/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_ALTERNATIVE_H
#define _ASM_X86_ALTERNATIVE_H

#include <linux/types.h>
#include <linux/stringify.h>
#include <asm/asm.h>

#define ALTINSTR_FLAG_INV       (1 << 15)
#define ALT_NOT(feat)           ((feat) | ALTINSTR_FLAG_INV)

#ifndef __ASSEMBLY__

#include <linux/stddef.h>

/*
 * Alternative inline assembly for SMP.
 *
 * The LOCK_PREFIX macro defined here replaces the LOCK and
 * LOCK_PREFIX macros used everywhere in the source tree.
 *
 * SMP alternatives use the same data structures as the other
 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
 * UP system running a SMP kernel.  The existing apply_alternatives()
 * works fine for patching a SMP kernel for UP.
 *
 * The SMP alternative tables can be kept after boot and contain both
 * UP and SMP versions of the instructions to allow switching back to
 * SMP at runtime, when hotplugging in a new CPU, which is especially
 * useful in virtualized environments.
 *
 * The very common lock prefix is handled as special case in a
 * separate table which is a pure address list without replacement ptr
 * and size information.  That keeps the table sizes small.
 */

#ifdef CONFIG_SMP
#define LOCK_PREFIX_HERE \
                ".pushsection .smp_locks,\"a\"\n"       \
                ".balign 4\n"                           \
                ".long 671f - .\n" /* offset */         \
                ".popsection\n"                         \
                "671:"

#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "

#else /* ! CONFIG_SMP */
#define LOCK_PREFIX_HERE ""
#define LOCK_PREFIX ""
#endif

/*
 * objtool annotation to ignore the alternatives and only consider the original
 * instruction(s).
 */
#define ANNOTATE_IGNORE_ALTERNATIVE                             \
        "999:\n\t"                                              \
        ".pushsection .discard.ignore_alts\n\t"                 \
        ".long 999b - .\n\t"                                    \
        ".popsection\n\t"

struct alt_instr {
        s32 instr_offset;       /* original instruction */
        s32 repl_offset;        /* offset to replacement instruction */
        u16 cpuid;              /* cpuid bit set for replacement */
        u8  instrlen;           /* length of original instruction */
        u8  replacementlen;     /* length of new instruction */
} __packed;

/*
 * Debug flag that can be tested to see whether alternative
 * instructions were patched in already:
 */
extern int alternatives_patched;

extern void alternative_instructions(void);
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);

struct module;

#ifdef CONFIG_SMP
extern void alternatives_smp_module_add(struct module *mod, char *name,
                                        void *locks, void *locks_end,
                                        void *text, void *text_end);
extern void alternatives_smp_module_del(struct module *mod);
extern void alternatives_enable_smp(void);
extern int alternatives_text_reserved(void *start, void *end);
extern bool skip_smp_alternatives;
#else
static inline void alternatives_smp_module_add(struct module *mod, char *name,
                                               void *locks, void *locks_end,
                                               void *text, void *text_end) {}
static inline void alternatives_smp_module_del(struct module *mod) {}
static inline void alternatives_enable_smp(void) {}
static inline int alternatives_text_reserved(void *start, void *end)
{
        return 0;
}
#endif  /* CONFIG_SMP */

#define b_replacement(num)      "664"#num
#define e_replacement(num)      "665"#num

#define alt_end_marker          "663"
#define alt_slen                "662b-661b"
#define alt_total_slen          alt_end_marker"b-661b"
#define alt_rlen(num)           e_replacement(num)"f-"b_replacement(num)"f"

#define OLDINSTR(oldinstr, num)                                         \
        "# ALT: oldnstr\n"                                              \
        "661:\n\t" oldinstr "\n662:\n"                                  \
        "# ALT: padding\n"                                              \
        ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * "          \
                "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"           \
        alt_end_marker ":\n"

/*
 * gas compatible max based on the idea from:
 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
 *
 * The additional "-" is needed because gas uses a "true" value of -1.
 */
#define alt_max_short(a, b)     "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"

/*
 * Pad the second replacement alternative with additional NOPs if it is
 * additionally longer than the first replacement alternative.
 */
#define OLDINSTR_2(oldinstr, num1, num2) \
        "# ALT: oldinstr2\n"                                                                    \
        "661:\n\t" oldinstr "\n662:\n"                                                          \
        "# ALT: padding2\n"                                                                     \
        ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * "  \
                "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n"  \
        alt_end_marker ":\n"

#define OLDINSTR_3(oldinsn, n1, n2, n3)                                                         \
        "# ALT: oldinstr3\n"                                                                    \
        "661:\n\t" oldinsn "\n662:\n"                                                           \
        "# ALT: padding3\n"                                                                     \
        ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))      \
                " - (" alt_slen ")) > 0) * "                                                    \
                "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))      \
                " - (" alt_slen ")), 0x90\n"                                                    \
        alt_end_marker ":\n"

#define ALTINSTR_ENTRY(feature, num)                                          \
        " .long 661b - .\n"                             /* label           */ \
        " .long " b_replacement(num)"f - .\n"           /* new instruction */ \
        " .word " __stringify(feature) "\n"             /* feature bit     */ \
        " .byte " alt_total_slen "\n"                   /* source len      */ \
        " .byte " alt_rlen(num) "\n"                    /* replacement len */

#define ALTINSTR_REPLACEMENT(newinstr, num)             /* replacement */       \
        "# ALT: replacement " #num "\n"                                         \
        b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"

/* alternative assembly primitive: */
#define ALTERNATIVE(oldinstr, newinstr, feature)                        \
        OLDINSTR(oldinstr, 1)                                           \
        ".pushsection .altinstructions,\"a\"\n"                         \
        ALTINSTR_ENTRY(feature, 1)                                      \
        ".popsection\n"                                                 \
        ".pushsection .altinstr_replacement, \"ax\"\n"                  \
        ALTINSTR_REPLACEMENT(newinstr, 1)                               \
        ".popsection\n"

#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
        OLDINSTR_2(oldinstr, 1, 2)                                      \
        ".pushsection .altinstructions,\"a\"\n"                         \
        ALTINSTR_ENTRY(feature1, 1)                                     \
        ALTINSTR_ENTRY(feature2, 2)                                     \
        ".popsection\n"                                                 \
        ".pushsection .altinstr_replacement, \"ax\"\n"                  \
        ALTINSTR_REPLACEMENT(newinstr1, 1)                              \
        ALTINSTR_REPLACEMENT(newinstr2, 2)                              \
        ".popsection\n"

/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
        ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,        \
                      newinstr_yes, feature)

#define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
        OLDINSTR_3(oldinsn, 1, 2, 3)                                            \
        ".pushsection .altinstructions,\"a\"\n"                                 \
        ALTINSTR_ENTRY(feat1, 1)                                                \
        ALTINSTR_ENTRY(feat2, 2)                                                \
        ALTINSTR_ENTRY(feat3, 3)                                                \
        ".popsection\n"                                                         \
        ".pushsection .altinstr_replacement, \"ax\"\n"                          \
        ALTINSTR_REPLACEMENT(newinsn1, 1)                                       \
        ALTINSTR_REPLACEMENT(newinsn2, 2)                                       \
        ALTINSTR_REPLACEMENT(newinsn3, 3)                                       \
        ".popsection\n"

/*
 * Alternative instructions for different CPU types or capabilities.
 *
 * This allows to use optimized instructions even on generic binary
 * kernels.
 *
 * length of oldinstr must be longer or equal the length of newinstr
 * It can be padded with nops as needed.
 *
 * For non barrier like inlines please define new variants
 * without volatile and memory clobber.
 */
#define alternative(oldinstr, newinstr, feature)                        \
        asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")

#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
        asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")

#define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \
        asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory")

/*
 * Alternative inline assembly with input.
 *
 * Peculiarities:
 * No memory clobber here.
 * Argument numbers start with 1.
 * Leaving an unused argument 0 to keep API compatibility.
 */
#define alternative_input(oldinstr, newinstr, feature, input...)        \
        asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature)   \
                : : "i" (0), ## input)

/*
 * This is similar to alternative_input. But it has two features and
 * respective instructions.
 *
 * If CPU has feature2, newinstr2 is used.
 * Otherwise, if CPU has feature1, newinstr1 is used.
 * Otherwise, oldinstr is used.
 */
#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2,        \
                           feature2, input...)                               \
        asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1,     \
                newinstr2, feature2)                                         \
                : : "i" (0), ## input)

/* Like alternative_input, but with a single output argument */
#define alternative_io(oldinstr, newinstr, feature, output, input...)   \
        asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature)   \
                : output : "i" (0), ## input)

/* Like alternative_io, but for replacing a direct call with another one. */
#define alternative_call(oldfunc, newfunc, feature, output, input...)   \
        asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
                : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)

/*
 * Like alternative_call, but there are two features and respective functions.
 * If CPU has feature2, function2 is used.
 * Otherwise, if CPU has feature1, function1 is used.
 * Otherwise, old function is used.
 */
#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2,   \
                           output, input...)                                  \
        asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
                "call %P[new2]", feature2)                                    \
                : output, ASM_CALL_CONSTRAINT                                 \
                : [old] "i" (oldfunc), [new1] "i" (newfunc1),                 \
                  [new2] "i" (newfunc2), ## input)

/*
 * use this macro(s) if you need more than one output parameter
 * in alternative_io
 */
#define ASM_OUTPUT2(a...) a

/*
 * use this macro if you need clobbers but no inputs in
 * alternative_{input,io,call}()
 */
#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr

#else /* __ASSEMBLY__ */

#ifdef CONFIG_SMP
        .macro LOCK_PREFIX
672:    lock
        .pushsection .smp_locks,"a"
        .balign 4
        .long 672b - .
        .popsection
        .endm
#else
        .macro LOCK_PREFIX
        .endm
#endif

/*
 * objtool annotation to ignore the alternatives and only consider the original
 * instruction(s).
 */
.macro ANNOTATE_IGNORE_ALTERNATIVE
        .Lannotate_\@:
        .pushsection .discard.ignore_alts
        .long .Lannotate_\@ - .
        .popsection
.endm

/*
 * Issue one struct alt_instr descriptor entry (need to put it into
 * the section .altinstructions, see below). This entry contains
 * enough information for the alternatives patching code to patch an
 * instruction. See apply_alternatives().
 */
.macro altinstruction_entry orig alt feature orig_len alt_len
        .long \orig - .
        .long \alt - .
        .word \feature
        .byte \orig_len
        .byte \alt_len
.endm

/*
 * Define an alternative between two instructions. If @feature is
 * present, early code in apply_alternatives() replaces @oldinstr with
 * @newinstr. ".skip" directive takes care of proper instruction padding
 * in case @newinstr is longer than @oldinstr.
 */
.macro ALTERNATIVE oldinstr, newinstr, feature
140:
        \oldinstr
141:
        .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
142:

        .pushsection .altinstructions,"a"
        altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f
        .popsection

        .pushsection .altinstr_replacement,"ax"
143:
        \newinstr
144:
        .popsection
.endm

#define old_len                 141b-140b
#define new_len1                144f-143f
#define new_len2                145f-144f

/*
 * gas compatible max based on the idea from:
 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
 *
 * The additional "-" is needed because gas uses a "true" value of -1.
 */
#define alt_max_short(a, b)     ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))


/*
 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
 * @feature2, it replaces @oldinstr with @feature2.
 */
.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
140:
        \oldinstr
141:
        .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
                (alt_max_short(new_len1, new_len2) - (old_len)),0x90
142:

        .pushsection .altinstructions,"a"
        altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f
        altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
        .popsection

        .pushsection .altinstr_replacement,"ax"
143:
        \newinstr1
144:
        \newinstr2
145:
        .popsection
.endm

/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
        ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS,        \
        newinstr_yes, feature

#endif /* __ASSEMBLY__ */

#endif /* _ASM_X86_ALTERNATIVE_H */