Placing functions and data at specific addresses
To place a single function or data item at a fixed address, you must enable the linker to process the function or data separately from the rest of the input files.
Where they are required, the compiler normally produces RO, RW, and ZI sections from a single source file. These sections contain all the code and data from the source file.
NoteFor images targeted at ARMv7-M or ARMv8-M, the compiler might generate execute-only (XO) sections.
Typically, you create a scatter file that defines an execution region at the required address with a section description that selects only one section.
To place a function or variable at a specific address, it must be placed in its own section. There are several ways to do this:
- Place the function or data item in its own source file.
__attribute__((section("to place functions and variables in a specially named section,
is the address to place the function or variable. For example,
To place ZI data at a specific address, use the variable attribute
__attribute__((section("with the special name
These specially named sections are called
.sectiondirective from assembly language. In assembly code, the smallest locatable unit is a
-ffunction-sectionscompiler option to generate one ELF section for each function in the source file.
This option results in a small increase in code size for some functions because it reduces the potential for sharing addresses, data, and string literals between functions. However, this can help to reduce the final image size overall by enabling the linker to remove unused functions when you specify
This section contains the following subsections: