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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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