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The old code was wrong as
uc_regs
is not a registers array, but rather anmcontext_t
pointer on glibc, therefore indexing it goes way past the memory bounds. The actual registers array isgregs
inside themcontext_t
structure.On non-glibc libcs (as well as inside the kernel headers that are the reference), the structure is defined differently, with
uc_mcontext
being an actual value member just like on ppc64, so we can use that. On glibc/ppc32,mcontext_t
is an union ofuc_regs
andregs
pointers, with the value of the member being a pointer to where the realuc_mcontext
field would be.Basically, this is how the structure looks like in the kernel as well as on
musl
etc:on glibc the layout is broken, supposedly for compatibility with extremely ancient kernels (think pre-2.4 series) and looks like this instead: