DRAFT: resources: Add gem5_bridge driver to x86-ubuntu build & boot #48
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This is to support backwards compatibility with the former /dev/mem pokes for disk images that do not or cannot yet support the driver. In the future, these can potentially be changed if there is a push for solely using the driver.
Harshil2107
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Feb 4, 2025
Adds a Linux kernel module for a character device that can facilitate address-type `gem5-bridge` commands with user permissions. This is an improvement over the current system as it no longer requires `sudo` permissions from the simulation as we replace accesses to `/dev/mem/` with accesses to `/dev/gem5_bridge` for which we can control permissions. Relates to gem5/gem5-resources#48 Adds `util/gem5_bridge` which includes the C source for the driver and a Makefile to build it from within the disk image -- building and launching the module are done here gem5/gem5-resources#48. The Makefile can take arguments to modify the base address for the gem5ops MMIO range by putting `GEM5OPS_BASE=<base_phys_addr>` at the end of the make command. Modifies `util/m5/src/m5_mmap.c` to mmap from our device `/dev/gem5_bridge` rather than `/dev/mem`. **Current Issues** - Requires the module to be built with the exact same version as the running kernel during simulation. This is most easily achieved by running the simulation with the `vmlinux` kernel extracted from the built disk image. However, need to find a proper solution to support multiple kernel versions. If the kernel headers are available on `apt`, then this has been shown to work, but efforts to acquire the headers for an arbitrary kernel version have so far failed.
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Adds commands to
scripts/post-installation.shto make the driver during disk building. The Makefile can take arguments to modify the base address for the gem5ops MMIO range by puttingGEM5OPS_BASE=<base_phys_addr>at the end of the make command.Adds commands to
files/gem5_init.shto detect and add the driver after kernel startup but just before the firstgem5-bridge exit.Relates to gem5/gem5#1480