ARM FAQ Summary

1. relocation truncated to fit: R_ARM_THM_CALL against symbol 'xxx'
There are several possible reasons:
1. The first one is that, as mentioned below, it exceeds the jump range of b/bl. This can be confirmed by looking at the compiled code address.
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2. The second possibility is that there is a problem with the section attribute where the code is located.
For example, the following compilation:
test is in the .startup section, and Test2 is in the .text section.
Test will call Test2, and an error will be reported during compilation:relocation truncated to fit: R_ARM_THM_CALL against symbol 'xxx'

            .thumb
            .section .startup 
            .align   2

            .thumb_func
            .type    test, %function
            .globl   test
            .fnstart

test:
                ldr      r0, =__stack
                msr      msp, r0
                ldr      r0, =__StackLimit
                msr      msplim, r0
                bl     Test2

…

....
                .thumb
                .section .text
                .align   2
 				.thumb_func
                .type    Test2, %function
                .globl   Test2
                .fnstart

Test2:     
....
....

This is actually because you did not specify its attributes for the startup section.

You can see the properties of each section by calling the following command

readelf xxx.elf

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How to add attributes to section? You can use the following command to add:

.section name [, flag]

Take the above example as an example:
you can define the startup section as distributable and executable, and there will be no problem with compiling.

            .thumb
            .section .startup ， “ax”
            .align   2

            .thumb_func
            .type    test, %function
            .globl   test
            .fnstart

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