s390/vdso: fix stack corruption

The kernel provided vdso functions do not get a stack frame from the
calling function and therefore may not change the stack contents, unless
they allocate space on their own.

This problem was exposed with 070b7be633dc "s390/vdso: replace stck with
stcke" which writes 16 bytes instead of 8 bytes into the stack frame. These
additional 8 bytes however were indeed used by the caller (glibc) to save
data and therefore this data was corrupted by the vdso code.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/vdso32/clock_gettime.S

@@ -19,6 +19,7 @@
 	.type  __kernel_clock_gettime,@function
 __kernel_clock_gettime:
 	.cfi_startproc
+	ahi	%r15,-16
 	basr	%r5,0
 0:	al	%r5,21f-0b(%r5)			/* get &_vdso_data */
 	chi	%r2,__CLOCK_REALTIME_COARSE
@@ -34,8 +35,8 @@ __kernel_clock_gettime:
 1:	l	%r4,__VDSO_UPD_COUNT+4(%r5)	/* load update counter */
 	tml	%r4,0x0001			/* pending update ? loop */
 	jnz	1b
-	stcke	24(%r15)			/* Store TOD clock */
-	lm	%r0,%r1,25(%r15)
+	stcke	0(%r15)				/* Store TOD clock */
+	lm	%r0,%r1,1(%r15)
 	s	%r0,__VDSO_XTIME_STAMP(%r5)	/* TOD - cycle_last */
 	sl	%r1,__VDSO_XTIME_STAMP+4(%r5)
 	brc	3,2f
@@ -70,6 +71,7 @@ __kernel_clock_gettime:
 8:	st	%r2,0(%r3)			/* store tp->tv_sec */
 	st	%r1,4(%r3)			/* store tp->tv_nsec */
 	lhi	%r2,0
+	ahi	%r15,16
 	br	%r14
 
 	/* CLOCK_MONOTONIC_COARSE */
@@ -96,8 +98,8 @@ __kernel_clock_gettime:
 11:	l	%r4,__VDSO_UPD_COUNT+4(%r5)	/* load update counter */
 	tml	%r4,0x0001			/* pending update ? loop */
 	jnz	11b
-	stcke	24(%r15)			/* Store TOD clock */
-	lm	%r0,%r1,25(%r15)
+	stcke	0(%r15)				/* Store TOD clock */
+	lm	%r0,%r1,1(%r15)
 	s	%r0,__VDSO_XTIME_STAMP(%r5)	/* TOD - cycle_last */
 	sl	%r1,__VDSO_XTIME_STAMP+4(%r5)
 	brc	3,12f
@@ -132,11 +134,13 @@ __kernel_clock_gettime:
 17:	st	%r2,0(%r3)			/* store tp->tv_sec */
 	st	%r1,4(%r3)			/* store tp->tv_nsec */
 	lhi	%r2,0
+	ahi	%r15,16
 	br	%r14
 
 	/* Fallback to system call */
 19:	lhi	%r1,__NR_clock_gettime
 	svc	0
+	ahi	%r15,16
 	br	%r14
 
 20:	.long	1000000000

arch/s390/kernel/vdso32/gettimeofday.S

@@ -19,6 +19,7 @@
 	.type  __kernel_gettimeofday,@function
 __kernel_gettimeofday:
 	.cfi_startproc
+	ahi	%r15,-16
 	basr	%r5,0
 0:	al	%r5,13f-0b(%r5)			/* get &_vdso_data */
 1:	ltr	%r3,%r3				/* check if tz is NULL */
@@ -29,30 +30,30 @@ __kernel_gettimeofday:
 	l	%r4,__VDSO_UPD_COUNT+4(%r5)	/* load update counter */
 	tml	%r4,0x0001			/* pending update ? loop */
 	jnz	1b
-	stcke	24(%r15)			/* Store TOD clock */
-	lm	%r0,%r1,25(%r15)
+	stcke	0(%r15)				/* Store TOD clock */
+	lm	%r0,%r1,1(%r15)
 	s	%r0,__VDSO_XTIME_STAMP(%r5)	/* TOD - cycle_last */
 	sl	%r1,__VDSO_XTIME_STAMP+4(%r5)
 	brc	3,3f
 	ahi	%r0,-1
 3:	ms	%r0,__VDSO_TK_MULT(%r5)		/*  * tk->mult */
-	st	%r0,24(%r15)
+	st	%r0,0(%r15)
 	l	%r0,__VDSO_TK_MULT(%r5)
 	ltr	%r1,%r1
 	mr	%r0,%r0
 	jnm	4f
 	a	%r0,__VDSO_TK_MULT(%r5)
-4:	al	%r0,24(%r15)
+4:	al	%r0,0(%r15)
 	al	%r0,__VDSO_XTIME_NSEC(%r5)	/*  + xtime */
 	al	%r1,__VDSO_XTIME_NSEC+4(%r5)
 	brc	12,5f
 	ahi	%r0,1
-5:	mvc	24(4,%r15),__VDSO_XTIME_SEC+4(%r5)
+5:	mvc	0(4,%r15),__VDSO_XTIME_SEC+4(%r5)
 	cl	%r4,__VDSO_UPD_COUNT+4(%r5)	/* check update counter */
 	jne	1b
 	l	%r4,__VDSO_TK_SHIFT(%r5)	/* Timekeeper shift */
 	srdl	%r0,0(%r4)			/*  >> tk->shift */
-	l	%r4,24(%r15)			/* get tv_sec from stack */
+	l	%r4,0(%r15)			/* get tv_sec from stack */
 	basr	%r5,0
 6:	ltr	%r0,%r0
 	jnz	7f
@@ -71,6 +72,7 @@ __kernel_gettimeofday:
 9:	srl	%r0,6
 	st	%r0,4(%r2)			/* store tv->tv_usec */
 10:	slr	%r2,%r2
+	ahi	%r15,16
 	br	%r14
 11:	.long	1000000000
 12:	.long	274877907

arch/s390/kernel/vdso64/clock_gettime.S

@@ -19,6 +19,7 @@
 	.type  __kernel_clock_gettime,@function
 __kernel_clock_gettime:
 	.cfi_startproc
+	aghi	%r15,-16
 	larl	%r5,_vdso_data
 	cghi	%r2,__CLOCK_REALTIME_COARSE
 	je	4f
@@ -37,10 +38,10 @@ __kernel_clock_gettime:
 0:	lg	%r4,__VDSO_UPD_COUNT(%r5)	/* load update counter */
 	tmll	%r4,0x0001			/* pending update ? loop */
 	jnz	0b
-	stcke	48(%r15)			/* Store TOD clock */
+	stcke	0(%r15)				/* Store TOD clock */
 	lgf	%r2,__VDSO_TK_SHIFT(%r5)	/* Timekeeper shift */
 	lg	%r0,__VDSO_WTOM_SEC(%r5)
-	lg	%r1,49(%r15)
+	lg	%r1,1(%r15)
 	sg	%r1,__VDSO_XTIME_STAMP(%r5)	/* TOD - cycle_last */
 	msgf	%r1,__VDSO_TK_MULT(%r5)		/*  * tk->mult */
 	alg	%r1,__VDSO_WTOM_NSEC(%r5)
@@ -56,6 +57,7 @@ __kernel_clock_gettime:
 2:	stg	%r0,0(%r3)			/* store tp->tv_sec */
 	stg	%r1,8(%r3)			/* store tp->tv_nsec */
 	lghi	%r2,0
+	aghi	%r15,16
 	br	%r14
 
 	/* CLOCK_MONOTONIC_COARSE */
@@ -82,9 +84,9 @@ __kernel_clock_gettime:
 5:	lg	%r4,__VDSO_UPD_COUNT(%r5)	/* load update counter */
 	tmll	%r4,0x0001			/* pending update ? loop */
 	jnz	5b
-	stcke	48(%r15)			/* Store TOD clock */
+	stcke	0(%r15)				/* Store TOD clock */
 	lgf	%r2,__VDSO_TK_SHIFT(%r5)	/* Timekeeper shift */
-	lg	%r1,49(%r15)
+	lg	%r1,1(%r15)
 	sg	%r1,__VDSO_XTIME_STAMP(%r5)	/* TOD - cycle_last */
 	msgf	%r1,__VDSO_TK_MULT(%r5)		/*  * tk->mult */
 	alg	%r1,__VDSO_XTIME_NSEC(%r5)	/*  + tk->xtime_nsec */
@@ -101,6 +103,7 @@ __kernel_clock_gettime:
 7:	stg	%r0,0(%r3)			/* store tp->tv_sec */
 	stg	%r1,8(%r3)			/* store tp->tv_nsec */
 	lghi	%r2,0
+	aghi	%r15,16
 	br	%r14
 
 	/* CLOCK_THREAD_CPUTIME_ID for this thread */
@@ -134,11 +137,13 @@ __kernel_clock_gettime:
 	slgr	%r4,%r0				/* r4 = tv_nsec */
 	stg	%r4,8(%r3)
 	lghi	%r2,0
+	aghi	%r15,16
 	br	%r14
 
 	/* Fallback to system call */
 12:	lghi	%r1,__NR_clock_gettime
 	svc	0
+	aghi	%r15,16
 	br	%r14
 
 13:	.quad	1000000000

arch/s390/kernel/vdso64/gettimeofday.S

@@ -19,6 +19,7 @@
 	.type  __kernel_gettimeofday,@function
 __kernel_gettimeofday:
 	.cfi_startproc
+	aghi	%r15,-16
 	larl	%r5,_vdso_data
 0:	ltgr	%r3,%r3				/* check if tz is NULL */
 	je	1f
@@ -28,8 +29,8 @@ __kernel_gettimeofday:
 	lg	%r4,__VDSO_UPD_COUNT(%r5)	/* load update counter */
 	tmll	%r4,0x0001			/* pending update ? loop */
 	jnz	0b
-	stcke	48(%r15)			/* Store TOD clock */
-	lg	%r1,49(%r15)
+	stcke	0(%r15)				/* Store TOD clock */
+	lg	%r1,1(%r15)
 	sg	%r1,__VDSO_XTIME_STAMP(%r5)	/* TOD - cycle_last */
 	msgf	%r1,__VDSO_TK_MULT(%r5)		/*  * tk->mult */
 	alg	%r1,__VDSO_XTIME_NSEC(%r5)	/*  + tk->xtime_nsec */
@@ -50,6 +51,7 @@ __kernel_gettimeofday:
 	srlg	%r0,%r0,6
 	stg	%r0,8(%r2)			/* store tv->tv_usec */
 4:	lghi	%r2,0
+	aghi	%r15,16
 	br	%r14
 5:	.quad	1000000000
 	.long	274877907