mach: Add __mach_setup_thread_call ()

This is just like mach_setup_thread (), but it's suitable for making the
thread call a function correctly, as opposed to explicitly setting the
thread's stack and instruction pointers to the given values. Internally,
it uses MACHINE_THREAD_STATE_SETUP_CALL.

Unlike mach_setup_thread (), which is exported via mach.h for the
benefit of the Hurd exec server, __mach_setup_thread_call () is private
to glibc for the time being.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230517191436.73636-5-bugaevc@gmail.com>

mach/mach.h

@@ -88,7 +88,11 @@ extern FILE *mach_open_devstream (mach_port_t device_port, const char *mode);
    If STACK_BASE is not null it is filled in with the chosen stack base.
    If STACK_SIZE is not null it is filled in with the chosen stack size.
    Regardless, an extra page of red zone is allocated off the end; this
-   is not included in *STACK_SIZE.  */
+   is not included in *STACK_SIZE.
+
+   Mote: this function is unsuitable for setting up the thread to call a
+   function at PC, since the architecture ABI may impose additional
+   requirements beyond setting PC and stack.  */
 kern_return_t __mach_setup_thread (task_t task, thread_t thread, void *pc,
 				   vm_address_t *stack_base,
 				   vm_size_t *stack_size);

mach/setup-thread.c

@@ -16,6 +16,7 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <mach.h>
+#include <mach/setup-thread.h>
 #include <thread_state.h>
 #include <string.h>
 #include <mach/machine/vm_param.h>
@@ -24,6 +25,58 @@
 
 #define	STACK_SIZE	(16 * 1024 * 1024) /* 16MB, arbitrary.  */
 
+static kern_return_t
+mach_setup_thread_impl (task_t task, thread_t thread, int is_call,
+			void *pc, vm_address_t *stack_base,
+			vm_size_t *stack_size)
+{
+  kern_return_t error;
+  struct machine_thread_state ts;
+  mach_msg_type_number_t tssize = MACHINE_THREAD_STATE_COUNT;
+  vm_address_t stack;
+  vm_size_t size;
+  int anywhere;
+
+  memset (&ts, 0, sizeof (ts));
+
+  size = stack_size ? *stack_size ? : STACK_SIZE : STACK_SIZE;
+  stack = stack_base ? *stack_base ? : 0 : 0;
+  anywhere = !stack_base || !*stack_base;
+
+  error = __vm_allocate (task, &stack, size + __vm_page_size, anywhere);
+  if (error)
+    return error;
+
+  if (stack_size)
+    *stack_size = size;
+
+#ifdef STACK_GROWTH_DOWN
+  if (stack_base)
+    *stack_base = stack + __vm_page_size;
+#elif defined (STACK_GROWTH_UP)
+  if (stack_base)
+    *stack_base = stack;
+  stack += size;
+#else
+  #error stack direction unknown
+#endif
+
+  if (is_call)
+    MACHINE_THREAD_STATE_SETUP_CALL (&ts, *stack_base, size, pc);
+  else
+    {
+      MACHINE_THREAD_STATE_SET_PC (&ts, pc);
+      MACHINE_THREAD_STATE_SET_SP (&ts, *stack_base, size);
+    }
+
+  /* Create the red zone.  */
+  if (error = __vm_protect (task, stack, __vm_page_size, 0, VM_PROT_NONE))
+    return error;
+
+  return __thread_set_state (thread, MACHINE_NEW_THREAD_STATE_FLAVOR,
+			     (natural_t *) &ts, tssize);
+}
+
 /* Give THREAD a stack and set it to run at PC when resumed.
    If *STACK_SIZE is nonzero, that size of stack is allocated.
    If *STACK_BASE is nonzero, that stack location is used.
@@ -36,49 +89,18 @@ kern_return_t
 __mach_setup_thread (task_t task, thread_t thread, void *pc,
 		     vm_address_t *stack_base, vm_size_t *stack_size)
 {
-  kern_return_t error;
+  return mach_setup_thread_impl (task, thread, 0, pc, stack_base, stack_size);
-  struct machine_thread_state ts;
-  mach_msg_type_number_t tssize = MACHINE_THREAD_STATE_COUNT;
-  vm_address_t stack;
-  vm_size_t size;
-  int anywhere;
-
-  size = stack_size ? *stack_size ? : STACK_SIZE : STACK_SIZE;
-  stack = stack_base ? *stack_base ? : 0 : 0;
-  anywhere = !stack_base || !*stack_base;
-
-  error = __vm_allocate (task, &stack, size + __vm_page_size, anywhere);
-  if (error)
-    return error;
-
-  if (stack_size)
-    *stack_size = size;
-
-  memset (&ts, 0, sizeof (ts));
-  MACHINE_THREAD_STATE_SET_PC (&ts, pc);
-#ifdef STACK_GROWTH_DOWN
-  if (stack_base)
-    *stack_base = stack + __vm_page_size;
-  ts.SP = stack + __vm_page_size + size;
-#elif defined (STACK_GROWTH_UP)
-  if (stack_base)
-    *stack_base = stack;
-  ts.SP = stack;
-  stack += size;
-#else
-  #error stack direction unknown
-#endif
-
-  /* Create the red zone.  */
-  if (error = __vm_protect (task, stack, __vm_page_size, 0, VM_PROT_NONE))
-    return error;
-
-  return __thread_set_state (thread, MACHINE_NEW_THREAD_STATE_FLAVOR,
-			     (natural_t *) &ts, tssize);
 }
 
 weak_alias (__mach_setup_thread, mach_setup_thread)
 
+kern_return_t
+__mach_setup_thread_call (task_t task, thread_t thread, void *pc,
+			  vm_address_t *stack_base, vm_size_t *stack_size)
+{
+  return mach_setup_thread_impl (task, thread, 1, pc, stack_base, stack_size);
+}
+
 /* Give THREAD a TLS area.  */
 kern_return_t
 __mach_setup_tls (thread_t thread)

mach/setup-thread.h

@@ -0,0 +1,32 @@
+/* Setup a Mach thread.
+   Copyright (C) 1993-2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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/>.  */
+
+#ifndef	_MACH_SETUP_THREAD_H
+
+#define	_MACH_SETUP_THREAD_H	1
+
+#include <mach.h>
+
+/* Like mach_setup_thread (), but suitable for setting up function
+   calls.  */
+kern_return_t __mach_setup_thread_call (task_t task, thread_t thread,
+					void *function,
+					vm_address_t *stack_base,
+					vm_size_t *stack_size);
+
+#endif	/* mach/setup-thread.h */