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    SubjectRe: [PATCH v2 24/37] arm64: mte: Add in-kernel tag fault handler
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    On 9/17/20 3:03 PM, Catalin Marinas wrote:
    > On Tue, Sep 15, 2020 at 11:16:06PM +0200, Andrey Konovalov wrote:
    >> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
    >> index a3bd189602df..cdc23662691c 100644
    >> --- a/arch/arm64/mm/fault.c
    >> +++ b/arch/arm64/mm/fault.c
    >> @@ -294,6 +295,18 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
    >> do_exit(SIGKILL);
    >> }
    >>
    >> +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;
    >> +
    >> + pr_alert("Memory Tagging Extension Fault in %pS\n", (void *)regs->pc);
    >> + pr_alert(" %s at address %lx\n", is_write ? "Write" : "Read", addr);
    >> + pr_alert(" Pointer tag: [%02x], memory tag: [%02x]\n",
    >> + mte_get_ptr_tag(addr),
    >> + mte_get_mem_tag((void *)addr));
    >> +}
    >> +
    >> static void __do_kernel_fault(unsigned long addr, unsigned int esr,
    >> struct pt_regs *regs)
    >> {
    >> @@ -641,10 +654,31 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
    >> return 0;
    >> }
    >>
    >> +static void do_tag_recovery(unsigned long addr, unsigned int esr,
    >> + struct pt_regs *regs)
    >> +{
    >> + report_tag_fault(addr, esr, regs);
    >
    > I'd only report this once since we expect it to be disabled lazily on
    > the other CPUs (i.e. just use a "static bool reported" to keep track).
    >

    Ok, I will fix it in the next version.

    >> +
    >> + /*
    >> + * Disable Memory Tagging Extension Tag Checking on the local CPU
    >
    > Too verbose, just say MTE tag checking, people reading this code should
    > have learnt already what MTE stands for ;).
    >

    All right, will change it ;)

    >> + * for the current EL.
    >> + * It will be done lazily on the other CPUs when they will hit a
    >> + * tag fault.
    >> + */
    >> + sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_NONE);
    >> + isb();
    >> +}
    >> +
    >> +
    >> static int do_tag_check_fault(unsigned long addr, unsigned int esr,
    >> struct pt_regs *regs)
    >> {
    >> - do_bad_area(addr, esr, regs);
    >> + /* The tag check fault (TCF) is per TTBR */
    >> + if (is_ttbr0_addr(addr))
    >> + do_bad_area(addr, esr, regs);
    >> + else
    >> + do_tag_recovery(addr, esr, regs);
    >
    > This part looks fine now.
    >

    Ok, thanks.

    --
    Regards,
    Vincenzo

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