| Message ID | 162859.1615542946@turing-police (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: kernel/sys.c - silence initialization warnings. | expand |
On Fri, Mar 12, 2021 at 04:55:46AM -0500, Valdis Klētnieks wrote: > Building arch/arm64/kernel/sys.o with W=1 throws over 300 warnings: > > /usr/src/linux-next/arch/arm64/kernel/sys.c:56:40: warning: initialized field overwritten [-Woverride-init] > 56 | #define __SYSCALL(nr, sym) [nr] = __arm64_##sym, > | ^~~~~~~~ > /usr/src/linux-next/include/uapi/asm-generic/unistd.h:29:37: note: in expansion of macro '__SYSCALL' > 29 | #define __SC_COMP(_nr, _sys, _comp) __SYSCALL(_nr, _sys) > | ^~~~~~~~~ > /usr/src/linux-next/include/uapi/asm-generic/unistd.h:34:1: note: in expansion of macro '__SC_COMP' > 34 | __SC_COMP(__NR_io_setup, sys_io_setup, compat_sys_io_setup) > | ^~~~~~~~~ > > We know that's pretty much the file's purpose in life, so tell the > build system to not remind us. This makes the 1 other warning a > lot more noticeable. > > Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu> > > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile > index ed65576ce710..916b21d2b35b 100644 > --- a/arch/arm64/kernel/Makefile > +++ b/arch/arm64/kernel/Makefile > @@ -8,6 +8,7 @@ CFLAGS_armv8_deprecated.o := -I$(src) > CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE) > CFLAGS_REMOVE_insn.o = $(CC_FLAGS_FTRACE) > CFLAGS_REMOVE_return_address.o = $(CC_FLAGS_FTRACE) > +CFLAGS_sys.o += $(call cc-disable-warning, override-init) We do similar initialisation in arch/arm64/kernel/sys32.c and arch/arm64/kernel/traps.c for example. It's a pretty common pattern throughout the kernel. So we either treat W=1 output as diff against the vanilla kernel when checking new patches or we remove override-init altogether from W=1. Mark Rutland pointed me to an older thread: https://lore.kernel.org/linux-arm-kernel/20190809083251.GA48423@lakrids.cambridge.arm.com/
On Mon, Mar 15, 2021 at 11:14:34AM +0000, Catalin Marinas wrote: > We do similar initialisation in arch/arm64/kernel/sys32.c and > arch/arm64/kernel/traps.c for example. It's a pretty common pattern > throughout the kernel. > > So we either treat W=1 output as diff against the vanilla kernel when > checking new patches or we remove override-init altogether from W=1. > Mark Rutland pointed me to an older thread: Please just remove the override-init warning, it is not helpful at all.
On Mon, 15 Mar 2021 19:23:00 -0000, Christoph Hellwig said: > On Mon, Mar 15, 2021 at 11:14:34AM +0000, Catalin Marinas wrote: > > We do similar initialisation in arch/arm64/kernel/sys32.c and > > arch/arm64/kernel/traps.c for example. It's a pretty common pattern > > throughout the kernel. > > > > So we either treat W=1 output as diff against the vanilla kernel when > > checking new patches or we remove override-init altogether from W=1. > > Mark Rutland pointed me to an older thread: > > Please just remove the override-init warning, it is not helpful at all. The tl;dr: Christoph is *probably* correct that it's not flagging any actual bugs. And since *my* interest is "get the kernel tree to a point where W=1 or sparse throwing a warning is something worth looking at", I'm not opposed to a patch to remove it from W=1 tree-wide if it has essentially zero chance of flagging an actual bug. The longer version: So I did a quick analysis... For an x86_64 allmodconfig, there's not that many left: 16 drivers/ata/ahci.h 1 drivers/ata/pata_atiixp.c 1 drivers/ata/pata_cs5520.c 1 drivers/ata/pata_cs5530.c 1 drivers/ata/pata_sc1200.c 1 drivers/ata/pata_serverworks.c 1 drivers/ata/sata_mv.c 4 drivers/ata/sata_nv.c 1 drivers/ata/sata_sil24.c 1 drivers/block/drbd/drbd_main.c 6 drivers/gpu/drm/amd/amdgpu/../include/asic_reg/dce/dce_6_0_d.h 2 drivers/gpu/drm/amd/amdgpu/../include/asic_reg/dce/dce_6_0_sh_mask.h 1 drivers/input/serio/i8042-x86ia64io.h 1 include/linux/blkdev.h 1 kernel/bpf/btf.c 4 kernel/time/hrtimer.c 1 lib/errname.c The drivers/ata *.c warnings all appear to be the same type of thing: static struct scsi_host_template serverworks_osb4_sht = { ATA_BMDMA_SHT(DRV_NAME), .sg_tablesize = LIBATA_DUMB_MAX_PRD, }; The preprocessor macro defining the struct contents, and then overriding one predefined value. So that's half of x64_64 done right there. There's a few corners still need looking at, like why drivers/ata/ahci.h throws 16 warnings on x64, but 30 on arm and 28 on arm64, and why there's 4 warnings on include/linux/stddef.h on arm64 but not arm or x86. But the number is certainly small enough that it's only a day or two's work at most to check every single one. If I go through the rest of x86 and arm and they're all legit, I'll send a patch to nuke it kernel-wide rather than piecemeal.
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index ed65576ce710..916b21d2b35b 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -8,6 +8,7 @@ CFLAGS_armv8_deprecated.o := -I$(src) CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_insn.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_return_address.o = $(CC_FLAGS_FTRACE) +CFLAGS_sys.o += $(call cc-disable-warning, override-init) # Object file lists. obj-y := debug-monitors.o entry.o irq.o fpsimd.o \
Building arch/arm64/kernel/sys.o with W=1 throws over 300 warnings: /usr/src/linux-next/arch/arm64/kernel/sys.c:56:40: warning: initialized field overwritten [-Woverride-init] 56 | #define __SYSCALL(nr, sym) [nr] = __arm64_##sym, | ^~~~~~~~ /usr/src/linux-next/include/uapi/asm-generic/unistd.h:29:37: note: in expansion of macro '__SYSCALL' 29 | #define __SC_COMP(_nr, _sys, _comp) __SYSCALL(_nr, _sys) | ^~~~~~~~~ /usr/src/linux-next/include/uapi/asm-generic/unistd.h:34:1: note: in expansion of macro '__SC_COMP' 34 | __SC_COMP(__NR_io_setup, sys_io_setup, compat_sys_io_setup) | ^~~~~~~~~ We know that's pretty much the file's purpose in life, so tell the build system to not remind us. This makes the 1 other warning a lot more noticeable. Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>