probe-run cannot load ELF linked with '-Tdefmt.x -Tlink.x'

[japaric]

app-template passes the flags '-Tlink.x -Tdefmt.x' to the linker. ELFs linked with those flags work fine.
if you modify app-template and pass the flags in the reverse order '-Tdefmt.x -Tlink.x' the output ELF doesn't work with probe-run.

You get this kind of output:

$ probe-run --chip nrf52840 bad-elf
  (HOST) INFO  flashing program (0.00 KiB)
Error: No loadable ELF sections were found.

The .text section is marked as allocatable in the ELF though:

$ readelf -S bad-elf
Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .defmt            PROGBITS        00000000 000054 000002 00      0   0  1
  [ 2] .debug_abbrev     PROGBITS        00000000 000056 004589 00      0   0  1
  [ 3] .debug_info       PROGBITS        00000000 0045df 03280b 00      0   0  1
  [ 4] .debug_aranges    PROGBITS        00000000 036df0 003378 00      0   0  8
  [ 5] .debug_ranges     PROGBITS        00000000 03a168 018420 00      0   0  1
  [ 6] .debug_str        PROGBITS        00000000 052588 039ad8 01  MS  0   0  1
  [ 7] .debug_pubnames   PROGBITS        00000000 08c060 00cb53 00      0   0  1
  [ 8] .debug_pubtypes   PROGBITS        00000000 098bb3 005f71 00      0   0  1
  [ 9] .ARM.attributes   ARM_ATTRIBUTES  00000000 09eb24 00003a 00      0   0  1
  [10] .debug_frame      PROGBITS        00000000 09eb60 008bc4 00      0   0  4
  [11] .debug_line       PROGBITS        00000000 0a7724 02ef8a 00      0   0  1
  [12] .debug_loc        PROGBITS        00000000 0d66ae 0002a9 00      0   0  1
  [13] .comment          PROGBITS        00000000 0d6957 00006d 01  MS  0   0  1
  [14] .symtab           SYMTAB          00000000 0d69c4 002ab0 10     16 456  4
  [15] .shstrtab         STRTAB          00000000 0d9474 0000f0 00      0   0  1
  [16] .strtab           STRTAB          00000000 0d9564 0048bd 00      0   0  1
  [17] .vector_table     PROGBITS        00000000 0dde24 000100 00   A  0   0  4
  [18] .text             PROGBITS        00000100 0ddf24 003de4 00  AX  0   0  4
  [19] .rodata           PROGBITS        00003ee4 0e1d10 000c34 00  AM  0   0 16
  [20] .data             PROGBITS        20000000 0e2944 000030 00  WA  0   0  4
  [21] .bss              NOBITS          20000030 0e2974 000008 00  WA  0   0  4
  [22] .uninit           NOBITS          20000038 0e2974 000400 00  WA  0   0  4

OpenOCD is able to flash this ELF file.

It was observed that if you link the ELF with '-Tlink.x -Tdefmt.x' the .text and other sections appear first in the above list of section headers (and have small offsets).

It seems that the object library is unable to find the .text section in the ELF.
probe-run uses the object library to report the size of loadable sections (the "0.00 KiB" part in the above output)
probe-rs also uses the object library to locate loadable sections that need to be flashed on the device.

[jonathanpallant]

The error "No loadable ELF sections were found", is the text associated with probe_rs::flashing::download::FileDownloadError::NoLoadableSegments.

This is only created in one place - probe_rs::flashing::loader::FlashLoader::load_elf_data when num_sections == 0.

The function the provides the sections is probe_rs::flashing::download::extract_from_elf.

[jonathanpallant]

The extract_from_elf function:

• Iterates through all the segments in the ELF header
• Checks if the segment is not empty, and has segment type PT_LOAD
• Iterates through all the sections in the binary
• Checks if they overlap and, if so, adds the segment to the output list

I'll build a test binary and try and flash it but with trace logging enabled.

[jonathanpallant]

My test program flashed and ran OK. Running readelf -S reports:

$ /opt/homebrew/opt/binutils/bin/readelf -S ./target/thumbv7em-none-eabihf/debug/hello 
There are 24 section headers, starting at offset 0x11cd0c:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .defmt            PROGBITS        00000000 001ba0 000009 00      0   0  1
  [ 2] .debug_loc        PROGBITS        00000000 001ba9 0082dc 00      0   0  1
  [ 3] .debug_abbrev     PROGBITS        00000000 009e85 00222f 00      0   0  1
  [ 4] .debug_info       PROGBITS        00000000 00c0b4 03f13a 00      0   0  1
  [ 5] .debug_aranges    PROGBITS        00000000 04b1ee 003598 00      0   0  1
  [ 6] .debug_ranges     PROGBITS        00000000 04e786 01be00 00      0   0  1
  [ 7] .debug_str        PROGBITS        00000000 06a586 057a5a 01  MS  0   0  1
  [ 8] .debug_pubnames   PROGBITS        00000000 0c1fe0 01b34c 00      0   0  1
  [ 9] .debug_pubtypes   PROGBITS        00000000 0dd32c 0078a5 00      0   0  1
  [10] .ARM.attributes   ARM_ATTRIBUTES  00000000 0e4bd1 00003a 00      0   0  1
  [11] .debug_frame      PROGBITS        00000000 0e4c0c 00916c 00      0   0  4
  [12] .debug_line       PROGBITS        00000000 0edd78 02ba87 00      0   0  1
  [13] .comment          PROGBITS        00000000 1197ff 000013 01  MS  0   0  1
  [14] .symtab           SYMTAB          00000000 119814 001390 10     16 162  4
  [15] .shstrtab         STRTAB          00000000 11aba4 0000fd 00      0   0  1
  [16] .strtab           STRTAB          00000000 11aca1 00206a 00      0   0  1
  [17] .vector_table     PROGBITS        00000000 000114 000100 00   A  0   0  4
  [18] .text             PROGBITS        00000100 000214 001500 00  AX  0   0  4
  [19] .rodata           PROGBITS        00001600 001720 00042c 00   A  0   0 16
  [20] .data             PROGBITS        2003fbc0 001b4c 000038 00  WA  0   0  4
  [21] .gnu.sgstubs      PROGBITS        00001a80 001ba0 000000 00  WA  0   0 32
  [22] .bss              NOBITS          2003fbf8 001ba0 000008 00  WA  0   0  4
  [23] .uninit           NOBITS          2003fc00 001ba0 000400 00  WA  0   0  4
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
  L (link order), O (extra OS processing required), G (group), T (TLS),
  C (compressed), x (unknown), o (OS specific), E (exclude),
  D (mbind), y (purecode), p (processor specific)

So this appears fixed?

[jonathanpallant]

Just to confirm I reset the link arguments and the sections are in the other order:

➜  test-pointers git:(main) ✗ /opt/homebrew/opt/binutils/bin/readelf -S ./target/thumbv7em-none-eabihf/debug/hello
There are 24 section headers, starting at offset 0x11cd0c:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .vector_table     PROGBITS        00000000 000114 000100 00   A  0   0  4
  [ 2] .text             PROGBITS        00000100 000214 001500 00  AX  0   0  4
  [ 3] .rodata           PROGBITS        00001600 001720 00042c 00   A  0   0 16
  [ 4] .data             PROGBITS        2003fbc0 001b4c 000038 00  WA  0   0  4
  [ 5] .gnu.sgstubs      PROGBITS        00001a80 001ba0 000000 00  WA  0   0 32
  [ 6] .bss              NOBITS          2003fbf8 001ba0 000008 00  WA  0   0  4
  [ 7] .uninit           NOBITS          2003fc00 001ba0 000400 00  WA  0   0  4
  [ 8] .defmt            PROGBITS        00000000 001ba0 000009 00      0   0  1
  [ 9] .debug_loc        PROGBITS        00000000 001ba9 0082dc 00      0   0  1
  [10] .debug_abbrev     PROGBITS        00000000 009e85 00222f 00      0   0  1
  [11] .debug_info       PROGBITS        00000000 00c0b4 03f13a 00      0   0  1
  [12] .debug_aranges    PROGBITS        00000000 04b1ee 003598 00      0   0  1
  [13] .debug_ranges     PROGBITS        00000000 04e786 01be00 00      0   0  1
  [14] .debug_str        PROGBITS        00000000 06a586 057a5a 01  MS  0   0  1
  [15] .debug_pubnames   PROGBITS        00000000 0c1fe0 01b34c 00      0   0  1
  [16] .debug_pubtypes   PROGBITS        00000000 0dd32c 0078a5 00      0   0  1
  [17] .ARM.attributes   ARM_ATTRIBUTES  00000000 0e4bd1 00003a 00      0   0  1
  [18] .debug_frame      PROGBITS        00000000 0e4c0c 00916c 00      0   0  4
  [19] .debug_line       PROGBITS        00000000 0edd78 02ba87 00      0   0  1
  [20] .comment          PROGBITS        00000000 1197ff 000013 01  MS  0   0  1
  [21] .symtab           SYMTAB          00000000 119814 001390 10     23 162  4
  [22] .shstrtab         STRTAB          00000000 11aba4 0000fd 00      0   0  1
  [23] .strtab           STRTAB          00000000 11aca1 00206a 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
  L (link order), O (extra OS processing required), G (group), T (TLS),
  C (compressed), x (unknown), o (OS specific), E (exclude),
  D (mbind), y (purecode), p (processor specific)

[jonathanpallant]

@Urhengulas are you happy we close this one?