On Wed, May 29, 2019 at 06:04:44PM +0530, Anshuman Khandual wrote: > This consolidates page fault information capture and move them bit earlier. > While here it also adds an wrapper is_write_abort(). It also saves some > cycles by replacing multiple user_mode() calls into a single one earlier > during the fault.
To be honest, I doubt this has any measureable impact, but I agree that using variables _may_ make the flow control easier to understand. > > Signed-off-by: Anshuman Khandual <[email protected]> > Cc: Catalin Marinas <[email protected]> > Cc: Will Deacon <[email protected]> > Cc: Mark Rutland <[email protected]> > Cc: James Morse <[email protected]> > Cc: Andrey Konovalov <[email protected]> > --- > arch/arm64/mm/fault.c | 22 +++++++++++++++------- > 1 file changed, 15 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index da02678..170c71f 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -435,6 +435,11 @@ static bool is_el0_instruction_abort(unsigned int esr) > return ESR_ELx_EC(esr) == ESR_ELx_EC_IABT_LOW; > } > > +static bool is_write_abort(unsigned int esr) > +{ > + return (esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM); > +} In off-list review, I mentioned that this isn't true for EL1, and I think that we should name this 'is_el0_write_abort()' or add a comment explaining the caveats if factored into a helper. Thanks, Mark. > + > static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, > struct pt_regs *regs) > { > @@ -443,6 +448,9 @@ 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_write = is_write_abort(esr); > > if (notify_page_fault(regs, esr)) > return 0; > @@ -454,12 +462,12 @@ 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_write) { > vm_flags = VM_WRITE; > mm_flags |= FAULT_FLAG_WRITE; > } > @@ -487,7 +495,7 @@ static int __kprobes do_page_fault(unsigned long addr, > unsigned int esr, > * we can bug out early if this is from code which shouldn't. > */ > if (!down_read_trylock(&mm->mmap_sem)) { > - if (!user_mode(regs) && !search_exception_tables(regs->pc)) > + if (!is_user && !search_exception_tables(regs->pc)) > goto no_context; > retry: > down_read(&mm->mmap_sem); > @@ -498,7 +506,7 @@ static int __kprobes do_page_fault(unsigned long addr, > unsigned int esr, > */ > might_sleep(); > #ifdef CONFIG_DEBUG_VM > - if (!user_mode(regs) && !search_exception_tables(regs->pc)) { > + if (!is_user && !search_exception_tables(regs->pc)) { > up_read(&mm->mmap_sem); > goto no_context; > } > @@ -516,7 +524,7 @@ static int __kprobes do_page_fault(unsigned long addr, > unsigned int esr, > * in __lock_page_or_retry in mm/filemap.c. > */ > if (fatal_signal_pending(current)) { > - if (!user_mode(regs)) > + if (!is_user) > goto no_context; > return 0; > } > @@ -561,7 +569,7 @@ static int __kprobes do_page_fault(unsigned long addr, > unsigned int esr, > * If we are in kernel mode at this point, we have no context to > * handle this fault with. > */ > - if (!user_mode(regs)) > + if (!is_user) > goto no_context; > > if (fault & VM_FAULT_OOM) { > -- > 2.7.4 >
