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# Configure printed libyang context address.
#
# The following variables are used:
# PRINTED_CONTEXT_ADDRESS - Pre-defined address to use for the printed context mapping, "" if not set, 0 if disabled
#
# The following cache variables are set:
# PRINTED_CONTEXT_ADDRESS - The final address used for printed context mapping
#
# Behavior:
# 1. Checks if MAP_FIXED_NOREPLACE is available on the system
# 2. If PRINTED_CONTEXT_ADDRESS is provided, uses that address
# 3. If not provided, attempts to calculate address using pctx_addr_calculator.c
# 4. If MAP_FIXED_NOREPLACE is unavailable:
# - Requires manual PRINTED_CONTEXT_ADDRESS and warns about ASLR
# - Falls back to MAP_FIXED with potential undefined behavior
# 5. Sets PRINTED_CONTEXT_ADDRESS for use in source code
#
# Author Roman Janota <janota@cesnet.cz>
# Copyright (c) 2025 CESNET, z.s.p.o.
#
# This source code is licensed under BSD 3-Clause License (the "License").
# You may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://opensource.org/licenses/BSD-3-Clause
#
function(SETUP_PRINTED_CONTEXT)
# get the docstring for the address
get_property(PRINTED_CONTEXT_ADDRESS_DOCSTRING CACHE PRINTED_CONTEXT_ADDRESS PROPERTY HELPSTRING)
# handle case when MAP_FIXED_NOREPLACE is not available
if(NOT HAVE_MAP_FIXED_NOREPLACE)
# MAP_FIXED_NOREPLACE is not available, but printed context may still be used with MAP_FIXED
if(NOT "${PRINTED_CONTEXT_ADDRESS}" STREQUAL "" AND NOT "${PRINTED_CONTEXT_ADDRESS}" STREQUAL "0")
message(WARNING "MAP_FIXED_NOREPLACE not available, but printed context enabled. "
"Consider disabling ASLR (Address Space Layout Randomization) to avoid overwriting existing memory mappings.")
message(STATUS "Printed context: enabled (using provided address ${PRINTED_CONTEXT_ADDRESS})")
else()
# no address provided, printed context cannot be used, we can end here
message(WARNING "MAP_FIXED_NOREPLACE not available and no valid address provided. "
"Provide page-aligned PRINTED_CONTEXT_ADDRESS to use printed context.")
message(STATUS "Printed context: disabled")
set(PRINTED_CONTEXT_ADDRESS 0 CACHE STRING "${PRINTED_CONTEXT_ADDRESS_DOCSTRING}" FORCE)
endif()
return()
endif()
# check if no address is provided
if("${PRINTED_CONTEXT_ADDRESS}" STREQUAL "")
# calculate printed context address
# no point compiling the calculator if sbrk() is not available
if (NOT HAVE_SBRK)
message(WARNING "sbrk() is required to calculate printed context address, but it is not available. "
"Provide PRINTED_CONTEXT_ADDRESS manually to enable printed context.")
message(STATUS "Printed context: disabled")
set(PRINTED_CONTEXT_ADDRESS 0 CACHE STRING "${PRINTED_CONTEXT_ADDRESS_DOCSTRING}" FORCE)
return()
endif()
# compile and run the address calculator
try_run(
exec_result compile_result
${CMAKE_BINARY_DIR}
SOURCES "${CMAKE_CURRENT_SOURCE_DIR}/CMakeModules/pctx_addr_calculator.c"
COMPILE_OUTPUT_VARIABLE compile_output
RUN_OUTPUT_STDOUT_VARIABLE calculated_addr
)
if (NOT compile_result)
message(WARNING "Failed to compile address calculator:\n${compile_output}\n"
"Provide PRINTED_CONTEXT_ADDRESS manually to enable printed context.")
message(STATUS "Printed context: disabled")
set(PRINTED_CONTEXT_ADDRESS 0 CACHE STRING "${PRINTED_CONTEXT_ADDRESS_DOCSTRING}" FORCE)
return()
endif()
if(exec_result EQUAL 0)
# overwrite the cached address
set(PRINTED_CONTEXT_ADDRESS ${calculated_addr} CACHE STRING "${PRINTED_CONTEXT_ADDRESS_DOCSTRING}" FORCE)
message(STATUS "Printed context: enabled (using generated address ${PRINTED_CONTEXT_ADDRESS})")
else()
message(WARNING "Address calculator failed to run. "
"Provide PRINTED_CONTEXT_ADDRESS manually to enable printed context.")
message(STATUS "Printed context: disabled")
set(PRINTED_CONTEXT_ADDRESS 0 CACHE STRING "${PRINTED_CONTEXT_ADDRESS_DOCSTRING}" FORCE)
endif()
elseif("${PRINTED_CONTEXT_ADDRESS}" STREQUAL "0")
# address is 0, printed context is disabled
message(STATUS "Printed context: disabled")
else()
# address provided, use it
message(STATUS "Printed context: enabled (using provided address ${PRINTED_CONTEXT_ADDRESS})")
endif()
endfunction()
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