linux-kernel - [PATCH 1/2] kbuild: keep __mcount_loc table through dead code elimination

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Date:   Thu, 22 Dec 2016 09:51:46 +0100
From:   Marcin Nowakowski <marcin.nowakowski@...tec.com>
To:     Arnd Bergmann <arnd@...db.de>, <linux-kernel@...r.kernel.org>
CC:     Nicholas Piggin <npiggin@...il.com>
Subject: [PATCH 1/2] kbuild: keep __mcount_loc table through dead code elimination

When CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is enabled we must ensure
__mcount_loc is preserved, as otherwise there are no valid entries for
ftrace to work with.

Fixes: 4b89b7f7aad5 ('kbuild: keep data tables through dead code elimination')

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@...tec.com>
Acked-by: Nicholas Piggin <npiggin@...il.com>
---
 include/asm-generic/vmlinux.lds.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 0968d13..f492aa4 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -89,7 +89,7 @@
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
 #define MCOUNT_REC()	. = ALIGN(8);				\
 			VMLINUX_SYMBOL(__start_mcount_loc) = .; \
-			*(__mcount_loc)				\
+			KEEP(*(__mcount_loc))			\
 			VMLINUX_SYMBOL(__stop_mcount_loc) = .;
 #else
 #define MCOUNT_REC()
-- 
2.7.4