Re: [PATCH 05/11] kasan, arm64: allow using KUnit tests with HW_TAGS mode

On Tue, Jan 12, 2021 at 8:01 PM Catalin Marinas [off-list ref] wrote:

On Tue, Jan 05, 2021 at 07:27:49PM +0100, Andrey Konovalov wrote:

quoted

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 3c40da479899..57d3f165d907 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c

@@ -302,12 +302,20 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
 static void report_tag_fault(unsigned long addr, unsigned int esr,
                           struct pt_regs *regs)
 {
-     bool is_write  = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;
+     static bool reported;
+     bool is_write;
+
+     if (READ_ONCE(reported))
+             return;
+
+     if (mte_report_once())
+             WRITE_ONCE(reported, true);

I guess the assumption here is that you don't get any report before the
tests start and temporarily set report_once to false. It's probably
fine, if we get a tag check failure we'd notice in the logs anyway.

Good point. I'll add a note in a comment in v4.

quoted

      /*
       * SAS bits aren't set for all faults reported in EL1, so we can't
       * find out access size.
       */
+     is_write = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;

I now noticed, you could write this in a shorter way:

        is_write = !!(esr & ESR_ELx_WNR);

quoted

      kasan_report(addr, 0, is_write, regs->pc);
 }

Will do in v4.

The patch looks fine to me.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

Thanks!

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