x86/insn: Add insn_has_rep_prefix() helper

Add a function to check whether an instruction has a REP prefix.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lkml.kernel.org/r/20200907131613.12703-12-joro@8bytes.org

diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h
index f748f57..a0f839a 100644 (file)
--- a/arch/x86/include/asm/insn-eval.h
+++ b/arch/x86/include/asm/insn-eval.h
@@ -15,6 +15,7 @@
 #define INSN_CODE_SEG_OPND_SZ(params) (params & 0xf)
 #define INSN_CODE_SEG_PARAMS(oper_sz, addr_sz) (oper_sz | (addr_sz << 4))
 
+bool insn_has_rep_prefix(struct insn *insn);
 void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs);
 int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs);
 int insn_get_modrm_reg_off(struct insn *insn, struct pt_regs *regs);

diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index f20942c..58f7fb9 100644 (file)
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -53,6 +53,30 @@ static bool is_string_insn(struct insn *insn)
        }
 }
 
+/**
+ * insn_has_rep_prefix() - Determine if instruction has a REP prefix
+ * @insn:      Instruction containing the prefix to inspect
+ *
+ * Returns:
+ *
+ * true if the instruction has a REP prefix, false if not.
+ */
+bool insn_has_rep_prefix(struct insn *insn)
+{
+       int i;
+
+       insn_get_prefixes(insn);
+
+       for (i = 0; i < insn->prefixes.nbytes; i++) {
+               insn_byte_t p = insn->prefixes.bytes[i];
+
+               if (p == 0xf2 || p == 0xf3)
+                       return true;
+       }
+
+       return false;
+}
+
 /**
  * get_seg_reg_override_idx() - obtain segment register override index
  * @insn:      Valid instruction with segment override prefixes