Introduction

When all libraries and application is compiled in instrumentation mode, some extra ELF sections are created by the compiler. In any examples, these additional section handling needs to be done in linker script.

If custom linker command file is used then changes in Memory Configurator (Memory Configurator) is not required.

Using Memory Configurator

Open Memory Configurator. And under that, open "`Section`". Something like following will be shown:

On top, it can be seen that there are a total of 14 sections that are present. In the same list, scroll down to Memory Segments and click on it. Show as following:

From here, delete .bss from the Output Section. The sections that are generated by the compiler for instrumented binaries are uninitialized sections. Section .bss is also an uninitialized section.

Add a new section by clicking add button at the top in the above image.

Name of this new section can be uninit_section.

Start Group field is __BSS_START.

End Group field is __BSS_END.

Make sure that Split Across Memories is un-checked.

Load Memory is selected to any destination memory as per application.

In the output section add following 3 sections.

Name	Start Section	End Section	Alignment
.bss			8
__llvm_prf_cnts			8
__llvm_prf_bits			8

Here, start section and end section fields for all output sections are to be left blank

After all of the above changes, the section would look like the following:

Above changes clubs all the uninit sections in input object files in one section in output ELF file which will be cleared on runtime in the application. This clearing is handled automatically by the startup code and no changes are required for this.

The generated linker file would contain the following:

GROUP :   {
    .bss : {
    } palign(8)
    __llvm_prf_cnts : {
    } palign(8)
    __llvm_prf_bits : {
    } palign(8)
} > MSRAM AT > MSRAM
RUN_START(__BSS_START)
RUN_END(__BSS_END)

In this particular example, load and run address is chosen as MSRAM which is just a representative name of a part of on chip RAM memory.

Linker changes

In the linker file, some change are required. Add following lines of code in linker file when using ti-arm-clang compiler. This code should be inside SECTIONS.

GROUP
{
    .bss:{} palign(8)
    __llvm_prf_cnts: {} align(8)
    __llvm_prf_bits: {} align(8)
} > OCRAM
RUN_START(__BSS_START)
RUN_END(__BSS_END)

Few things to keep tack of:

Sections .bss, __llvm_prf_cnts and __llvm_prf_bits should not be present anywhere else in the linker file.
OCRAM should be replaced with correct memory name.

Table of Contents

Introduction

Using Memory Configurator

Linker changes