On Wed, Mar 21, 2018 at 5:58 AM, Ram Pai <linux...@us.ibm.com> wrote:
> On Fri, Mar 09, 2018 at 11:43:00AM +0800, Li Wang wrote:
> > On Fri, Mar 9, 2018 at 12:45 AM, Ram Pai <[1]linux...@us.ibm.com>
> wrote:
> >
> > On Thu, Mar 08, 2018 at 11:19:12PM +1100, Michael Ellerman wrote:
> > > Li Wang <[2]liw...@redhat.com> writes:
> > > > Hi,
> > > >
> > > > ltp/mprotect04[1] crashed by SEGV_PKUERR on ppc64(LPAR on P730,
> > Power 8
> > > > 8247-22L) with kernel-v4.16.0-rc4.
> > > >
> > > > 10000000-10020000 r-xp 00000000 fd:00 167223
> mprotect04
> > > > 10020000-10030000 r--p 00010000 fd:00 167223
> mprotect04
> > > > 10030000-10040000 rw-p 00020000 fd:00 167223
> mprotect04
> > > > 1001a380000-1001a3b0000 rw-p 00000000 00:00 0 [heap]
> > > > 7fffa6c60000-7fffa6c80000 --xp 00000000 00:00 0
> > > >
> > > > &exec_func = 0x10030170
> > > >
> > > > &func = 0x7fffa6c60170
> > > >
> > > > While perform
> > > > "(*func)();" we get the
> > > > segmentation fault.
> > > >
> > > >
> > > > strace log:
> > > >
> > > > -------------------
> > > > mprotect(0x7fffaed00000, 131072, PROT_EXEC) = 0
> > > > rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
> > > > --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_PKUERR,
> > si_addr=0x7fffaed00170}
> > > > ---
> > >
> > > Looks like a bug to me.
> > >
> > > Please Cc linuxppc-dev on powerpc bugs.
> > >
> > > I also can't reproduce this failure on my machine.
> > > Not sure what's going on?
> >
> > I could reproduce it on a power7 lpar. But not on a power8 lpar.
> >
> > The problem seems to be that the cpu generates a key exception if
> > the page with Read/Write-disable-but-execute-enable key is executed
> > on power7. If I enable read on that key, the exception disappears.
> >
> > After adding read permission on that key, reproducer get PASS on my
> power8
> > machine too.
> > (mprotect(..,PROT_READ | PROT_EXEC))
> >
> >
> > BTW: the testcase executes
> > mprotect(..,PROT_EXEC).
> > The mprotect(, PROT_EXEC) system call internally generates a
> > execute-only key and associates it with the pages in the
> address-range.
> >
> > Now since Li Wang claims that he can reproduce it on power8 as
> well, i
> > am wondering if the slightly different cpu behavior is dependent on
> the
> > version of the firmware/microcode?
> >
> > I also run this reproducer on series ppc kvm machines, but none of
> them
> > get the FAIL.
> > If you need some more HW info, pls let me know.
>
> Hi Li,
>
> Can you try the following patch and see if it solves your problem.
>
It only works on power7 lpar machine.
But for p8 lpar, it still get failure as that before, the thing I wondered
is
that why not disable the pkey_execute_disable_supported on p8 machine?
I tried to modify your patch and get PASS with the mprotect04 test on
power8 lpar machine.
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -105,7 +105,9 @@ int pkey_initialize(void)
* The device tree cannot be relied to indicate support for
* execute_disable support. Instead we use a PVR check.
*/
- if (pvr_version_is(PVR_POWER7) || pvr_version_is(PVR_POWER7p))
+ if (pvr_version_is(PVR_POWER7) || pvr_version_is(PVR_POWER7p) \
+ || pvr_version_is(PVR_POWER8E) ||
pvr_version_is(PVR_POWER8NVL) \
+ || pvr_version_is(PVR_POWER8))
pkey_execute_disable_supported = false;
else
pkey_execute_disable_supported = true;
@@ -395,7 +397,7 @@ int __arch_override_mprotect_pkey(struct vm_area_struct
*vma, int prot,
* The requested protection is execute-only. Hence let's use an
* execute-only pkey.
*/
- if (prot == PROT_EXEC) {
+ if (prot == PROT_EXEC && pkey_execute_disable_supported) {
pkey = execute_only_pkey(vma->vm_mm);
if (pkey > 0)
return pkey;
>
>
> diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
> index c269817..184a10a 100644
> --- a/arch/powerpc/mm/pkeys.c
> +++ b/arch/powerpc/mm/pkeys.c
> @@ -421,7 +421,7 @@ int __arch_override_mprotect_pkey(struct
> vm_area_struct *vma, int prot,
> * The requested protection is execute-only. Hence let's use an
> * execute-only pkey.
> */
> - if (prot == PROT_EXEC) {
>
> + if (prot == PROT_EXEC && pkey_execute_disable_supported) {
> pkey = execute_only_pkey(vma->vm_mm);
> if (pkey > 0)
> return pkey;
>
>
> Thanks
> RP
>
>
--
Li Wang
liw...@redhat.com
