[PATCH 5.10 58/63] s390: always clear kernel stack backchain before calling functions

Greg Kroah-Hartman
2021-01-04T16:03:35Z

From: Heiko Carstens <hca@linux.ibm.com>

[ Upstream commit 9365965db0c7ca7fc81eee27c21d8522d7102c32 ]

Clear the kernel stack backchain before potentially calling the
lockdep trace_hardirqs_off/on functions. Without this walking the
kernel backchain, e.g. during a panic, might stop too early.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/kernel/entry.S | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 6343dca0dbeb6..71203324ff42b 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -406,6 +406,7 @@ ENTRY(system_call)
mvc __PT_PSW(16,%r11),__LC_SVC_OLD_PSW
mvc __PT_INT_CODE(4,%r11),__LC_SVC_ILC
stg %r14,__PT_FLAGS(%r11)
+ xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
ENABLE_INTS
.Lsysc_do_svc:
# clear user controlled register to prevent speculative use
@@ -422,7 +423,6 @@ ENTRY(system_call)
jnl .Lsysc_nr_ok
slag %r8,%r1,3
.Lsysc_nr_ok:
- xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
stg %r2,__PT_ORIG_GPR2(%r11)
stg %r7,STACK_FRAME_OVERHEAD(%r15)
lg %r9,0(%r8,%r10) # get system call add.
@@ -712,8 +712,8 @@ ENTRY(pgm_check_handler)
mvc __THREAD_per_address(8,%r14),__LC_PER_ADDRESS
mvc __THREAD_per_cause(2,%r14),__LC_PER_CODE
mvc __THREAD_per_paid(1,%r14),__LC_PER_ACCESS_ID
-6: RESTORE_SM_CLEAR_PER
- xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
+6: xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
+ RESTORE_SM_CLEAR_PER
larl %r1,pgm_check_table
llgh %r10,__PT_INT_CODE+2(%r11)
nill %r10,0x007f
@@ -734,8 +734,8 @@ ENTRY(pgm_check_handler)
# PER event in supervisor state, must be kprobes
#
.Lpgm_kprobe:
- RESTORE_SM_CLEAR_PER
xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
+ RESTORE_SM_CLEAR_PER
lgr %r2,%r11 # pass pointer to pt_regs
brasl %r14,do_per_trap
j .Lpgm_return
@@ -777,10 +777,10 @@ ENTRY(io_int_handler)
stmg %r8,%r9,__PT_PSW(%r11)
mvc __PT_INT_CODE(12,%r11),__LC_SUBCHANNEL_ID
xc __PT_FLAGS(8,%r11),__PT_FLAGS(%r11)
+ xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
TSTMSK __LC_CPU_FLAGS,_CIF_IGNORE_IRQ
jo .Lio_restore
TRACE_IRQS_OFF
- xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
.Lio_loop:
lgr %r2,%r11 # pass pointer to pt_regs
lghi %r3,IO_INTERRUPT
@@ -980,10 +980,10 @@ ENTRY(ext_int_handler)
mvc __PT_INT_PARM(4,%r11),__LC_EXT_PARAMS
mvc __PT_INT_PARM_LONG(8,%r11),0(%r1)
xc __PT_FLAGS(8,%r11),__PT_FLAGS(%r11)
+ xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
TSTMSK __LC_CPU_FLAGS,_CIF_IGNORE_IRQ
jo .Lio_restore
TRACE_IRQS_OFF
- xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
lgr %r2,%r11 # pass pointer to pt_regs
lghi %r3,EXT_INTERRUPT
brasl %r14,do_IRQ
--
2.27.0