From 1163f1377212c45c1d0bf43ae6028885f3b61f6c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C5=8Dshin?= <git@wholezero.org>
Date: Sun, 24 Dec 2023 17:29:33 -0500
Subject: [PATCH] cosmo2 receives os from loader

FreeBSD aarch64 now traps early rather than pretending to be Linux.
o/aarch64/examples/env.com still works on Linux and Xnu.
---
 libc/runtime/cosmo2.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/libc/runtime/cosmo2.c b/libc/runtime/cosmo2.c
index 57067b5ab..7b7569851 100644
--- a/libc/runtime/cosmo2.c
+++ b/libc/runtime/cosmo2.c
@@ -78,7 +78,8 @@ static const char *DecodeMagnum(const char *p, long *r) {
   return *r = x, p;
 }
 
-wontreturn textstartup void cosmo(long *sp, struct Syslib *m1, char *exename) {
+wontreturn textstartup void cosmo(long *sp, struct Syslib *m1, char *exename,
+                                  int os) {
 
   // get startup timestamp as early as possible
   // its used by --strace and also kprintf() %T
@@ -111,14 +112,26 @@ wontreturn textstartup void cosmo(long *sp, struct Syslib *m1, char *exename) {
   __program_executable_name = exename;
   program_invocation_name = argv[0];
   __oldstack = (intptr_t)sp;
+  if (os) {
+    hostos = os;
+  } else {
+    /* old loader */
+    if (SupportsXnu() && m1) {
+      hostos = _HOSTXNU;
+    } else if (SupportsLinux()) {
+      hostos = _HOSTLINUX;
+    } else {
+      notpossible;
+    }
+  }
 
-  // detect apple m1 environment
   const char *magnums;
-  if (SupportsXnu() && (__syslib = m1)) {
-    hostos = _HOSTXNU;
+  if (IsXnu()) {
+    if (!(__syslib = m1)) {
+      notpossible;
+    }
     magnums = syscon_xnu;
-  } else if (SupportsLinux()) {
-    hostos = _HOSTLINUX;
+  } else if (IsLinux()) {
     magnums = syscon_linux;
   } else {
     notpossible;
@@ -130,7 +143,7 @@ wontreturn textstartup void cosmo(long *sp, struct Syslib *m1, char *exename) {
   }
 
   // check system call abi compatibility
-  if (SupportsXnu() && __syslib && __syslib->__version < SYSLIB_VERSION) {
+  if (IsXnu() && __syslib->__version < SYSLIB_VERSION) {
     sys_write(2, "need newer ape loader\n", 22);
     _Exit(127);
   }