parisc: Fix some PTE/TLB race conditions and optimize __flush_tlb_range based on timing results

The increased use of pdtlb/pitlb instructions seemed to increase the
frequency of random segmentation faults building packages. Further, we
had a number of cases where TLB inserts would repeatedly fail and all
forward progress would stop. The Haskell ghc package caused a lot of
trouble in this area. The final indication of a race in pte handling was
this syslog entry on sibaris (C8000):

 swap_free: Unused swap offset entry 00000004
 BUG: Bad page map in process mysqld  pte:00000100 pmd:019bbec5
 addr:00000000ec464000 vm_flags:00100073 anon_vma:0000000221023828 mapping: (null) index:ec464
 CPU: 1 PID: 9176 Comm: mysqld Not tainted 4.0.0-2-parisc64-smp #1 Debian 4.0.5-1
 Backtrace:
  [<0000000040173eb0>] show_stack+0x20/0x38
  [<0000000040444424>] dump_stack+0x9c/0x110
  [<00000000402a0d38>] print_bad_pte+0x1a8/0x278
  [<00000000402a28b8>] unmap_single_vma+0x3d8/0x770
  [<00000000402a4090>] zap_page_range+0xf0/0x198
  [<00000000402ba2a4>] SyS_madvise+0x404/0x8c0

Note that the pte value is 0 except for the accessed bit 0x100. This bit
shouldn't be set without the present bit.

It should be noted that the madvise system call is probably a trigger for many
of the random segmentation faults.

In looking at the kernel code, I found the following problems:

1) The pte_clear define didn't take TLB lock when clearing a pte.
2) We didn't test pte present bit inside lock in exception support.
3) The pte and tlb locks needed to merged in order to ensure consistency
between page table and TLB. This also has the effect of serializing TLB
broadcasts on SMP systems.

The attached change implements the above and a few other tweaks to try
to improve performance. Based on the timing code, TLB purges are very
slow (e.g., ~ 209 cycles per page on rp3440). Thus, I think it
beneficial to test the split_tlb variable to avoid duplicate purges.
Probably, all PA 2.0 machines have combined TLBs.

I dropped using __flush_tlb_range in flush_tlb_mm as I realized all
applications and most threads have a stack size that is too large to
make this useful. I added some comments to this effect.

Since implementing 1 through 3, I haven't had any random segmentation
faults on mx3210 (rp3440) in about one week of building code and running
as a Debian buildd.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # v3.18+
Signed-off-by: Helge Deller <deller@gmx.de>

3 files changed, 146 insertions, 126 deletions

diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index f6448c7c62b5..cda6dbbe9842 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -342,12 +342,15 @@ EXPORT_SYMBOL(flush_data_cache_local);
 EXPORT_SYMBOL(flush_kernel_icache_range_asm);
 
 #define FLUSH_THRESHOLD 0x80000 /* 0.5MB */
-int parisc_cache_flush_threshold __read_mostly = FLUSH_THRESHOLD;
+static unsigned long parisc_cache_flush_threshold __read_mostly = FLUSH_THRESHOLD;
+
+#define FLUSH_TLB_THRESHOLD (2*1024*1024) /* 2MB initial TLB threshold */
+static unsigned long parisc_tlb_flush_threshold __read_mostly = FLUSH_TLB_THRESHOLD;
 
 void __init parisc_setup_cache_timing(void)
 {
 	unsigned long rangetime, alltime;
-	unsigned long size;
+	unsigned long size, start;
 
 	alltime = mfctl(16);
 	flush_data_cache();
@@ -364,14 +367,43 @@ void __init parisc_setup_cache_timing(void)
 	/* Racy, but if we see an intermediate value, it's ok too... */
 	parisc_cache_flush_threshold = size * alltime / rangetime;
 
-	parisc_cache_flush_threshold = (parisc_cache_flush_threshold + L1_CACHE_BYTES - 1) &~ (L1_CACHE_BYTES - 1); 
+	parisc_cache_flush_threshold = L1_CACHE_ALIGN(parisc_cache_flush_threshold);
 	if (!parisc_cache_flush_threshold)
 		parisc_cache_flush_threshold = FLUSH_THRESHOLD;
 
 	if (parisc_cache_flush_threshold > cache_info.dc_size)
 		parisc_cache_flush_threshold = cache_info.dc_size;
 
-	printk(KERN_INFO "Setting cache flush threshold to %x (%d CPUs online)\n", parisc_cache_flush_threshold, num_online_cpus());
+	printk(KERN_INFO "Setting cache flush threshold to %lu kB\n",
+		parisc_cache_flush_threshold/1024);
+
+	/* calculate TLB flush threshold */
+
+	alltime = mfctl(16);
+	flush_tlb_all();
+	alltime = mfctl(16) - alltime;
+
+	size = PAGE_SIZE;
+	start = (unsigned long) _text;
+	rangetime = mfctl(16);
+	while (start < (unsigned long) _end) {
+		flush_tlb_kernel_range(start, start + PAGE_SIZE);
+		start += PAGE_SIZE;
+		size += PAGE_SIZE;
+	}
+	rangetime = mfctl(16) - rangetime;
+
+	printk(KERN_DEBUG "Whole TLB flush %lu cycles, flushing %lu bytes %lu cycles\n",
+		alltime, size, rangetime);
+
+	parisc_tlb_flush_threshold = size * alltime / rangetime;
+	parisc_tlb_flush_threshold *= num_online_cpus();
+	parisc_tlb_flush_threshold = PAGE_ALIGN(parisc_tlb_flush_threshold);
+	if (!parisc_tlb_flush_threshold)
+		parisc_tlb_flush_threshold = FLUSH_TLB_THRESHOLD;
+
+	printk(KERN_INFO "Setting TLB flush threshold to %lu kB\n",
+		parisc_tlb_flush_threshold/1024);
 }
 
 extern void purge_kernel_dcache_page_asm(unsigned long);
@@ -403,48 +435,45 @@ void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,
 }
 EXPORT_SYMBOL(copy_user_page);
 
-void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
-{
-	unsigned long flags;
-
-	/* Note: purge_tlb_entries can be called at startup with
-	   no context.  */
-
-	purge_tlb_start(flags);
-	mtsp(mm->context, 1);
-	pdtlb(addr);
-	pitlb(addr);
-	purge_tlb_end(flags);
-}
-EXPORT_SYMBOL(purge_tlb_entries);
-
-void __flush_tlb_range(unsigned long sid, unsigned long start,
-		       unsigned long end)
+/* __flush_tlb_range()
+ *
+ * returns 1 if all TLBs were flushed.
+ */
+int __flush_tlb_range(unsigned long sid, unsigned long start,
+		      unsigned long end)
 {
-	unsigned long npages;
+	unsigned long flags, size;
 
-	npages = ((end - (start & PAGE_MASK)) + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
-	if (npages >= 512)  /* 2MB of space: arbitrary, should be tuned */
+	size = (end - start);
+	if (size >= parisc_tlb_flush_threshold) {
 		flush_tlb_all();
-	else {
-		unsigned long flags;
+		return 1;
+	}
 
+	/* Purge TLB entries for small ranges using the pdtlb and
+	   pitlb instructions.  These instructions execute locally
+	   but cause a purge request to be broadcast to other TLBs.  */
+	if (likely(!split_tlb)) {
+		while (start < end) {
+			purge_tlb_start(flags);
+			mtsp(sid, 1);
+			pdtlb(start);
+			purge_tlb_end(flags);
+			start += PAGE_SIZE;
+		}
+		return 0;
+	}
+
+	/* split TLB case */
+	while (start < end) {
 		purge_tlb_start(flags);
 		mtsp(sid, 1);
-		if (split_tlb) {
-			while (npages--) {
-				pdtlb(start);
-				pitlb(start);
-				start += PAGE_SIZE;
-			}
-		} else {
-			while (npages--) {
-				pdtlb(start);
-				start += PAGE_SIZE;
-			}
-		}
+		pdtlb(start);
+		pitlb(start);
 		purge_tlb_end(flags);
+		start += PAGE_SIZE;
 	}
+	return 0;
 }
 
 static void cacheflush_h_tmp_function(void *dummy)
diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index 75819617f93b..c5ef4081b01d 100644
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -45,7 +45,7 @@
 	.level 2.0
 #endif
 
-	.import         pa_dbit_lock,data
+	.import		pa_tlb_lock,data
 
 	/* space_to_prot macro creates a prot id from a space id */
 
@@ -420,8 +420,8 @@
 	SHLREG		%r9,PxD_VALUE_SHIFT,\pmd
 	extru		\va,31-PAGE_SHIFT,ASM_BITS_PER_PTE,\index
 	dep		%r0,31,PAGE_SHIFT,\pmd  /* clear offset */
-	shladd		\index,BITS_PER_PTE_ENTRY,\pmd,\pmd
-	LDREG		%r0(\pmd),\pte		/* pmd is now pte */
+	shladd		\index,BITS_PER_PTE_ENTRY,\pmd,\pmd /* pmd is now pte */
+	LDREG		%r0(\pmd),\pte
 	bb,>=,n		\pte,_PAGE_PRESENT_BIT,\fault
 	.endm
 
@@ -453,57 +453,53 @@
 	L2_ptep		\pgd,\pte,\index,\va,\fault
 	.endm
 
-	/* Acquire pa_dbit_lock lock. */
-	.macro		dbit_lock	spc,tmp,tmp1
+	/* Acquire pa_tlb_lock lock and recheck page is still present. */
+	.macro		tlb_lock	spc,ptp,pte,tmp,tmp1,fault
 #ifdef CONFIG_SMP
 	cmpib,COND(=),n	0,\spc,2f
-	load32		PA(pa_dbit_lock),\tmp
+	load32		PA(pa_tlb_lock),\tmp
 1:	LDCW		0(\tmp),\tmp1
 	cmpib,COND(=)	0,\tmp1,1b
 	nop
+	LDREG		0(\ptp),\pte
+	bb,<,n		\pte,_PAGE_PRESENT_BIT,2f
+	b		\fault
+	stw		 \spc,0(\tmp)
 2:
 #endif
 	.endm
 
-	/* Release pa_dbit_lock lock without reloading lock address. */
-	.macro		dbit_unlock0	spc,tmp
+	/* Release pa_tlb_lock lock without reloading lock address. */
+	.macro		tlb_unlock0	spc,tmp
 #ifdef CONFIG_SMP
 	or,COND(=)	%r0,\spc,%r0
 	stw             \spc,0(\tmp)
 #endif
 	.endm
 
-	/* Release pa_dbit_lock lock. */
-	.macro		dbit_unlock1	spc,tmp
+	/* Release pa_tlb_lock lock. */
+	.macro		tlb_unlock1	spc,tmp
 #ifdef CONFIG_SMP
-	load32		PA(pa_dbit_lock),\tmp
-	dbit_unlock0	\spc,\tmp
+	load32		PA(pa_tlb_lock),\tmp
+	tlb_unlock0	\spc,\tmp
 #endif
 	.endm
 
 	/* Set the _PAGE_ACCESSED bit of the PTE.  Be clever and
 	 * don't needlessly dirty the cache line if it was already set */
-	.macro		update_ptep	spc,ptep,pte,tmp,tmp1
-#ifdef CONFIG_SMP
-	or,COND(=)	%r0,\spc,%r0
-	LDREG		0(\ptep),\pte
-#endif
+	.macro		update_accessed	ptp,pte,tmp,tmp1
 	ldi		_PAGE_ACCESSED,\tmp1
 	or		\tmp1,\pte,\tmp
 	and,COND(<>)	\tmp1,\pte,%r0
-	STREG		\tmp,0(\ptep)
+	STREG		\tmp,0(\ptp)
 	.endm
 
 	/* Set the dirty bit (and accessed bit).  No need to be
 	 * clever, this is only used from the dirty fault */
-	.macro		update_dirty	spc,ptep,pte,tmp
-#ifdef CONFIG_SMP
-	or,COND(=)	%r0,\spc,%r0
-	LDREG		0(\ptep),\pte
-#endif
+	.macro		update_dirty	ptp,pte,tmp
 	ldi		_PAGE_ACCESSED|_PAGE_DIRTY,\tmp
 	or		\tmp,\pte,\pte
-	STREG		\pte,0(\ptep)
+	STREG		\pte,0(\ptp)
 	.endm
 
 	/* bitshift difference between a PFN (based on kernel's PAGE_SIZE)
@@ -1148,14 +1144,14 @@ dtlb_miss_20w:
 
 	L3_ptep		ptp,pte,t0,va,dtlb_check_alias_20w
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,dtlb_check_alias_20w
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb	spc,pte,prot
 	
 	idtlbt          pte,prot
-	dbit_unlock1	spc,t0
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1174,14 +1170,14 @@ nadtlb_miss_20w:
 
 	L3_ptep		ptp,pte,t0,va,nadtlb_check_alias_20w
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,nadtlb_check_alias_20w
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb	spc,pte,prot
 
 	idtlbt          pte,prot
-	dbit_unlock1	spc,t0
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1202,20 +1198,20 @@ dtlb_miss_11:
 
 	L2_ptep		ptp,pte,t0,va,dtlb_check_alias_11
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,dtlb_check_alias_11
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb_11	spc,pte,prot
 
-	mfsp		%sr1,t0  /* Save sr1 so we can use it in tlb inserts */
+	mfsp		%sr1,t1  /* Save sr1 so we can use it in tlb inserts */
 	mtsp		spc,%sr1
 
 	idtlba		pte,(%sr1,va)
 	idtlbp		prot,(%sr1,va)
 
-	mtsp		t0, %sr1	/* Restore sr1 */
-	dbit_unlock1	spc,t0
+	mtsp		t1, %sr1	/* Restore sr1 */
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1235,21 +1231,20 @@ nadtlb_miss_11:
 
 	L2_ptep		ptp,pte,t0,va,nadtlb_check_alias_11
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,nadtlb_check_alias_11
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb_11	spc,pte,prot
 
-
-	mfsp		%sr1,t0  /* Save sr1 so we can use it in tlb inserts */
+	mfsp		%sr1,t1  /* Save sr1 so we can use it in tlb inserts */
 	mtsp		spc,%sr1
 
 	idtlba		pte,(%sr1,va)
 	idtlbp		prot,(%sr1,va)
 
-	mtsp		t0, %sr1	/* Restore sr1 */
-	dbit_unlock1	spc,t0
+	mtsp		t1, %sr1	/* Restore sr1 */
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1269,16 +1264,16 @@ dtlb_miss_20:
 
 	L2_ptep		ptp,pte,t0,va,dtlb_check_alias_20
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,dtlb_check_alias_20
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb	spc,pte,prot
 
-	f_extend	pte,t0
+	f_extend	pte,t1
 
 	idtlbt          pte,prot
-	dbit_unlock1	spc,t0
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1297,16 +1292,16 @@ nadtlb_miss_20:
 
 	L2_ptep		ptp,pte,t0,va,nadtlb_check_alias_20
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,nadtlb_check_alias_20
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb	spc,pte,prot
 
-	f_extend	pte,t0
+	f_extend	pte,t1
 	
-        idtlbt          pte,prot
-	dbit_unlock1	spc,t0
+	idtlbt		pte,prot
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1406,14 +1401,14 @@ itlb_miss_20w:
 
 	L3_ptep		ptp,pte,t0,va,itlb_fault
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,itlb_fault
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb	spc,pte,prot
 	
 	iitlbt          pte,prot
-	dbit_unlock1	spc,t0
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1430,14 +1425,14 @@ naitlb_miss_20w:
 
 	L3_ptep		ptp,pte,t0,va,naitlb_check_alias_20w
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,naitlb_check_alias_20w
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb	spc,pte,prot
 
 	iitlbt          pte,prot
-	dbit_unlock1	spc,t0
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1458,20 +1453,20 @@ itlb_miss_11:
 
 	L2_ptep		ptp,pte,t0,va,itlb_fault
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,itlb_fault
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb_11	spc,pte,prot
 
-	mfsp		%sr1,t0  /* Save sr1 so we can use it in tlb inserts */
+	mfsp		%sr1,t1  /* Save sr1 so we can use it in tlb inserts */
 	mtsp		spc,%sr1
 
 	iitlba		pte,(%sr1,va)
 	iitlbp		prot,(%sr1,va)
 
-	mtsp		t0, %sr1	/* Restore sr1 */
-	dbit_unlock1	spc,t0
+	mtsp		t1, %sr1	/* Restore sr1 */
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1482,20 +1477,20 @@ naitlb_miss_11:
 
 	L2_ptep		ptp,pte,t0,va,naitlb_check_alias_11
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,naitlb_check_alias_11
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb_11	spc,pte,prot
 
-	mfsp		%sr1,t0  /* Save sr1 so we can use it in tlb inserts */
+	mfsp		%sr1,t1  /* Save sr1 so we can use it in tlb inserts */
 	mtsp		spc,%sr1
 
 	iitlba		pte,(%sr1,va)
 	iitlbp		prot,(%sr1,va)
 
-	mtsp		t0, %sr1	/* Restore sr1 */
-	dbit_unlock1	spc,t0
+	mtsp		t1, %sr1	/* Restore sr1 */
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1516,16 +1511,16 @@ itlb_miss_20:
 
 	L2_ptep		ptp,pte,t0,va,itlb_fault
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,itlb_fault
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb	spc,pte,prot
 
-	f_extend	pte,t0	
+	f_extend	pte,t1
 
 	iitlbt          pte,prot
-	dbit_unlock1	spc,t0
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1536,16 +1531,16 @@ naitlb_miss_20:
 
 	L2_ptep		ptp,pte,t0,va,naitlb_check_alias_20
 
-	dbit_lock	spc,t0,t1
-	update_ptep	spc,ptp,pte,t0,t1
+	tlb_lock	spc,ptp,pte,t0,t1,naitlb_check_alias_20
+	update_accessed	ptp,pte,t0,t1
 
 	make_insert_tlb	spc,pte,prot
 
-	f_extend	pte,t0
+	f_extend	pte,t1
 
 	iitlbt          pte,prot
-	dbit_unlock1	spc,t0
 
+	tlb_unlock1	spc,t0
 	rfir
 	nop
 
@@ -1568,14 +1563,14 @@ dbit_trap_20w:
 
 	L3_ptep		ptp,pte,t0,va,dbit_fault
 
-	dbit_lock	spc,t0,t1
-	update_dirty	spc,ptp,pte,t1
+	tlb_lock	spc,ptp,pte,t0,t1,dbit_fault
+	update_dirty	ptp,pte,t1
 
 	make_insert_tlb	spc,pte,prot
 		
 	idtlbt          pte,prot
-	dbit_unlock0	spc,t0
 
+	tlb_unlock0	spc,t0
 	rfir
 	nop
 #else
@@ -1588,8 +1583,8 @@ dbit_trap_11:
 
 	L2_ptep		ptp,pte,t0,va,dbit_fault
 
-	dbit_lock	spc,t0,t1
-	update_dirty	spc,ptp,pte,t1
+	tlb_lock	spc,ptp,pte,t0,t1,dbit_fault
+	update_dirty	ptp,pte,t1
 
 	make_insert_tlb_11	spc,pte,prot
 
@@ -1600,8 +1595,8 @@ dbit_trap_11:
 	idtlbp		prot,(%sr1,va)
 
 	mtsp            t1, %sr1     /* Restore sr1 */
-	dbit_unlock0	spc,t0
 
+	tlb_unlock0	spc,t0
 	rfir
 	nop
 
@@ -1612,16 +1607,16 @@ dbit_trap_20:
 
 	L2_ptep		ptp,pte,t0,va,dbit_fault
 
-	dbit_lock	spc,t0,t1
-	update_dirty	spc,ptp,pte,t1
+	tlb_lock	spc,ptp,pte,t0,t1,dbit_fault
+	update_dirty	ptp,pte,t1
 
 	make_insert_tlb	spc,pte,prot
 
 	f_extend	pte,t1
 	
-        idtlbt          pte,prot
-	dbit_unlock0	spc,t0
+	idtlbt		pte,prot
 
+	tlb_unlock0	spc,t0
 	rfir
 	nop
 #endif
diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index 6548fd1d2e62..b99b39f1da02 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -43,10 +43,6 @@
 
 #include "../math-emu/math-emu.h"	/* for handle_fpe() */
 
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
-DEFINE_SPINLOCK(pa_dbit_lock);
-#endif
-
 static void parisc_show_stack(struct task_struct *task, unsigned long *sp,
 	struct pt_regs *regs);