Commit a8df7d0e authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
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objtool: Fix INSN_CONTEXT_SWITCH handling in validate_unret() 



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: a09a6e23 ("objtool: Add entry UNRET validation")
Reported-by: default avatarAndrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/f5eda46fd09f15b1f5cde3d9ae3b92b958342add.1744095216.git.jpoimboe@kernel.org
parent 0af2f6be

tools/objtool/check.c

+5 −0
Original line number Diff line number Diff line
@@ -3886,6 +3886,11 @@ 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;