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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cmpxchg.h (1984B)

      1/* SPDX-License-Identifier: GPL-2.0-only */
      2/*
      3 * xchg/cmpxchg operations for the Hexagon architecture
      4 *
      5 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
      6 */
      7
      8#ifndef _ASM_CMPXCHG_H
      9#define _ASM_CMPXCHG_H
     10
     11/*
     12 * __xchg - atomically exchange a register and a memory location
     13 * @x: value to swap
     14 * @ptr: pointer to memory
     15 * @size:  size of the value
     16 *
     17 * Only 4 bytes supported currently.
     18 *
     19 * Note:  there was an errata for V2 about .new's and memw_locked.
     20 *
     21 */
     22static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
     23				   int size)
     24{
     25	unsigned long retval;
     26
     27	/*  Can't seem to use printk or panic here, so just stop  */
     28	if (size != 4) do { asm volatile("brkpt;\n"); } while (1);
     29
     30	__asm__ __volatile__ (
     31	"1:	%0 = memw_locked(%1);\n"    /*  load into retval */
     32	"	memw_locked(%1,P0) = %2;\n" /*  store into memory */
     33	"	if (!P0) jump 1b;\n"
     34	: "=&r" (retval)
     35	: "r" (ptr), "r" (x)
     36	: "memory", "p0"
     37	);
     38	return retval;
     39}
     40
     41/*
     42 * Atomically swap the contents of a register with memory.  Should be atomic
     43 * between multiple CPU's and within interrupts on the same CPU.
     44 */
     45#define arch_xchg(ptr, v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), \
     46	sizeof(*(ptr))))
     47
     48/*
     49 *  see rt-mutex-design.txt; cmpxchg supposedly checks if *ptr == A and swaps.
     50 *  looks just like atomic_cmpxchg on our arch currently with a bunch of
     51 *  variable casting.
     52 */
     53
     54#define arch_cmpxchg(ptr, old, new)				\
     55({								\
     56	__typeof__(ptr) __ptr = (ptr);				\
     57	__typeof__(*(ptr)) __old = (old);			\
     58	__typeof__(*(ptr)) __new = (new);			\
     59	__typeof__(*(ptr)) __oldval = 0;			\
     60								\
     61	asm volatile(						\
     62		"1:	%0 = memw_locked(%1);\n"		\
     63		"	{ P0 = cmp.eq(%0,%2);\n"		\
     64		"	  if (!P0.new) jump:nt 2f; }\n"		\
     65		"	memw_locked(%1,p0) = %3;\n"		\
     66		"	if (!P0) jump 1b;\n"			\
     67		"2:\n"						\
     68		: "=&r" (__oldval)				\
     69		: "r" (__ptr), "r" (__old), "r" (__new)		\
     70		: "memory", "p0"				\
     71	);							\
     72	__oldval;						\
     73})
     74
     75#endif /* _ASM_CMPXCHG_H */