linux-kernel - [PATCH] x86/mm: annotate no_context with UNWIND

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Date:   Sun, 14 Oct 2018 17:37:26 -0700
From:   Nick Desaulniers <nick.desaulniers@...il.com>
To:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com
Cc:     natechancellor@...il.com,
        Nick Desaulniers <nick.desaulniers@...il.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] x86/mm: annotate no_context with UNWIND_HINTS

Fixes the objtool warning:
arch/x86/mm/fault.o: warning: objtool: no_context()+0x220: unreachable
instruction

Link: https://github.com/ClangBuiltLinux/linux/issues/204
Signed-off-by: Nick Desaulniers <nick.desaulniers@...il.com>
---
 arch/x86/mm/fault.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 47bebfe6efa7..057d2178fa19 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -760,9 +760,11 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 		 * and then double-fault, though, because we're likely to
 		 * break the console driver and lose most of the stack dump.
 		 */
-		asm volatile ("movq %[stack], %%rsp\n\t"
+		asm volatile (UNWIND_HINT_SAVE
+			      "movq %[stack], %%rsp\n\t"
 			      "call handle_stack_overflow\n\t"
-			      "1: jmp 1b"
+			      "1: jmp 1b\n\t"
+			      UNWIND_HINT_RESTORE
 			      : ASM_CALL_CONSTRAINT
 			      : "D" ("kernel stack overflow (page fault)"),
 				"S" (regs), "d" (address),
-- 
2.17.1