Gnu linker disregards linker script and pulls in unrequested code

Question

I am writing a cpm-like os for a Cortex-m microprocessor (Ti Tiva-C) using Ti CCS v12 IDE. It is a teaching/student project for junior students. The project will be divided in sub-project and assigned to students.

The project requires to allocate code at specific adresses/region of microcontroller memory, using a custom linker script.

However the linker largely ignores the code layout in the linker script and includes in the output code not requested in the linker script.

I removed the "(.text)" and "(.text.)" snippets that should include all the code and replaced with actual filenames of objects files "tpa_(.text)", divided into different output section.

It did not work, the code was moved around.

As a test, I completely removed all the reference to code in the linker script, but the linker still includes all the objects it founds in the command line.

Moving the location counter in the linker script moves the code in the output, hence the linker script is really read.

minimal linker script which reproduces the problem:

MEMORY
{
    FLASH (RX) : ORIGIN = 0x00000000, LENGTH = 0x00040000
    SRAM (WX)  : ORIGIN = 0x20000000, LENGTH = 0x00008000
}

REGION_ALIAS("REGION_TEXT", FLASH);


SECTIONS {


    .text : {
    . = 12k; /* just to check that this file is really read by linker */
    /*KEEP (./bios/bios_startup_cpm_gcc.o(.intvecs)) */
    } > REGION_TEXT


     __data_start__ = .; /* to avoid unresolved external errors */
     __data_load__  = .;
     __data_end__   = .;

}

linker invocation

Building target: "test-linker.out"
Invoking: GNU Linker
"/Applications/ti/ccs1271/ccs/tools/compiler/gcc-arm-none-eabi-9-2019-q4-major/bin/arm-none-eabi-gcc-9.2.1" -mfpu=fpv4-sp-d16 -DPART_TM4C123GH6PM -Og -ffunction-sections -fdata-sections -g -gdwarf-3 -gstrict-dwarf -Wall -specs="nosys.specs" -march=armv7e-m -mthumb -mfloat-abi=soft -Wl,-Map,"test-linker.map" -nostartfiles -nodefaultlibs -nostdlib -static -o"test-linker.out"  "./tpa/libbios.o" "./tpa/tpa_test.o" "./bios/bios_startup_cpm_gcc.o" "./bios/bios_util.o" "./bios/fixed_dispatch.o" -Wl,-T"../cpm.lds" "./bios/bios_test.o" 
Finished building target: "test-linker.out"
 

output linker map

Memory Configuration

Name             Origin             Length             Attributes
FLASH            0x0000000000000000 0x0000000000040000 xr
SRAM             0x0000000020000000 0x0000000000008000 xw
*default*        0x0000000000000000 0xffffffffffffffff

Linker script and memory map

LOAD ./tpa/libbios.o
LOAD ./tpa/tpa_test.o
LOAD ./bios/bios_startup_cpm_gcc.o
LOAD ./bios/bios_util.o
LOAD ./bios/fixed_dispatch.o

.text           0x0000000000000000     0x3024
                0x0000000000003000                . = 0x3000
 *fill*         0x0000000000000000     0x3000 
 .text          0x0000000000003000       0x20 ./tpa/libbios.o
                0x0000000000003000                call_const
                0x0000000000003006                call_conin
                0x000000000000300c                call_conout
 .text          0x0000000000003020        0x0 ./tpa/tpa_test.o
 .text          0x0000000000003020        0x0 ./bios/bios_startup_cpm_gcc.o
 .text          0x0000000000003020        0x4 ./bios/bios_util.o
                0x0000000000003020                noop
 .text          0x0000000000003024        0x0 ./bios/fixed_dispatch.o
 .text          0x0000000000003024        0x0 ./bios/bios_test.o
                0x0000000000003024                __data_start__ = .
                0x0000000000003024                __data_load__ = .
                0x0000000000003024                __data_end__ = .
LOAD ./bios/bios_test.o
OUTPUT(test-linker.out elf32-littlearm)

.data           0x0000000000003024        0x0
 .data          0x0000000000003024        0x0 ./tpa/libbios.o
 .data          0x0000000000003024        0x0 ./tpa/tpa_test.o
 .data          0x0000000000003024        0x0 ./bios/bios_startup_cpm_gcc.o
 .data          0x0000000000003024        0x0 ./bios/bios_util.o
 .data          0x0000000000003024        0x0 ./bios/fixed_dispatch.o
 .data          0x0000000000003024        0x0 ./bios/bios_test.o

.igot.plt       0x0000000000003024        0x0
 .igot.plt      0x0000000000003024        0x0 ./tpa/libbios.o

.glue_7         0x0000000000003024        0x0
 .glue_7        0x0000000000003024        0x0 linker stubs

.glue_7t        0x0000000000003024        0x0
 .glue_7t       0x0000000000003024        0x0 linker stubs

.vfp11_veneer   0x0000000000003024        0x0
 .vfp11_veneer  0x0000000000003024        0x0 linker stubs

.v4_bx          0x0000000000003024        0x0
 .v4_bx         0x0000000000003024        0x0 linker stubs

.iplt           0x0000000000003024        0x0
 .iplt          0x0000000000003024        0x0 ./tpa/libbios.o

.text.tpa_start
                0x0000000000003024       0x18
 .text.tpa_start
                0x0000000000003024       0x18 ./tpa/tpa_test.o
                0x0000000000003024                tpa_start

.text.NmiSR     0x000000000000303c        0x2
 .text.NmiSR    0x000000000000303c        0x2 ./bios/bios_startup_cpm_gcc.o

.text.IntDefaultHandler
                0x000000000000303e        0x2
 .text.IntDefaultHandler
                0x000000000000303e        0x2 ./bios/bios_startup_cpm_gcc.o

.text.FaultISR  0x0000000000003040        0x8
 .text.FaultISR
                0x0000000000003040        0x8 ./bios/bios_startup_cpm_gcc.o

.text.ResetISR  0x0000000000003048       0x3c
 .text.ResetISR
                0x0000000000003048       0x3c ./bios/bios_startup_cpm_gcc.o
                0x0000000000003048                ResetISR

.text.bios_dispatch
                0x0000000000003084        0xa
 .text.bios_dispatch
                0x0000000000003084        0xa ./bios/fixed_dispatch.o
                0x0000000000003084                bios_dispatch

.text.main      0x000000000000308e        0xa
 .text.main     0x000000000000308e        0xa ./bios/bios_test.o
                0x000000000000308e                main

.intvecs        0x0000000000003098      0x26c
 .intvecs       0x0000000000003098      0x26c ./bios/bios_startup_cpm_gcc.o
                0x0000000000003098                g_pfnVectors

.rel.dyn        0x0000000000003304        0x0
 .rel.iplt      0x0000000000003304        0x0 ./tpa/libbios.o

.bss            0x0000000000003304        0x0
 .bss           0x0000000000003304        0x0 ./tpa/libbios.o
 .bss           0x0000000000003304        0x0 ./tpa/tpa_test.o
 .bss           0x0000000000003304        0x0 ./bios/bios_startup_cpm_gcc.o
 .bss           0x0000000000003304        0x0 ./bios/bios_util.o
 .bss           0x0000000000003304        0x0 ./bios/fixed_dispatch.o
 .bss           0x0000000000003304        0x0 ./bios/bios_test.o

For some reason the linker includes all the code in the command line disregarding the requests in the linke script.