Ibrahim Youssef
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Read from and write to I/O registers and memory
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Ibrahim Youssef
03/28/2024 3:44 PM
post122514
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Read from and write to I/O registers and memory
Hello all,
BACKGROUND:
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I am working on a project that is using QNX 7.1.0 2023/07/14-18:28:39EDT NXP_i.MX8QXP_CPU_Board aarch64le
I am currently working on features related to IFS authentication, and will eventually want to program the OTP memory
with public keys to allow authentication to proceed with correctly signed IFSs. Before burning the OTP fuses, I would
like to test that my pki/signing/authentication are functioning correctly. For this reason, I'd like to leverage the i.
MX8QXP shadow registers to simulate writing/reading the OTP memory. As per page 194, section 7.1.2 of the reference
manual, this should be possible:
"If not locked then it can be read sensed and programmed and the shadow registers can be overwritten (to allow emulation
of programming without actually blowing fuses)."
QUESTION:
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I am unable to use QNX utilities like `io` or even `dd` to read from these shadow registers. For example, I have tried
to read the default (unprogrammed) UNIQUE_ID value from shadow register 0x0900 with the following commands as root user:
# io b 0x0900
# dd if=/dev/mem skip=$((0x0900)) bs=16 count=1
Both commands fail. I have attached the error output for both commands to this forum post. Any ideas about what I might
be misunderstanding/overlooking would be greatly appreciated!
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