Hi Takahiro, Thanks for your reply. On 22/06/2016:02:59:41 PM, AKASHI Takahiro wrote: > On Mon, Jun 20, 2016 at 11:02:22AM +0530, Pratyush Anand wrote: > > +Atsushi > > > > Hi Takahiro, > > > > On 16/06/2016:11:48:28 PM, Geoff Levand wrote: > > > From: AKASHI Takahiro <takahiro.akashi at linaro.org> > > > > > > For the current crash utility, we need to know, at least, > > > - kimage_voffset > > > - PHYS_OFFSET > > > to handle the contents of core dump file (/proc/vmcore) correctly due to > > > the introduction of KASLR (CONFIG_RANDOMIZE_BASE) in v4.6. > > > This patch puts them as VMCOREINFO's into the file. > > > > > > - VA_BITS > > > is also added for makedumpfile command. > > > > Thanks for adding them. They are quite helpful for makedumpfile as well. > > > > > More VMCOREINFO's may be added later. > > > > Yes, we will need to pass VMCOREINFO_SYMBOL(_text) and VMCOREINFO_SYMBOL(_end) > > in order to work with makedumpfile. > > I know that adding those symbols is the easiest way, but > theoretically, if we know the physical address of "swapper_pg_dir", But, we know only it's virtual address. > instead of its virtual address, we can access all the memory pointed to > by any kernel virtual address. > How do you rationalize that we need to know "_text" and "_end"? Well, we need some mechanism so that we can decide if an address can be translated using linear mapping of virt_to_phys(). Alternatively, probably we can do like this: -- Translate all address between "SYMBOL(swapper_pg_dir)" and "SYMBOL(swapper_pg_dir) + SWAPPER_DIR_SIZE" using virt_to_phys() and now we can read values from dumpfile using that physical address. This way we can get PGD/PMD/PUD values. -- PTE values may lie out side this range, however that address should still be linearly translatable. We can use virt_to_phys() macro from them as well. In summary, we can translate address of PGD/PMD/PUD/PTE using virt_to_phys() and rest all can be translated using page table entries. ~Pratyush
