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Date: Wed, 31 Jan 2024 07:21:27 -0000
From: "tip-bot2 for H. Peter Anvin (Intel)" <tip-bot2@linutronix.de>
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Subject: [tip: x86/fred] x86/objtool: Teach objtool about ERET[US]
Cc: "H. Peter Anvin (Intel)" <hpa@zytor.com>, Xin Li <xin3.li@intel.com>,
 Thomas Gleixner <tglx@linutronix.de>, Shan Kang <shan.kang@intel.com>,
 x86@kernel.org, linux-kernel@vger.kernel.org
In-Reply-To: <20231205105030.8698-11-xin3.li@intel.com>
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The following commit has been merged into the x86/fred branch of tip:

Commit-ID:     379ae086a73c804df39866d28eb4ce693e7af486
Gitweb:        https://git.kernel.org/tip/379ae086a73c804df39866d28eb4ce693e7af486
Author:        H. Peter Anvin (Intel) <hpa@zytor.com>
AuthorDate:    Tue, 05 Dec 2023 02:49:59 -08:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Tue, 30 Jan 2024 18:20:34 +01:00

x86/objtool: Teach objtool about ERET[US]

Update the objtool decoder to know about the ERET[US] instructions
(type INSN_CONTEXT_SWITCH).

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-11-xin3.li@intel.com

---
 tools/objtool/arch/x86/decode.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index e327cd8..3a1d80a 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -509,11 +509,20 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
 
 		if (op2 == 0x01) {
 
-			if (modrm == 0xca)
-				insn->type = INSN_CLAC;
-			else if (modrm == 0xcb)
-				insn->type = INSN_STAC;
-
+			switch (insn_last_prefix_id(&ins)) {
+			case INAT_PFX_REPE:
+			case INAT_PFX_REPNE:
+				if (modrm == 0xca)
+					/* eretu/erets */
+					insn->type = INSN_CONTEXT_SWITCH;
+				break;
+			default:
+				if (modrm == 0xca)
+					insn->type = INSN_CLAC;
+				else if (modrm == 0xcb)
+					insn->type = INSN_STAC;
+				break;
+			}
 		} else if (op2 >= 0x80 && op2 <= 0x8f) {
 
 			insn->type = INSN_JUMP_CONDITIONAL;