On Tue, Apr 09, 2024 at 04:41:24PM -0700, Kees Cook wrote: > On Tue, Apr 09, 2024 at 07:11:56PM -0400, Steven Rostedt wrote: > > On Tue, 9 Apr 2024 15:23:07 -0700 > > Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > > > > Do we need to involve e820 at all? I think it might be possible to just > > > have pstore call request_mem_region() very early? Or does KASLR make > > > that unstable? > > > > Yeah, would that give the same physical memory each boot, and can we > > guarantee that KASLR will not map the kernel over the previous location? > > Hm, no, for physical memory it needs to get excluded very early, which > means e820. Whatever memory is reserved in arch/x86/kernel/e820.c, that happens after kaslr, so to begin with, a new memmap parameter should be also added to parse_memmap in arch/x86/boot/compressed/kaslr.c to ensure the same physical address will be available after KASLR. More generally, memmap= is x86 specific and a bit of a hack. Why won't you add a new kernel parameter that will be parsed in, say, mm/mm_init.c and will create the mmap_map (or whatever it will be named) and reserve that memory in memblock rather than in e820? This still will require update to arch/x86/boot/compressed/kaslr.c of course. > So, yeah, your proposal makes sense. I'm not super excited > about this be x86-only though. What does arm64 for for memmap? > > -- > Kees Cook > -- Sincerely yours, Mike.
