[tip: x86/fred] x86/objtool: Teach objtool about ERET[US]

tip-bot2 for H. Peter Anvin (Intel)
2024-01-31T21:14:56Z

Commit-ID: cd19bab825bda5bb192ef1d22e67d069daf2efb8
Gitweb: https://git.kernel.org/tip/cd19bab825bda5bb192ef1d22e67d069daf2efb8
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: Wed, 31 Jan 2024 22:00:30 +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>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.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;