running through the full test suite, but this was
> enough to load dtracell (quite slow under KMSAN) and run some simple
> scripts.

Wow, thanks!  I'll try it out later today.