cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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process.c (4850B)


      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Process creation support for Hexagon
      4 *
      5 * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
      6 */
      7
      8#include <linux/sched.h>
      9#include <linux/sched/debug.h>
     10#include <linux/sched/task.h>
     11#include <linux/sched/task_stack.h>
     12#include <linux/types.h>
     13#include <linux/module.h>
     14#include <linux/tick.h>
     15#include <linux/uaccess.h>
     16#include <linux/slab.h>
     17#include <linux/resume_user_mode.h>
     18
     19/*
     20 * Program thread launch.  Often defined as a macro in processor.h,
     21 * but we're shooting for a small footprint and it's not an inner-loop
     22 * performance-critical operation.
     23 *
     24 * The Hexagon ABI specifies that R28 is zero'ed before program launch,
     25 * so that gets automatically done here.  If we ever stop doing that here,
     26 * we'll probably want to define the ELF_PLAT_INIT macro.
     27 */
     28void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
     29{
     30	/* We want to zero all data-containing registers. Is this overkill? */
     31	memset(regs, 0, sizeof(*regs));
     32	/* We might want to also zero all Processor registers here */
     33	pt_set_usermode(regs);
     34	pt_set_elr(regs, pc);
     35	pt_set_rte_sp(regs, sp);
     36}
     37
     38/*
     39 *  Spin, or better still, do a hardware or VM wait instruction
     40 *  If hardware or VM offer wait termination even though interrupts
     41 *  are disabled.
     42 */
     43void arch_cpu_idle(void)
     44{
     45	__vmwait();
     46	/*  interrupts wake us up, but irqs are still disabled */
     47	raw_local_irq_enable();
     48}
     49
     50/*
     51 * Copy architecture-specific thread state
     52 */
     53int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
     54{
     55	unsigned long clone_flags = args->flags;
     56	unsigned long usp = args->stack;
     57	unsigned long tls = args->tls;
     58	struct thread_info *ti = task_thread_info(p);
     59	struct hexagon_switch_stack *ss;
     60	struct pt_regs *childregs;
     61	asmlinkage void ret_from_fork(void);
     62
     63	childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
     64					sizeof(*childregs));
     65
     66	ti->regs = childregs;
     67
     68	/*
     69	 * Establish kernel stack pointer and initial PC for new thread
     70	 * Note that unlike the usual situation, we do not copy the
     71	 * parent's callee-saved here; those are in pt_regs and whatever
     72	 * we leave here will be overridden on return to userland.
     73	 */
     74	ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
     75						    sizeof(*ss));
     76	ss->lr = (unsigned long)ret_from_fork;
     77	p->thread.switch_sp = ss;
     78	if (unlikely(args->fn)) {
     79		memset(childregs, 0, sizeof(struct pt_regs));
     80		/* r24 <- fn, r25 <- arg */
     81		ss->r24 = (unsigned long)args->fn;
     82		ss->r25 = (unsigned long)args->fn_arg;
     83		pt_set_kmode(childregs);
     84		return 0;
     85	}
     86	memcpy(childregs, current_pt_regs(), sizeof(*childregs));
     87	ss->r2524 = 0;
     88
     89	if (usp)
     90		pt_set_rte_sp(childregs, usp);
     91
     92	/* Child sees zero return value */
     93	childregs->r00 = 0;
     94
     95	/*
     96	 * The clone syscall has the C signature:
     97	 * int [r0] clone(int flags [r0],
     98	 *           void *child_frame [r1],
     99	 *           void *parent_tid [r2],
    100	 *           void *child_tid [r3],
    101	 *           void *thread_control_block [r4]);
    102	 * ugp is used to provide TLS support.
    103	 */
    104	if (clone_flags & CLONE_SETTLS)
    105		childregs->ugp = tls;
    106
    107	/*
    108	 * Parent sees new pid -- not necessary, not even possible at
    109	 * this point in the fork process
    110	 */
    111
    112	return 0;
    113}
    114
    115/*
    116 * Release any architecture-specific resources locked by thread
    117 */
    118void release_thread(struct task_struct *dead_task)
    119{
    120}
    121
    122/*
    123 * Some archs flush debug and FPU info here
    124 */
    125void flush_thread(void)
    126{
    127}
    128
    129/*
    130 * The "wait channel" terminology is archaic, but what we want
    131 * is an identification of the point at which the scheduler
    132 * was invoked by a blocked thread.
    133 */
    134unsigned long __get_wchan(struct task_struct *p)
    135{
    136	unsigned long fp, pc;
    137	unsigned long stack_page;
    138	int count = 0;
    139
    140	stack_page = (unsigned long)task_stack_page(p);
    141	fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
    142	do {
    143		if (fp < (stack_page + sizeof(struct thread_info)) ||
    144			fp >= (THREAD_SIZE - 8 + stack_page))
    145			return 0;
    146		pc = ((unsigned long *)fp)[1];
    147		if (!in_sched_functions(pc))
    148			return pc;
    149		fp = *(unsigned long *) fp;
    150	} while (count++ < 16);
    151
    152	return 0;
    153}
    154
    155/*
    156 * Called on the exit path of event entry; see vm_entry.S
    157 *
    158 * Interrupts will already be disabled.
    159 *
    160 * Returns 0 if there's no need to re-check for more work.
    161 */
    162
    163int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
    164{
    165	if (!(thread_info_flags & _TIF_WORK_MASK)) {
    166		return 0;
    167	}  /* shortcut -- no work to be done */
    168
    169	local_irq_enable();
    170
    171	if (thread_info_flags & _TIF_NEED_RESCHED) {
    172		schedule();
    173		return 1;
    174	}
    175
    176	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
    177		do_signal(regs);
    178		return 1;
    179	}
    180
    181	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
    182		resume_user_mode_work(regs);
    183		return 1;
    184	}
    185
    186	/* Should not even reach here */
    187	panic("%s: bad thread_info flags 0x%08x\n", __func__,
    188		thread_info_flags);
    189}