Update posix_mapping.h

Author: MacroModel

include/fast_io_hosted/platforms/posix_mapping.h

@@ -11,6 +11,36 @@ namespace details
 inline ::std::byte *sys_mmap(void *addr, ::std::size_t len, int prot, int flags, int fd, ::std::uintmax_t offset)
 {
 #if defined(__linux__) && defined(__NR_mmap) && !defined(__NR_mmap2)
+#if defined(__s390__) || defined(__s390x__)
+    // s390 __NR_mmap is the old single-argument entry; pass the kernel's mmap argument block.
+    struct s390_mmap_arg_struct
+    {
+        unsigned long addr;
+        unsigned long len;
+        unsigned long prot;
+        unsigned long flags;
+        unsigned long fd;
+        unsigned long offset;
+    };
+
+    if constexpr (sizeof(::std::uintmax_t) > sizeof(unsigned long))
+    {
+        if (offset > static_cast<::std::uintmax_t>(::std::numeric_limits<unsigned long>::max()))
+        {
+            throw_posix_error(EINVAL);
+        }
+    }
+    s390_mmap_arg_struct args{
+        reinterpret_cast<unsigned long>(addr),
+        static_cast<unsigned long>(len),
+        static_cast<unsigned long>(prot),
+        static_cast<unsigned long>(flags),
+        static_cast<unsigned long>(fd),
+        static_cast<unsigned long>(offset)};
+    ::std::ptrdiff_t ret{system_call<__NR_mmap, ::std::ptrdiff_t>(__builtin_addressof(args))};
+    system_call_throw_error(ret);
+    return reinterpret_cast<::std::byte *>(static_cast<::std::uintptr_t>(ret));
+#else
     if constexpr (sizeof(::std::uintmax_t) > sizeof(off_t))
     {
         if (offset > static_cast<::std::uintmax_t>(::std::numeric_limits<off_t>::max()))
@@ -21,6 +51,7 @@ inline ::std::byte *sys_mmap(void *addr, ::std::size_t len, int prot, int flags,
     ::std::ptrdiff_t ret{system_call<__NR_mmap, ::std::ptrdiff_t>(addr, len, prot, flags, fd, offset)};
     system_call_throw_error(ret);
     return reinterpret_cast<::std::byte *>(static_cast<::std::uintptr_t>(ret));
+#endif
 #elif defined(HAVE_MMAP64)
 	if constexpr (sizeof(::std::uintmax_t) > sizeof(off64_t))
 	{