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authorSven Schnelle <svens@linux.ibm.com>2024-02-20 16:21:14 +0300
committerHeiko Carstens <hca@linux.ibm.com>2024-03-17 21:08:49 +0300
commitc239c83ed5c558be3b5926c7f11639f02c8acd00 (patch)
tree91765253d3ca0266bfde62f9652b58fb8ac0bd0a
parent481ec3b37678639ec1f8197c92b6e604b9549b2d (diff)
downloadlinux-c239c83ed5c558be3b5926c7f11639f02c8acd00.tar.xz
s390/entry: add CIF_SIE flag and remove sie64a() address check
When a program check, interrupt or machine check is triggered, the PSW address is compared to a certain range of the sie64a() function to figure out whether SIE was interrupted and a cleanup of SIE is needed. This doesn't work with kprobes: If kprobes probes an instruction, it copies the instruction to the kprobes instruction page and overwrites the original instruction with an undefind instruction (Opcode 00). When this instruction is hit later, kprobes single-steps the instruction on the kprobes_instruction page. However, if this instruction is a relative branch instruction it will now point to a different location in memory due to being moved to the kprobes instruction page. If the new branch target points into sie64a() the kernel assumes it interrupted SIE when processing the breakpoint and will crash trying to access the SIE control block. Instead of comparing the address, introduce a new CIF_SIE flag which indicates whether SIE was interrupted. Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Suggested-by: Heiko Carstens <hca@linux.ibm.com> Reviewed-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
-rw-r--r--arch/s390/include/asm/processor.h2
-rw-r--r--arch/s390/kernel/entry.S17
2 files changed, 16 insertions, 3 deletions
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 7cf00cf8fb0b..db9982f0e8cd 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -14,11 +14,13 @@
#include <linux/bits.h>
+#define CIF_SIE 0 /* CPU needs SIE exit cleanup */
#define CIF_NOHZ_DELAY 2 /* delay HZ disable for a tick */
#define CIF_ENABLED_WAIT 5 /* in enabled wait state */
#define CIF_MCCK_GUEST 6 /* machine check happening in guest */
#define CIF_DEDICATED_CPU 7 /* this CPU is dedicated */
+#define _CIF_SIE BIT(CIF_SIE)
#define _CIF_NOHZ_DELAY BIT(CIF_NOHZ_DELAY)
#define _CIF_ENABLED_WAIT BIT(CIF_ENABLED_WAIT)
#define _CIF_MCCK_GUEST BIT(CIF_MCCK_GUEST)
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index fc5277eab554..4e0ff79ffee3 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -146,6 +146,7 @@ _LPP_OFFSET = __LC_LPP
lg %r9,__SF_SIE_CONTROL(%r15) # get control block pointer
ni __SIE_PROG0C+3(%r9),0xfe # no longer in SIE
lctlg %c1,%c1,__LC_KERNEL_ASCE # load primary asce
+ ni __LC_CPU_FLAGS+7,255-_CIF_SIE
larl %r9,sie_exit # skip forward to sie_exit
.endm
#endif
@@ -214,6 +215,7 @@ SYM_FUNC_START(__sie64a)
lg %r14,__LC_GMAP # get gmap pointer
ltgr %r14,%r14
jz .Lsie_gmap
+ oi __LC_CPU_FLAGS+7,_CIF_SIE
lctlg %c1,%c1,__GMAP_ASCE(%r14) # load primary asce
.Lsie_gmap:
lg %r14,__SF_SIE_CONTROL(%r15) # get control block pointer
@@ -235,6 +237,7 @@ SYM_FUNC_START(__sie64a)
ni __SIE_PROG0C+3(%r14),0xfe # no longer in SIE
lctlg %c1,%c1,__LC_KERNEL_ASCE # load primary asce
.Lsie_done:
+ ni __LC_CPU_FLAGS+7,255-_CIF_SIE
# some program checks are suppressing. C code (e.g. do_protection_exception)
# will rewind the PSW by the ILC, which is often 4 bytes in case of SIE. There
# are some corner cases (e.g. runtime instrumentation) where ILC is unpredictable.
@@ -346,7 +349,8 @@ SYM_CODE_START(pgm_check_handler)
.Lpgm_skip_asce:
#if IS_ENABLED(CONFIG_KVM)
# cleanup critical section for program checks in __sie64a
- OUTSIDE %r9,.Lsie_gmap,.Lsie_done,1f
+ TSTMSK __LC_CPU_FLAGS,_CIF_SIE
+ jz 1f
BPENTER __SF_SIE_FLAGS(%r15),_TIF_ISOLATE_BP_GUEST
SIEEXIT
lghi %r10,_PIF_GUEST_FAULT
@@ -416,7 +420,8 @@ SYM_CODE_START(\name)
tmhh %r8,0x0001 # interrupting from user ?
jnz 1f
#if IS_ENABLED(CONFIG_KVM)
- OUTSIDE %r9,.Lsie_gmap,.Lsie_done,0f
+ TSTMSK __LC_CPU_FLAGS,_CIF_SIE
+ jz 0f
BPENTER __SF_SIE_FLAGS(%r15),_TIF_ISOLATE_BP_GUEST
SIEEXIT
#endif
@@ -513,7 +518,13 @@ SYM_CODE_START(mcck_int_handler)
TSTMSK __LC_MCCK_CODE,MCCK_CODE_PSW_IA_VALID
jno .Lmcck_panic
#if IS_ENABLED(CONFIG_KVM)
- OUTSIDE %r9,.Lsie_gmap,.Lsie_done,.Lmcck_user
+ TSTMSK __LC_CPU_FLAGS,_CIF_SIE
+ jz .Lmcck_user
+ # Need to compare the address instead of a CIF_SIE* flag.
+ # Otherwise there would be a race between setting the flag
+ # and entering SIE (or leaving and clearing the flag). This
+ # would cause machine checks targeted at the guest to be
+ # handled by the host.
OUTSIDE %r9,.Lsie_entry,.Lsie_leave,4f
oi __LC_CPU_FLAGS+7, _CIF_MCCK_GUEST
4: BPENTER __SF_SIE_FLAGS(%r15),_TIF_ISOLATE_BP_GUEST