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powerpc/64s/hash: Add some SLB debugging tests

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This adds CONFIG_DEBUG_VM checks to ensure:
  - The kernel stack is in the SLB after it's flushed and bolted.
  - We don't insert an SLB for an address that is aleady in the SLB.
  - The kernel SLB miss handler does not take an SLB miss.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2018-10-03 00:27:59 +10:00 committed by Michael Ellerman
parent 94ee42727c
commit e15a4fea4d
2 changed files with 53 additions and 3 deletions
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3
arch/powerpc/include/asm/paca.h
View File

@ -115,6 +115,9 @@ struct paca_struct {
u16 vmalloc_sllp;
u8 slb_cache_ptr;
u8 stab_rr; /* stab/slb round-robin counter */
#ifdef CONFIG_DEBUG_VM
u8 in_kernel_slb_handler;
#endif
u32 slb_used_bitmap; /* Bitmaps for first 32 SLB entries. */
u32 slb_kern_bitmap;
u32 slb_cache[SLB_CACHE_ENTRIES];

53
arch/powerpc/mm/slb.c
View File

@ -58,6 +58,30 @@ static inline unsigned long mk_vsid_data(unsigned long ea, int ssize,
return __mk_vsid_data(get_kernel_vsid(ea, ssize), ssize, flags);
}
static void assert_slb_exists(unsigned long ea)
{
#ifdef CONFIG_DEBUG_VM
unsigned long tmp;
WARN_ON_ONCE(mfmsr() & MSR_EE);
asm volatile("slbfee. %0, %1" : "=r"(tmp) : "r"(ea) : "cr0");
WARN_ON(tmp == 0);
#endif
}
static void assert_slb_notexists(unsigned long ea)
{
#ifdef CONFIG_DEBUG_VM
unsigned long tmp;
WARN_ON_ONCE(mfmsr() & MSR_EE);
asm volatile("slbfee. %0, %1" : "=r"(tmp) : "r"(ea) : "cr0");
WARN_ON(tmp != 0);
#endif
}
static inline void slb_shadow_update(unsigned long ea, int ssize,
unsigned long flags,
enum slb_index index)
@ -90,6 +114,7 @@ static inline void create_shadowed_slbe(unsigned long ea, int ssize,
*/
slb_shadow_update(ea, ssize, flags, index);
assert_slb_notexists(ea);
asm volatile("slbmte %0,%1" :
: "r" (mk_vsid_data(ea, ssize, flags)),
"r" (mk_esid_data(ea, ssize, index))
@ -111,6 +136,8 @@ void __slb_restore_bolted_realmode(void)
: "r" (be64_to_cpu(p->save_area[index].vsid)),
"r" (be64_to_cpu(p->save_area[index].esid)));
}
assert_slb_exists(local_paca->kstack);
}
/*
@ -158,6 +185,7 @@ void slb_flush_and_restore_bolted(void)
:: "r" (be64_to_cpu(p->save_area[KSTACK_INDEX].vsid)),
"r" (be64_to_cpu(p->save_area[KSTACK_INDEX].esid))
: "memory");
assert_slb_exists(get_paca()->kstack);
get_paca()->slb_cache_ptr = 0;
@ -410,9 +438,17 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
unsigned long slbie_data = 0;
for (i = 0; i < offset; i++) {
/* EA */
slbie_data = (unsigned long)
unsigned long ea;
ea = (unsigned long)
get_paca()->slb_cache[i] << SID_SHIFT;
/*
* Could assert_slb_exists here, but hypervisor
* or machine check could have come in and
* removed the entry at this point.
*/
slbie_data = ea;
slbie_data |= user_segment_size(slbie_data)
<< SLBIE_SSIZE_SHIFT;
slbie_data |= SLBIE_C; /* user slbs have C=1 */
@ -640,6 +676,7 @@ static long slb_insert_entry(unsigned long ea, unsigned long context,
* User preloads should add isync afterwards in case the kernel
* accesses user memory before it returns to userspace with rfid.
*/
assert_slb_notexists(ea);
asm volatile("slbmte %0, %1" : : "r" (vsid_data), "r" (esid_data));
barrier();
@ -740,7 +777,17 @@ long do_slb_fault(struct pt_regs *regs, unsigned long ea)
* if they go via fast_exception_return too.
*/
if (id >= KERNEL_REGION_ID) {
return slb_allocate_kernel(ea, id);
long err;
#ifdef CONFIG_DEBUG_VM
/* Catch recursive kernel SLB faults. */
BUG_ON(local_paca->in_kernel_slb_handler);
local_paca->in_kernel_slb_handler = 1;
#endif
err = slb_allocate_kernel(ea, id);
#ifdef CONFIG_DEBUG_VM
local_paca->in_kernel_slb_handler = 0;
#endif
return err;
} else {
struct mm_struct *mm = current->mm;
long err;