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SubjectRe: [PATCH V2 3/4] arm64/mm: Consolidate page fault information capture
On Mon, Jun 03, 2019 at 12:11:24PM +0530, Anshuman Khandual wrote:
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index da02678..4bb65f3 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -435,6 +435,14 @@ static bool is_el0_instruction_abort(unsigned int esr)
> return ESR_ELx_EC(esr) == ESR_ELx_EC_IABT_LOW;
> }
>
> +/*
> + * This is applicable only for EL0 write aborts.
> + */
> +static bool is_el0_write_abort(unsigned int esr)
> +{
> + return (esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM);
> +}

What makes this EL0 only?

> +
> static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
> struct pt_regs *regs)
> {
> @@ -443,6 +451,9 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
> vm_fault_t fault, major = 0;
> unsigned long vm_flags = VM_READ | VM_WRITE;
> unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
> + bool is_user = user_mode(regs);
> + bool is_el0_exec = is_el0_instruction_abort(esr);
> + bool is_el0_write = is_el0_write_abort(esr);
>
> if (notify_page_fault(regs, esr))
> return 0;
> @@ -454,12 +465,12 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
> if (faulthandler_disabled() || !mm)
> goto no_context;
>
> - if (user_mode(regs))
> + if (is_user)
> mm_flags |= FAULT_FLAG_USER;
>
> - if (is_el0_instruction_abort(esr)) {
> + if (is_el0_exec) {
> vm_flags = VM_EXEC;
> - } else if ((esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM)) {
> + } else if (is_el0_write) {
> vm_flags = VM_WRITE;
> mm_flags |= FAULT_FLAG_WRITE;
> }

This can be triggered by an EL1 write to a user mapping, so is_el0_write
is misleading.

--
Catalin

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