Message-ID: <CAJfuBxy2w8g8yML=Lzc0RxiPb_QmD09wdmihHp60GvwO2pDXvA@mail.gmail.com>
Date:   Tue, 21 Mar 2023 06:20:57 -0600
From:   jim.cromie@...il.com
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Jason Baron <jbaron@...mai.com>,
        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 Tue, Mar 21, 2023 at 12:45 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> On Tue, Mar 21, 2023 at 5:00 AM <jim.cromie@...il.com> wrote:
> >
> > 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]
>
> Maybe more.
>
> We have almost 100 'main.c' files.
>
> $ find . -name main.c | wc
>      97      97    3473
>

yes.  I just picked [main] as the example cuz it was the biggest
bucket of unrelateds.

there are other oddities:

"power" module ( subsystem ?) has 2 names matching/picked-by basename

drivers/base/power/main.c:467 [main]dpm_show_time =_ "%s%s%s of
devices %s after %ld.%03ld msecs\n"
drivers/base/power/domain.c:582 [domain]_genpd_power_on =_ "%s:
Power-%s latency exceeded, new value %lld ns\n"

"power" also has 4 other "mod-names", all matching basename

kernel/power/suspend.c:580 [suspend]enter_state =_ "Preparing system
for sleep (%s)\n"
kernel/power/hibernate.c:691 [hibernate]load_image_and_restore =_
"Loading hibernation image.\n"
kernel/power/snapshot.c:1083 [snapshot]mark_nosave_pages =p "Marking
nosave pages: [mem %#010llx-%#010llx]\n"
kernel/power/swap.c:1509 [swap]swsusp_read =p "Error %d resuming\n"

others have distinct [modnames], where/how do they get set ?

drivers/base/firmware_loader/main.c:1442
[firmware_class]device_uncache_fw_images =_ "%s\n"
drivers/media/rc/rc-main.c:230 [rc_core]ir_create_table =_ "Allocated
space for %u keycode entries (%u bytes)\n"



>
>
>
>
> > 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.
>
>
> I do not understand what you mean.
>

stable names   ===    modprobe foo working whether module is builtin or loadable

>
> KBUILD_MODNAME is not affected by the y/m configuration.
>
>
>
>
> If an object is a member of a composite object, which
> does not necessarily be a real module, KBUILD_MODNAME
> refers to the name of the composite.
> Otherwise, the basename of the source file.
>
>
> Examples:
>
>
> obj-y += alias-name.o
> alias-name-objs := foo.o
>
>   -->  KBUILD_MODNAME is "alias-name"
>
>
>
> obj-y += foo.o
>
>   -->  KBUILD_MODNAME is "foo"
>

taken-from-basename   correctly characterizes that.


>
>
> This is about how you write Makefile code.
> CONFIG options are unrelated.
>

in kernel/power/Makefile, there is:

     obj-$(CONFIG_HIBERNATION) += hibernate.o snapshot.o swap.o

and those 3 objects each get their own [mod-name]

>
>
>
>
>
>
> > 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
>
>
>
> --
> Best Regards
> Masahiro Yamada

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