s390/vdso: revise CFI annotations of vDSO functions

Revise and add CFI CFA and register rule annotations to the vDSO
functions for proper stack unwinding and debugging.

Because glibc might call the vDSO in special ways, the vDSO code
does not rely on a stack frame created by the caller.  The TOD clock
value can be therefore not stored in the pre-allocated stack area
and additional stack space is required.
To correctly annotate these situations with CFI, the .cfi_val_offset
directive is required to create relative offsets on the value of the
stack register %r15.  Because the .cfi_val_offset directive is
available with recent GNU assembler versions only, additional checks
are necessary.

Note that if the vDSO is assembled with an older assembler version,
stack unwinding and debugging from within the vDSO code might not
be possible.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

4 files changed, 28 insertions, 8 deletions

diff --git a/arch/s390/kernel/vdso64/clock_getres.S b/arch/s390/kernel/vdso64/clock_getres.S
index 5b0d9c380de2..081435398e0a 100644
--- a/arch/s390/kernel/vdso64/clock_getres.S
+++ b/arch/s390/kernel/vdso64/clock_getres.S
@@ -16,7 +16,7 @@
 	.globl __kernel_clock_getres
 	.type  __kernel_clock_getres,@function
 __kernel_clock_getres:
-	.cfi_startproc
+	CFI_STARTPROC
 	larl	%r1,4f
 	cghi	%r2,__CLOCK_REALTIME_COARSE
 	je	0f
@@ -44,7 +44,7 @@ __kernel_clock_getres:
 2:	lghi	%r1,__NR_clock_getres		/* fallback to svc */
 	svc	0
 	br	%r14
+	CFI_ENDPROC
 3:	.quad	__CLOCK_REALTIME_RES
 4:	.quad	__CLOCK_COARSE_RES
-	.cfi_endproc
 	.size	__kernel_clock_getres,.-__kernel_clock_getres
diff --git a/arch/s390/kernel/vdso64/clock_gettime.S b/arch/s390/kernel/vdso64/clock_gettime.S
index deccd793b279..fac3ab5ec83a 100644
--- a/arch/s390/kernel/vdso64/clock_gettime.S
+++ b/arch/s390/kernel/vdso64/clock_gettime.S
@@ -16,8 +16,10 @@
 	.globl __kernel_clock_gettime
 	.type  __kernel_clock_gettime,@function
 __kernel_clock_gettime:
-	.cfi_startproc
+	CFI_STARTPROC
 	aghi	%r15,-16
+	CFI_DEF_CFA_OFFSET 176
+	CFI_VAL_OFFSET 15, -160
 	larl	%r5,_vdso_data
 	cghi	%r2,__CLOCK_REALTIME_COARSE
 	je	4f
@@ -54,9 +56,13 @@ __kernel_clock_gettime:
 	stg	%r1,8(%r3)			/* store tp->tv_nsec */
 	lghi	%r2,0
 	aghi	%r15,16
+	CFI_DEF_CFA_OFFSET 160
+	CFI_RESTORE 15
 	br	%r14
 
 	/* CLOCK_MONOTONIC_COARSE */
+	CFI_DEF_CFA_OFFSET 176
+	CFI_VAL_OFFSET 15, -160
 3:	lg	%r4,__VDSO_UPD_COUNT(%r5)	/* load update counter */
 	tmll	%r4,0x0001			/* pending update ? loop */
 	jnz	3b
@@ -109,9 +115,13 @@ __kernel_clock_gettime:
 	stg	%r1,8(%r3)			/* store tp->tv_nsec */
 	lghi	%r2,0
 	aghi	%r15,16
+	CFI_DEF_CFA_OFFSET 160
+	CFI_RESTORE 15
 	br	%r14
 
 	/* CPUCLOCK_VIRT for this thread */
+	CFI_DEF_CFA_OFFSET 176
+	CFI_VAL_OFFSET 15, -160
 9:	lghi	%r4,0
 	icm	%r0,15,__VDSO_ECTG_OK(%r5)
 	jz	12f
@@ -132,15 +142,21 @@ __kernel_clock_gettime:
 	stg	%r4,8(%r3)
 	lghi	%r2,0
 	aghi	%r15,16
+	CFI_DEF_CFA_OFFSET 160
+	CFI_RESTORE 15
 	br	%r14
 
 	/* Fallback to system call */
+	CFI_DEF_CFA_OFFSET 176
+	CFI_VAL_OFFSET 15, -160
 12:	lghi	%r1,__NR_clock_gettime
 	svc	0
 	aghi	%r15,16
+	CFI_DEF_CFA_OFFSET 160
+	CFI_RESTORE 15
 	br	%r14
+	CFI_ENDPROC
 
 13:	.quad	1000000000
 14:	.quad	19342813113834067
-	.cfi_endproc
 	.size	__kernel_clock_gettime,.-__kernel_clock_gettime
diff --git a/arch/s390/kernel/vdso64/getcpu.S b/arch/s390/kernel/vdso64/getcpu.S
index 022acdecd5b9..2446e9dac8ab 100644
--- a/arch/s390/kernel/vdso64/getcpu.S
+++ b/arch/s390/kernel/vdso64/getcpu.S
@@ -15,7 +15,7 @@
 	.globl __kernel_getcpu
 	.type  __kernel_getcpu,@function
 __kernel_getcpu:
-	.cfi_startproc
+	CFI_STARTPROC
 	la	%r4,0
 	sacf	256
 	l	%r5,__VDSO_CPU_NR(%r4)
@@ -29,5 +29,5 @@ __kernel_getcpu:
 	st	%r4,0(%r3)
 3:	lghi	%r2,0
 	br	%r14
-	.cfi_endproc
+	CFI_ENDPROC
 	.size	__kernel_getcpu,.-__kernel_getcpu
diff --git a/arch/s390/kernel/vdso64/gettimeofday.S b/arch/s390/kernel/vdso64/gettimeofday.S
index 964afb1de06d..6e1f0b421695 100644
--- a/arch/s390/kernel/vdso64/gettimeofday.S
+++ b/arch/s390/kernel/vdso64/gettimeofday.S
@@ -16,8 +16,10 @@
 	.globl __kernel_gettimeofday
 	.type  __kernel_gettimeofday,@function
 __kernel_gettimeofday:
-	.cfi_startproc
+	CFI_STARTPROC
 	aghi	%r15,-16
+	CFI_ADJUST_CFA_OFFSET 16
+	CFI_VAL_OFFSET 15, -160
 	larl	%r5,_vdso_data
 0:	ltgr	%r3,%r3				/* check if tz is NULL */
 	je	1f
@@ -59,8 +61,10 @@ __kernel_gettimeofday:
 	stg	%r0,8(%r2)			/* store tv->tv_usec */
 4:	lghi	%r2,0
 	aghi	%r15,16
+	CFI_ADJUST_CFA_OFFSET -16
+	CFI_RESTORE 15
 	br	%r14
+	CFI_ENDPROC
 5:	.quad	1000000000
 	.long	274877907
-	.cfi_endproc
 	.size	__kernel_gettimeofday,.-__kernel_gettimeofday