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//=============================================================================

//

//      tls.c

//

//      Support for the per-thread data expected by parts of gcc

//

//=============================================================================

// ####ECOSGPLCOPYRIGHTBEGIN####                                            

// -------------------------------------------                              

// This file is part of eCos, the Embedded Configurable Operating System.   

// Copyright (C) 2009 Free Software Foundation, Inc.                  

//

// eCos is free software; you can redistribute it and/or modify it under    

// the terms of the GNU General Public License as published by the Free     

// Software Foundation; either version 2 or (at your option) any later      

// version.                                                                 

//

// eCos 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 General Public License    

// for more details.                                                        

//

// You should have received a copy of the GNU General Public License        

// along with eCos; if not, write to the Free Software Foundation, Inc.,    

// 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.            

//

// As a special exception, if other files instantiate templates or use      

// macros or inline functions from this file, or you compile this file      

// and link it with other works to produce a work based on this file,       

// this file does not by itself cause the resulting work to be covered by   

// the GNU General Public License. However the source code for this file    

// must still be made available in accordance with section (3) of the GNU   

// General Public License v2.                                               

//

// This exception does not invalidate any other reasons why a work based    

// on this file might be covered by the GNU General Public License.         

// -------------------------------------------                              

// ####ECOSGPLCOPYRIGHTEND####                                              

//=============================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):    bartv

// Contributors: bartv

// Date:         2009-08-09

//

//####DESCRIPTIONEND####

//=============================================================================

#include <pkgconf/mlt_synth_i386_rom.h>

#include <cyg/hal/hal_arch.h>

// At the time of writing some parts of gcc assume thread-local storage as

// provided by glibc. Of particular concern is -fstack-protector which is

// enabled by default in some distros. Without matching target-side support

// this causes synthetic target eCos applications to SEGV early on.

// eCos only needs a single TLS data structure. This will need alignment

// suitable for filling in an x86 descriptor table entry, so the linker

// script places this structure right at the start of RAM.

//

// Installing a TLS area involves a system call set_thread_area().

// This system call should be called from the assembler startup

// before any C code starts running, or we'll run into problems with

// -fstack-protector-all. However all relevant data can be

// statically initialized.

_HAL_TLS_Data _hal_synth_tls_data __attribute__ ((section (".tls._hal_synth_tls_data") )) = {

    // The meaning of most of the tls fields is not clear, so just

    // initialize them to 0 for now - until something else

    // stops working.

    .tls_tcb                = (void*) 0,

    .tls_dtv                = (void*) 0,

    .tls_self               = (void*) 0,

    .tls_multiple_threads   = 0,

    .tls_sysinfo            = (void*) 0,

    // This is the important one for the purposes of -fstack-protector.

    // The compiler assumes that %gs:0x14 points at the base of the stack.

    // For now we just point at the start of RAM. It should be possible

    // to update this during context switches and at the start of interrupt

    // handling to get a partial implementation of stack overflow checking.

    .tls_stack_guard        = (void*) CYGMEM_REGION_ram,

    .tls_pointer_guard      = (void*) 0,

    .tls_gscope_flag        = 0,

    .tls_private_futex      = 0,

    .tls_private_tm[0]      = (void*) 0,

    .tls_private_tm[1]      = (void*) 0,

    .tls_private_tm[2]      = (void*) 0,

    .tls_private_tm[3]      = (void*) 0,

    .tls_private_tm[4]      = (void*) 0

};

// The argument to set_thread_area() is not a _hal_synth_tls_data,

// unfortunately. Instead it is a user_desc structure as per

// <asm/ldt.h>.

typedef struct _HAL_user_desc {

    int             ud_entry_number;

    unsigned long   ud_base_addr;

    int             ud_limits;

    int             ud_flags;

} _HAL_user_desc;

#define _HAL_USER_DESC_FLAGS_SEG_32BIT          (0x01 << 0)

#define _HAL_USER_DESC_FLAGS_CONTENTS_MASK      (0x03 << 1)

#define _HAL_USER_DESC_FLAGS_CONTENTS_SHIFT     1

#define _HAL_USER_DESC_FLAGS_CONTENTS_DATA      (0x00 << 1)

#define _HAL_USER_DESC_FLAGS_CONTENTS_STACK     (0x01 << 1)

#define _HAL_USER_DESC_FLAGS_CONTENTS_CODE      (0x02 << 1)

#define _HAL_USER_DESC_FLAGS_READ_EXEC_ONLY     (0x01 << 3)

#define _HAL_USER_DESC_FLAGS_LIMIT_IN_PAGES     (0x01 << 4)

#define _HAL_USER_DESC_FLAGS_SEG_NOT_PRESENT    (0x01 << 5)

#define _HAL_USER_DESC_FLAGS_USEABLE            (0x01 << 6)

// And it can also be statically initialized. There is no need to worry

// about alignment this time. Note that one of the fields gets updated

// by the system call so this cannot be a const structure.

_HAL_user_desc   _hal_synth_user_desc = {

    .ud_entry_number        = -1,   // Let the kernel pick the descriptor table entry

    .ud_base_addr           = (unsigned long) &_hal_synth_tls_data,

    .ud_limits              = 1,    // A single page will do

    .ud_flags               = (_HAL_USER_DESC_FLAGS_SEG_32BIT       |

                               _HAL_USER_DESC_FLAGS_CONTENTS_DATA   |

                               _HAL_USER_DESC_FLAGS_READ_EXEC_ONLY  |

                               _HAL_USER_DESC_FLAGS_LIMIT_IN_PAGES  |

                               _HAL_USER_DESC_FLAGS_USEABLE)

};