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From:   Joerg Roedel <joro@8bytes.org>
To:     x86@kernel.org
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Subject: [PATCH v4 10/75] x86/insn: Add insn_has_rep_prefix() helper
Date:   Tue, 14 Jul 2020 14:08:12 +0200
Message-Id: <20200714120917.11253-11-joro@8bytes.org>
In-Reply-To: <20200714120917.11253-1-joro@8bytes.org>
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From: Joerg Roedel <jroedel@suse.de>

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

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/include/asm/insn-eval.h |  1 +
 arch/x86/lib/insn-eval.c         | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h
index f748f57f1491..a0f839aa144d 100644
--- 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 a8ac5c5e94f0..8ed9d645259c 100644
--- 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
-- 
2.27.0