b69d0da82d
This patch adds a x86_64 architecture and qemu_x86_64 board to Zephyr. Only the basic architecture support needed to run 64 bit code is added; no drivers are added, though a low-level console exists and is wired to printk(). The support is built on top of a "X86 underkernel" layer, which can be built in isolation as a unit test on a Linux host. Limitations: + Right now the SDK lacks an x86_64 toolchain. The build will fall back to a host toolchain if it finds no cross compiler defined, which is tested to work on gcc 8.2.1 right now. + No x87/SSE/AVX usage is allowed. This is a stronger limitation than other architectures where the instructions work from one thread even if the context switch code doesn't support it. We are passing -no-sse to prevent gcc from automatically generating SSE instructions for non-floating-point purposes, which has the side effect of changing the ABI. Future work to handle the FPU registers will need to be combined with an "application" ABI distinct from the kernel one (or just to require USERSPACE). + Paging is enabled (it has to be in long mode), but is a 1:1 mapping of all memory. No MMU/USERSPACE support yet. + We are building with -mno-red-zone for stack size reasons, but this is a valuable optimization. Enabling it requires automatic stack switching, which requires a TSS, which means it has to happen after MMU support. + The OS runs in 64 bit mode, but for compatibility reasons is compiled to the 32 bit "X32" ABI. So while the full 64 bit registers and instruction set are available, C pointers are 32 bits long and Zephyr is constrained to run in the bottom 4G of memory. Signed-off-by: Andy Ross <andrew.j.ross@intel.com> |
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| src | ||
| CMakeLists.txt | ||
| README.txt | ||
| prj.conf | ||
| sample.yaml | ||
README.txt
Title: Thermometer
Description:
A simple thermometer example
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Building and Running Project:
This project writes the temperature to the console once per second.
It can be built and executed on bbc_microbit as follows:
make
Sample Output:
Thermometer Example!
arm temp device is 0x20000184, name is TEMP_0
Temperature is 29.5C
Temperature is 29.5C
Temperature is 29.5C