Linux/preinstalled_signal.cpp FAILs on Linux/sparc64

[rorth]

With ASan testing enabled on SPARC as per PR #107405, the

  AddressSanitizer-sparc-linux-dynamic :: TestCases/Linux/preinstalled_signal.cpp

test FAILs on Linux/sparc64. There are several issues here:

• The sparc layout of struct KernelSigaction/struct sigaction differs from other targets:`

@@ -34,6 +34,13 @@ struct KernelSigaction {
 #if defined(__mips__)
   unsigned long flags;
   __sighandler_t handler;
+#elif defined(__sparc__)
+  __sighandler_t handler;
+  __sigset_t mask;
+#  if __WORDSIZE == 64
+  int __glibc_reserved0;
+#  endif
+  int flags;
 #else
   __sighandler_t handler;
   unsigned long flags;

• When using syscall(__NR_rt_sigaction), the syscall returns EINVAL. As can be seen in glibc sysdeps/unix/sysv/linux/sparc/sparc{32,64}/libc_sigaction.c (STUB), the sparc version of the syscall takes an additional arg, however the stub functions passed there aren't exported from libc and thus cannot be used outside.
• When using sigaction instead, several assertions fail. The problem turns out to be that those sigaction calls trigger the interceptor, which again changes the order in which AsanInitInternal and Init are called.
• The same behaviour can be seen e.g. on Linux/i386 when using sigaction instead of syscall(__NR_rt_sigaction).

It seems the test relies heavily on the (undefined!?) relative execution order of AsanInitInternal and Init`, falling apart if that
changes for whatever reason.