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 /* SPDX-License-Identifier: BSD-2-Clause */
 
 /**
  * @file
  *
  * @ingroup rtems_rtl
  *
  * @brief RTEMS Run-Time Linker Object File Trampoline Relocations Table.
  *
  * Cache relocation records that could result in a trampoline. The unresolved
  * symbol table holds variable the symbol name (length string) and the object
  * file's relocation records that reference the unresolved symbol. The
  * trampoline cache is an extension to this table to reuse the code and memory
  * and support trampolines.
  *
  * Some architectures require trampolines or veneers to extend the range of
  * some instructions. The compiler generates small optimized instructions
  * assuming most destinations are within the range of the instruction. The
  * instructions are smaller in size and can have a number of encodings with
  * different ranges. If a relocation record points to a symbol that is out of
  * range for the instruction a trampoline is used to extend the instruction's
  * range. A trampoline is a small fragment of architecture specific
  * instructions located within the range of the relocation record instruction
  * that can reach the entire address range. The trampoline's execution is
  * transparent to the execution of the object file.
  *
  * An object file that needs a trampoline has a table allocated close to the
  * text section. It has to be close to ensure the largest possible object file
  * can be spported. The number of slots in a table depends on:
  *
  *  # Location of the code
  *  # The type of relocation records in the object file
  *  # The instruction encoding the relocation record points too
  *  # The landing address of the instruction
  *
  * The allocation of the text segment and the trampoline table have to happen
  * with the allocator lock being locked and held to make sure no other
  * allocations happen inbetween the text section allocation and the trampoline
  * table. Holding an allocator lock limits what the link editor can do when
  * when the default heap allocator is being used. If calls any operating
  * system services including the file system use the same allocator a deadlock
  * will occur. This creates a conflict between performing the allocations
  * together and reading the instructions while holding the allocator lock.
  *
  * The trampoline cache holds the parsed relocation records that could result
  * in a trampoline. These records can be exaimined after the allocation of the
  * text segment to determine how many relocation record target's are out of
  * range. The minimum range for a specific type of relocation record has to be
  * used as the instructions cannot be loaded.
  */
 
 /*
  *  COPYRIGHT (c) 2019 Chris Johns <chrisj@rtems.org>
  *
  * 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
  */
 
 #if !defined (_RTEMS_RTL_TRAMPOLINE_H_)
 #define _RTEMS_RTL_TRAMPOLINE_H_
 
 #include <rtems/rtl/rtl-unresolved.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif /* __cplusplus */
 
 /**
  * Add a relocation to the list of trampolinr relocations.
  *
  * @param obj The object table the relocation record is for.
  * @param flags Format specific flags.
  * @param sect The target section number the relocation references.
  * @param symvalue The symbol's value.
  * @param rel The format specific relocation data.
  * @retval true The relocation has been added.
  * @retval false The relocation could not be added.
  */
 bool rtems_rtl_trampoline_add (rtems_rtl_obj*        obj,
                                const uint16_t        flags,
                                const uint16_t        sect,
                                const rtems_rtl_word  symvalue,
                                const rtems_rtl_word* rel);
 
 /**
  * Remove the relocation records for an object file.
  *
  * @param obj The object table the symbols are for.
  */
 void rtems_rtl_trampoline_remove (rtems_rtl_obj* obj);
 
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
 
 #endif

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