Messages in this thread | | | Date | Mon, 21 Apr 2014 18:52:32 +0800 | From | WANG Chao <> | Subject | kaslr relocation incompitable with kernel loaded high |
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Hi, Kees
When I'm testing kaslr with kdump, I find that when 2nd kernel is loaded high, it doesn't boot.
I reserved 128M memory at high with kernel cmdline "crashkernel=128M,high crashkernel=0,low", and for which I got:
[ 0.000000] Reserving 128MB of memory at 6896MB for crashkernel (System RAM: 6013MB)
Then I load kdump kernel into the reserved memory region, using a local modified kexec-tools which is passing e820 in boot_params.
The e820 map of system RAM passed to 2nd kernel:
E820 memmap (of RAM): 0000000000001000-000000000009e3ff (1) 00000001af000000-00000001b6f5dfff (1) 00000001b6fff400-00000001b6ffffff (1)
In which, 2nd kernel is loaded at 0x1b5000000.
After triggerred a system crash, 2nd kernel doesn't boot even with "nokaslr" cmdline:
# echo c > /proc/sysrq-trigger [..]
I'm in purgatory early console in decompress_kernel KASLR disabled...
Decompressing Linux... Parsing ELF... Performing relocations...
32-bit relocation outside of kernel!
-- System halted
I know 32bit relocation code has recently moved to misc.c and it's a ground work for kaslr on x86_64. However it doesn't work out on a kernel high loaded case.
I'm not quite familiar with this. But I'm wondering if it makes sense to skip handle_relocation() if kaslr doesn't take effects (nokaslr or kaslr failed to find suitable area).
Thanks WANG Chao
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