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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suspend.c (2109B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Copyright (c) 2021 Western Digital Corporation or its affiliates.
      4 * Copyright (c) 2022 Ventana Micro Systems Inc.
      5 */
      6
      7#include <linux/ftrace.h>
      8#include <asm/csr.h>
      9#include <asm/suspend.h>
     10
     11static void suspend_save_csrs(struct suspend_context *context)
     12{
     13	context->scratch = csr_read(CSR_SCRATCH);
     14	context->tvec = csr_read(CSR_TVEC);
     15	context->ie = csr_read(CSR_IE);
     16
     17	/*
     18	 * No need to save/restore IP CSR (i.e. MIP or SIP) because:
     19	 *
     20	 * 1. For no-MMU (M-mode) kernel, the bits in MIP are set by
     21	 *    external devices (such as interrupt controller, timer, etc).
     22	 * 2. For MMU (S-mode) kernel, the bits in SIP are set by
     23	 *    M-mode firmware and external devices (such as interrupt
     24	 *    controller, etc).
     25	 */
     26
     27#ifdef CONFIG_MMU
     28	context->satp = csr_read(CSR_SATP);
     29#endif
     30}
     31
     32static void suspend_restore_csrs(struct suspend_context *context)
     33{
     34	csr_write(CSR_SCRATCH, context->scratch);
     35	csr_write(CSR_TVEC, context->tvec);
     36	csr_write(CSR_IE, context->ie);
     37
     38#ifdef CONFIG_MMU
     39	csr_write(CSR_SATP, context->satp);
     40#endif
     41}
     42
     43int cpu_suspend(unsigned long arg,
     44		int (*finish)(unsigned long arg,
     45			      unsigned long entry,
     46			      unsigned long context))
     47{
     48	int rc = 0;
     49	struct suspend_context context = { 0 };
     50
     51	/* Finisher should be non-NULL */
     52	if (!finish)
     53		return -EINVAL;
     54
     55	/* Save additional CSRs*/
     56	suspend_save_csrs(&context);
     57
     58	/*
     59	 * Function graph tracer state gets incosistent when the kernel
     60	 * calls functions that never return (aka finishers) hence disable
     61	 * graph tracing during their execution.
     62	 */
     63	pause_graph_tracing();
     64
     65	/* Save context on stack */
     66	if (__cpu_suspend_enter(&context)) {
     67		/* Call the finisher */
     68		rc = finish(arg, __pa_symbol(__cpu_resume_enter),
     69			    (ulong)&context);
     70
     71		/*
     72		 * Should never reach here, unless the suspend finisher
     73		 * fails. Successful cpu_suspend() should return from
     74		 * __cpu_resume_entry()
     75		 */
     76		if (!rc)
     77			rc = -EOPNOTSUPP;
     78	}
     79
     80	/* Enable function graph tracer */
     81	unpause_graph_tracing();
     82
     83	/* Restore additional CSRs */
     84	suspend_restore_csrs(&context);
     85
     86	return rc;
     87}