feat: extend alarmdefault and argecho

user/crt.S

@@ -2,6 +2,11 @@
 .global _start
 _start:
     xorq %rbp, %rbp
+    /* Real x86_64 SysV process entry: rsp points at argc, with argv[0..]
+       and a NULL terminator right above it (elfBuildInitialStack,
+       elf.c/syscall.c doExec/doSpawn, kmain.c spawnUser). */
+    movq (%rsp), %rdi
+    leaq 8(%rsp), %rsi
     call main
     movq %rax, %rdi
     movq $0, %rax