From 95f5016955e519c392c746e38e0c9460f2c1aa0c Mon Sep 17 00:00:00 2001
From: Julien Lepiller <julien@lepiller.eu>
Date: Sun, 19 Feb 2023 09:58:57 +0100
Subject: [PATCH] Dynamically allocate the alternate signal stack.

This patch is a backport of https://github.com/ocaml/ocaml/pull/10266.
---
 runtime/signals_nat.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/runtime/signals_nat.c b/runtime/signals_nat.c
index 29a5f49..a193fc2 100644
--- a/runtime/signals_nat.c
+++ b/runtime/signals_nat.c
@@ -182,7 +182,6 @@ DECLARE_SIGNAL_HANDLER(trap_handler)
 #ifdef HAS_STACK_OVERFLOW_DETECTION
 
 static char * system_stack_top;
-static char sig_alt_stack[SIGSTKSZ];
 
 #if defined(SYS_linux)
 /* PR#4746: recent Linux kernels with support for stack randomization
@@ -274,15 +273,19 @@ void caml_init_signals(void)
 #ifdef HAS_STACK_OVERFLOW_DETECTION
   {
     stack_t stk;
-    struct sigaction act;
-    stk.ss_sp = sig_alt_stack;
+    stk.ss_sp = malloc(SIGSTKSZ);
     stk.ss_size = SIGSTKSZ;
     stk.ss_flags = 0;
-    SET_SIGACT(act, segv_handler);
-    act.sa_flags |= SA_ONSTACK | SA_NODEFER;
-    sigemptyset(&act.sa_mask);
-    system_stack_top = (char *) &act;
-    if (sigaltstack(&stk, NULL) == 0) { sigaction(SIGSEGV, &act, NULL); }
+    if (stk.ss_sp != NULL) {
+      if (sigaltstack(&stk, NULL) != -1) {
+        struct sigaction act;
+        SET_SIGACT(act, segv_handler);
+        act.sa_flags |= SA_ONSTACK | SA_NODEFER;
+        sigemptyset(&act.sa_mask);
+        system_stack_top = (char *) &act;
+        sigaction(SIGSEGV, &act, NULL);
+      }
+    }
   }
 #endif
 }
-- 
2.38.1

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<div class='path'>path: <a href='/guix/log/?id=5721c0f03de384e59504f4083ca73315b3ea6b34'>root</a>/<a href='/guix/log/bootstrap?id=5721c0f03de384e59504f4083ca73315b3ea6b34'>bootstrap</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/bootstrap?id=5721c0f03de384e59504f4083ca73315b3ea6b34&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-02-17 11:49:08 +0100'>2020-02-17</span></td><td><a href='/guix/commit/bootstrap?id=3dd311e3a059131ef245417106d4fb659222ef3c'>bootstrap: Fix typo.</a><span class='msg-avail'>...<span class='msg-tooltip'>* bootstrap: Substitute ‘guix-cookbook’ for copy/pasted ‘guix-manual’.

Reported-by: jetomit on #guix
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-09-18 11:38:14 +0200'>2019-09-18</span></td><td><a href='/guix/commit/bootstrap?id=7bc46ecc34ceb042ff890e5d306d0a2a736e891d'>doc: Add Guix Cookbook.</a><span class='msg-avail'>...<span class='msg-tooltip'>* .gitignore: Update ignore list.
* Makefile.am (assert-no-store-file-names): Exclude the cookbook.
* bootstrap: Generate po files for cookbook translations.
* doc/guix-cookbook.texi: New file.
* doc/local.mk (info_TEXINFOS): Add it; add a rule to build cookbook
translations.
* po/doc/local.mk (DOC_COOKBOOK_PO_FILES): New variable.
(EXTRA_DIST): Add cookbook pot file and po files.
(doc-po-update-cookbook-%): New target.
(doc-pot-update): Also update cookbook pot file.
(doc-po-update): Also update cookbook po files.
</span></span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2019-04-26 11:21:32 +0200'>2019-04-26</span></td><td><a href='/guix/commit/bootstrap?id=9ca5ff882e2ac4eaab02eb0fde545bd784af478b'>bootstrap: Break automake dependency on generated files.</a><span class='msg-avail'>...<span class='msg-tooltip'>* bootstrap: Generate stub files for the manual translations whose
generated files are not included in the VCS.
* doc/contributing.de.texi: Remove file.
* doc/contributing.es.texi: Remove file.
* doc/contributing.fr.texi: Remove file.
* doc/contributing.zh_CN.texi: Remove file.
* doc/guix.de.texi: Remove file.
* doc/guix.es.texi: Remove file.
* doc/guix.fr.texi: Remove file.
* doc/guix.zh_CN.texi: Remove file.
* .gitignore: Add them.

Signed-off-by: Julien Lepiller &lt;julien@lepiller.eu&gt;
</span></span></td><td>Miguel Ángel Arruga Vivas</td></tr>