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174 | ------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- S Y S T E M . S E M I H O S T I N G --
-- --
-- B o d y --
-- --
-- Copyright (C) 2017-2023, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with Interfaces; use Interfaces;
with System.Machine_Code; use System.Machine_Code;
with Ada.Unchecked_Conversion;
package body System.Semihosting is
type SH_Word is new Interfaces.Unsigned_32;
function To_SH_Word is new Ada.Unchecked_Conversion
(Source => System.Address, Target => SH_Word);
function Generic_SH_Call (R0, R1 : SH_Word) return SH_Word;
-- Handles the low-level part of semihosting, setting the registers and
-- executing a breakpoint instruction.
subtype Syscall is SH_Word;
SYS_WRITEC : constant Syscall := 16#03#;
SYS_WRITE0 : constant Syscall := 16#04#;
SYS_READC : constant Syscall := 16#07#;
-- Output buffer
-- Because most of the time required for semihosting is not consumed for
-- the data itself but rather in the handling of breakpoint and
-- communication between the target and debugger, sending one byte costs
-- almost as much time as sending a buffer of multiple bytes.
--
-- For this reason, we use an output buffer for the semihosting Put
-- functions. The buffer is flushed when full or when a line feed or NUL
-- character is transmitted.
Buffer_Size : constant := 128;
type Buffer_Range is range 1 .. Buffer_Size;
Buffer : array (Buffer_Range) of Unsigned_8;
Buffer_Index : Buffer_Range := Buffer_Range'First;
procedure Flush;
-- Send the content of the buffer with semihosting WRITE0 call
---------------------
-- Generic_SH_Call --
---------------------
function Generic_SH_Call (R0, R1 : SH_Word) return SH_Word is
Ret : SH_Word;
begin
Asm ("mov r0, %1" & ASCII.LF & ASCII.HT &
"mov r1, %2" & ASCII.LF & ASCII.HT &
"bkpt #0xAB" & ASCII.LF & ASCII.HT &
"mov %0, r0",
Outputs => (SH_Word'Asm_Output ("=r", Ret)),
Inputs => (SH_Word'Asm_Input ("r", R0),
SH_Word'Asm_Input ("r", R1)),
Volatile => True,
Clobber => ("r1, r0"));
return Ret;
end Generic_SH_Call;
-----------
-- Flush --
-----------
procedure Flush is
Unref : SH_Word;
pragma Unreferenced (Unref);
begin
if Buffer_Index /= Buffer'First then
-- Set null-termination
Buffer (Buffer_Index) := 0;
-- Send the buffer with a semihosting call
Unref := Generic_SH_Call (SYS_WRITE0, To_SH_Word (Buffer'Address));
-- Reset buffer index
Buffer_Index := Buffer'First;
end if;
end Flush;
---------
-- Put --
---------
procedure Put (Item : Character) is
Unref : SH_Word;
pragma Unreferenced (Unref);
C : Character with Volatile;
-- Use a volatile variable to avoid compiler's optimization
begin
if Item = ASCII.NUL then
-- The WRITE0 semihosting call that we use to send the output buffer
-- expects a null terminated C string. Therefore it is not possible
-- to have an ASCII.NUL character in the middle of the buffer as this
-- would truncate the buffer.
--
-- For this reason the ASCII.NUL character is sent separately with a
-- WRITEC semihosting call.
-- Flush the current buffer
Flush;
-- Send the ASCII.NUL with a WRITEC semihosting call
C := Item;
Unref := Generic_SH_Call (SYS_WRITEC, To_SH_Word (C'Address));
else
Buffer (Buffer_Index) := Character'Pos (Item);
Buffer_Index := Buffer_Index + 1;
-- Flush the buffer when it is full or if the character is a line
-- feed.
if Buffer_Index = Buffer'Last or else Item = ASCII.LF then
Flush;
end if;
end if;
end Put;
---------
-- Put --
---------
procedure Put (Item : String) is
begin
for Index in Item'Range loop
Put (Item (Index));
end loop;
end Put;
---------
-- Get --
---------
procedure Get (Item : out Character) is
Ret : SH_Word;
begin
Ret := Generic_SH_Call (SYS_READC, 0);
Item := Character'Val (Ret);
end Get;
end System.Semihosting;
|