[PATCH v2 14/20] hurd: Implement TLS on AArch64

[Sergey Bugaev <bugaevc@gmail.com>]

This is using TLS_DTV_AT_TP, aka "Variant I" layout. tpidr_el0, which is
both readable and writable from userspace, is used as the thread pointer.

We store our Hurd-specific data (sigstate and reply port) *before* the
TCB head, in a tcbprehead_t structure. This tcbprehead_t structure is
also what THREAD_SELF, THREAD_GETMEM, and THREAD_SETMEM macros access.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
---
 .../mach/hurd/aarch64/dl-tls-initialized.c    |  19 ++
 sysdeps/mach/hurd/aarch64/tls.h               | 206 ++++++++++++++++++
 2 files changed, 225 insertions(+)
 create mode 100644 sysdeps/mach/hurd/aarch64/dl-tls-initialized.c
 create mode 100644 sysdeps/mach/hurd/aarch64/tls.h

diff --git a/sysdeps/mach/hurd/aarch64/dl-tls-initialized.c b/sysdeps/mach/hurd/aarch64/dl-tls-initialized.c
new file mode 100644
index 00000000..9beafec3
--- /dev/null
+++ b/sysdeps/mach/hurd/aarch64/dl-tls-initialized.c
@@ -0,0 +1,19 @@
+/* Determine whether TLS is initialized, for AArch64/Hurd.
+   Copyright (C) 1995-2024 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/>.  */
+
+/* Nothing here, it's all handled in tls.h */
diff --git a/sysdeps/mach/hurd/aarch64/tls.h b/sysdeps/mach/hurd/aarch64/tls.h
new file mode 100644
index 00000000..712134e1
--- /dev/null
+++ b/sysdeps/mach/hurd/aarch64/tls.h
@@ -0,0 +1,206 @@
+/* Copyright (C) 2005-2024 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 _AARCH64_TLS_H
+#define _AARCH64_TLS_H	1
+
+/* Some things really need not be machine-dependent.  */
+#include <sysdeps/mach/hurd/tls.h>
+
+#include <dl-sysdep.h>
+
+#ifndef __ASSEMBLER__
+# include <assert.h>
+# include <stdbool.h>
+# include <stddef.h>
+# include <stdint.h>
+# include <dl-dtv.h>
+# include <errno.h>
+# include <thread_state.h>
+#endif /* __ASSEMBLER__ */
+
+#ifndef __ASSEMBLER__
+
+/* Get system call information.  */
+# include <sysdep.h>
+
+/* The TP points to the start of the thread blocks.  */
+# define TLS_DTV_AT_TP	1
+# define TLS_TCB_AT_TP	0
+
+typedef struct
+{
+  /* Used by the exception handling implementation in the dynamic loader.  */
+  struct rtld_catch *rtld_catch;
+
+  struct hurd_sigstate *_hurd_sigstate;
+  mach_port_t reply_port;      /* This thread's reply port.  */
+
+  int gscope_flag;
+} tcbprehead_t;
+
+typedef struct
+{
+  dtv_t *dtv;
+  void *private;
+} tcbhead_t;
+
+/* This is the size of the initial TCB.  */
+# define TLS_INIT_TCB_SIZE	sizeof (tcbhead_t)
+
+/* This is the size we need before TCB.  */
+# define TLS_PRE_TCB_SIZE	sizeof (tcbprehead_t)
+
+# define TCB_ALIGNMENT		64
+
+/* Install new dtv for current thread.  */
+# define INSTALL_NEW_DTV(dtv) \
+  (THREAD_DTV() = (dtv))
+
+/* Return the address of the dtv for the current thread.  */
+# define THREAD_DTV() \
+  (((tcbhead_t *) __builtin_thread_pointer ())->dtv)
+
+/* Return the thread descriptor for the current thread.  */
+# define THREAD_SELF \
+ ((tcbprehead_t *)__builtin_thread_pointer () - 1)
+
+/* Read member of the thread descriptor directly.  */
+# define THREAD_GETMEM(descr, member) \
+  ((descr)->member)
+
+/* Write member of the thread descriptor directly.  */
+# define THREAD_SETMEM(descr, member, value) \
+  ((descr)->member = (value))
+
+/* Return the TCB address of a thread given its state.
+   Note: this is expensive.  */
+static inline tcbprehead_t * __attribute__ ((unused))
+THREAD_TCB (thread_t thread,
+            struct machine_thread_all_state *all_state)
+{
+  int ok;
+  const struct aarch64_thread_state *state;
+  tcbhead_t *tcb;
+
+  ok = machine_get_basic_state (thread, all_state);
+  assert (ok);
+  state = &((struct machine_thread_all_state *) all_state)->basic;
+  tcb = (tcbhead_t *) state->tpidr_el0;
+  return (tcbprehead_t *) tcb - 1;
+}
+
+/* From hurd.h, reproduced here to avoid a circular include.  */
+extern thread_t __hurd_thread_self (void);
+libc_hidden_proto (__hurd_thread_self);
+
+/* Set up TLS in the new thread of a fork child, copying from the original.  */
+static inline kern_return_t __attribute__ ((unused))
+_hurd_tls_fork (thread_t child, thread_t orig,
+                struct aarch64_thread_state *state)
+{
+  error_t err;
+  struct aarch64_thread_state orig_state;
+  mach_msg_type_number_t state_count = AARCH64_THREAD_STATE_COUNT;
+
+  if (orig != __hurd_thread_self ())
+    {
+      err = __thread_get_state (orig, AARCH64_THREAD_STATE,
+				(thread_state_t) &orig_state,
+				&state_count);
+      if (err)
+        return err;
+      assert (state_count == AARCH64_THREAD_STATE_COUNT);
+      state->tpidr_el0 = orig_state.tpidr_el0;
+    }
+  else
+    state->tpidr_el0 = (uintptr_t) __builtin_thread_pointer ();
+  return 0;
+}
+
+static inline kern_return_t __attribute__ ((unused))
+_hurd_tls_new (thread_t child, tcbhead_t *tcb)
+{
+  error_t err;
+  struct aarch64_thread_state state;
+  mach_msg_type_number_t state_count = AARCH64_THREAD_STATE_COUNT;
+
+  err = __thread_get_state (child, AARCH64_THREAD_STATE,
+			    (thread_state_t) &state,
+			    &state_count);
+  if (err)
+    return err;
+  assert (state_count == AARCH64_THREAD_STATE_COUNT);
+
+  state.tpidr_el0 = (uintptr_t) tcb;
+
+  return __thread_set_state (child, AARCH64_THREAD_STATE,
+			     (thread_state_t) &state,
+			     state_count);
+}
+
+# if !defined (SHARED) || IS_IN (rtld)
+#  define __LIBC_NO_TLS() __builtin_expect (!__builtin_thread_pointer (), 0)
+
+static inline bool __attribute__ ((unused))
+_hurd_tls_init (tcbhead_t *tcb, bool full)
+{
+  extern mach_port_t __hurd_reply_port0;
+
+  if (full)
+    /* Take over the reply port we've been using.  */
+    (((tcbprehead_t *) tcb) - 1)->reply_port = __hurd_reply_port0;
+
+  __asm __volatile ("msr tpidr_el0, %0" : : "r" (tcb));
+  if (full)
+    /* This port is now owned by the TCB.  */
+    __hurd_reply_port0 = MACH_PORT_NULL;
+  return true;
+}
+
+#  define TLS_INIT_TP(descr) _hurd_tls_init ((tcbhead_t *) (descr), 1)
+# else /* defined (SHARED) && !IS_IN (rtld) */
+#  define __LIBC_NO_TLS() 0
+# endif
+
+/* Global scope switch support.  */
+# define THREAD_GSCOPE_FLAG_UNUSED 0
+# define THREAD_GSCOPE_FLAG_USED   1
+# define THREAD_GSCOPE_FLAG_WAIT   2
+
+# define THREAD_GSCOPE_SET_FLAG() \
+  do									     \
+    {									     \
+      THREAD_SELF->gscope_flag = THREAD_GSCOPE_FLAG_USED;		     \
+      atomic_write_barrier ();						     \
+    }									     \
+  while (0)
+
+# define THREAD_GSCOPE_RESET_FLAG() \
+  do									     \
+    { int __flag							     \
+	= atomic_exchange_release (&THREAD_SELF->gscope_flag,		     \
+				   THREAD_GSCOPE_FLAG_UNUSED);		     \
+      if (__flag == THREAD_GSCOPE_FLAG_WAIT)				     \
+	lll_wake (THREAD_SELF->gscope_flag, LLL_PRIVATE);		     \
+    }									     \
+  while (0)
+
+# endif /* __ASSEMBLER__ */
+
+#endif	/* tls.h */
-- 
2.44.0