Re: [Crash-utility] [PATCH v5] arm64: fix kernel memory map handling for kaslr-enabled

> Dave, > > On Mon, Jun 13, 2016 at 04:06:22PM -0400, Dave Anderson wrote: > > > > > > ----- Original Message ----- > > > In my next version of kdump patch, the following VMCOREINFO will be > > > added: > > > NUMBER(VA_BITS) > > > NUMBER(kimage_voffset) > > > NUMBER(PHYS_OFFSET) > > > KERNELOFFSET > > Is "KERNELOFFSET" useful for arm64? > As you said, this value is used as a trigger of KASLR_CHECK, > but the current kernel doesn't have "randomize_modules". Right, so AIUI, this crash-7.0.7 update is not valid for Linux 4.1 and later kernels where "randomize_modules" was removed: - Linux 3.15 and later kernels configured with CONFIG_RANDOMIZE_BASE can be now be readily identified because of new kernel symbols that have been added. For those kernels, the new "--kaslr=<offset>" and/or "--kaslr=auto" options are not necessary for ELF or compressed kdump vmcores, or for live systems that have /proc/kallsyms showing the relocated symbol values. A new KASLR initialization function called kaslr_init() is now called by symtab_init() prior to the initial symbol-sorting operation. If kaslr_init() determines that KASLR may be in effect, it will trigger a search for the relevant vmlinux symbols during the sorting operation, which in turn will cause the relocation value to be automatically calculated. (anderson(a)redhat.com) So for those kernels, --kaslr would be required. But it appears that I can just change crash to look for "module_load_offset", which went into the kernel at the same time as "randomize_modules": +#ifdef CONFIG_RANDOMIZE_BASE +static unsigned long module_load_offset; +static int randomize_modules = 1; + and still exists after it was removed from arch/x86/kernel/module.c: #ifdef CONFIG_RANDOMIZE_BASE static unsigned long module_load_offset; -static int randomize_modules = 1; For arm64 in the crash utility, I see that you would never use KASLR_CHECK because (RELOC_AUTO|KASLR) gets set by default if NEW_VMEMMAP is set. Would it be useful for makedumpfile?

And while I understand you're dead set against adding anything that could be considered superfluous, but since it does exist for x86_64, it seems natural to include it for arm64. Dave > Thanks, > -Takahiro AKASHI > -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility