note: I don't know linux...
Is it possible to get the GPU to copy kernel / system memory to the framebuffer, then read that back with user space app? I.e. can we convince the GPU or framebuffer to give us the contents of protected system memory?
Is it possible to get the GPU to copy kernel / system memory to the framebuffer, then read that back with user space app? I.e. can we convince the GPU or framebuffer to give us the contents of protected system memory?
Otherwise, it simply depends on system hardware architecture and drivers.
If the GPU is in a position to read and write physical memory (bus master DMA), and there's no hardware level protection like IOMMU or it's not properly configured, operating system has very little say in the matter, be it Linux or anything else.