[RFC PATCH v2 08/32] x86/objtool: teach objtool about ERETU and ERETS

From: Xin Li
Date: Fri Jan 06 2023 - 04:21:56 EST


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

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

Signed-off-by: H. Peter Anvin (Intel) <hpa@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
---
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