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s390/entry: compare gmap asce to determine guest/host fault 

With the current implementation, there are some cornercases where
a host fault would be treated as a guest fault, for example
when the sie instruction causes a program check. Therefore store
the gmap asce in ptregs, and use that to compare the primary asce
from the fault instead of matching instruction addresses.

Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Sven Schnelle 2024-03-13 09:51:22 +01:00 committed by Heiko Carstens
parent 29e5bc0f02
commit 64c3431808
3 changed files with 18 additions and 19 deletions
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2
arch/s390/include/asm/ptrace.h
View File

@ -14,13 +14,11 @@
#define PIF_SYSCALL 0 /* inside a system call */
#define PIF_EXECVE_PGSTE_RESTART 1 /* restart execve for PGSTE binaries */
#define PIF_SYSCALL_RET_SET 2 /* return value was set via ptrace */
#define PIF_GUEST_FAULT 3 /* indicates program check in sie64a */
#define PIF_FTRACE_FULL_REGS 4 /* all register contents valid (ftrace) */
#define _PIF_SYSCALL BIT(PIF_SYSCALL)
#define _PIF_EXECVE_PGSTE_RESTART BIT(PIF_EXECVE_PGSTE_RESTART)
#define _PIF_SYSCALL_RET_SET BIT(PIF_SYSCALL_RET_SET)
#define _PIF_GUEST_FAULT BIT(PIF_GUEST_FAULT)
#define _PIF_FTRACE_FULL_REGS BIT(PIF_FTRACE_FULL_REGS)
#define PSW32_MASK_PER _AC(0x40000000, UL)

31
arch/s390/kernel/entry.S
View File

@ -119,8 +119,8 @@ _LPP_OFFSET = __LC_LPP
.endm
#if IS_ENABLED(CONFIG_KVM)
.macro SIEEXIT
lg %r9,__SF_SIE_CONTROL(%r15) # get control block pointer
.macro SIEEXIT sie_control
lg %r9,\sie_control # 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
@ -316,21 +316,13 @@ SYM_CODE_START(pgm_check_handler)
stpt __LC_SYS_ENTER_TIMER
BPOFF
stmg %r8,%r15,__LC_SAVE_AREA_SYNC
lghi %r10,0
lgr %r10,%r15
lmg %r8,%r9,__LC_PGM_OLD_PSW
tmhh %r8,0x0001 # coming from user space?
jno .Lpgm_skip_asce
lctlg %c1,%c1,__LC_KERNEL_ASCE
j 3f # -> fault in user space
.Lpgm_skip_asce:
#if IS_ENABLED(CONFIG_KVM)
# cleanup critical section for program checks in __sie64a
TSTMSK __LC_CPU_FLAGS,_CIF_SIE
jz 1f
BPENTER __SF_SIE_FLAGS(%r15),_TIF_ISOLATE_BP_GUEST
SIEEXIT
lghi %r10,_PIF_GUEST_FAULT
#endif
1: tmhh %r8,0x4000 # PER bit set in old PSW ?
jnz 2f # -> enabled, can't be a double fault
tm __LC_PGM_ILC+3,0x80 # check for per exception
@ -341,13 +333,20 @@ SYM_CODE_START(pgm_check_handler)
CHECK_VMAP_STACK __LC_SAVE_AREA_SYNC,4f
3: lg %r15,__LC_KERNEL_STACK
4: la %r11,STACK_FRAME_OVERHEAD(%r15)
stg %r10,__PT_FLAGS(%r11)
xc __PT_FLAGS(8,%r11),__PT_FLAGS(%r11)
xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
stmg %r0,%r7,__PT_R0(%r11)
mvc __PT_R8(64,%r11),__LC_SAVE_AREA_SYNC
mvc __PT_LAST_BREAK(8,%r11),__LC_PGM_LAST_BREAK
stmg %r8,%r9,__PT_PSW(%r11)
stctg %c1,%c1,__PT_CR1(%r11)
#if IS_ENABLED(CONFIG_KVM)
lg %r12,__LC_GMAP
clc __GMAP_ASCE(8,%r12), __PT_CR1(%r11)
jne 5f
BPENTER __SF_SIE_FLAGS(%r10),_TIF_ISOLATE_BP_GUEST
SIEEXIT __SF_SIE_CONTROL(%r10)
#endif
5: stmg %r8,%r9,__PT_PSW(%r11)
# clear user controlled registers to prevent speculative use
xgr %r0,%r0
xgr %r1,%r1
@ -399,7 +398,7 @@ SYM_CODE_START(\name)
TSTMSK __LC_CPU_FLAGS,_CIF_SIE
jz 0f
BPENTER __SF_SIE_FLAGS(%r15),_TIF_ISOLATE_BP_GUEST
SIEEXIT
SIEEXIT __SF_SIE_CONTROL(%r15)
#endif
0: CHECK_STACK __LC_SAVE_AREA_ASYNC
aghi %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
@ -507,7 +506,7 @@ SYM_CODE_START(mcck_int_handler)
clgrjhe %r9,%r14, 4f
oi __LC_CPU_FLAGS+7, _CIF_MCCK_GUEST
4: BPENTER __SF_SIE_FLAGS(%r15),_TIF_ISOLATE_BP_GUEST
SIEEXIT
SIEEXIT __SF_SIE_CONTROL(%r15)
#endif
.Lmcck_user:
lg %r15,__LC_MCCK_STACK

4
arch/s390/mm/fault.c
View File

@ -67,13 +67,15 @@ early_initcall(fault_init);
static enum fault_type get_fault_type(struct pt_regs *regs)
{
union teid teid = { .val = regs->int_parm_long };
struct gmap *gmap;
if (likely(teid.as == PSW_BITS_AS_PRIMARY)) {
if (user_mode(regs))
return USER_FAULT;
if (!IS_ENABLED(CONFIG_PGSTE))
return KERNEL_FAULT;
if (test_pt_regs_flag(regs, PIF_GUEST_FAULT))
gmap = (struct gmap *)S390_lowcore.gmap;
if (regs->cr1 == gmap->asce)
return GMAP_FAULT;
return KERNEL_FAULT;
}