linux-kernel - Re: RFC - KBUILD_MODNAME is misleading in builtins, as seen in /proc/dynamic

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Message-ID: <CAJfuBxyoeuurDoUe2tLs=JbX=BbxGdYpf2yBEP6bkhtFh2XTtQ@mail.gmail.com>
Date:   Mon, 20 Mar 2023 13:59:28 -0600
From:   jim.cromie@...il.com
To:     Jason Baron <jbaron@...mai.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-kbuild@...r.kernel.org,
        Greg KH <gregkh@...uxfoundation.org>,
        Luis Chamberlain <mcgrof@...nel.org>
Subject: Re: RFC - KBUILD_MODNAME is misleading in builtins, as seen in /proc/dynamic_debug/control

On Mon, Mar 20, 2023 at 12:35 PM Jason Baron <jbaron@...mai.com> wrote:
>
>
>
> On 3/20/23 1:05 AM, jim.cromie@...il.com wrote:
> > dynamic-debug METADATA uses KBUILD_MODNAME as:
> >
> > #define DEFINE_DYNAMIC_DEBUG_METADATA_CLS(name, cls, fmt)       \
> >          static struct _ddebug  __aligned(8)                     \
> >          __section("__dyndbg") name = {                          \
> >                  .modname = KBUILD_MODNAME,                      \
> >
> > This is going amiss for some builtins, ie those enabled here, by:
> >
> >      echo module main +pmf > /proc/dynamic_debug_control
> >      grep =pmf /proc/dynamic_debug/control
> >
> > init/main.c:1187 [main]initcall_blacklist =pmf "blacklisting initcall %s\n"
> > init/main.c:1226 [main]initcall_blacklisted =pmf "initcall %s blacklisted\n"
> > init/main.c:1432 [main]run_init_process =pmf "  with arguments:\n"
> > init/main.c:1434 [main]run_init_process =pmf "    %s\n"
> > init/main.c:1435 [main]run_init_process =pmf "  with environment:\n"
> > init/main.c:1437 [main]run_init_process =pmf "    %s\n"
>
>
> Hi Jim,
>
> So if I'm following correctly, this is not a new issue, the 'module'
> name for dynamic debug has always been this way for builtin.

It is not a new issue - both PM and init-main have been in [main] for some time.

I believe that with
cfc1d277891e module: Move all into module/

module's module-name joined them, changing from [module] to [main]


We could do
> something simple and just normalize it when we initially create the
> table, but setting the 'module name' to 'core' or 'builtin' or something
> for all these?

core and builtin would both lump all those separate modules together,
making it less meaningful.

having stable names independent of M vs Y config choices is imperative, ISTM.

Also, I dont think "only builtins are affected" captures the whole problem.
I dont recall amdgpu or other modules changing when built with =y

Theres some subtlety in how KBUILD_MODNAME is set,
and probably many current users who like its current behavior.
A new var ?

1st, I think that anything tristate gets a sensible value,
but at least some of the builtin-only "modules" get basenames, by default.

arch/x86/events/amd/ibs.c:1398 [ibs]force_ibs_eilvt_setup =_ "No EILVT
entry available\n"
arch/x86/events/intel/pt.c:797 [pt]pt_topa_dump =_ "# table @%p, off
%llx size %zx\n"w=%16llx\n"

kvm gets a solid name, because tristate ?

arch/x86/kvm/mmu/mmu.c:6661 [kvm]kvm_mmu_invalidate_mmio_sptes =_
"kvm: kvm [%i]: zapping shadow pages for mmio generation wraparound\n"
arch/x86/kvm/hyperv.c:1402 [kvm]kvm_hv_set_msr_pw =_ "kvm [%i]: vcpu%i
hv crash (0x%llx 0x%llx 0x%llx 0x%llx 0x%llx)\n"

kvm-intel and kvm-amd get their names elsewhere.

arch/x86/kvm/vmx/nested.c:207 [kvm_intel]nested_vmx_abort =_
"kvm_intel: nested vmx abort, indicator %d\n"
arch/x86/kvm/vmx/nested.c:913 [kvm_intel]nested_vmx_load_msr =_
"kvm_intel: %s cannot read MSR entry (%u, 0x%08llx)\n"

arch/x86/kvm/svm/avic.c:860 [kvm_amd]get_pi_vcpu_info =_ "SVM: %s: use
GA mode for irq %u\n"
arch/x86/kvm/svm/avic.c:889 [kvm_amd]avic_pi_update_irte =_ "SVM: %s:
host_irq=%#x, guest_irq=%#x, set=%#x\n"

iow, I dont know..

>
> Thanks,
>
> -Jason