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/*
* Copyright (c) 2018.
* Amaan Cheval <amaan.cheval@gmail.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <rtems/score/cpu.h>
#include <rtems/score/tls.h>
/*
* Stack alignment note:
*
* Per the x86-64 SysV ABI, the stack frame layout is as follows:
* optional args
* ------ (16-byte alignment boundary)
* RSP-> return_addr (RSP is moved lower as needed for this frame)
*
* Per the ABI:
*
* > The end of the input argument area shall be aligned on a 16 (32 or 64, if
* __m256 or __m512 is passed on stack) byte boundary.
*
* > In other words, the value (%rsp + 8) is always a multiple of 16 (32 or 64)
* when control is transferred to the function entry point.
*
* We want the stack to look to the '_entry_point' routine
* like an ordinary stack frame as if '_entry_point' was
* called from C-code.
* Note that '_entry_point' is jumped-to by the 'ret'
* instruction returning from _CPU_Context_switch() or
* _CPU_Context_restore() thus popping the _entry_point
* from the stack.
*
* Hence we must initialize the stack as follows
*
* [arg0 (aligned)]: n/a
* [ret. addr ]: NULL
* RSP-> [jump-target ]: _entry_point
*
* When Context_switch returns it pops the _entry_point from
* the stack which then finds a standard layout.
*/
void _CPU_Context_Initialize(
Context_Control *the_context,
void *stack_area_begin,
size_t stack_area_size,
uint32_t new_level,
void (*entry_point)( void ),
bool is_fp,
void *tls_area
)
{
uintptr_t _stack;
/* avoid warning for being unused */
(void) is_fp;
// XXX: Should be used in the future
(void) tls_area;
if ( new_level ) {
the_context->rflags = CPU_EFLAGS_INTERRUPTS_OFF;
}
else {
the_context->rflags = CPU_EFLAGS_INTERRUPTS_ON;
}
_stack = ((uintptr_t) stack_area_begin) + stack_area_size;
_stack &= ~(CPU_STACK_ALIGNMENT - 1);
_stack -= sizeof(uintptr_t); /* fake return address for entry_point's frame;
* this allows rsp+8 to be an aligned boundary */
*((void (**)(void)) _stack) = entry_point;
the_context->rbp = (void *) 0;
the_context->rsp = (void *) _stack;
// XXX: Initialize thread-local storage area (TLS / TCB)
}
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