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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jump_label.h (1976B)

      1/* SPDX-License-Identifier: GPL-2.0 */
      2#ifndef _ASM_ARC_JUMP_LABEL_H
      3#define _ASM_ARC_JUMP_LABEL_H
      4
      5#ifndef __ASSEMBLY__
      6
      7#include <linux/stringify.h>
      8#include <linux/types.h>
      9
     10#define JUMP_LABEL_NOP_SIZE 4
     11
     12/*
     13 * NOTE about '.balign 4':
     14 *
     15 * To make atomic update of patched instruction available we need to guarantee
     16 * that this instruction doesn't cross L1 cache line boundary.
     17 *
     18 * As of today we simply align instruction which can be patched by 4 byte using
     19 * ".balign 4" directive. In that case patched instruction is aligned with one
     20 * 16-bit NOP_S if this is required.
     21 * However 'align by 4' directive is much stricter than it actually required.
     22 * It's enough that our 32-bit instruction don't cross L1 cache line boundary /
     23 * L1 I$ fetch block boundary which can be achieved by using
     24 * ".bundle_align_mode" assembler directive. That will save us from adding
     25 * useless NOP_S padding in most of the cases.
     26 *
     27 * TODO: switch to ".bundle_align_mode" directive using whin it will be
     28 * supported by ARC toolchain.
     29 */
     30
     31static __always_inline bool arch_static_branch(struct static_key *key,
     32					       bool branch)
     33{
     34	asm_volatile_goto(".balign "__stringify(JUMP_LABEL_NOP_SIZE)"	\n"
     35		 "1:							\n"
     36		 "nop							\n"
     37		 ".pushsection __jump_table, \"aw\"			\n"
     38		 ".word 1b, %l[l_yes], %c0				\n"
     39		 ".popsection						\n"
     40		 : : "i" (&((char *)key)[branch]) : : l_yes);
     41
     42	return false;
     43l_yes:
     44	return true;
     45}
     46
     47static __always_inline bool arch_static_branch_jump(struct static_key *key,
     48						    bool branch)
     49{
     50	asm_volatile_goto(".balign "__stringify(JUMP_LABEL_NOP_SIZE)"	\n"
     51		 "1:							\n"
     52		 "b %l[l_yes]						\n"
     53		 ".pushsection __jump_table, \"aw\"			\n"
     54		 ".word 1b, %l[l_yes], %c0				\n"
     55		 ".popsection						\n"
     56		 : : "i" (&((char *)key)[branch]) : : l_yes);
     57
     58	return false;
     59l_yes:
     60	return true;
     61}
     62
     63typedef u32 jump_label_t;
     64
     65struct jump_entry {
     66	jump_label_t code;
     67	jump_label_t target;
     68	jump_label_t key;
     69};
     70
     71#endif  /* __ASSEMBLY__ */
     72#endif