From 41b3e8b9893a8561af7e85ca98444bc284b4013d Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@swtch.com>
Date: Sun, 19 Jan 2020 22:39:22 -0500
Subject: libthread: use consistent stack calculation code in makecontext

Also reduce duplication: makecontext is per-arch not per-os-arch.

May fix #353.
---
 src/libthread/386-ucontext.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 src/libthread/386-ucontext.c

(limited to 'src/libthread/386-ucontext.c')

diff --git a/src/libthread/386-ucontext.c b/src/libthread/386-ucontext.c
new file mode 100644
index 00000000..3afa9513
--- /dev/null
+++ b/src/libthread/386-ucontext.c
@@ -0,0 +1,22 @@
+#include "threadimpl.h"
+
+void
+makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
+{
+	int *sp;
+
+	sp = USPALIGN(ucp, 4);
+	sp -= argc;
+	memmove(sp, &argc+1, argc*sizeof(int));
+	*--sp = 0;		/* return address */
+	ucp->uc_mcontext.mc_eip = (long)func;
+	ucp->uc_mcontext.mc_esp = (int)sp;
+}
+
+int
+swapcontext(ucontext_t *oucp, ucontext_t *ucp)
+{
+	if(getcontext(oucp) == 0)
+		setcontext(ucp);
+	return 0;
+}
-- 
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