Commit a638b0461b58 for kernel

commit a638b0461b58aa3205cd9d5f14d6f703d795b4af
Author: Sergey Matyukevich <sergey.matyukevich@syntacore.com>
Date:   Thu May 23 11:43:23 2024 +0300

    riscv: prevent pt_regs corruption for secondary idle threads

    Top of the kernel thread stack should be reserved for pt_regs. However
    this is not the case for the idle threads of the secondary boot harts.
    Their stacks overlap with their pt_regs, so both may get corrupted.

    Similar issue has been fixed for the primary hart, see c7cdd96eca28
    ("riscv: prevent stack corruption by reserving task_pt_regs(p) early").
    However that fix was not propagated to the secondary harts. The problem
    has been noticed in some CPU hotplug tests with V enabled. The function
    smp_callin stored several registers on stack, corrupting top of pt_regs
    structure including status field. As a result, kernel attempted to save
    or restore inexistent V context.

    Fixes: 9a2451f18663 ("RISC-V: Avoid using per cpu array for ordered booting")
    Fixes: 2875fe056156 ("RISC-V: Add cpu_ops and modify default booting method")
    Signed-off-by: Sergey Matyukevich <sergey.matyukevich@syntacore.com>
    Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
    Link: https://lore.kernel.org/r/20240523084327.2013211-1-geomatsi@gmail.com
    Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c
index 1cc7df740edd..e6fbaaf54956 100644
--- a/arch/riscv/kernel/cpu_ops_sbi.c
+++ b/arch/riscv/kernel/cpu_ops_sbi.c
@@ -72,7 +72,7 @@ static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle)
 	/* Make sure tidle is updated */
 	smp_mb();
 	bdata->task_ptr = tidle;
-	bdata->stack_ptr = task_stack_page(tidle) + THREAD_SIZE;
+	bdata->stack_ptr = task_pt_regs(tidle);
 	/* Make sure boot data is updated */
 	smp_mb();
 	hsm_data = __pa(bdata);
diff --git a/arch/riscv/kernel/cpu_ops_spinwait.c b/arch/riscv/kernel/cpu_ops_spinwait.c
index 613872b0a21a..24869eb88908 100644
--- a/arch/riscv/kernel/cpu_ops_spinwait.c
+++ b/arch/riscv/kernel/cpu_ops_spinwait.c
@@ -34,8 +34,7 @@ static void cpu_update_secondary_bootdata(unsigned int cpuid,

 	/* Make sure tidle is updated */
 	smp_mb();
-	WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid],
-		   task_stack_page(tidle) + THREAD_SIZE);
+	WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid], task_pt_regs(tidle));
 	WRITE_ONCE(__cpu_spinwait_task_pointer[hartid], tidle);
 }