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s390/mm: add debug user asce support

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Verify on exit to user space that always
- the primary ASCE (cr1) is set to kernel ASCE
- the secondary ASCE (cr7) is set to user ASCE

If this is not the case: panic since something went terribly wrong.

Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2020-11-16 08:06:41 +01:00
parent 0290c9e328
commit 062e527956
5 changed files with 35 additions and 0 deletions
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8
arch/s390/Kconfig.debug
View file

@ -5,3 +5,11 @@ config TRACE_IRQFLAGS_SUPPORT
config EARLY_PRINTK
def_bool y
config DEBUG_USER_ASCE
bool "Debug User ASCE"
help
Check on exit to user space that address space control
elements are setup correctly.
If unsure, say N.

1
arch/s390/configs/debug_defconfig
View file

@ -826,6 +826,7 @@ CONFIG_FTRACE_SYSCALLS=y
CONFIG_BLK_DEV_IO_TRACE=y
CONFIG_BPF_KPROBE_OVERRIDE=y
CONFIG_HIST_TRIGGERS=y
CONFIG_DEBUG_USER_ASCE=y
CONFIG_NOTIFIER_ERROR_INJECTION=m
CONFIG_NETDEV_NOTIFIER_ERROR_INJECT=m
CONFIG_FAULT_INJECTION=y

2
arch/s390/include/asm/uaccess.h
View file

@ -18,6 +18,8 @@
#include <asm/extable.h>
#include <asm/facility.h>
void debug_user_asce(void);
static inline int __range_ok(unsigned long addr, unsigned long size)
{
return 1;

8
arch/s390/kernel/entry.S
View file

@ -90,6 +90,12 @@ _LPP_OFFSET = __LC_LPP
#endif
.endm
.macro DEBUG_USER_ASCE
#ifdef CONFIG_DEBUG_USER_ASCE
brasl %r14,debug_user_asce
#endif
.endm
.macro CHECK_VMAP_STACK savearea,oklabel
#ifdef CONFIG_VMAP_STACK
lgr %r14,%r15
@ -428,6 +434,7 @@ ENTRY(system_call)
jnz .Lsysc_work
TSTMSK __TI_flags(%r12),_TIF_WORK
jnz .Lsysc_work # check for work
DEBUG_USER_ASCE
lctlg %c1,%c1,__LC_USER_ASCE
BPEXIT __TI_flags(%r12),_TIF_ISOLATE_BP
TSTMSK __LC_CPU_FLAGS, _CIF_FPU
@ -793,6 +800,7 @@ ENTRY(io_int_handler)
mvc __LC_RETURN_PSW(16),__PT_PSW(%r11)
tm __PT_PSW+1(%r11),0x01 # returning to user ?
jno .Lio_exit_kernel
DEBUG_USER_ASCE
lctlg %c1,%c1,__LC_USER_ASCE
BPEXIT __TI_flags(%r12),_TIF_ISOLATE_BP
stpt __LC_EXIT_TIMER

16
arch/s390/lib/uaccess.c
View file

@ -16,6 +16,22 @@
#include <asm/mmu_context.h>
#include <asm/facility.h>
#ifdef CONFIG_DEBUG_USER_ASCE
void debug_user_asce(void)
{
unsigned long cr1, cr7;
__ctl_store(cr1, 1, 1);
__ctl_store(cr7, 7, 7);
if (cr1 == S390_lowcore.kernel_asce && cr7 == S390_lowcore.user_asce)
return;
panic("incorrect ASCE on kernel exit\n"
"cr1: %016lx cr7: %016lx\n"
"kernel: %016llx user: %016llx\n",
cr1, cr7, S390_lowcore.kernel_asce, S390_lowcore.user_asce);
}
#endif /*CONFIG_DEBUG_USER_ASCE */
#ifndef CONFIG_HAVE_MARCH_Z10_FEATURES
static DEFINE_STATIC_KEY_FALSE(have_mvcos);