[PATCH v2 2/3] lkdtm/powerpc: Add SLB multihit test
Michal Suchánek
msuchanek at suse.de
Wed Sep 30 01:01:17 AEST 2020
Hello,
On Fri, Sep 25, 2020 at 12:57:33PM -0700, Kees Cook wrote:
> On Fri, Sep 25, 2020 at 04:01:22PM +0530, Ganesh Goudar wrote:
> > Add support to inject slb multihit errors, to test machine
> > check handling.
>
> Thank you for more tests in here!
Thanks for working on integrating this.
>
> >
> > Based on work by Mahesh Salgaonkar and Michal Suchánek.
> >
> > Cc: Mahesh Salgaonkar <mahesh at linux.ibm.com>
> > Cc: Michal Suchánek <msuchanek at suse.de>
>
> Should these be Co-developed-by: with S-o-b?
I don't think I wrote any of this code. I packaged it for SUSE and maybe
changed some constants based on test result discussion.
I compared this code to my saved snapshots of past versions of the test
module and this covers all the test cases I have. The only difference is that
the development modules have verbose prints showing what's going on.
It is true that without the verbose prints some explanatory comments
could be helpful.
Reviewed-by: Michal Suchánek <msuchanek at suse.de>
>
> > Signed-off-by: Ganesh Goudar <ganeshgr at linux.ibm.com>
> > ---
> > drivers/misc/lkdtm/Makefile | 4 ++
> > drivers/misc/lkdtm/core.c | 3 +
> > drivers/misc/lkdtm/lkdtm.h | 3 +
> > drivers/misc/lkdtm/powerpc.c | 132 +++++++++++++++++++++++++++++++++++
> > 4 files changed, 142 insertions(+)
> > create mode 100644 drivers/misc/lkdtm/powerpc.c
> >
> > diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile
> > index c70b3822013f..6a82f407fbcd 100644
> > --- a/drivers/misc/lkdtm/Makefile
> > +++ b/drivers/misc/lkdtm/Makefile
> > @@ -11,6 +11,10 @@ lkdtm-$(CONFIG_LKDTM) += usercopy.o
> > lkdtm-$(CONFIG_LKDTM) += stackleak.o
> > lkdtm-$(CONFIG_LKDTM) += cfi.o
> >
> > +ifeq ($(CONFIG_PPC64),y)
> > +lkdtm-$(CONFIG_LKDTM) += powerpc.o
> > +endif
>
> This can just be:
>
> lkdtm-$(CONFIG_PPC64) += powerpc.o
>
> > +
> > KASAN_SANITIZE_stackleak.o := n
> > KCOV_INSTRUMENT_rodata.o := n
> >
> > diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
> > index a5e344df9166..8d5db42baa90 100644
> > --- a/drivers/misc/lkdtm/core.c
> > +++ b/drivers/misc/lkdtm/core.c
> > @@ -178,6 +178,9 @@ static const struct crashtype crashtypes[] = {
> > #ifdef CONFIG_X86_32
> > CRASHTYPE(DOUBLE_FAULT),
> > #endif
> > +#ifdef CONFIG_PPC64
> > + CRASHTYPE(PPC_SLB_MULTIHIT),
> > +#endif
> > };
> >
> >
> > diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
> > index 8878538b2c13..b305bd511ee5 100644
> > --- a/drivers/misc/lkdtm/lkdtm.h
> > +++ b/drivers/misc/lkdtm/lkdtm.h
> > @@ -104,4 +104,7 @@ void lkdtm_STACKLEAK_ERASING(void);
> > /* cfi.c */
> > void lkdtm_CFI_FORWARD_PROTO(void);
> >
> > +/* powerpc.c */
> > +void lkdtm_PPC_SLB_MULTIHIT(void);
> > +
> > #endif
> > diff --git a/drivers/misc/lkdtm/powerpc.c b/drivers/misc/lkdtm/powerpc.c
> > new file mode 100644
> > index 000000000000..d6db18444757
> > --- /dev/null
> > +++ b/drivers/misc/lkdtm/powerpc.c
> > @@ -0,0 +1,132 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
>
> Please #include "lkdtm.h" here to get the correct pr_fmt heading (and
> any future header adjustments).
>
> > +#include <linux/slab.h>
> > +#include <linux/vmalloc.h>
> > +
> > +static inline unsigned long get_slb_index(void)
> > +{
> > + unsigned long index;
> > +
> > + index = get_paca()->stab_rr;
> > +
> > + /*
> > + * simple round-robin replacement of slb starting at SLB_NUM_BOLTED.
> > + */
> > + if (index < (mmu_slb_size - 1))
> > + index++;
> > + else
> > + index = SLB_NUM_BOLTED;
> > + get_paca()->stab_rr = index;
> > + return index;
> > +}
> > +
> > +#define slb_esid_mask(ssize) \
> > + (((ssize) == MMU_SEGSIZE_256M) ? ESID_MASK : ESID_MASK_1T)
> > +
> > +static inline unsigned long mk_esid_data(unsigned long ea, int ssize,
> > + unsigned long slot)
> > +{
> > + return (ea & slb_esid_mask(ssize)) | SLB_ESID_V | slot;
> > +}
> > +
> > +#define slb_vsid_shift(ssize) \
> > + ((ssize) == MMU_SEGSIZE_256M ? SLB_VSID_SHIFT : SLB_VSID_SHIFT_1T)
> > +
> > +static inline unsigned long mk_vsid_data(unsigned long ea, int ssize,
> > + unsigned long flags)
> > +{
> > + return (get_kernel_vsid(ea, ssize) << slb_vsid_shift(ssize)) | flags |
> > + ((unsigned long)ssize << SLB_VSID_SSIZE_SHIFT);
> > +}
> > +
> > +static void insert_slb_entry(char *p, int ssize)
> > +{
> > + unsigned long flags, entry;
> > +
> > + flags = SLB_VSID_KERNEL | mmu_psize_defs[MMU_PAGE_64K].sllp;
> > + preempt_disable();
> > +
> > + entry = get_slb_index();
> > + asm volatile("slbmte %0,%1" :
> > + : "r" (mk_vsid_data((unsigned long)p, ssize, flags)),
> > + "r" (mk_esid_data((unsigned long)p, ssize, entry))
> > + : "memory");
> > +
> > + entry = get_slb_index();
> > + asm volatile("slbmte %0,%1" :
> > + : "r" (mk_vsid_data((unsigned long)p, ssize, flags)),
> > + "r" (mk_esid_data((unsigned long)p, ssize, entry))
> > + : "memory");
> > + preempt_enable();
> > + p[0] = '!';
> > +}
>
> Can you add some comments to these helpers? It'll help people (me) with
> understanding what is actually being done here (and more importantly,
> what is _expected_ to happen).
>
> > +
> > +static void inject_vmalloc_slb_multihit(void)
> > +{
> > + char *p;
> > +
> > + p = vmalloc(2048);
> > + if (!p)
> > + return;
> > +
> > + insert_slb_entry(p, MMU_SEGSIZE_1T);
> > + vfree(p);
> > +}
> > +
> > +static void inject_kmalloc_slb_multihit(void)
> > +{
> > + char *p;
> > +
> > + p = kmalloc(2048, GFP_KERNEL);
> > + if (!p)
> > + return;
> > +
> > + insert_slb_entry(p, MMU_SEGSIZE_1T);
> > + kfree(p);
> > +}
>
> It looks like the expected failure injection is actually the "p[0] = '!'" line in the
> "insert" helper? I would expect pr_info/pr_err wrappers, etc, as in
> other lkdtm tests.
>
> If this is the negative test, what does the positive test look like?
> e.g. in other lkdtm tests, first a positive test is done, then a
> negative: first run a legit function, then run a function from a bad
> location.
>
> > +
> > +static void insert_dup_slb_entry_0(void)
> > +{
> > + unsigned long test_address = 0xC000000000000000;
> > + volatile unsigned long *test_ptr;
> > + unsigned long entry, i = 0;
> > + unsigned long esid, vsid;
> > +
> > + test_ptr = (unsigned long *)test_address;
> > + preempt_disable();
> > +
> > + asm volatile("slbmfee %0,%1" : "=r" (esid) : "r" (i));
> > + asm volatile("slbmfev %0,%1" : "=r" (vsid) : "r" (i));
> > + entry = get_slb_index();
> > +
> > + /* for i !=0 we would need to mask out the old entry number */
> > + asm volatile("slbmte %0,%1" :
> > + : "r" (vsid),
> > + "r" (esid | entry)
> > + : "memory");
> > +
> > + asm volatile("slbmfee %0,%1" : "=r" (esid) : "r" (i));
> > + asm volatile("slbmfev %0,%1" : "=r" (vsid) : "r" (i));
> > + entry = get_slb_index();
> > +
> > + /* for i !=0 we would need to mask out the old entry number */
> > + asm volatile("slbmte %0,%1" :
> > + : "r" (vsid),
> > + "r" (esid | entry)
> > + : "memory");
> > +
> > + pr_info("lkdtm: %s accessing test address 0x%lx: 0x%lx\n",
> > + __func__, test_address, *test_ptr);
> > +
> > + preempt_enable();
> > +}
>
> What does this do?
>
> > +
> > +void lkdtm_PPC_SLB_MULTIHIT(void)
> > +{
> > + if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) {
> > + inject_vmalloc_slb_multihit();
> > + inject_kmalloc_slb_multihit();
> > + insert_dup_slb_entry_0();
> > + }
> > + pr_info("Recovered from SLB multihit. (Ignore this message on non HPTE machines)");
>
> Is this bad? If so, I'd expect pr_err("FAIL: ...") Can HPTE machines be
> detected so that an XFAIL can be emitted instead?
>
> Since there are three (two?) distinct regions being tested, should these
> be separate tests? Right now there is no way to separate a vmalloc
> failure from a kmalloc failure, and no way to fail the first without
> hiding the result from the latter (or maybe the machine cannot survive
> this test? ... which should also be a comment.)
>
> And finally, assuming a successful test (or testing from a separate
> thread later), so there any state that needs to be restored (or cleaned
> up before doing the "insert" calls)?
>
> Thanks!
>
> --
> Kees Cook
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