bcc: Use direct parameter assignment for syscall probe s390.

1. Commit fa697140f9a2 ("syscalls/x86: Use 'struct pt_regs' based
   syscall calling convention for 64-bit syscalls") changed the raw
   parameter passed to the syscall entry function from a list of
   parameters supplied in user space to a single `pt_regs *` parameter
   (ARCH_HAS_SYSCALL_WRAPPER)

2. But ARCH_HAS_SYSCALL_WRAPPER in s390 is not used for that purpose.
   See commit a18f03cd89e9 ("s390: autogenerate compat syscall
   wrappers")

3. Use direct parameter assignment assumption for s390 syscall probe
   instead.

Signed-off-by: Sumanth Korikkar <[email protected]>

Author: sumanthkorikkar

src/cc/frontends/clang/b_frontend_action.cc

@@ -726,7 +726,7 @@ void BTypeVisitor::rewriteFuncParam(FunctionDecl *D) {
     // it in case of "syscall__" for other architectures.
     if (strncmp(D->getName().str().c_str(), "syscall__", 9) == 0 ||
         strncmp(D->getName().str().c_str(), "kprobe____x64_sys_", 18) == 0) {
-      preamble += "#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER\n";
+      preamble += "#if defined(CONFIG_ARCH_HAS_SYSCALL_WRAPPER) && !defined(__s390x__)\n";
       genParamIndirectAssign(D, preamble, calling_conv_regs);
       preamble += "\n#else\n";
       genParamDirectAssign(D, preamble, calling_conv_regs);