From 883d68803d17d6f64cdabf2c8ef846345e2d0094 Mon Sep 17 00:00:00 2001
From: Julien Lepiller <julien@lepiller.eu>
Date: Sun, 19 Feb 2023 10:20:19 +0100
Subject: [PATCH] Dynamically allocate the alternate signal stack.

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

diff --git a/ocaml-src/asmrun/signals_asm.c b/ocaml-src/asmrun/signals_asm.c
index 3895d75..d37b481 100644
--- a/ocaml-src/asmrun/signals_asm.c
+++ b/ocaml-src/asmrun/signals_asm.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=dc2df5b86942e70c4d9f24533f6609153e9b2889'>root</a>/<a href='/guix/log/tests?id=dc2df5b86942e70c4d9f24533f6609153e9b2889'>tests</a>/<a href='/guix/log/tests/cve-sample.json?id=dc2df5b86942e70c4d9f24533f6609153e9b2889'>cve-sample.json</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/tests/cve-sample.json?id=dc2df5b86942e70c4d9f24533f6609153e9b2889&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-12-21 17:47:35 +0100'>2020-12-21</span></td><td><a href='/guix/commit/tests/cve-sample.json?id=9608f4003dedd8dfe99327c15668ca1a43ebd93b'>tests: Fix malformed JSON.</a><span class='msg-avail'>...<span class='msg-tooltip'>Guile-JSON 4.3.2 would parse in spite of these typos, but 4.4.1 is
stricter.

* tests/swh.scm (%directory-entries): Add missing comma.
* tests/cve-sample.json: Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
ssues.guix.gnu.org/55521&gt;.

* guix/scripts/shell.scm (export-manifest): When computing 'manifest',
honor the 'profile key.
* tests/guix-shell-export-manifest.sh: Add test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-06-01 22:22:19 +0200'>2022-06-01</span></td><td><a href='/guix/commit/tests/guix-shell-export-manifest.sh?id=2acc83daa5a3dd1b4ed3f8c32ecadf1313e6fd18'>shell: '--export-manifest -D x -D y' generates a valid manifest.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/shell.scm (manifest-&gt;code*): Add missing 'list' in
generated 'concatenate-manifests' call.
* tests/guix-shell-export-manifest.sh: Add test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-04-08 18:14:35 +0200'>2022-04-08</span></td><td><a href='/guix/commit/tests/guix-shell-export-manifest.sh?id=20691c70cf2c5a61af7f906b65d57a524ecfc4f3'>tests: 'guix shell --export-manifest' test no longer needs networking.</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/guix-shell-export-manifest.sh: Use '--with-input' rather than
'--with-latest' as the latter would crash in the absence of network
access.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-04-04 22:58:04 +0200'>2022-04-04</span></td><td><a href='/guix/commit/tests/guix-shell-export-manifest.sh?id=c42b7baf13c7633b4512e94da7445299c57b247d'>shell: Add '--export-manifest'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/shell.scm (show-help, %options): Add '--export-manifest'.
(manifest-entry-version-prefix, manifest-&gt;code*)
(export-manifest): New procedures.
(guix-shell): Honor '--export-manifest'.
* tests/guix-shell-export-manifest.sh: New file.
* Makefile.am (SH_TESTS): Add it.
* doc/guix.texi (Invoking guix shell): Document '--export-manifest'.
(Invoking guix environment): Link to it.
(Invoking guix pack): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>