From: Joerg Roedel <jroedel@suse.de>
Date: Mon, 7 Sep 2020 15:15:12 +0200
Subject: x86/insn: Add insn_has_rep_prefix() helper
Git-commit: 5901781a11175a5e5ee91746ec8627f18d47eebd
Patch-mainline: v5.10-rc1
References: jsc#SLE-14337

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
---
 arch/x86/include/asm/insn-eval.h |    1 +
 arch/x86/lib/insn-eval.c         |   24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

--- 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);
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -54,6 +54,30 @@ static bool is_string_insn(struct 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
  *