From 952b9009e8a2faf22b7614481d42e9801edf6804 Mon Sep 17 00:00:00 2001
From: Justine Tunney <jtunney@gmail.com>
Date: Wed, 8 May 2024 01:00:58 -0700
Subject: [PATCH] Avoid crash looping on AARCH64

---
 libc/intrin/feenableexcept.c | 15 ++++++---------
 libc/log/oncrash_arm64.c     |  2 ++
 libc/runtime/enable_tls.c    |  4 ++--
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/libc/intrin/feenableexcept.c b/libc/intrin/feenableexcept.c
index 503dee61a..bbf79ad7c 100644
--- a/libc/intrin/feenableexcept.c
+++ b/libc/intrin/feenableexcept.c
@@ -78,17 +78,14 @@ int feenableexcept(int excepts) {
 
 #elif defined(__aarch64__)
 
-  unsigned fpcr;
-  unsigned fpcr2;
-  unsigned updated_fpcr;
-  fpcr = __builtin_aarch64_get_fpcr();
-  fpcr2 = fpcr | (excepts << 8);
+  unsigned fpcr = __builtin_aarch64_get_fpcr();
+  unsigned want = excepts << 8;
+  unsigned fpcr2 = fpcr | want;
   if (fpcr != fpcr2) {
     __builtin_aarch64_set_fpcr(fpcr2);
-    // floating point exception trapping is optional in aarch64
-    updated_fpcr = __builtin_aarch64_get_fpsr();
-    if (fpcr2 & ~updated_fpcr)
-      return -1;
+    fpcr2 = __builtin_aarch64_get_fpsr();
+    if ((fpcr2 & want) != want)
+      return -1;  // not supported by cpu
   }
   return (fpcr >> 8) & FE_ALL_EXCEPT;
 
diff --git a/libc/log/oncrash_arm64.c b/libc/log/oncrash_arm64.c
index 2ab6d31a1..9229d6cf0 100644
--- a/libc/log/oncrash_arm64.c
+++ b/libc/log/oncrash_arm64.c
@@ -394,6 +394,8 @@ relegated void __oncrash(int sig, struct siginfo *si, void *arg) {
   BLOCK_CANCELATION;
   SpinLock(&lock);
   __oncrash_impl(sig, si, arg);
+  if (sig != SIGQUIT && sig != SIGTRAP)
+    _exit(1);
   SpinUnlock(&lock);
   ALLOW_CANCELATION;
 }
diff --git a/libc/runtime/enable_tls.c b/libc/runtime/enable_tls.c
index 045740baf..2be328cc1 100644
--- a/libc/runtime/enable_tls.c
+++ b/libc/runtime/enable_tls.c
@@ -68,13 +68,13 @@ static unsigned long ParseMask(const char *str) {
  *
  *                           __get_tls()
  *                               │
- *                              %fs Linux/BSDs
+ *                              %fs OpenBSD/NetBSD
  *            _Thread_local      │
  *     ┌───┬──────────┬──────────┼───┐
  *     │pad│  .tdata  │  .tbss   │tib│
  *     └───┴──────────┴──────────┼───┘
  *                               │
- *                  Windows/Mac %gs
+ *    Linux/FreeBSD/Windows/Mac %gs
  *
  * Here's the TLS memory layout on aarch64:
  *