On Wed, May 26, 2021 at 1:33 AM Michal Suchánek <msuchanek@xxxxxxx> wrote:
>
> On Wed, May 26, 2021 at 09:07:41AM +0100, Mel Gorman wrote:
> > Michal Suchanek reported the following problem with linux-next
> >
> > [ 0.000000] Linux version 5.13.0-rc2-next-20210519-1.g3455ff8-vanilla (geeko@buildhost) (gcc (SUSE Linux) 10.3.0, GNU ld (GNU Binutils; openSUSE Tumbleweed) 2.36.1.20210326-3) #1 SMP Wed May 19 10:05:10 UTC 2021 (3455ff8)
> > [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.13.0-rc2-next-20210519-1.g3455ff8-vanilla root=UUID=ec42c33e-a2c2-4c61-afcc-93e9527 8f687 plymouth.enable=0 resume=/dev/disk/by-uuid/f1fe4560-a801-4faf-a638-834c407027c7 mitigations=auto earlyprintk initcall_debug nomodeset earlycon ignore_loglevel console=ttyS0,115200
> > ...
> > [ 26.093364] calling tracing_set_default_clock+0x0/0x62 @ 1
> > [ 26.098937] initcall tracing_set_default_clock+0x0/0x62 returned 0 after 0 usecs
> > [ 26.106330] calling acpi_gpio_handle_deferred_request_irqs+0x0/0x7c @ 1
> > [ 26.113033] initcall acpi_gpio_handle_deferred_request_irqs+0x0/0x7c returned 0 after 3 usecs
> > [ 26.121559] calling clk_disable_unused+0x0/0x102 @ 1
> > [ 26.126620] initcall clk_disable_unused+0x0/0x102 returned 0 after 0 usecs
> > [ 26.133491] calling regulator_init_complete+0x0/0x25 @ 1
> > [ 26.138890] initcall regulator_init_complete+0x0/0x25 returned 0 after 0 usecs
> > [ 26.147816] Freeing unused decrypted memory: 2036K
> > [ 26.153682] Freeing unused kernel image (initmem) memory: 2308K
> > [ 26.165776] Write protecting the kernel read-only data: 26624k
> > [ 26.173067] Freeing unused kernel image (text/rodata gap) memory: 2036K
> > [ 26.180416] Freeing unused kernel image (rodata/data gap) memory: 1184K
> > [ 26.187031] Run /init as init process
> > [ 26.190693] with arguments:
> > [ 26.193661] /init
> > [ 26.195933] with environment:
> > [ 26.199079] HOME=/
> > [ 26.201444] TERM=linux
> > [ 26.204152] BOOT_IMAGE=/boot/vmlinuz-5.13.0-rc2-next-20210519-1.g3455ff8-vanilla
> > [ 26.254154] BPF: type_id=35503 offset=178440 size=4
> > [ 26.259125] BPF:
> > [ 26.261054] BPF:Invalid offset
> > [ 26.264119] BPF:
> > [ 26.264119]
> > [ 26.267437] failed to validate module [efivarfs] BTF: -22
> >
> > Andrii Nakryiko bisected the problem to the commit "mm/page_alloc: convert
> > per-cpu list protection to local_lock" currently staged in mmotm. In his
> > own words
> >
> > The immediate problem is two different definitions of numa_node per-cpu
> > variable. They both are at the same offset within .data..percpu ELF
> > section, they both have the same name, but one of them is marked as
> > static and another as global. And one is int variable, while another
> > is struct pagesets. I'll look some more tomorrow, but adding Jiri and
> > Arnaldo for visibility.
> >
> > [110907] DATASEC '.data..percpu' size=178904 vlen=303
> > ...
> > type_id=27753 offset=163976 size=4 (VAR 'numa_node')
> > type_id=27754 offset=163976 size=4 (VAR 'numa_node')
> >
> > [27753] VAR 'numa_node' type_id=27556, linkage=static
> > [27754] VAR 'numa_node' type_id=20, linkage=global
> >
> > [20] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
> >
> > [27556] STRUCT 'pagesets' size=0 vlen=1
> > 'lock' type_id=507 bits_offset=0
> >
> > [506] STRUCT '(anon)' size=0 vlen=0
> > [507] TYPEDEF 'local_lock_t' type_id=506
> >
> > The patch in question introduces a zero-sized per-cpu struct and while
> > this is not wrong, versions of pahole prior to 1.22 (unreleased) get
> > confused during BTF generation with two separate variables occupying the
> > same address.
> >
> > This patch checks for older versions of pahole and forces struct pagesets
> > to be non-zero sized as a workaround when CONFIG_DEBUG_INFO_BTF is set. A
> > warning is omitted so that distributions can update pahole when 1.22
> > is released.
> >
> > Reported-by: Michal Suchanek <msuchanek@xxxxxxx>
> > Reported-by: Hritik Vijay <hritikxx8@xxxxxxxxx>
> > Debugged-by: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
> > Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> > ---
> > lib/Kconfig.debug | 3 +++
> > mm/page_alloc.c | 11 +++++++++++
> > 2 files changed, 14 insertions(+)
> >
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 678c13967580..f88a155b80a9 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -313,6 +313,9 @@ config DEBUG_INFO_BTF
> > config PAHOLE_HAS_SPLIT_BTF
> > def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119")
> >
> > +config PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT
> > + def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "122")
> > +
>
> This does not seem workable with dummy-tools.
>
> Do we even have dummy pahole?
>
I don't know what dummy-tools is, so probably no. But if you don't
have pahole on the build host, you can't have DEBUG_INFO_BTF=y
anyways. As in, your build will fail because it will be impossible to
generate BTF information. So you'll have to disable DEBUG_INFO_BTF if
you can't get pahole onto your build host for some reason.
> Thanks
>
> Michal
>
> > config DEBUG_INFO_BTF_MODULES
> > def_bool y
> > depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index ff8f706839ea..1d56d3de8e08 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -124,6 +124,17 @@ static DEFINE_MUTEX(pcp_batch_high_lock);
> >
> > struct pagesets {
> > local_lock_t lock;
> > +#if defined(CONFIG_DEBUG_INFO_BTF) && \
> > + !defined(CONFIG_DEBUG_LOCK_ALLOC) && \
> > + !defined(CONFIG_PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT)
> > + /*
> > + * pahole 1.21 and earlier gets confused by zero-sized per-CPU
> > + * variables and produces invalid BTF. Ensure that
> > + * sizeof(struct pagesets) != 0 for older versions of pahole.
> > + */
> > + char __pahole_hack;
> > + #warning "pahole too old to support zero-sized struct pagesets"
> > +#endif
> > };
> > static DEFINE_PER_CPU(struct pagesets, pagesets) = {
> > .lock = INIT_LOCAL_LOCK(lock),
