/*      $OpenBSD: codepatch.h,v 1.19 2024/02/12 01:18:17 guenther Exp $    */
/*
 * Copyright (c) 2014-2015 Stefan Fritsch <sf@sfritsch.de>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef _MACHINE_CODEPATCH_H_
#define _MACHINE_CODEPATCH_H_

#include <machine/param.h>

#ifndef _LOCORE

/* code in this section will be unmapped after boot */
#define __cptext __attribute__((section(".cptext")))

__cptext void *codepatch_maprw(vaddr_t *nva, vaddr_t dest);
__cptext void codepatch_unmaprw(vaddr_t nva);
__cptext void codepatch_fill_nop(void *caddr, uint16_t len);
__cptext void codepatch_nop(uint16_t tag);
__cptext void codepatch_replace(uint16_t tag, const void *code, size_t len);
__cptext void codepatch_call(uint16_t _tag, void *_func);
__cptext void codepatch_jmp(uint16_t _tag, void *_func);
void codepatch_disable(void);

#endif /* !_LOCORE */

/*
 * Mark the start of some code snippet to be patched.
 */
#define CODEPATCH_START 998:
/*
 * Mark the end of some code to be patched, and assign the given tag.
 */
#define CODEPATCH_END2(startnum,tag)             \
        999:                                     \
        .section .codepatch, "a"                ;\
        .quad startnum##b                       ;\
        .short (999b - startnum##b)             ;\
        .short tag                              ;\
        .int 0                                  ;\
        .previous
#define CODEPATCH_END(tag)      CODEPATCH_END2(998,tag)

#define CPTAG_STAC              1
#define CPTAG_CLAC              2
#define CPTAG_EOI               3
#define CPTAG_XRSTOR            4
#define CPTAG_XSAVE             5
#define CPTAG_MELTDOWN_NOP      6
#define CPTAG_MELTDOWN_ALLTRAPS 7
#define CPTAG_PCID_SET_REUSE    8
#define CPTAG_MDS               9
#define CPTAG_MDS_VMM           10
#define CPTAG_FENCE_SWAPGS_MIS_TAKEN    11
#define CPTAG_FENCE_NO_SAFE_SMAP        12
#define CPTAG_XRSTORS                   13
#define CPTAG_RETPOLINE_RAX             14
#define CPTAG_RETPOLINE_R11             15
#define CPTAG_RETPOLINE_R13             16
#define CPTAG_IBPB_NOP                  17

/*
 * stac/clac SMAP instructions have lfence like semantics.  Let's
 * guarantee those semantics on older cpus.
 */
#define SMAP_NOP        lfence
#define SMAP_STAC       CODEPATCH_START                 ;\
                        SMAP_NOP                        ;\
                        CODEPATCH_END(CPTAG_STAC)
#define SMAP_CLAC       CODEPATCH_START                 ;\
                        SMAP_NOP                        ;\
                        CODEPATCH_END(CPTAG_CLAC)

/* CVE-2019-1125: block speculation after swapgs */
#define FENCE_SWAPGS_MIS_TAKEN \
        CODEPATCH_START                         ; \
        lfence                                  ; \
        CODEPATCH_END(CPTAG_FENCE_SWAPGS_MIS_TAKEN)
/* block speculation when a correct SMAP impl would have been enough */
#define FENCE_NO_SAFE_SMAP \
        CODEPATCH_START                         ; \
        lfence                                  ; \
        CODEPATCH_END(CPTAG_FENCE_NO_SAFE_SMAP)

#define PCID_SET_REUSE_SIZE     12
#define PCID_SET_REUSE_NOP                                      \
        997:                                                    ;\
        .byte   0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00  ;\
        .byte   0x0f, 0x1f, 0x40, 0x00                          ;\
        CODEPATCH_END2(997, CPTAG_PCID_SET_REUSE)

/* Would be neat if these could be in something like .cptext */
#define CODEPATCH_CODE(symbol, instructions...)         \
        .section .rodata;                               \
        .globl  symbol;                                 \
symbol: instructions;                                   \
        .size   symbol, . - symbol

/* provide a (short) variable with the length of the patch */
#define CODEPATCH_CODE_LEN(symbol, instructions...)     \
        CODEPATCH_CODE(symbol, instructions);           \
996:    .globl  symbol##_len;                           \
        .align  2;                                      \
symbol##_len:                                           \
        .short  996b - symbol;                          \
        .size   symbol##_len, 2

#endif /* _MACHINE_CODEPATCH_H_ */