[sanitizer] [SystemZ] Implement internal_mmap.

[• koriakin]

Summary

mmap on s390 is quite a special snowflake: since it has too many
parameters to pass them in registers, it passes a pointer to a struct
with all the parameters instead.

This is for PR23433.

[aizatsky]

lgtm

compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc

 #include "sanitizer_syscall_linux_aarch64.inc"
 #else
 #include "sanitizer_syscall_generic.inc"
 #endif
 
 // --------------- sanitizer_libc.h
 uptr internal_mmap(void *addr, uptr length, int prot, int flags, int fd,
                    OFF_T offset) {
-#if SANITIZER_FREEBSD || SANITIZER_LINUX_USES_64BIT_SYSCALLS
+#ifdef __s390__
+  struct s390_mmap_params {
+    unsigned long addr;
+    unsigned long length;
+    unsigned long prot;
+    unsigned long flags;
+    unsigned long fd;
+    unsigned long offset;
+  } params = {
+    (unsigned long)addr,
+    (unsigned long)length,
+    (unsigned long)prot,
+    (unsigned long)flags,
+    (unsigned long)fd,
+# ifdef __s390x__
+    (unsigned long)offset,
+# else
+    (unsigned long)(offset / 4096),
+# endif
+  };
+# ifdef __s390x__
+  return internal_syscall(SYSCALL(mmap), &params);
+# else
+  return internal_syscall(SYSCALL(mmap2), &params);
+# endif
+#elif SANITIZER_FREEBSD || SANITIZER_LINUX_USES_64BIT_SYSCALLS
   return internal_syscall(SYSCALL(mmap), (uptr)addr, length, prot, flags, fd,
                           offset);
 #else
   // mmap2 specifies file offset in 4096-byte units.
   CHECK(IsAligned(offset, 4096));
   return internal_syscall(SYSCALL(mmap2), addr, length, prot, flags, fd,
                           offset / 4096);
 #endif