[PATCH v2] mm/page_alloc: Work around a pahole limitation with zero-sized struct pagesets
From: Mel Gorman
Date: Thu May 27 2021 - 08:03:02 EST
This patch replaces
mm-page_alloc-convert-per-cpu-list-protection-to-local_lock-fix.patch in
Andrew's tree.
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 only allows
DEBUG_INFO_BTF_MODULES if pahole supports zero-sized per-cpu structures.
DEBUG_INFO_BTF is still allowed as a KVM boot test passed with pahole
v1.19. While pahole 1.22 does not exist yet, it is assumed that Hritik's
fix that allows DEBUG_INFO_BTF_MODULES to work will be included in that
release.
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 | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 678c13967580..51b355cbe6d7 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -313,9 +313,12 @@ 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")
+
config DEBUG_INFO_BTF_MODULES
def_bool y
- depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
+ depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF && PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT
help
Generate compact split BTF type information for kernel modules.