linux-kernel - [PATCH 41/46] x86/lib, lto: Mark 32bit mem{cpy,move,set} as _

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Message-Id: <20221114114344.18650-42-jirislaby@kernel.org>
Date:   Mon, 14 Nov 2022 12:43:39 +0100
From:   "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Martin Liska <mliska@...e.cz>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 41/46] x86/lib, lto: Mark 32bit mem{cpy,move,set} as __used

From: Andi Kleen <ak@...ux.intel.com>

gcc doesn't always recognize that memcpy/set/move called through
__builtins are referenced because the reference happens too late in the
RTL expansion phase. This can make LTO to drop them, leading to
undefined symbols. Mark them as __used to avoid that.

This is only needed on 32bit, on 64bit they're assembler anyways.

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Martin Liska <mliska@...e.cz>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/x86/lib/memcpy_32.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/memcpy_32.c b/arch/x86/lib/memcpy_32.c
index ef3af7ff2c8a..53fa1cac79d1 100644
--- a/arch/x86/lib/memcpy_32.c
+++ b/arch/x86/lib/memcpy_32.c
@@ -6,19 +6,19 @@
 #undef memset
 #undef memmove
 
-__visible void *memcpy(void *to, const void *from, size_t n)
+__used __visible void *memcpy(void *to, const void *from, size_t n)
 {
 	return __memcpy(to, from, n);
 }
 EXPORT_SYMBOL(memcpy);
 
-__visible void *memset(void *s, int c, size_t count)
+__used __visible void *memset(void *s, int c, size_t count)
 {
 	return __memset(s, c, count);
 }
 EXPORT_SYMBOL(memset);
 
-__visible void *memmove(void *dest, const void *src, size_t n)
+__used __visible void *memmove(void *dest, const void *src, size_t n)
 {
 	int d0,d1,d2,d3,d4,d5;
 	char *ret = dest;
-- 
2.38.1