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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vm_switch.S (2389B)

      1/* SPDX-License-Identifier: GPL-2.0-only */
      2/*
      3 * Context switch support for Hexagon
      4 *
      5 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
      6 */
      7
      8#include <asm/asm-offsets.h>
      9
     10.text
     11
     12/*
     13 * The register used as a fast-path thread information pointer
     14 * is determined as a kernel configuration option.  If it happens
     15 * to be a callee-save register, we're going to be saving and
     16 * restoring it twice here.
     17 *
     18 * This code anticipates a revised ABI where R20-23 are added
     19 * to the set of callee-save registers, but this should be
     20 * backward compatible to legacy tools.
     21 */
     22
     23
     24/*
     25 *	void switch_to(struct task_struct *prev,
     26 *		struct task_struct *next, struct task_struct *last);
     27 */
     28	.p2align 2
     29	.globl __switch_to
     30	.type	__switch_to, @function
     31
     32/*
     33 * When we exit the wormhole, we need to store the previous task
     34 * in the new R0's pointer.  Technically it should be R2, but they should
     35 * be the same; seems like a legacy thing.  In short, don't butcher
     36 * R0, let it go back out unmolested.
     37 */
     38
     39__switch_to:
     40	/*
     41	 * Push callee-saves onto "prev" stack.
     42	 * Here, we're sneaky because the LR and FP
     43	 * storage of the thread_stack structure
     44	 * is automagically allocated by allocframe,
     45	 * so we pass struct size less 8.
     46	 */
     47	allocframe(#(_SWITCH_STACK_SIZE - 8));
     48	memd(R29+#(_SWITCH_R2726))=R27:26;
     49	memd(R29+#(_SWITCH_R2524))=R25:24;
     50	memd(R29+#(_SWITCH_R2322))=R23:22;
     51	memd(R29+#(_SWITCH_R2120))=R21:20;
     52	memd(R29+#(_SWITCH_R1918))=R19:18;
     53	memd(R29+#(_SWITCH_R1716))=R17:16;
     54	/* Stash thread_info pointer in task_struct */
     55	memw(R0+#_TASK_THREAD_INFO) = THREADINFO_REG;
     56	memw(R0 +#(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)) = R29;
     57	/* Switch to "next" stack and restore callee saves from there */
     58	R29 = memw(R1 + #(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP));
     59	{
     60	    R27:26 = memd(R29+#(_SWITCH_R2726));
     61	    R25:24 = memd(R29+#(_SWITCH_R2524));
     62	}
     63	{
     64	    R23:22 = memd(R29+#(_SWITCH_R2322));
     65	    R21:20 = memd(R29+#(_SWITCH_R2120));
     66	}
     67	{
     68	    R19:18 = memd(R29+#(_SWITCH_R1918));
     69	    R17:16 = memd(R29+#(_SWITCH_R1716));
     70	}
     71	{
     72	    /* THREADINFO_REG is currently one of the callee-saved regs
     73	     * above, and so be sure to re-load it last.
     74	     */
     75	    THREADINFO_REG = memw(R1 + #_TASK_THREAD_INFO);
     76	    R31:30 = memd(R29+#_SWITCH_FP);
     77	}
     78	{
     79	    R29 = add(R29,#_SWITCH_STACK_SIZE);
     80	    jumpr R31;
     81	}
     82	.size	__switch_to, .-__switch_to