[S390] addressing mode limits and psw address wrapping

An instruction with an address right below the adress limit for the
current addressing mode will wrap. The instruction restart logic in
the protection fault handler and the signal code need to follow the
wrapping rules to find the correct instruction address.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

4 files changed, 29 insertions, 4 deletions

diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index a4b6229e5d4b..306c93c1b184 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -187,7 +187,6 @@ static inline void __load_psw(psw_t psw)
  * Set PSW mask to specified value, while leaving the
  * PSW addr pointing to the next instruction.
  */
-
 static inline void __load_psw_mask (unsigned long mask)
 {
         unsigned long addr;
@@ -212,6 +211,27 @@ static inline void __load_psw_mask (unsigned long mask)
                 : "=&d" (addr), "=Q" (psw) : "Q" (psw) : "memory", "cc");
 #endif /* __s390x__ */
 }
+
+/*
+ * Rewind PSW instruction address by specified number of bytes.
+ */
+static inline unsigned long __rewind_psw(psw_t psw, unsigned long ilc)
+{
+#ifndef __s390x__
+        if (psw.addr & PSW_ADDR_AMODE)
+                /* 31 bit mode */
+                return (psw.addr - ilc) | PSW_ADDR_AMODE;
+        /* 24 bit mode */
+        return (psw.addr - ilc) & ((1UL << 24) - 1);
+#else
+        unsigned long mask;
+
+        mask = (psw.mask & PSW_MASK_EA) ? -1UL :
+               (psw.mask & PSW_MASK_BA) ? (1UL << 31) - 1 :
+                                          (1UL << 24) - 1;
+        return (psw.addr - ilc) & mask;
+#endif
+}
  
 /*
  * Function to stop a processor until an interruption occurred
diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h
index 93c907b4776f..2904cc66967a 100644
--- a/arch/s390/include/asm/ptrace.h
+++ b/arch/s390/include/asm/ptrace.h
@@ -236,6 +236,8 @@ typedef struct
 #define PSW_MASK_ASC            0x0000C000UL
 #define PSW_MASK_CC             0x00003000UL
 #define PSW_MASK_PM             0x00000F00UL
+#define PSW_MASK_EA             0x00000000UL
+#define PSW_MASK_BA             0x00000000UL
 
 #define PSW_ADDR_AMODE          0x80000000UL
 #define PSW_ADDR_INSN           0x7FFFFFFFUL
@@ -261,6 +263,8 @@ typedef struct
 #define PSW_MASK_ASC            0x0000C00000000000UL
 #define PSW_MASK_CC             0x0000300000000000UL
 #define PSW_MASK_PM             0x00000F0000000000UL
+#define PSW_MASK_EA             0x0000000100000000UL
+#define PSW_MASK_BA             0x0000000080000000UL
 
 #define PSW_ADDR_AMODE          0x0000000000000000UL
 #define PSW_ADDR_INSN           0xFFFFFFFFFFFFFFFFUL
diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index e751cab80e04..058e372bada1 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -447,8 +447,9 @@ void do_signal(struct pt_regs *regs)
                         /* fallthrough */
                         case -ERESTARTNOINTR:
                                 regs->gprs[2] = regs->orig_gpr2;
-                                regs->psw.addr = regs->psw.addr -
-                                        (regs->svc_code >> 16);
+                                regs->psw.addr =
+                                        __rewind_psw(regs->psw,
+                                                     regs->svc_code >> 16);
                                 break;
                         }
                         /* No longer in a system call */
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 9564fc779b27..a90fd91a9c72 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -393,7 +393,7 @@ void __kprobes do_protection_exception(struct pt_regs *regs, long pgm_int_code,
         int fault;
 
         /* Protection exception is suppressing, decrement psw address. */
-        regs->psw.addr -= (pgm_int_code >> 16);
+        regs->psw.addr = __rewind_psw(regs->psw, pgm_int_code >> 16);
         /*
          * Check for low-address protection.  This needs to be treated
          * as a special case because the translation exception code