[RFC PATCH glibc 17/34] hurd: Implement x86_64/intr-msg.h

[Sergey Bugaev <bugaevc@gmail.com>]

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
---

This is a prelimenary version of intr-msg.h. I can't know whether or not
it works until we can test it. The code relies on syscall preserving values
of the registers used to pass syscall arguments. The code in SYSCALL_EXAMINE
that just compares two bytes to the encoded syscall instruction is sure to
give many false positives; we're going to need to come up with a more reliable
scheme.

 sysdeps/mach/hurd/x86_64/intr-msg.h | 119 ++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 sysdeps/mach/hurd/x86_64/intr-msg.h

diff --git a/sysdeps/mach/hurd/x86_64/intr-msg.h b/sysdeps/mach/hurd/x86_64/intr-msg.h
new file mode 100644
index 00000000..5d94c85f
--- /dev/null
+++ b/sysdeps/mach/hurd/x86_64/intr-msg.h
@@ -0,0 +1,119 @@
+/* Machine-dependent details of interruptible RPC messaging.  x86_64 version.
+   Copyright (C) 1995-2023 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/>.  */
+
+
+/* Note that we must mark OPTION and TIMEOUT as outputs of this operation,
+   to indicate that the signal thread might mutate them as part
+   of sending us to a signal handler.  */
+
+#define INTR_MSG_TRAP(msg, option, send_size, rcv_size, rcv_name, timeout, notify, cancel_p, intr_port_p) \
+({									      \
+  error_t err;								      \
+  register uintptr_t rcv_size_r10 asm ("r10") = rcv_size;		      \
+  register uintptr_t rcv_name_r8 asm ("r8") = rcv_name;			      \
+  register uintptr_t timeout_r9 asm ("r9") = timeout;			      \
+  asm volatile (							      \
+       ".globl _hurd_intr_rpc_msg_about_to\n"				      \
+       ".globl _hurd_intr_rpc_msg_setup_done\n"				      \
+       ".globl _hurd_intr_rpc_msg_in_trap\n"				      \
+       /* Clear rax before we do the check for cancel below.  This is to
+          detect rax being set to non-zero (actually MACH_SEND_INTERRUPTED)
+          from the outside (namely, _hurdsig_abort_rpcs), which signals us
+          to skip the trap we were about to enter.  */			      \
+       "				xor %[err], %[err]\n"		      \
+       "_hurd_intr_rpc_msg_about_to:"					      \
+       /* We need to make a last check of cancel, in case we got interrupted
+          right before _hurd_intr_rpc_msg_about_to.  */			      \
+       "				cmpl $0, %[cancel]\n"		      \
+       "				jz _hurd_intr_rpc_msg_do\n"	      \
+       /* We got interrupted, note so and return EINTR.  */		      \
+       "				movl $0, %[intr_port]\n"	      \
+       "				movl %[eintr], %[err]\n"	      \
+       "				jmp _hurd_intr_rpc_msg_sp_restored\n" \
+       "_hurd_intr_rpc_msg_do:"						      \
+       /* Ok, prepare the mach_msg_trap arguments.  We pass the first 6 args
+          in registers, and push the last one and a fake return address.  */  \
+       "				pushq %[notify]\n"		      \
+       "				pushq $0\n"			      \
+       "_hurd_intr_rpc_msg_setup_done:"					      \
+       /* From here on, it is safe to make us jump over the syscall.  Now
+          check if we have been told to skip the syscall while running
+          the above.  */						      \
+       "				test %[err], %[err]\n"		      \
+       "				jnz _hurd_intr_rpc_msg_in_trap\n"     \
+       /* Do the actual syscall.  */					      \
+       "				movq $-25, %%rax\n"		      \
+       "_hurd_intr_rpc_msg_do_trap:	syscall # status in %[err]\n"	      \
+       "_hurd_intr_rpc_msg_in_trap:"					      \
+       /* Clean the arguments.  */					      \
+       "				addq $16, %%rsp\n"		      \
+       "_hurd_intr_rpc_msg_sp_restored:"				      \
+       : [err] "=&a" (err), "+S" (option), [intr_port] "=m" (*intr_port_p),   \
+         "+r" (timeout_r9)						      \
+       : "D" (msg), "d" (send_size), "r" (rcv_size_r10), "r" (rcv_name_r8),   \
+         [notify] "rm" ((uintptr_t) notify), [cancel] "m" (*cancel_p),	      \
+         [eintr] "i" (EINTR)						      \
+       : "rcx", "r11");							      \
+  timeout = timeout_r9;							      \
+  err;									      \
+})
+\f
+#include "hurdfault.h"
+
+/* This cannot be an inline function because it calls setjmp.  */
+#define SYSCALL_EXAMINE(state, callno)					      \
+({									      \
+  struct { unsigned char c[2]; } *p = (void *) ((state)->rip - 2);	      \
+  int result;								      \
+  if (_hurdsig_catch_memory_fault (p))					      \
+    return 0;								      \
+  if (result = p->c[0] == 0xf && p->c[1] == 0x5)			      \
+    /* The PC appears to be just after a `syscall' instruction.		      \
+       This is a system call in progress; %rax holds the call number.  */     \
+    *(callno) = (state)->rax;						      \
+  _hurdsig_end_catch_fault ();						      \
+  result;								      \
+})
+
+
+/* This cannot be an inline function because it calls setjmp.  */
+#define MSG_EXAMINE(state, msgid, rcvname, send_name, opt, tmout)	      \
+({									      \
+  int ret = 0;								      \
+  const struct machine_thread_state *s = (state);			      \
+  const mach_msg_header_t *msg = (const void *) s->rdi;			      \
+  *(rcvname) = s->r8;							      \
+  *(opt) = s->rsi;							      \
+  *(tmout) = s->r9;							      \
+  if (msg == 0)								      \
+    {									      \
+      *(send_name) = MACH_PORT_NULL;					      \
+      *(msgid) = 0;							      \
+    }									      \
+  else									      \
+    {									      \
+      ret = _hurdsig_catch_memory_fault (msg) ? -1 : 0;			      \
+      if (ret == 0)							      \
+        {								      \
+          *(send_name) = msg->msgh_remote_port;				      \
+          *(msgid) = msg->msgh_id;					      \
+          _hurdsig_end_catch_fault ();					      \
+	}								      \
+    }									      \
+  ret;									      \
+})
-- 
2.39.2