On Nov 23, 2016 10:16 AM, "Dmitry Safonov" [off-list ref] wrote:

From commit 90954e7b9407 ("x86/coredump: Use pr_reg size, rather that
TIF_IA32 flag") elf coredump file is constructed according to register
set size - and that's good: if binary crashes with 32-bit code selector,
generate 32-bit ELF core, otherwise - 64-bit core.
That was made for restoring 32-bit applications on x86_64: we want
32-bit application after restore to generate 32-bit ELF dump on crash.
All was quite good and recently I started reworking 32-bit applications
dumping part of CRIU: now it has two parasites (32 and 64) for seizing
compat/native tasks, after rework it'll have one parasite, working in
64-bit mode, to which 32-bit prologue long-jumps during infection.

And while it has worked for my work machine, in VM with
!CONFIG_X86_X32_ABI during reworking I faced that segfault in 32-bit
binary, that has long-jumped to 64-bit mode results in dereference
of garbage:

Can you point to the actual line that's crashing?  I'm wondering if we
have code that should be made more robust.

--Andy

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