Commit e15a4fea authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

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



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: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 94ee4272

arch/powerpc/include/asm/paca.h

+3 −0
Original line number Diff line number Diff line
@@ -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];

arch/powerpc/mm/slb.c

+50 −3
Original line number Diff line number Diff line
@@ -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;

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