hurd: Add getcontext, makecontext, setcontext, swapcontext

Adapted from the Linux x86 functions.

Not thoroughly tested, but manual testing as well as glibc tests look fine, and
manual -lpthread testing also looks fine (within the given bounds for a new
stack to be used with makecontext).

This has also been in use in Debian since 2013.

1 files changed, 74 insertions, 0 deletions

diff --git a/sysdeps/mach/hurd/i386/getcontext.S b/sysdeps/mach/hurd/i386/getcontext.S
new file mode 100644
index 0000000000..cad6762db2
--- /dev/null
+++ b/sysdeps/mach/hurd/i386/getcontext.S
@@ -0,0 +1,74 @@
+/* Save current context.
+   Copyright (C) 2001-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@redhat.com>, 2001.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+
+#include "ucontext_i.h"
+
+
+ENTRY(__getcontext)
+	/* Load address of the context data structure.  */
+	movl	4(%esp), %eax
+
+	/* Return value of getcontext.  EAX is the only register whose
+	   value is not preserved.  */
+	movl	$0, oEAX(%eax)
+
+	/* Save the 32-bit register values and the return address.  */
+	movl	%ecx, oECX(%eax)
+	movl	%edx, oEDX(%eax)
+	movl	%edi, oEDI(%eax)
+	movl	%esi, oESI(%eax)
+	movl	%ebp, oEBP(%eax)
+	movl	(%esp), %ecx
+	movl	%ecx, oEIP(%eax)
+	leal	4(%esp), %ecx		/* Exclude the return address.  */
+	movl	%ecx, oESP(%eax)
+	movl	%ebx, oEBX(%eax)
+
+	/* Save the FS segment register.  We don't touch the GS register
+	   since it is used for threads.  */
+	xorl	%edx, %edx
+	movw	%fs, %dx
+	movl	%edx, oFS(%eax)
+
+	leal	oFPREGS(%eax), %ecx
+	/* Save the floating-point context.  */
+	fnstenv	(%ecx)
+	/* And load it right back since the processor changes the mask.
+	   Intel thought this opcode to be used in interrupt handlers which
+	   would block all exceptions.  */
+	fldenv	(%ecx)
+
+	/* Save the current signal mask.  */
+	subl	$12, %esp
+	cfi_adjust_cfa_offset (12)
+	leal	oSIGMASK(%eax), %eax
+	movl	%eax, 8(%esp)
+	movl	$0, 4(%esp)
+	movl	$SIG_BLOCK, (%esp)
+	call	HIDDEN_JUMPTARGET (__sigprocmask)
+	addl	$12, %esp
+	cfi_adjust_cfa_offset (-12)
+	/* Propagate %eax (and errno, in case).  */
+
+	ret
+PSEUDO_END(__getcontext)
+
+weak_alias (__getcontext, getcontext)