[PATCH 2/7] ARM: Pass task to secondary_start_kernel

Keith Packard
2021-09-07T22:00:51Z

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@amazon.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