linux-kernel - [PATCH 16/46] x86, lto: Mark gdt_page and native_sched_clock() as _

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Date:   Mon, 14 Nov 2022 12:43:14 +0100
From:   "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Andi Kleen <andi@...stfloor.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Martin Liska <mliska@...e.cz>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 16/46] x86, lto: Mark gdt_page and native_sched_clock() as __visible

From: Andi Kleen <andi@...stfloor.org>

Symbols referenced from assembler (either directly or e.f. from
DEFINE_STATIC_KEY()) need to be global and visible in gcc LTO because
they could end up in a different object file than the assembler. This
can lead to linker errors without this patch.

So mark gdt_page and native_sched_clock() as __visible.

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: <x86@...nel.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Martin Liska <mliska@...e.cz>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/x86/kernel/cpu/common.c | 2 +-
 arch/x86/kernel/tsc.c        | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 3e508f239098..5417a8fd7a45 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -201,7 +201,7 @@ static const struct cpu_dev default_cpu = {
 
 static const struct cpu_dev *this_cpu = &default_cpu;
 
-DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
+__visible DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
 #ifdef CONFIG_X86_64
 	/*
 	 * We need valid kernel segments for data and code in long mode too
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index cafacb2e58cc..df1589482662 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -215,7 +215,7 @@ static void __init cyc2ns_init_secondary_cpus(void)
 /*
  * Scheduler clock - returns current time in nanosec units.
  */
-u64 native_sched_clock(void)
+__visible u64 native_sched_clock(void)
 {
 	if (static_branch_likely(&__use_tsc)) {
 		u64 tsc_now = rdtsc();
-- 
2.38.1