Hi Catalin, On 1/19/21 2:45 PM, Catalin Marinas wrote: > On Mon, Jan 18, 2021 at 06:30:33PM +0000, Vincenzo Frascino wrote: >> mte_assign_mem_tag_range() is called on production KASAN HW hot >> paths. It makes sense to inline it in an attempt to reduce the >> overhead. >> >> Inline mte_assign_mem_tag_range() based on the indications provided at >> [1]. >> >> [1] >> https://lore.kernel.org/r/caaehk+wco+j7d1_t89dg+jjrplk3x9rsgfkxjgd0zcufjqt...@mail.gmail.com/ >> >> Cc: Catalin Marinas <[email protected]> >> Cc: Will Deacon <[email protected]> >> Signed-off-by: Vincenzo Frascino <[email protected]> >> --- >> arch/arm64/include/asm/mte.h | 26 +++++++++++++++++++++++++- >> arch/arm64/lib/mte.S | 15 --------------- >> 2 files changed, 25 insertions(+), 16 deletions(-) >> >> diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h >> index 237bb2f7309d..1a6fd53f82c3 100644 >> --- a/arch/arm64/include/asm/mte.h >> +++ b/arch/arm64/include/asm/mte.h >> @@ -49,7 +49,31 @@ long get_mte_ctrl(struct task_struct *task); >> int mte_ptrace_copy_tags(struct task_struct *child, long request, >> unsigned long addr, unsigned long data); >> >> -void mte_assign_mem_tag_range(void *addr, size_t size); >> +static inline void mte_assign_mem_tag_range(void *addr, size_t size) >> +{ >> + u64 _addr = (u64)addr; >> + u64 _end = _addr + size; >> + >> + /* >> + * This function must be invoked from an MTE enabled context. >> + * >> + * Note: The address must be non-NULL and MTE_GRANULE_SIZE aligned and >> + * size must be non-zero and MTE_GRANULE_SIZE aligned. >> + */ >> + do { >> + /* >> + * 'asm volatile' is required to prevent the compiler to move >> + * the statement outside of the loop. >> + */ >> + asm volatile(__MTE_PREAMBLE "stg %0, [%0]" >> + : >> + : "r" (_addr) >> + : "memory"); >> + >> + _addr += MTE_GRANULE_SIZE; >> + } while (_addr != _end); >> +} > > While I'm ok with moving this function to C, I don't think it solves the > inlining in the kasan code. The only interface we have to kasan is via > mte_{set,get}_mem_tag_range(), so the above function doesn't need to > live in a header. > > If you do want inlining all the way to the kasan code, we should > probably move the mte_{set,get}_mem_tag_range() functions to the header > as well (and ideally backed by some numbers to show that it matters). > > Moving it to mte.c also gives us more control on how it's called (we > have the WARN_ONs in place in the callers). >
Based on the thread [1] this patch contains only an intermediate step to allow KASAN to call directly mte_assign_mem_tag_range() in future. At that point I think that mte_set_mem_tag_range() can be removed. If you agree, I would live the things like this to give to Andrey a chance to execute on the original plan with a separate series. I agree though that this change alone does not bring huge benefits but regressions neither. If you want I can add something to the commit message in the next version to make this more explicit. Let me know how do you want me to proceed. -- Regards, Vincenzo
