AN3350 datasheet(78/185 Pages) STMICROELECTRONICS

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Working with the ELF linker

AN3350

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Doc ID 018512 Rev 2

segment_2 (RX): ORIGIN = 0x801000, LENGTH = 0x19000

}

The (RWX) portion specifies these ELF flags:

●

— read

●

— write

●

— executable code

ORIGIN

represents the memory segment’s start address. The address may also denote the

relevant memory space (c:0x800000), if the memory space is omitted, then the memory

space is determined according to the ELF flags.

LENGTH

represents the memory segment’s size.

Note:

If you cannot predict how much space a segment requires, you can use the function AFTER

and LENGTH = 0 (unlimited length) to have the linker automatically fill in the unknown

values.

11.2.2

Sections segment

The sections segment defines the contents of memory segments and defines global

symbols used in the output file. Section 11.4.8: SECTIONS explains this segment type.

Example 13 shows an example SECTIONS segment.

Example 13 Example SECTIONS segment

SECTIONS {

.section_name :

//the section name is for your reference

{

//the section name must begin with a '.'

filename.o (.text) //put the .text section from filename.o

filename2.o (.text) //then the .text section from filename2.o

. = ALIGN (0x10);

//align next section on 16-byte boundary.

} > segment_1

//this means "map these contents to

segment_1"

.next_section_name:

{

(more content descriptions)

} > segment_x

// end of .next_section_name

definition}

// end of the sections block

11.2.3

Closure blocks

The linker can automatically remove unused code and data (see Section 11.3.4: Dead strip

prevention). Sometimes, however, certain symbols must be kept in output files, even if code

does not directly reference those symbols. For example, interrupt handlers are usually

linked at special addresses without any explicit jumps to transfer control to these addresses.

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