linux-kernel - [PATCH 5.15 54/89] x86/xen: Add UNTRAIN

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Date:   Fri, 22 Jul 2022 11:11:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Subject: [PATCH 5.15 54/89] x86/xen: Add UNTRAIN_RET

From: Peter Zijlstra <peterz@...radead.org>

commit d147553b64bad34d2f92cb7d8ba454ae95c3baac upstream.

Ensure the Xen entry also passes through UNTRAIN_RET.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/entry/entry_64.S |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -320,6 +320,12 @@ SYM_CODE_END(ret_from_fork)
 #endif
 .endm
 
+SYM_CODE_START_LOCAL(xen_error_entry)
+	UNWIND_HINT_FUNC
+	UNTRAIN_RET
+	RET
+SYM_CODE_END(xen_error_entry)
+
 /**
  * idtentry_body - Macro to emit code calling the C function
  * @cfunc:		C function to be called
@@ -339,7 +345,7 @@ SYM_CODE_END(ret_from_fork)
 	 * switch the CR3.  So it can skip invoking error_entry().
 	 */
 	ALTERNATIVE "call error_entry; movq %rax, %rsp", \
-		"", X86_FEATURE_XENPV
+		    "call xen_error_entry", X86_FEATURE_XENPV
 
 	ENCODE_FRAME_POINTER
 	UNWIND_HINT_REGS