| Message ID | 1471831017-18167-2-git-send-email-bsingharora@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
Balbir Singh <bsingharora@gmail.com> writes: > ISA 3 allows for prevention of instruction fetch and execution > of user mode pages. If such an error occurs, SRR1 bit 35 > reports the error. We catch and report the error in do_page_fault() > But what does the error mean ? A buggy application ? IIUC, it indicate a buggy kernel isn't it ?. So should we kill the application or panic() ? > Signed-off-by: Balbir Singh <bsingharora@gmail.com> > --- > arch/powerpc/mm/fault.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > index a4db22f..f162e77 100644 > --- a/arch/powerpc/mm/fault.c > +++ b/arch/powerpc/mm/fault.c > @@ -404,6 +404,10 @@ good_area: > (cpu_has_feature(CPU_FTR_NOEXECUTE) || > !(vma->vm_flags & (VM_READ | VM_WRITE)))) > goto bad_area; > +#ifdef CONFIG_PPC_RADIX_MMU > + if (radix_enabled() && regs->msr & PPC_BIT(35)) > + goto bad_area; > +#endif > #ifdef CONFIG_PPC_STD_MMU > /* > * protfault should only happen due to us -aneesh
On Mon, Aug 22, 2016 at 11:35:36AM +0530, Aneesh Kumar K.V wrote: > Balbir Singh <bsingharora@gmail.com> writes: > > > ISA 3 allows for prevention of instruction fetch and execution > > of user mode pages. If such an error occurs, SRR1 bit 35 > > reports the error. We catch and report the error in do_page_fault() > > > > But what does the error mean ? A buggy application ? IIUC, it indicate a > buggy kernel isn't it ?. So should we kill the application or panic() ? > We oops.. basically we get a kernel fault. We handle it the same way we handle other kernel faults. > > > Signed-off-by: Balbir Singh <bsingharora@gmail.com> > > --- > > arch/powerpc/mm/fault.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > > index a4db22f..f162e77 100644 > > --- a/arch/powerpc/mm/fault.c > > +++ b/arch/powerpc/mm/fault.c > > @@ -404,6 +404,10 @@ good_area: > > (cpu_has_feature(CPU_FTR_NOEXECUTE) || > > !(vma->vm_flags & (VM_READ | VM_WRITE)))) > > goto bad_area; > > +#ifdef CONFIG_PPC_RADIX_MMU > > + if (radix_enabled() && regs->msr & PPC_BIT(35)) > > + goto bad_area; > > +#endif > > #ifdef CONFIG_PPC_STD_MMU > > /* > > * protfault should only happen due to us > > -aneesh >
On Mon, 2016-22-08 at 01:56:57 UTC, Balbir Singh wrote: > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > index a4db22f..f162e77 100644 > --- a/arch/powerpc/mm/fault.c > +++ b/arch/powerpc/mm/fault.c > @@ -404,6 +404,10 @@ good_area: > (cpu_has_feature(CPU_FTR_NOEXECUTE) || > !(vma->vm_flags & (VM_READ | VM_WRITE)))) > goto bad_area; > +#ifdef CONFIG_PPC_RADIX_MMU We shouldn't need the #ifdef, radix_enabled() will be false. > + if (radix_enabled() && regs->msr & PPC_BIT(35)) > + goto bad_area; Is it really architected as radix only? Personally I dislike PPC_BIT(), I'd rather you just used 0x10000000. That way when I'm staring at a register dump I have some chance of spotting that mask. Also brackets around the bitwise & would make me feel more comfortable. cheers
On 20/09/16 16:35, Michael Ellerman wrote: > On Mon, 2016-22-08 at 01:56:57 UTC, Balbir Singh wrote: >> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c >> index a4db22f..f162e77 100644 >> --- a/arch/powerpc/mm/fault.c >> +++ b/arch/powerpc/mm/fault.c >> @@ -404,6 +404,10 @@ good_area: >> (cpu_has_feature(CPU_FTR_NOEXECUTE) || >> !(vma->vm_flags & (VM_READ | VM_WRITE)))) >> goto bad_area; >> +#ifdef CONFIG_PPC_RADIX_MMU > > We shouldn't need the #ifdef, radix_enabled() will be false. > >> + if (radix_enabled() && regs->msr & PPC_BIT(35)) >> + goto bad_area; > > Is it really architected as radix only? > > Personally I dislike PPC_BIT(), I'd rather you just used 0x10000000. That way > when I'm staring at a register dump I have some chance of spotting that mask. > > Also brackets around the bitwise & would make me feel more comfortable. > > cheers > Will make the changes and submit Balbir
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index a4db22f..f162e77 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -404,6 +404,10 @@ good_area: (cpu_has_feature(CPU_FTR_NOEXECUTE) || !(vma->vm_flags & (VM_READ | VM_WRITE)))) goto bad_area; +#ifdef CONFIG_PPC_RADIX_MMU + if (radix_enabled() && regs->msr & PPC_BIT(35)) + goto bad_area; +#endif #ifdef CONFIG_PPC_STD_MMU /* * protfault should only happen due to us
ISA 3 allows for prevention of instruction fetch and execution of user mode pages. If such an error occurs, SRR1 bit 35 reports the error. We catch and report the error in do_page_fault() Signed-off-by: Balbir Singh <bsingharora@gmail.com> --- arch/powerpc/mm/fault.c | 4 ++++ 1 file changed, 4 insertions(+)