linux-kernel - [RFC PATCH 08/32] x86/objtool: teach objtool about ERETU and ERETS

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Date:   Mon, 19 Dec 2022 22:36:34 -0800
From:   Xin Li <xin3.li@...el.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, peterz@...radead.org,
        andrew.cooper3@...rix.com, seanjc@...gle.com, pbonzini@...hat.com,
        ravi.v.shankar@...el.com
Subject: [RFC PATCH 08/32] x86/objtool: teach objtool about ERETU and ERETS

From: "H. Peter Anvin (Intel)" <hpa@...or.com>

Update the objtool decoder to know about the ERETU and ERETS
instructions (type INSN_CONTEXT_SWITCH.)

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
Signed-off-by: Xin Li <xin3.li@...el.com>
---
 tools/objtool/arch/x86/decode.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 1c253b4b7ce0..fbfe0a39599a 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -480,12 +480,22 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
 	case 0x0f:
 
 		if (op2 == 0x01) {
-
-			if (modrm == 0xca)
-				*type = INSN_CLAC;
-			else if (modrm == 0xcb)
-				*type = INSN_STAC;
-
+			switch (insn_last_prefix_id(&insn)) {
+			case INAT_PFX_REPE:
+			case INAT_PFX_REPNE:
+				if (modrm == 0xca) {
+					/* eretu/erets */
+					*type = INSN_CONTEXT_SWITCH;
+				}
+				break;
+			default:
+				if (modrm == 0xca) {
+					*type = INSN_CLAC;
+				} else if (modrm == 0xcb) {
+					*type = INSN_STAC;
+				}
+				break;
+			}
 		} else if (op2 >= 0x80 && op2 <= 0x8f) {
 
 			*type = INSN_JUMP_CONDITIONAL;
-- 
2.34.1