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49 lines
2.1 KiB
Plaintext
49 lines
2.1 KiB
Plaintext
So to make a Linux initrd:
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(1) mkdir .../initrd
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(2) mkdir -p .../initrd/boot/defaults
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(3) cd src/stand; make install DESTDIR=.../initrd
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(4) Copy kernel to .../initrd/boot/kernel
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(5) cd .../initrd
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(6) cp boot/loader.kboot init
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(7) find . | sort | cpio -o -H newc | gzip > /tmp/initrd.cpio
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(8) download or build your linux kernel
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(9) qemu-system-x86_64 -kernel ~/vmlinuz-5.19.0-051900-generic \
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-initrd /tmp/initrd.cpio \
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-m 256m -nographic \
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-monitor telnet::4444,server,nowait -serial stdio \
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-append "console=ttyS0"
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(though you may need more than 256M of ram to actually boot FreeBSD and do
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anything interesting with it and the serial console to stdio bit hasn't
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been the most stable recipe lately).
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Notes:
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For #6 you might need to strip loader.kboot if you copy it directly and don't
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use make install.
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For #7 the sort is important, and you may need LC_ALL=C for its invocation
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For #7 gzip is but one of many methods, but it's the simplest to do.
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For #9, this means we can automate it using methods from
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src/tools/boot/rootgen.sh when the time comes.
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#9 also likely generalizes to other architectures
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For #8, see https://kernel.ubuntu.com/~kernel-ppa/mainline/ to download
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a kernel suitable for testing... For arm, I've been using the
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non 64k page kernels and 5.19 seems to not suck.
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aarch64:
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qemu-system-aarch64 -m 1024 -cpu cortex-a57 -M virt \
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-kernel ~/linuxboot/arm64/kernel/boot/vmlinuz-5.19.0-051900-generic \
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-initrd ~/linuxboot/arm64/initrd.img -m 256m -nographic \
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-monitor telnet::4444,server,nowait -serial stdio \
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-append "console=ttyAMA0"
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General
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Add -g -G to have gdb stop and wait for the debugger. This is useful for
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debugging the trampoline (hbreak will set a hardware break that's durable across
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code changes). If you set the breakpoint for the trampoline and it never hits,
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then there's likely no RAM there and you got the PA to load to wrong. When
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debugging the trampiline and up to that, use gdb /boot/loader. When debugging
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the kernel, use kernel.full to get all the debugging. hbreak panic() is useful
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on the latter since you'll see the original panic, not the panic you get from
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there not being an early console.
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