linux-kernel - [PATCH 2/7] ARM: Pass task to secondary_start

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Message-Id: <20210907220038.91021-3-keithpac@amazon.com>
Date:   Tue,  7 Sep 2021 15:00:33 -0700
From:   Keith Packard <keithpac@...zon.com>
To:     linux-kernel@...r.kernel.org
Cc:     Abbott Liu <liuwenliang@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Christoph Lameter <cl@...ux.com>,
        Dennis Zhou <dennis@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Jens Axboe <axboe@...nel.dk>, Joe Perches <joe@...ches.com>,
        Kees Cook <keescook@...omium.org>,
        Keith Packard <keithpac@...zon.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        Manivannan Sadhasivam <mani@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Mike Rapoport <rppt@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nick Desaulniers <ndesaulniers@...ogle.com>,
        Nicolas Pitre <nico@...xnic.net>,
        Russell King <linux@...linux.org.uk>,
        Tejun Heo <tj@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Valentin Schneider <valentin.schneider@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Wolfram Sang (Renesas)" <wsa+renesas@...g-engineering.com>,
        YiFei Zhu <yifeifz2@...inois.edu>
Subject: [PATCH 2/7] ARM: Pass task to secondary_start_kernel

This avoids needing to compute the task pointer in this function,
allowing it to be used as the source of identification in the future.

Signed-off-by: Keith Packard <keithpac@...zon.com>
---
 arch/arm/include/asm/smp.h   | 3 ++-
 arch/arm/kernel/head-nommu.S | 1 +
 arch/arm/kernel/head.S       | 1 +
 arch/arm/kernel/smp.c        | 8 +++++---
 4 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
index 86a7fd721556..d43b64635d77 100644
--- a/arch/arm/include/asm/smp.h
+++ b/arch/arm/include/asm/smp.h
@@ -48,7 +48,7 @@ extern void set_smp_ipi_range(int ipi_base, int nr_ipi);
  * Called from platform specific assembly code, this is the
  * secondary CPU entry point.
  */
-asmlinkage void secondary_start_kernel(unsigned int cpu);
+asmlinkage void secondary_start_kernel(unsigned int cpu, struct task_struct *task);
 
 
 /*
@@ -62,6 +62,7 @@ struct secondary_data {
 	unsigned long swapper_pg_dir;
 	void *stack;
 	unsigned int cpu;
+	struct task_struct *task;
 };
 extern struct secondary_data secondary_data;
 extern void secondary_startup(void);
diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S
index 5aa8ef42717f..218715c135ed 100644
--- a/arch/arm/kernel/head-nommu.S
+++ b/arch/arm/kernel/head-nommu.S
@@ -115,6 +115,7 @@ ENTRY(secondary_startup)
 	ret	r12
 1:	bl	__after_proc_init
 	ldr	r0, [r7, #16]			@ set up cpu number
+	ldr	r1, [r7, #20]			@ set up task pointer
 	ldr	sp, [r7, #12]			@ set up the stack pointer
 	mov	fp, #0
 	b	secondary_start_kernel
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 0e541af738e2..4a6cb0b0808b 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -395,6 +395,7 @@ ENDPROC(secondary_startup_arm)
 ENTRY(__secondary_switched)
 	ldr_l	r7, secondary_data + 12		@ get secondary_data.stack
 	ldr_l	r0, secondary_data + 16		@ get secondary_data.cpu
+	ldr_l	r1, secondary_data + 20		@ get secondary_data.task
 	mov	sp, r7
 	mov	fp, #0
 	b	secondary_start_kernel
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 55cb1689a4b3..5e999f1f1aea 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -154,6 +154,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	secondary_data.swapper_pg_dir = get_arch_pgd(swapper_pg_dir);
 #endif
 	secondary_data.cpu = cpu;
+	secondary_data.task = idle;
 	sync_cache_w(&secondary_data);
 
 	/*
@@ -375,13 +376,14 @@ void arch_cpu_idle_dead(void)
 	 * to be repeated to undo the effects of taking the CPU offline.
 	 */
 	__asm__("mov	r0, %1\n"
+	"	mov	r1, %2\n"
 	"	mov	sp, %0\n"
 	"	mov	fp, #0\n"
 	"	b	secondary_start_kernel"
 		:
 		: "r" (task_stack_page(current) + THREAD_SIZE - 8),
-		  "r" (cpu)
-		: "r0");
+		  "r" (cpu), "r" (current)
+		: "r0", "r1");
 }
 #endif /* CONFIG_HOTPLUG_CPU */
 
@@ -404,7 +406,7 @@ static void smp_store_cpu_info(unsigned int cpuid)
  * This is the secondary CPU boot entry.  We're using this CPUs
  * idle thread stack, but a set of temporary page tables.
  */
-asmlinkage void secondary_start_kernel(unsigned int cpu)
+asmlinkage void secondary_start_kernel(unsigned int cpu, struct task_struct *task)
 {
 	struct mm_struct *mm = &init_mm;
 
-- 
2.33.0