Provide a new function, insn_to_mnemonic, by which e.g. kvm can obtain
a human-readable decoding of an instruction's opcode.

Reviewed-by: Christian Borntraeger <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Cornelia Huck <[email protected]>
---
 arch/s390/include/asm/processor.h |  1 +
 arch/s390/kernel/dis.c            | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/arch/s390/include/asm/processor.h 
b/arch/s390/include/asm/processor.h
index 20d0585..dc99b6e 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -140,6 +140,7 @@ extern int kernel_thread(int (*fn)(void *), void * arg, 
unsigned long flags);
 extern unsigned long thread_saved_pc(struct task_struct *t);
 
 extern void show_code(struct pt_regs *regs);
+extern int insn_to_mnemonic(unsigned char *instruction, char buf[8]);
 
 unsigned long get_wchan(struct task_struct *p);
 #define task_pt_regs(tsk) ((struct pt_regs *) \
diff --git a/arch/s390/kernel/dis.c b/arch/s390/kernel/dis.c
index 3221c6f..8e7088e 100644
--- a/arch/s390/kernel/dis.c
+++ b/arch/s390/kernel/dis.c
@@ -1469,6 +1469,33 @@ static struct insn *find_insn(unsigned char *code)
        return NULL;
 }
 
+/**
+ * insn_to_mnemonic - decode an s390 instruction
+ * @instruction: instruction to decode
+ * @buf: buffer to fill with mnemonic
+ *
+ * Decode the instruction at @instruction and store the corresponding
+ * mnemonic into @buf.
+ * @buf is left unchanged if the instruction could not be decoded.
+ * Returns:
+ *  %0 on success, %-ENOENT if the instruction was not found.
+ */
+int insn_to_mnemonic(unsigned char *instruction, char buf[8])
+{
+       struct insn *insn;
+
+       insn = find_insn(instruction);
+       if (!insn)
+               return -ENOENT;
+       if (insn->name[0] == '\0')
+               snprintf(buf, sizeof(buf), "%s",
+                        long_insn_name[(int) insn->name[1]]);
+       else
+               snprintf(buf, sizeof(buf), "%.5s", insn->name);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(insn_to_mnemonic);
+
 static int print_insn(char *buffer, unsigned char *code, unsigned long addr)
 {
        struct insn *insn;
-- 
1.7.11.2

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