| Message ID | 1559133285-27986-4-git-send-email-anshuman.khandual@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64/mm: Fixes and cleanups for do_page_fault() | expand |
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 <anshuman.khandual@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: James Morse <james.morse@arm.com> > Cc: Andrey Konovalov <andreyknvl@google.com> > --- > 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 >
On 05/29/2019 08:23 PM, Mark Rutland wrote: > 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 <anshuman.khandual@arm.com> >> Cc: Catalin Marinas <catalin.marinas@arm.com> >> Cc: Will Deacon <will.deacon@arm.com> >> Cc: Mark Rutland <mark.rutland@arm.com> >> Cc: James Morse <james.morse@arm.com> >> Cc: Andrey Konovalov <andreyknvl@google.com> >> --- >> 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. Okay will change the wrapper name to is_el0_write_abort() and add a comment explaining how this is only applicable to aborts originating from EL0.
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); +} + 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) {
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. Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: James Morse <james.morse@arm.com> Cc: Andrey Konovalov <andreyknvl@google.com> --- arch/arm64/mm/fault.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-)