From 70fd6b3b230f58782a196b1075513a24f2376077 Mon Sep 17 00:00:00 2001
From: Sergey Bugaev <bugaevc@gmail.com>
Date: Wed, 17 May 2023 22:14:34 +0300
Subject: hurd: Fix setting up pthreads

On x86_64, we have to pass function arguments in registers, not on the
stack. We also have to align the stack pointer in a specific way. Since
sharing the logic with i386 does not bring much benefit, split the file
back into i386- and x86_64-specific versions, and fix the x86_64 version
to set up the thread properly.

Bonus: i386 keeps doing the extra RPC inside __thread_set_pcsptp to
fetch the state of the thread before setting it; but x86_64 no lnoger
does that.

Checked on x86_64-gnu and i686-gnu.

Fixes be6d002ca277ffc90058d382396150cb0e785b9c
"hurd: Set up the basic tree for x86_64-gnu"

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230517191436.73636-9-bugaevc@gmail.com>
---
 sysdeps/mach/hurd/i386/htl/pt-setup.c | 100 ++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 sysdeps/mach/hurd/i386/htl/pt-setup.c

(limited to 'sysdeps/mach/hurd/i386/htl')

diff --git a/sysdeps/mach/hurd/i386/htl/pt-setup.c b/sysdeps/mach/hurd/i386/htl/pt-setup.c
new file mode 100644
index 0000000000..ba108b9611
--- /dev/null
+++ b/sysdeps/mach/hurd/i386/htl/pt-setup.c
@@ -0,0 +1,100 @@
+/* Setup thread stack.  Hurd/i386 version.
+   Copyright (C) 2000-2023 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/>.  */
+
+#include <stdint.h>
+#include <assert.h>
+#include <mach.h>
+#include <hurd.h>
+
+#include <pt-internal.h>
+
+/* The stack layout used on the x86 is:
+
+    -----------------
+   |  ARG            |
+    -----------------
+   |  START_ROUTINE  |
+    -----------------
+   |  0              |
+    -----------------
+ */
+
+/* Set up the stack for THREAD, such that it appears as if
+   START_ROUTINE and ARG were passed to the new thread's entry-point.
+   Return the stack pointer for the new thread.  */
+static void *
+stack_setup (struct __pthread *thread,
+	     void *(*start_routine) (void *), void *arg)
+{
+  error_t err;
+  uintptr_t *bottom, *top;
+
+  /* Calculate the top of the new stack.  */
+  bottom = thread->stackaddr;
+  top = (uintptr_t *) ((uintptr_t) bottom + thread->stacksize
+		       + ((thread->guardsize + __vm_page_size - 1)
+			  / __vm_page_size) * __vm_page_size);
+
+  if (start_routine != NULL)
+    {
+      /* And then the call frame.  */
+      top -= 3;
+      top = (uintptr_t *) ((uintptr_t) top & ~0xf);
+      top[2] = (uintptr_t) arg;	/* Argument to START_ROUTINE.  */
+      top[1] = (uintptr_t) start_routine;
+      top[0] = (uintptr_t) thread;
+      *--top = 0;		/* Fake return address.  */
+    }
+
+  if (thread->guardsize)
+    {
+      err = __vm_protect (__mach_task_self (), (vm_address_t) bottom,
+			  thread->guardsize, 0, 0);
+      assert_perror (err);
+    }
+
+  return top;
+}
+
+int
+__pthread_setup (struct __pthread *thread,
+		 void (*entry_point) (struct __pthread *, void *(*)(void *),
+				      void *), void *(*start_routine) (void *),
+		 void *arg)
+{
+  error_t err;
+
+  if (thread->kernel_thread == hurd_thread_self ())
+    /* Fix up the TCB for the main thread.  The C library has already
+       installed a TCB, which we want to keep using.  This TCB must not
+       be freed so don't register it in the thread structure.  On the
+       other hand, it's not yet possible to reliably release a TCB.
+       Leave the unused one registered so that it doesn't leak.  */
+    return 0;
+
+  thread->mcontext.pc = entry_point;
+  thread->mcontext.sp = stack_setup (thread, start_routine, arg);
+
+  err = __thread_set_pcsptp (thread->kernel_thread,
+			     1, thread->mcontext.pc,
+			     1, thread->mcontext.sp,
+			     1, thread->tcb);
+  assert_perror (err);
+
+  return 0;
+}
-- 
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