/* SPDX-License-Identifier: GPL-2.0 */
/*
 * syscall_wrapper.h - x86 specific wrappers to syscall definitions
 */

#ifndef _ASM_X86_SYSCALL_WRAPPER_H
#define _ASM_X86_SYSCALL_WRAPPER_H

#include <asm/ptrace.h>

extern long __x64_sys_ni_syscall(const struct pt_regs *regs);
extern long __ia32_sys_ni_syscall(const struct pt_regs *regs);

/*
 * Instead of the generic __SYSCALL_DEFINEx() definition, the x86 version takes
 * struct pt_regs *regs as the only argument of the syscall stub(s) named as:
 * __x64_sys_*()         - 64-bit native syscall
 * __ia32_sys_*()        - 32-bit native syscall or common compat syscall
 * __ia32_compat_sys_*() - 32-bit compat syscall
 * __x64_compat_sys_*()  - 64-bit X32 compat syscall
 *
 * The registers are decoded according to the ABI:
 * 64-bit: RDI, RSI, RDX, R10, R8, R9
 * 32-bit: EBX, ECX, EDX, ESI, EDI, EBP
 *
 * The stub then passes the decoded arguments to the __se_sys_*() wrapper to
 * perform sign-extension (omitted for zero-argument syscalls).  Finally the
 * arguments are passed to the __do_sys_*() function which is the actual
 * syscall.  These wrappers are marked as inline so the compiler can optimize
 * the functions where appropriate.
 *
 * Example assembly (slightly re-ordered for better readability):
 *
 * <__x64_sys_recv>:            <-- syscall with 4 parameters
 *      callq   <__fentry__>
 *
 *      mov     0x70(%rdi),%rdi <-- decode regs->di
 *      mov     0x68(%rdi),%rsi <-- decode regs->si
 *      mov     0x60(%rdi),%rdx <-- decode regs->dx
 *      mov     0x38(%rdi),%rcx <-- decode regs->r10
 *
 *      xor     %r9d,%r9d       <-- clear %r9
 *      xor     %r8d,%r8d       <-- clear %r8
 *
 *      callq   __sys_recvfrom  <-- do the actual work in __sys_recvfrom()
 *                                  which takes 6 arguments
 *
 *      cltq                    <-- extend return value to 64-bit
 *      retq                    <-- return
 *
 * This approach avoids leaking random user-provided register content down
 * the call chain.
 */

/* Mapping of registers to parameters for syscalls on x86-64 and x32 */
#define SC_X86_64_REGS_TO_ARGS(x, ...)                                  \
        __MAP(x,__SC_ARGS                                               \
                ,,regs->di,,regs->si,,regs->dx                          \
                ,,regs->r10,,regs->r8,,regs->r9)                        \


/* SYSCALL_PT_ARGS is Adapted from s390x */
#define SYSCALL_PT_ARG6(m, t1, t2, t3, t4, t5, t6)                      \
        SYSCALL_PT_ARG5(m, t1, t2, t3, t4, t5), m(t6, (regs->bp))
#define SYSCALL_PT_ARG5(m, t1, t2, t3, t4, t5)                          \
        SYSCALL_PT_ARG4(m, t1, t2, t3, t4),  m(t5, (regs->di))
#define SYSCALL_PT_ARG4(m, t1, t2, t3, t4)                              \
        SYSCALL_PT_ARG3(m, t1, t2, t3),  m(t4, (regs->si))
#define SYSCALL_PT_ARG3(m, t1, t2, t3)                                  \
        SYSCALL_PT_ARG2(m, t1, t2), m(t3, (regs->dx))
#define SYSCALL_PT_ARG2(m, t1, t2)                                      \
        SYSCALL_PT_ARG1(m, t1), m(t2, (regs->cx))
#define SYSCALL_PT_ARG1(m, t1) m(t1, (regs->bx))
#define SYSCALL_PT_ARGS(x, ...) SYSCALL_PT_ARG##x(__VA_ARGS__)

#define __SC_COMPAT_CAST(t, a)                                          \
        (__typeof(__builtin_choose_expr(__TYPE_IS_L(t), 0, 0U)))        \
        (unsigned int)a

/* Mapping of registers to parameters for syscalls on i386 */
#define SC_IA32_REGS_TO_ARGS(x, ...)                                    \
        SYSCALL_PT_ARGS(x, __SC_COMPAT_CAST,                            \
                        __MAP(x, __SC_TYPE, __VA_ARGS__))               \

#define __SYS_STUB0(abi, name)                                          \
        long __##abi##_##name(const struct pt_regs *regs);              \
        ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO);                 \
        long __##abi##_##name(const struct pt_regs *regs)               \
                __alias(__do_##name);

#define __SYS_STUBx(abi, name, ...)                                     \
        long __##abi##_##name(const struct pt_regs *regs);              \
        ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO);                 \
        long __##abi##_##name(const struct pt_regs *regs)               \
        {                                                               \
                return __se_##name(__VA_ARGS__);                        \
        }

#define __COND_SYSCALL(abi, name)                                       \
        __weak long __##abi##_##name(const struct pt_regs *__unused);   \
        __weak long __##abi##_##name(const struct pt_regs *__unused)    \
        {                                                               \
                return sys_ni_syscall();                                \
        }

#ifdef CONFIG_X86_64
#define __X64_SYS_STUB0(name)                                           \
        __SYS_STUB0(x64, sys_##name)

#define __X64_SYS_STUBx(x, name, ...)                                   \
        __SYS_STUBx(x64, sys##name,                                     \
                    SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))

#define __X64_COND_SYSCALL(name)                                        \
        __COND_SYSCALL(x64, sys_##name)

#else /* CONFIG_X86_64 */
#define __X64_SYS_STUB0(name)
#define __X64_SYS_STUBx(x, name, ...)
#define __X64_COND_SYSCALL(name)
#endif /* CONFIG_X86_64 */

#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
#define __IA32_SYS_STUB0(name)                                          \
        __SYS_STUB0(ia32, sys_##name)

#define __IA32_SYS_STUBx(x, name, ...)                                  \
        __SYS_STUBx(ia32, sys##name,                                    \
                    SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))

#define __IA32_COND_SYSCALL(name)                                       \
        __COND_SYSCALL(ia32, sys_##name)

#else /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
#define __IA32_SYS_STUB0(name)
#define __IA32_SYS_STUBx(x, name, ...)
#define __IA32_COND_SYSCALL(name)
#endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */

#ifdef CONFIG_IA32_EMULATION
/*
 * For IA32 emulation, we need to handle "compat" syscalls *and* create
 * additional wrappers (aptly named __ia32_sys_xyzzy) which decode the
 * ia32 regs in the proper order for shared or "common" syscalls. As some
 * syscalls may not be implemented, we need to expand COND_SYSCALL in
 * kernel/sys_ni.c to cover this case as well.
 */
#define __IA32_COMPAT_SYS_STUB0(name)                                   \
        __SYS_STUB0(ia32, compat_sys_##name)

#define __IA32_COMPAT_SYS_STUBx(x, name, ...)                           \
        __SYS_STUBx(ia32, compat_sys##name,                             \
                    SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))

#define __IA32_COMPAT_COND_SYSCALL(name)                                \
        __COND_SYSCALL(ia32, compat_sys_##name)

#else /* CONFIG_IA32_EMULATION */
#define __IA32_COMPAT_SYS_STUB0(name)
#define __IA32_COMPAT_SYS_STUBx(x, name, ...)
#define __IA32_COMPAT_COND_SYSCALL(name)
#endif /* CONFIG_IA32_EMULATION */


#ifdef CONFIG_X86_X32_ABI
/*
 * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware
 * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common
 * with x86_64 obviously do not need such care.
 */
#define __X32_COMPAT_SYS_STUB0(name)                                    \
        __SYS_STUB0(x64, compat_sys_##name)

#define __X32_COMPAT_SYS_STUBx(x, name, ...)                            \
        __SYS_STUBx(x64, compat_sys##name,                              \
                    SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))

#define __X32_COMPAT_COND_SYSCALL(name)                                 \
        __COND_SYSCALL(x64, compat_sys_##name)

#else /* CONFIG_X86_X32_ABI */
#define __X32_COMPAT_SYS_STUB0(name)
#define __X32_COMPAT_SYS_STUBx(x, name, ...)
#define __X32_COMPAT_COND_SYSCALL(name)
#endif /* CONFIG_X86_X32_ABI */


#ifdef CONFIG_COMPAT
/*
 * Compat means IA32_EMULATION and/or X86_X32. As they use a different
 * mapping of registers to parameters, we need to generate stubs for each
 * of them.
 */
#define COMPAT_SYSCALL_DEFINE0(name)                                    \
        static long                                                     \
        __do_compat_sys_##name(const struct pt_regs *__unused);         \
        __IA32_COMPAT_SYS_STUB0(name)                                   \
        __X32_COMPAT_SYS_STUB0(name)                                    \
        static long                                                     \
        __do_compat_sys_##name(const struct pt_regs *__unused)

#define COMPAT_SYSCALL_DEFINEx(x, name, ...)                                    \
        static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));      \
        static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
        __IA32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__)                           \
        __X32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__)                            \
        static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))       \
        {                                                                       \
                return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
        }                                                                       \
        static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))

/*
 * As some compat syscalls may not be implemented, we need to expand
 * COND_SYSCALL_COMPAT in kernel/sys_ni.c to cover this case as well.
 */
#define COND_SYSCALL_COMPAT(name)                                       \
        __IA32_COMPAT_COND_SYSCALL(name)                                \
        __X32_COMPAT_COND_SYSCALL(name)

#endif /* CONFIG_COMPAT */

#define __SYSCALL_DEFINEx(x, name, ...)                                 \
        static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));     \
        static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
        __X64_SYS_STUBx(x, name, __VA_ARGS__)                           \
        __IA32_SYS_STUBx(x, name, __VA_ARGS__)                          \
        static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))      \
        {                                                               \
                long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
                __MAP(x,__SC_TEST,__VA_ARGS__);                         \
                __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));       \
                return ret;                                             \
        }                                                               \
        static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))

/*
 * As the generic SYSCALL_DEFINE0() macro does not decode any parameters for
 * obvious reasons, and passing struct pt_regs *regs to it in %rdi does not
 * hurt, we only need to re-define it here to keep the naming congruent to
 * SYSCALL_DEFINEx() -- which is essential for the COND_SYSCALL() macro
 * to work correctly.
 */
#define SYSCALL_DEFINE0(sname)                                          \
        SYSCALL_METADATA(_##sname, 0);                                  \
        static long __do_sys_##sname(const struct pt_regs *__unused);   \
        __X64_SYS_STUB0(sname)                                          \
        __IA32_SYS_STUB0(sname)                                         \
        static long __do_sys_##sname(const struct pt_regs *__unused)

#define COND_SYSCALL(name)                                              \
        __X64_COND_SYSCALL(name)                                        \
        __IA32_COND_SYSCALL(name)


/*
 * For VSYSCALLS, we need to declare these three syscalls with the new
 * pt_regs-based calling convention for in-kernel use.
 */
long __x64_sys_getcpu(const struct pt_regs *regs);
long __x64_sys_gettimeofday(const struct pt_regs *regs);
long __x64_sys_time(const struct pt_regs *regs);

#endif /* _ASM_X86_SYSCALL_WRAPPER_H */