The Overtone Scale?

If you look at the overtone series, specifically from the 8th to the 16th, you’lll notice that they fit into an octave and almost, but not quite, make up a major scale.. I’d like to look a little closer at that difference.

If we start on a C, the notes of the series are (almost)

C D E F# G Ab Bb B C

I say almost because they are not actually these notes…these are merely the closest approximations to the notes if you are playing a well-tempered clavier or its descendants. If you are playing something a little more flexible, such as a fretless string instrument like the violin, you can adjust your playing and play exactly these pitches.

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Enabling ARM64 CPU Capabilities in the Linux Kernel

ARM64 design defines features long before there is a CPU that can implement those features. Since the ARM ecosystem is so varied, there are many different CPU designs out there with different capabilities. A general purpose linux Kernel build put out by a major distribution has to work across a wide array of chips by a large nuymber of vendors. Thus, there is an enumeration of the capabilities inside the Kernel and mechnism for describing how to probe each of these capabilities.

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Finding Linux Kernel Config options in menuconfig

We have reason to believe that we should not be setting CONFIG_EFI_DISABLE_RUNTIME=y In our Kernel configs. I want to perform a controlled expereient booting two Kernel builds, one with this option set and one with it disabled. Since I have the option set, building that Kernel is trivial.

 make olddefconfig
 make -j$(nproc)  rpm-pkg

Now, to turn that option off, I could just edit the .config file. However, it is possible that there are other config options linked to that one, and there is logic to modify them together. I want to see what happens if I use make menuconfig to change the option to confirm (or deny) that only that option gets changed. But where do I find this option in the menu?

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Building and Running the Linux Kernel Selftests on AARCH64/ Fedora

I won’t go into checking out or building the Kernel, as that is covered elsewhere. Assuming you have a buildable Kernel, you can build the tests with:

make -C tools/testing/selftests

But you are probably going to see errors like this:

ksm_tests.c:7:10: fatal error: numa.h: No such file or directory
    7 | #include <numa.h>
      |          ^~~~~~~~
compilation terminated.

The userland test suites use several libraries and need headers to compile the tests that call those libraries. Here is the yum, line I ran to get the dependencies I needed for my system:

sudo yum install libmnl-devel fuse-devel numactl-devel libcap-ng-devel alsa-lib-devel

With those installed, the make line succeeded.

Running the test like this CRASHED THE SYSTEM. Don’t do this.

 make -C tools/testing/selftests run_tests

A more sensible test to run is the example on the Docs page:

# make -C tools/testing/selftests TARGETS=ptrace run_tests
make: Entering directory '/root/linux/tools/testing/selftests'
make --no-builtin-rules ARCH=arm64 -C ../../.. headers_install
make[1]: Entering directory '/root/linux'
  INSTALL ./usr/include
make[1]: Leaving directory '/root/linux'
make[1]: Entering directory '/root/linux/tools/testing/selftests/ptrace'
make[1]: Nothing to be done for 'all'.
make[1]: Leaving directory '/root/linux/tools/testing/selftests/ptrace'
make[1]: Entering directory '/root/linux/tools/testing/selftests/ptrace'
TAP version 13
# selftests: ptrace: get_syscall_info
# TAP version 13
# 1..1
# # Starting 1 tests from 1 test cases.
# #  RUN           global.get_syscall_info ...
# #            OK  global.get_syscall_info
# ok 1 global.get_syscall_info
# # PASSED: 1 / 1 tests passed.
# # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
ok 1 selftests: ptrace: get_syscall_info
# selftests: ptrace: peeksiginfo
ok 2 selftests: ptrace: peeksiginfo
# selftests: ptrace: vmaccess
# TAP version 13
# 1..2
# # Starting 2 tests from 1 test cases.
# #  RUN           global.vmaccess ...
# #            OK  global.vmaccess
# ok 1 global.vmaccess
# #  RUN           global.attach ...
# # attach: Test terminated by timeout
# #          FAIL  global.attach
# not ok 2 global.attach
# # FAILED: 1 / 2 tests passed.
# # Totals: pass:1 fail:1 xfail:0 xpass:0 skip:0 error:0
not ok 3 selftests: ptrace: vmaccess # exit=1
make[1]: Leaving directory '/root/linux/tools/testing/selftests/ptrace'
make: Leaving directory '/root/linux/tools/testing/selftests'

Next up is to write my own stub test.