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SubjectRe: [PATCH v2 24/37] arm64: mte: Add in-kernel tag fault handler
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).

> +
> + /*
> + * 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 ;).

> + * 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.

--
Catalin

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