[Bug ld/30354] New: Debug info is lost for functions only called from functions marked with cmse_nonsecure_entry

[torbjorn.svensson at foss dot st.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30354

            Bug ID: 30354
           Summary: Debug info is lost for functions only called from
                    functions marked with cmse_nonsecure_entry
           Product: binutils
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: torbjorn.svensson at foss dot st.com
  Target Milestone: ---

Created attachment 14826
  --> https://sourceware.org/bugzilla/attachment.cgi?id=14826&action=edit
Demo

In order to generate an implib containing the addresses required to jump from a
non-secure function to a secure function, the secure function needs to use the
attribute cmse_nonsecure_entry. With this attribute, a certain .gnu.sgstubs
section in the ELF file is produced that contains these "secure callable
functions".

If the function with the attribute cmse_nonsecure_entry is calling some other
function that happens to be in a compile unit that does not have any other
function that is called from the main() function, then the debug information
for this compile unit is GCed if the application is linked with --gc-sections.

Attached is a small demonstration of what's happening.

The linker script in the attached example is the default one with one addition:
.gnu.sgstubs    : { *(.gnu.sgstubs*) }
I suppose this is an overlook and that this section should be added to the
default linker script for Arm targets in order to not force the user to define
there own linker script.


The output when building the demonstration is this:

$ make
arm-none-eabi-gcc -mcpu=cortex-m33 -std=gnu11 -g3 -mcmse -ffunction-sections
-fdata-sections -c -o bar.o bar.c 
arm-none-eabi-gcc -mcpu=cortex-m33 -std=gnu11 -g3 -mcmse -ffunction-sections
-fdata-sections -c -o main.o main.c 
arm-none-eabi-gcc -mcpu=cortex-m33 -std=gnu11 -g3 -mcmse -ffunction-sections
-fdata-sections -c -o foo.o foo.c 
arm-none-eabi-gcc -mcpu=cortex-m33 -T link.ld -static -Wl,--gc-sections
-Wl,--print-gc-sections -Wl,--cmse-implib -Wl,--out-implib=./secure_nsclib.o -o
test.elf bar.o main.o foo.o 2>&1 | grep -E 'removing unused section .* in file
.[a-z]+\.o.'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.group' in file
'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.debug_info' in
file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.debug_abbrev'
in file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.debug_aranges'
in file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.debug_ranges'
in file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.debug_macro'
in file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section
'.debug_macro[wm4.0.c063f11b96416a377bbfa49196ca6eec]' in file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.debug_line' in
file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.debug_str' in
file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.comment' in
file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.debug_frame'
in file 'bar.o'
c:\toolchain\arm-none-eabi\bin\ld.exe: removing unused section '.comment' in
file 'foo.o'


I've verified that the bug still exists with
acdf60711d44d20608873bec0376688c9a80e281 and it's not limited to Windows
although the output above was produced on Windows.

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