Hi Bhupesh,
On Mon, May 28, 2018 at 2:33 AM, Bhupesh Sharma <bhsharma@xxxxxxxxxx> wrote:
> Hi ARM64 maintainers,
[...]
>
> 4. Since 'memstart_addr' indicates the start of physical RAM, we
> randomize the same on basis of 'memstart_offset_seed' value above.
> Also the 'memstart_addr' value is available in '/proc/kallsyms' and
> hence can be accessed by user-space applications to read the
> 'memstart_addr' value.
User space can read, only when a system has either CONFIG_DEVMEM or
CONFIG_PROC_KCORE enabled. But, we can have a system which has
CONFIG_RANDOMIZE_BASE enabled but none of the kernel memory access
interface (other than kdump/vmcore).
>
> 5. Now since the PAGE_OFFSET value is also used by several user space
> tools (for e.g. makedumpfile tool uses the same to determine the start
> of linear region and hence to read PT_NOTE fields from /proc/kcore), I
> am not sure how to read the randomized value of the same in the KASLR
> enabled case.
>
Do we have a use case other than makedumpfile (I mean where we do not
have vmcore access)? For makedumpfile, we have following information
in vmcore, and I hope, that should be sufficient to find physical
address of any symbol from vmcore.
358 VMCOREINFO_NUMBER(VA_BITS);
359 /* Please note VMCOREINFO_NUMBER() uses "%d", not "%x" */
360 vmcoreinfo_append_str("NUMBER(kimage_voffset)=0x%llx\n",
361 kimage_voffset);
362 vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%llx\n",
363 PHYS_OFFSET);
Regards
Pratyush
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