std.os.linux: fallback to pagesize when MMAP2_UNIT isn't comptime known

Author: sweiglbosker

lib/std/os/linux.zig

@@ -907,7 +907,7 @@ pub fn mmap(address: ?[*]u8, length: usize, prot: usize, flags: MAP, fd: i32, of
             prot,
             @as(u32, @bitCast(flags)),
             @bitCast(@as(isize, fd)),
-            @truncate(@as(u64, @bitCast(offset)) / MMAP2_UNIT),
+            @truncate(@as(u64, @bitCast(offset)) / (MMAP2_UNIT orelse std.heap.pageSize())),
         );
     } else {
         // The s390x mmap() syscall existed before Linux supported syscalls with 5+ parameters, so

lib/std/os/linux/m68k.zig

@@ -286,7 +286,7 @@ pub const Elf_Symndx = u32;
 
 // m68k has multiple minimum page sizes.
 // glibc sets MMAP2_PAGE_UNIT to -1 so it is queried at runtime.
-pub const MMAP2_UNIT = -1;
+pub const MMAP2_UNIT = null;
 
 // glibc 112a0ae18b831bf31f44d81b82666980312511d6
 pub const VDSO = null;

lib/std/os/linux/tls.zig

@@ -539,7 +539,7 @@ inline fn mmap(address: ?[*]u8, length: usize, prot: usize, flags: linux.MAP, fd
             prot,
             @as(u32, @bitCast(flags)),
             @as(usize, @bitCast(@as(isize, fd))),
-            @as(usize, @truncate(@as(u64, @bitCast(offset)) / linux.MMAP2_UNIT)),
+            @as(usize, @truncate(@as(u64, @bitCast(offset)) / (linux.MMAP2_UNIT orelse std.heap.pageSize()))),
         });
     } else {
         // The s390x mmap() syscall existed before Linux supported syscalls with 5+ parameters, so