process.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Author: Huacai Chen <[email protected]>
 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
 *
 * Derived from MIPS:
 * Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
 * Copyright (C) 2005, 2006 by Ralf Baechle ([email protected])
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 * Copyright (C) 2004 Thiemo Seufer
 * Copyright (C) 2013  Imagination Technologies Ltd.
 */
#include <linux/cpu.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/entry-common.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/hw_breakpoint.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/export.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/personality.h>
#include <linux/sys.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
#include <linux/random.h>
#include <linux/prctl.h>
#include <linux/nmi.h>

#include <asm/asm.h>
#include <asm/asm-prototypes.h>
#include <asm/bootinfo.h>
#include <asm/cpu.h>
#include <asm/elf.h>
#include <asm/exec.h>
#include <asm/fpu.h>
#include <asm/lbt.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/irq_regs.h>
#include <asm/loongarch.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/reg.h>
#include <asm/switch_to.h>
#include <asm/unwind.h>
#include <asm/vdso.h>

#ifdef CONFIG_STACKPROTECTOR
#include <linux/stackprotector.h>
unsigned long __stack_chk_guard __read_mostly;
EXPORT_SYMBOL(__stack_chk_guard);
#endif

/*
 * Idle related variables and functions
 */

unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
EXPORT_SYMBOL(boot_option_idle_override);

asmlinkage void restore_and_ret(void);
asmlinkage void ret_from_fork_asm(void);
asmlinkage void ret_from_kernel_thread_asm(void);

void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
{
	unsigned long crmd;
	unsigned long prmd;
	unsigned long euen;

	/* New thread loses kernel privileges. */
	crmd = regs->csr_crmd & ~(PLV_MASK);
	crmd |= PLV_USER;
	regs->csr_crmd = crmd;

	prmd = regs->csr_prmd & ~(PLV_MASK);
	prmd |= PLV_USER;
	regs->csr_prmd = prmd;

	euen = regs->csr_euen & ~(CSR_EUEN_FPEN);
	regs->csr_euen = euen;
	lose_fpu(0);
	lose_lbt(0);
	current->thread.fpu.fcsr = boot_cpu_data.fpu_csr0;

	clear_thread_flag(TIF_LSX_CTX_LIVE);
	clear_thread_flag(TIF_LASX_CTX_LIVE);
	clear_thread_flag(TIF_LBT_CTX_LIVE);
	clear_used_math();
	regs->csr_era = pc;
	regs->regs[3] = sp;
}

void flush_thread(void)
{
	flush_ptrace_hw_breakpoint(current);
}

void exit_thread(struct task_struct *tsk)
{
}

int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
	/*
	 * Save any process state which is live in hardware registers to the
	 * parent context prior to duplication. This prevents the new child
	 * state becoming stale if the parent is preempted before copy_thread()
	 * gets a chance to save the parent's live hardware registers to the
	 * child context.
	 */
	preempt_disable();

	if (is_fpu_owner()) {
		if (is_lasx_enabled())
			save_lasx(current);
		else if (is_lsx_enabled())
			save_lsx(current);
		else
			save_fp(current);
	}

	preempt_enable();

	if (IS_ENABLED(CONFIG_RANDSTRUCT)) {
		memcpy(dst, src, sizeof(struct task_struct));
		return 0;
	}

	if (!used_math())
		memcpy(dst, src, offsetof(struct task_struct, thread.fpu.fpr));
	else
		memcpy(dst, src, offsetof(struct task_struct, thread.lbt.scr0));

#ifdef CONFIG_CPU_HAS_LBT
	memcpy(&dst->thread.lbt, &src->thread.lbt, sizeof(struct loongarch_lbt));
#endif

	return 0;
}

asmlinkage void noinstr __no_stack_protector ret_from_fork(struct task_struct *prev,
							   struct pt_regs *regs)
{
	schedule_tail(prev);
	syscall_exit_to_user_mode(regs);
}

asmlinkage void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev,
								    struct pt_regs *regs,
								    int (*fn)(void *),
								    void *fn_arg)
{
	schedule_tail(prev);
	fn(fn_arg);
	syscall_exit_to_user_mode(regs);
}

/*
 * Copy architecture-specific thread state
 */
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
	unsigned long childksp;
	unsigned long tls = args->tls;
	unsigned long usp = args->stack;
	u64 clone_flags = args->flags;
	struct pt_regs *childregs, *regs = current_pt_regs();

	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE;

	/* set up new TSS. */
	childregs = (struct pt_regs *) childksp - 1;
	/*  Put the stack after the struct pt_regs.  */
	childksp = (unsigned long) childregs;
	p->thread.sched_cfa = 0;
	p->thread.csr_euen = 0;
	p->thread.csr_crmd = csr_read32(LOONGARCH_CSR_CRMD);
	p->thread.csr_prmd = csr_read32(LOONGARCH_CSR_PRMD);
	p->thread.csr_ecfg = csr_read32(LOONGARCH_CSR_ECFG);
	if (unlikely(args->fn)) {
		/* kernel thread */
		p->thread.reg03 = childksp;
		p->thread.reg23 = (unsigned long)args->fn;
		p->thread.reg24 = (unsigned long)args->fn_arg;
		p->thread.reg01 = (unsigned long)ret_from_kernel_thread_asm;
		p->thread.sched_ra = (unsigned long)ret_from_kernel_thread_asm;
		memset(childregs, 0, sizeof(struct pt_regs));
		childregs->csr_euen = p->thread.csr_euen;
		childregs->csr_crmd = p->thread.csr_crmd;
		childregs->csr_prmd = p->thread.csr_prmd;
		childregs->csr_ecfg = p->thread.csr_ecfg;
		goto out;
	}

	/* user thread */
	*childregs = *regs;
	childregs->regs[4] = 0; /* Child gets zero as return value */
	if (usp)
		childregs->regs[3] = usp;

	p->thread.reg03 = (unsigned long) childregs;
	p->thread.reg01 = (unsigned long) ret_from_fork_asm;
	p->thread.sched_ra = (unsigned long) ret_from_fork_asm;

	/*
	 * New tasks lose permission to use the fpu. This accelerates context
	 * switching for most programs since they don't use the fpu.
	 */
	childregs->csr_euen = 0;

	if (clone_flags & CLONE_SETTLS)
		childregs->regs[2] = tls;

out:
	ptrace_hw_copy_thread(p);
	clear_tsk_thread_flag(p, TIF_USEDFPU);
	clear_tsk_thread_flag(p, TIF_USEDSIMD);
	clear_tsk_thread_flag(p, TIF_USEDLBT);
	clear_tsk_thread_flag(p, TIF_LSX_CTX_LIVE);
	clear_tsk_thread_flag(p, TIF_LASX_CTX_LIVE);
	clear_tsk_thread_flag(p, TIF_LBT_CTX_LIVE);

	return 0;
}

unsigned long __get_wchan(struct task_struct *task)
{
	unsigned long pc = 0;
	struct unwind_state state;

	if (!try_get_task_stack(task))
		return 0;

	for (unwind_start(&state, task, NULL);
	     !unwind_done(&state); unwind_next_frame(&state)) {
		pc = unwind_get_return_address(&state);
		if (!pc)
			break;
		if (in_sched_functions(pc))
			continue;
		break;
	}

	put_task_stack(task);

	return pc;
}

bool in_irq_stack(unsigned long stack, struct stack_info *info)
{
	unsigned long nextsp;
	unsigned long begin = (unsigned long)this_cpu_read(irq_stack);
	unsigned long end = begin + IRQ_STACK_START;

	if (stack < begin || stack >= end)
		return false;

	nextsp = *(unsigned long *)end;
	if (nextsp & (SZREG - 1))
		return false;

	info->begin = begin;
	info->end = end;
	info->next_sp = nextsp;
	info->type = STACK_TYPE_IRQ;

	return true;
}

bool in_task_stack(unsigned long stack, struct task_struct *task,
			struct stack_info *info)
{
	unsigned long begin = (unsigned long)task_stack_page(task);
	unsigned long end = begin + THREAD_SIZE;

	if (stack < begin || stack >= end)
		return false;

	info->begin = begin;
	info->end = end;
	info->next_sp = 0;
	info->type = STACK_TYPE_TASK;

	return true;
}

int get_stack_info(unsigned long stack, struct task_struct *task,
		   struct stack_info *info)
{
	task = task ? : current;

	if (!stack || stack & (SZREG - 1))
		goto unknown;

	if (in_task_stack(stack, task, info))
		return 0;

	if (task != current)
		goto unknown;

	if (in_irq_stack(stack, info))
		return 0;

unknown:
	info->type = STACK_TYPE_UNKNOWN;
	return -EINVAL;
}

unsigned long stack_top(void)
{
	unsigned long top = TASK_SIZE & PAGE_MASK;

	if (current->thread.vdso) {
		/* Space for the VDSO & data page */
		top -= PAGE_ALIGN(current->thread.vdso->size);
		top -= VVAR_SIZE;

		/* Space to randomize the VDSO base */
		if (current->flags & PF_RANDOMIZE)
			top -= VDSO_RANDOMIZE_SIZE;
	}

	return top;
}

/*
 * Don't forget that the stack pointer must be aligned on a 8 bytes
 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 */
unsigned long arch_align_stack(unsigned long sp)
{
	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
		sp -= get_random_u32_below(PAGE_SIZE);

	return sp & STACK_ALIGN;
}

static DEFINE_PER_CPU(call_single_data_t, backtrace_csd);
static struct cpumask backtrace_csd_busy;

static void handle_backtrace(void *info)
{
	nmi_cpu_backtrace(get_irq_regs());
	cpumask_clear_cpu(smp_processor_id(), &backtrace_csd_busy);
}

static void raise_backtrace(cpumask_t *mask)
{
	call_single_data_t *csd;
	int cpu;

	for_each_cpu(cpu, mask) {
		/*
		 * If we previously sent an IPI to the target CPU & it hasn't
		 * cleared its bit in the busy cpumask then it didn't handle
		 * our previous IPI & it's not safe for us to reuse the
		 * call_single_data_t.
		 */
		if (cpumask_test_and_set_cpu(cpu, &backtrace_csd_busy)) {
			pr_warn("Unable to send backtrace IPI to CPU%u - perhaps it hung?\n",
				cpu);
			continue;
		}

		csd = &per_cpu(backtrace_csd, cpu);
		csd->func = handle_backtrace;
		smp_call_function_single_async(cpu, csd);
	}
}

void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
{
	nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_backtrace);
}

#ifdef CONFIG_32BIT
void loongarch_dump_regs32(u32 *uregs, const struct pt_regs *regs)
#else
void loongarch_dump_regs64(u64 *uregs, const struct pt_regs *regs)
#endif
{
	unsigned int i;

	for (i = LOONGARCH_EF_R1; i <= LOONGARCH_EF_R31; i++) {
		uregs[i] = regs->regs[i - LOONGARCH_EF_R0];
	}

	uregs[LOONGARCH_EF_ORIG_A0] = regs->orig_a0;
	uregs[LOONGARCH_EF_CSR_ERA] = regs->csr_era;
	uregs[LOONGARCH_EF_CSR_BADV] = regs->csr_badvaddr;
	uregs[LOONGARCH_EF_CSR_CRMD] = regs->csr_crmd;
	uregs[LOONGARCH_EF_CSR_PRMD] = regs->csr_prmd;
	uregs[LOONGARCH_EF_CSR_EUEN] = regs->csr_euen;
	uregs[LOONGARCH_EF_CSR_ECFG] = regs->csr_ecfg;
	uregs[LOONGARCH_EF_CSR_ESTAT] = regs->csr_estat;
}