linux-kernel - [PATCH 1/7] x86/entry: Anchor annotation

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Date:   Thu, 26 May 2022 12:52:53 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, jpoimboe@...hat.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        elver@...gle.com, jbaron@...mai.com, rostedt@...dmis.org,
        ardb@...nel.org, mark.rutland@....com
Subject: [PATCH 1/7] x86/entry: Anchor annotation

x86_64-allmodconfig gives:

  vmlinux.o: warning: objtool: entry_SYSCALL_compat+0x0: ANNOTATE_NOENDBR on ENDBR

This is due to:

	ANNOTATE_NOENDBR
SYM_CODE_END(entry_SYSENTER_compat)
SYM_CODE_START(entry_SYSCALL_compat)
	UNWIND_HINT_EMPTY
	ENDBR

And the hint then landing on the first instruction of the next symbol,
which happens to be ENDBR. Stick in an int3 to anchor the annotation
in the previous symbol.

Fixes: 3e3f06950434 ("x86/ibt: Annotate text references")
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/entry/entry_64_compat.S |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -124,6 +124,7 @@ SYM_INNER_LABEL(entry_SYSENTER_compat_af
 	jmp	.Lsysenter_flags_fixed
 SYM_INNER_LABEL(__end_entry_SYSENTER_compat, SYM_L_GLOBAL)
 	ANNOTATE_NOENDBR // is_sysenter_singlestep
+	int3
 SYM_CODE_END(entry_SYSENTER_compat)
 
 /*