s390/smp: make absolute lowcore / cpu restart parameter accesses more robust

Setting the cpu restart parameters is done in three different fashions:
- directly setting the four parameters individually
- copying the four parameters with memcpy (using 4 * sizeof(long))
- copying the four parameters using a private structure

In addition code in entry*.S relies on a certain order of the restart
members of struct _lowcore.

Make all of this more robust to future changes by adding a
mem_absolute_assign(dest, val) define, which assigns val to dest
using absolute addressing mode. Also the load multiple instructions
in entry*.S have been split into separate load instruction so the
order of the struct _lowcore members doesn't matter anymore.

In addition move the prototypes of memcpy_real/absolute from uaccess.h
to processor.h. These memcpy* variants are not related to uaccess at all.
string.h doesn't seem to match as well, so lets use processor.h.

Also replace the eight byte array in struct _lowcore which represents a
misaliged u64 with a u64. The compiler will always create code that
handles the misaligned u64 correctly.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

10 files changed, 39 insertions, 36 deletions

diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index 47853debb3b9..a47c6e221a95 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -302,12 +302,7 @@ struct _lowcore {
          */
         __u64   ipib;                           /* 0x0e00 */
         __u32   ipib_checksum;                  /* 0x0e08 */
-        /*
-         * Because the vmcore_info pointer is not 8 byte aligned it never
-         * should not be accessed directly. For accessing the pointer, first
-         * copy it to a local pointer variable.
-         */
-        __u8    vmcore_info[8];                 /* 0x0e0c */
+        __u64   vmcore_info;                    /* 0x0e0c */
         __u8    pad_0x0e14[0x0e18-0x0e14];      /* 0x0e14 */
         __u64   os_info;                        /* 0x0e18 */
         __u8    pad_0x0e20[0x0f00-0x0e20];      /* 0x0e20 */
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 20d0585cf905..f1700c5c8884 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -348,4 +348,14 @@ extern void (*s390_base_ext_handler_fn)(void);
         ".previous\n"
 #endif
 
+extern int memcpy_real(void *, void *, size_t);
+extern void memcpy_absolute(void *, void *, size_t);
+
+#define mem_assign_absolute(dest, val) {                        \
+        __typeof__(dest) __tmp = (val);                         \
+                                                                \
+        BUILD_BUG_ON(sizeof(__tmp) != sizeof(val));             \
+        memcpy_absolute(&(dest), &__tmp, sizeof(__tmp));        \
+}
+
 #endif                                 /* __ASM_S390_PROCESSOR_H           */
diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index 1f3a79bcd262..7e7285179aad 100644
--- a/arch/s390/include/asm/uaccess.h
+++ b/arch/s390/include/asm/uaccess.h
@@ -381,8 +381,6 @@ clear_user(void __user *to, unsigned long n)
         return n;
 }
 
-extern int memcpy_real(void *, void *, size_t);
-extern void memcpy_absolute(void *, void *, size_t);
 extern int copy_to_user_real(void __user *dest, void *src, size_t count);
 extern int copy_from_user_real(void *dest, void __user *src, size_t count);
 
diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index 83e6edf5cf17..0e974ddd156b 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -131,6 +131,8 @@ int main(void)
         DEFINE(__LC_PANIC_STACK, offsetof(struct _lowcore, panic_stack));
         DEFINE(__LC_RESTART_STACK, offsetof(struct _lowcore, restart_stack));
         DEFINE(__LC_RESTART_FN, offsetof(struct _lowcore, restart_fn));
+        DEFINE(__LC_RESTART_DATA, offsetof(struct _lowcore, restart_data));
+        DEFINE(__LC_RESTART_SOURCE, offsetof(struct _lowcore, restart_source));
         DEFINE(__LC_USER_ASCE, offsetof(struct _lowcore, user_asce));
         DEFINE(__LC_INT_CLOCK, offsetof(struct _lowcore, int_clock));
         DEFINE(__LC_MCCK_CLOCK, offsetof(struct _lowcore, mcck_clock));
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 3787f9e6907a..4ea53cd7c8c3 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -724,7 +724,9 @@ ENTRY(restart_int_handler)
         mvc     __PT_PSW(8,%r15),__LC_RST_OLD_PSW # store restart old psw
         ahi     %r15,-STACK_FRAME_OVERHEAD      # create stack frame on stack
         xc      0(STACK_FRAME_OVERHEAD,%r15),0(%r15)
-        lm      %r1,%r3,__LC_RESTART_FN         # load fn, parm & source cpu
+        l       %r1,__LC_RESTART_FN             # load fn, parm & source cpu
+        l       %r2,__LC_RESTART_DATA
+        l       %r3,__LC_RESTART_SOURCE
         ltr     %r3,%r3                         # test source cpu address
         jm      1f                              # negative -> skip source stop
 0:      sigp    %r4,%r3,SIGP_SENSE              # sigp sense to source cpu
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index d5f02e480e51..2813e831ba32 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -751,7 +751,9 @@ ENTRY(restart_int_handler)
         mvc     __PT_PSW(16,%r15),__LC_RST_OLD_PSW # store restart old psw
         aghi    %r15,-STACK_FRAME_OVERHEAD      # create stack frame on stack
         xc      0(STACK_FRAME_OVERHEAD,%r15),0(%r15)
-        lmg     %r1,%r3,__LC_RESTART_FN         # load fn, parm & source cpu
+        lg      %r1,__LC_RESTART_FN             # load fn, parm & source cpu
+        lg      %r2,__LC_RESTART_DATA
+        lg      %r3,__LC_RESTART_SOURCE
         ltgr    %r3,%r3                         # test source cpu address
         jm      1f                              # negative -> skip source stop
 0:      sigp    %r4,%r3,SIGP_SENSE              # sigp sense to source cpu
diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
index 2f6cfd460cb6..25241cd8ddd8 100644
--- a/arch/s390/kernel/ipl.c
+++ b/arch/s390/kernel/ipl.c
@@ -1528,15 +1528,12 @@ static struct shutdown_action __refdata dump_action = {
 
 static void dump_reipl_run(struct shutdown_trigger *trigger)
 {
-        struct {
-                void    *addr;
-                __u32   csum;
-        } __packed ipib;
-
-        ipib.csum = csum_partial(reipl_block_actual,
-                                 reipl_block_actual->hdr.len, 0);
-        ipib.addr = reipl_block_actual;
-        memcpy_absolute(&S390_lowcore.ipib, &ipib, sizeof(ipib));
+        unsigned long ipib = (unsigned long) &reipl_block_actual;
+        unsigned int csum;
+
+        csum = csum_partial(reipl_block_actual, reipl_block_actual->hdr.len, 0);
+        mem_assign_absolute(S390_lowcore.ipib, ipib);
+        mem_assign_absolute(S390_lowcore.ipib_checksum, csum);
         dump_run(trigger);
 }
 
diff --git a/arch/s390/kernel/os_info.c b/arch/s390/kernel/os_info.c
index 95fa5ac6c4ce..46480d81df00 100644
--- a/arch/s390/kernel/os_info.c
+++ b/arch/s390/kernel/os_info.c
@@ -60,7 +60,7 @@ void __init os_info_init(void)
         os_info.version_minor = OS_INFO_VERSION_MINOR;
         os_info.magic = OS_INFO_MAGIC;
         os_info.csum = os_info_csum(&os_info);
-        memcpy_absolute(&S390_lowcore.os_info, &ptr, sizeof(ptr));
+        mem_assign_absolute(S390_lowcore.os_info, (unsigned long) ptr);
 }
 
 #ifdef CONFIG_CRASH_DUMP
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 489d1d8d96b0..49158cb19274 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -430,10 +430,11 @@ static void __init setup_lowcore(void)
         lc->restart_source = -1UL;
 
         /* Setup absolute zero lowcore */
-        memcpy_absolute(&S390_lowcore.restart_stack, &lc->restart_stack,
-                        4 * sizeof(unsigned long));
-        memcpy_absolute(&S390_lowcore.restart_psw, &lc->restart_psw,
-                        sizeof(lc->restart_psw));
+        mem_assign_absolute(S390_lowcore.restart_stack, lc->restart_stack);
+        mem_assign_absolute(S390_lowcore.restart_fn, lc->restart_fn);
+        mem_assign_absolute(S390_lowcore.restart_data, lc->restart_data);
+        mem_assign_absolute(S390_lowcore.restart_source, lc->restart_source);
+        mem_assign_absolute(S390_lowcore.restart_psw, lc->restart_psw);
 
         set_prefix((u32)(unsigned long) lc);
         lowcore_ptr[0] = lc;
@@ -598,9 +599,7 @@ static void __init setup_memory_end(void)
 static void __init setup_vmcoreinfo(void)
 {
 #ifdef CONFIG_KEXEC
-        unsigned long ptr = paddr_vmcoreinfo_note();
-
-        memcpy_absolute(&S390_lowcore.vmcore_info, &ptr, sizeof(ptr));
+        mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
 #endif
 }
 
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index e01408429ad6..dc602a61233f 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -273,26 +273,24 @@ static void pcpu_delegate(struct pcpu *pcpu, void (*func)(void *),
                           void *data, unsigned long stack)
 {
         struct _lowcore *lc = lowcore_ptr[pcpu - pcpu_devices];
-        struct {
-                unsigned long   stack;
-                void            *func;
-                void            *data;
-                unsigned long   source;
-        } restart = { stack, func, data, stap() };
+        unsigned long source_cpu = stap();
 
         __load_psw_mask(psw_kernel_bits);
-        if (pcpu->address == restart.source)
+        if (pcpu->address == source_cpu)
                 func(data);     /* should not return */
         /* Stop target cpu (if func returns this stops the current cpu). */
         pcpu_sigp_retry(pcpu, SIGP_STOP, 0);
         /* Restart func on the target cpu and stop the current cpu. */
-        memcpy_absolute(&lc->restart_stack, &restart, sizeof(restart));
+        mem_assign_absolute(lc->restart_stack, stack);
+        mem_assign_absolute(lc->restart_fn, (unsigned long) func);
+        mem_assign_absolute(lc->restart_data, (unsigned long) data);
+        mem_assign_absolute(lc->restart_source, source_cpu);
         asm volatile(
                 "0:     sigp    0,%0,%2 # sigp restart to target cpu\n"
                 "       brc     2,0b    # busy, try again\n"
                 "1:     sigp    0,%1,%3 # sigp stop to current cpu\n"
                 "       brc     2,1b    # busy, try again\n"
-                : : "d" (pcpu->address), "d" (restart.source),
+                : : "d" (pcpu->address), "d" (source_cpu),
                     "K" (SIGP_RESTART), "K" (SIGP_STOP)
                 : "0", "1", "cc");
         for (;;) ;