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50 lines
1.4 KiB
Plaintext
50 lines
1.4 KiB
Plaintext
[[qemu-user-mode]]
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= QEMU user mode
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This has nothing to do with the Linux kernel, but it is cool:
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....
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sudo apt-get install qemu-user
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./build -a arm
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cd buildroot/output.arm~/target
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qemu-arm -L . bin/ls
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....
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This uses QEMU's user-mode emulation mode that allows us to run
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cross-compiled userland programs directly on the host.
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The reason this is cool, is that `ls` is not statically compiled, but
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since we have the Buildroot image, we are still able to find the shared
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linker and the shared library at the given path.
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In other words, much cooler than:
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....
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arm-linux-gnueabi-gcc -o hello -static hello.c
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qemu-arm hello
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....
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It is also possible to compile QEMU user mode from source with
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`BR2_PACKAGE_HOST_QEMU_LINUX_USER_MODE=y`, but then your compilation
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will likely fail with:
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....
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package/qemu/qemu.mk:110: *** "Refusing to build qemu-user: target Linux version newer than host's.". Stop.
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....
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since we are using a bleeding edge kernel, which is a sanity check in
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the Buildroot QEMU package.
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Anyways, this warns us that the userland emulation will likely not be
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reliable, which is good to know. TODO: where is it documented the host
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kernel must be as new as the target one?
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GDB step debugging is also possible with:
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....
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qemu-arm -g 1234 -L . bin/ls
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../host/usr/bin/arm-buildroot-linux-uclibcgnueabi-gdb -ex 'target remote localhost:1234'
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....
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TODO: find source. Lazy now.
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