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objtool: Fix INSN_CONTEXT_SWITCH handling in validate_unret()

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[ Upstream commit a8df7d0ef92eca28c610206c6748daf537ac0586 ]

The !CONFIG_IA32_EMULATION version of xen_entry_SYSCALL_compat() ends
with a SYSCALL instruction which is classified by objtool as
INSN_CONTEXT_SWITCH.

Unlike validate_branch(), validate_unret() doesn't consider
INSN_CONTEXT_SWITCH in a non-function to be a dead end, so it keeps
going past the end of xen_entry_SYSCALL_compat(), resulting in the
following warning:

  vmlinux.o: warning: objtool: xen_reschedule_interrupt+0x2a: RET before UNTRAIN

Fix that by adding INSN_CONTEXT_SWITCH handling to validate_unret() to
match what validate_branch() is already doing.

Fixes: a09a6e2399 ("objtool: Add entry UNRET validation")
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/f5eda46fd09f15b1f5cde3d9ae3b92b958342add.1744095216.git.jpoimboe@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Josh Poimboeuf
2025-04-08 00:02:13 -07:00
committed by Greg Kroah-Hartman
parent ee2b0301d6
commit 1b7685256d
1 changed files with 5 additions and 0 deletions
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5
tools/objtool/check.c
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@@ -3990,6 +3990,11 @@ static int validate_unret(struct objtool_file *file, struct instruction *insn)
WARN_INSN(insn, "RET before UNTRAIN");
return 1;
case INSN_CONTEXT_SWITCH:
if (insn_func(insn))
break;
return 0;
case INSN_NOP:
if (insn->retpoline_safe)
return 0;