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".byte 0x3f" instructions in disassembly

Posted: Thu Jul 06, 2023 9:46 pm
by Graggi
Hi,

I'm using xtensa-esp32-elf-objdump[1] to analysis some ESP32-Binaries. I noticed that sometimes 0x3f single byte instructions(?) can be found in the disassembly.

For example:
3f.png
3f.png (69.07 KiB) Viewed 31137 times
I could not find any mentioning of this in the Xtensa-ISA[2]. Why are they placed there?

Regards

[1] https://github.com/badgeteam/xtensa-esp ... master/bin
[2] https://esp32.com/download/file.php?id=10134

Re: ".byte 0x3f" instructions in disassembly

Posted: Fri Jul 07, 2023 8:52 am
by ESP_Sprite
Objdump is not very smart and may be trying to decode non-instruction areas, like literal pools.

Re: ".byte 0x3f" instructions in disassembly

Posted: Fri Jul 07, 2023 7:03 pm
by ESP_igrr
This could also be caused by the ELF file missing additional xtensa-specific sections; we have fixed this issue in https://github.com/espressif/esp-idf/co ... 98277fb3bb, but it could be that your ELF file was built with an IDF version which doesn't contain that fix.