/* 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 <linux/objtool.h>
#include <asm/asm.h>
#include <asm/bug.h>

#define ALT_FLAGS_SHIFT         16

#define ALT_FLAG_NOT            (1 << 0)
#define ALT_NOT(feature)        ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
#define ALT_FLAG_DIRECT_CALL    (1 << 1)
#define ALT_DIRECT_CALL(feature) ((ALT_FLAG_DIRECT_CALL << ALT_FLAGS_SHIFT) | (feature))
#define ALT_CALL_ALWAYS         ALT_DIRECT_CALL(X86_FEATURE_ALWAYS)

#ifndef __ASSEMBLER__

#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

/*
 * The patching flags are part of the upper bits of the @ft_flags parameter when
 * specifying them. The split is currently like this:
 *
 * [31... flags ...16][15... CPUID feature bit ...0]
 *
 * but since this is all hidden in the macros argument being split, those fields can be
 * extended in the future to fit in a u64 or however the need arises.
 */
struct alt_instr {
        s32 instr_offset;       /* original instruction */
        s32 repl_offset;        /* offset to replacement instruction */

        union {
                struct {
                        u32 cpuid: 16;  /* CPUID bit set for replacement */
                        u32 flags: 16;  /* patching control flags */
                };
                u32 ft_flags;
        };

        u8  instrlen;           /* length of original instruction */
        u8  replacementlen;     /* length of new instruction */
} __packed;

extern struct alt_instr __alt_instructions[], __alt_instructions_end[];

extern s32 __retpoline_sites[], __retpoline_sites_end[];
extern s32 __return_sites[],    __return_sites_end[];
extern s32 __cfi_sites[],       __cfi_sites_end[];
extern s32 __ibt_endbr_seal[],  __ibt_endbr_seal_end[];
extern s32 __smp_locks[],       __smp_locks_end[];

/*
 * 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);
extern void apply_retpolines(s32 *start, s32 *end);
extern void apply_returns(s32 *start, s32 *end);
extern void apply_seal_endbr(s32 *start, s32 *end);
extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
                          s32 *start_cfi, s32 *end_cfi);

struct module;

struct callthunk_sites {
        s32                             *call_start, *call_end;
};

#ifdef CONFIG_CALL_THUNKS
extern void callthunks_patch_builtin_calls(void);
extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
                                          struct module *mod);
extern void *callthunks_translate_call_dest(void *dest);
extern int x86_call_depth_emit_accounting(u8 **pprog, void *func, void *ip);
#else
static __always_inline void callthunks_patch_builtin_calls(void) {}
static __always_inline void
callthunks_patch_module_calls(struct callthunk_sites *sites,
                              struct module *mod) {}
static __always_inline void *callthunks_translate_call_dest(void *dest)
{
        return dest;
}
static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
                                                          void *func, void *ip)
{
        return 0;
}
#endif

#ifdef CONFIG_MITIGATION_ITS
extern void its_init_mod(struct module *mod);
extern void its_fini_mod(struct module *mod);
extern void its_free_mod(struct module *mod);
extern u8 *its_static_thunk(int reg);
#else /* CONFIG_MITIGATION_ITS */
static inline void its_init_mod(struct module *mod) { }
static inline void its_fini_mod(struct module *mod) { }
static inline void its_free_mod(struct module *mod) { }
static inline u8 *its_static_thunk(int reg)
{
        WARN_ONCE(1, "ITS not compiled in");

        return NULL;
}
#endif

#if defined(CONFIG_MITIGATION_RETHUNK) && defined(CONFIG_OBJTOOL)
extern bool cpu_wants_rethunk(void);
extern bool cpu_wants_rethunk_at(void *addr);
#else
static __always_inline bool cpu_wants_rethunk(void)
{
        return false;
}
static __always_inline bool cpu_wants_rethunk_at(void *addr)
{
        return false;
}
#endif

#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 ALT_CALL_INSTR          "call BUG_func"

#define alt_slen                "772b-771b"
#define alt_total_slen          "773b-771b"
#define alt_rlen                "775f-774f"

#define OLDINSTR(oldinstr)                                              \
        "# ALT: oldinstr\n"                                             \
        "771:\n\t" oldinstr "\n772:\n"                                  \
        "# ALT: padding\n"                                              \
        ".skip -(((" alt_rlen ")-(" alt_slen ")) > 0) * "               \
                "((" alt_rlen ")-(" alt_slen ")),0x90\n"                \
        "773:\n"

#define ALTINSTR_ENTRY(ft_flags)                                              \
        ".pushsection .altinstructions, \"aM\", @progbits, "                  \
                      __stringify(ALT_INSTR_SIZE) "\n"                        \
        " .long 771b - .\n"                             /* label           */ \
        " .long 774f - .\n"                             /* new instruction */ \
        " .4byte " __stringify(ft_flags) "\n"           /* feature + flags */ \
        " .byte " alt_total_slen "\n"                   /* source len      */ \
        " .byte " alt_rlen "\n"                         /* replacement len */ \
        ".popsection\n"

#define ALTINSTR_REPLACEMENT(newinstr)          /* replacement */       \
        ".pushsection .altinstr_replacement, \"ax\"\n"                  \
        ANNOTATE_DATA_SPECIAL "\n"                                      \
        "# ALT: replacement\n"                                          \
        "774:\n\t" newinstr "\n775:\n"                                  \
        ".popsection\n"

/* alternative assembly primitive: */
#define ALTERNATIVE(oldinstr, newinstr, ft_flags)                       \
        OLDINSTR(oldinstr)                                              \
        ALTINSTR_ENTRY(ft_flags)                                        \
        ALTINSTR_REPLACEMENT(newinstr)

#define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
        ALTERNATIVE(ALTERNATIVE(oldinstr, newinstr1, ft_flags1), newinstr2, ft_flags2)

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

#define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \
                        newinstr3, ft_flags3)                           \
        ALTERNATIVE(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \
                      newinstr3, ft_flags3)

/*
 * 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, ft_flags)                       \
        asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")

#define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
        asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "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, ft_flags, input...)       \
        asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \
                : : "i" (0), ## input)

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

/*
 * Like alternative_io, but for replacing a direct call with another one.
 *
 * Use the %c operand modifier which is the generic way to print a bare
 * constant expression with all syntax-specific punctuation omitted. %P
 * is the x86-specific variant which can handle constants too, for
 * historical reasons, but it should be used primarily for PIC
 * references: i.e., if used for a function, it would add the PLT
 * suffix.
 */
#define alternative_call(oldfunc, newfunc, ft_flags, output, input, clobbers...)        \
        asm_inline volatile(ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags)       \
                : ALT_OUTPUT_SP(output)                                                 \
                : [old] "i" (oldfunc), [new] "i" (newfunc)                              \
                  COMMA(input)                                                          \
                : clobbers)

/*
 * 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, ft_flags1, newfunc2, ft_flags2,           \
                           output, input, clobbers...)                                  \
        asm_inline volatile(ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1,   \
                "call %c[new2]", ft_flags2)                                             \
                : ALT_OUTPUT_SP(output)                                                 \
                : [old] "i" (oldfunc), [new1] "i" (newfunc1),                           \
                  [new2] "i" (newfunc2)                                                 \
                  COMMA(input)                                                          \
                : clobbers)

#define ALT_OUTPUT_SP(...) ASM_CALL_CONSTRAINT, ## __VA_ARGS__

/* Macro for creating assembler functions avoiding any C magic. */
#define DEFINE_ASM_FUNC(func, instr, sec)               \
        asm (".pushsection " #sec ", \"ax\"\n"          \
             ".global " #func "\n\t"                    \
             ".type " #func ", @function\n\t"           \
             ASM_FUNC_ALIGN "\n"                        \
             #func ":\n\t"                              \
             ASM_ENDBR                                  \
             instr "\n\t"                               \
             ASM_RET                                    \
             ".size " #func ", . - " #func "\n\t"       \
             ".popsection")

void BUG_func(void);
void nop_func(void);

#else /* __ASSEMBLER__ */

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

/*
 * 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 altinstr_entry orig alt ft_flags orig_len alt_len
        .long \orig - .
        .long \alt - .
        .4byte \ft_flags
        .byte \orig_len
        .byte \alt_len
.endm

.macro ALT_CALL_INSTR
        call BUG_func
.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.
 */
#define __ALTERNATIVE(oldinst, newinst, flag)                           \
740:                                                                    \
        oldinst ;                                                       \
741:                                                                    \
        .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;\
742:                                                                    \
        .pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE ;\
        altinstr_entry 740b,743f,flag,742b-740b,744f-743f ;             \
        .popsection ;                                                   \
        .pushsection .altinstr_replacement,"ax" ;                       \
743:                                                                    \
        ANNOTATE_DATA_SPECIAL ;                                         \
        newinst ;                                                       \
744:                                                                    \
        .popsection ;

.macro ALTERNATIVE oldinstr, newinstr, ft_flags
        __ALTERNATIVE(\oldinstr, \newinstr, \ft_flags)
.endm

/*
 * 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, ft_flags1, newinstr2, ft_flags2
        __ALTERNATIVE(__ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1),
                      \newinstr2, \ft_flags2)
.endm

.macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
        __ALTERNATIVE(ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2),
                      \newinstr3, \ft_flags3)
.endm

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

#endif /* __ASSEMBLER__ */

#endif /* _ASM_X86_ALTERNATIVE_H */