Messages in this thread | | | Date | Tue, 2 May 2017 10:26:18 -0700 | From | Matthias Kaehlcke <> | Subject | Re: [PATCH] arm64: Fix multiple 'asm-operand-widths' warnings |
| |
Hi Mark,
El Tue, May 02, 2017 at 11:27:18AM +0100 Mark Rutland ha dit:
> On Mon, May 01, 2017 at 02:26:22PM -0700, Matthias Kaehlcke wrote: > > clang raises 'asm-operand-widths' warnings in inline assembly code when > > the size of an operand is < 64 bits and the operand width is unspecified. > > Most warnings are raised in macros, i.e. the datatype of the operand may > > vary. Forcing the use of an x register through the 'x' operand modifier > > would silence the warning however it involves the risk that for operands > > < 64 bits 'unused' bits may be assigned to 64-bit values (more details at > > http://lists.infradead.org/pipermail/linux-arm-kernel/2017-April/503816.html). > > Instead we cast the operand to 64 bits, which also forces the use of a > > x register, but without the unexpected behavior. > > > > In gic_write_bpr1() use write_sysreg_s() to write the register. This > > aligns the functions with others in this header and fixes an > > 'asm-operand-widths' warning. > > > > Signed-off-by: Matthias Kaehlcke <mka@chromium.org> > > --- > > arch/arm64/include/asm/arch_gicv3.h | 2 +- > > arch/arm64/include/asm/barrier.h | 2 +- > > arch/arm64/include/asm/uaccess.h | 2 +- > > arch/arm64/kernel/armv8_deprecated.c | 2 +- > > 4 files changed, 4 insertions(+), 4 deletions(-) > > Thanks for putting this together. > > Just to check, are these the only instances that you see clang warning > about?
Yes, these are the only warnings clang raises in my builds (custom and defconfig).
> There are a number of other cases where we can see similar problems > (e.g. passing a u8 value to an smp_store_release() on a u32 variable), > so we need to fix more than the clang warnings. > > I'm currently attempting a systematic audit of our inline asm to correct > all instances, looking at: > > git grep -e asm \ > --and --not -e 'include' \ > --and --not -e 'asmlinkage' \ > -- arch/arm64 > > I hope to have patches shortly, and will keep you informed.
Sounds good!
Thanks
Matthias
| |