RE: [Jikesrvm-core] cTrapHandler does not work for null pointer dereference on PPC64 Linux

[Eliot M. <mo...@cs...>]

>>>>> "Sergiy" == Sergiy Kyrylkov <se...@cs...> writes:

    Sergiy> Eliot,
    Sergiy> I found the correct value:

    Sergiy> ......................
    Sergiy> Program received signal SIGSEGV, Segmentation fault.
    Sergiy> 0x0000000060226a88 in ?? ()
    Sergiy> (gdb) c
    Sergiy> Continuing.

    Sergiy> Breakpoint 1, getLinuxSavedContext(int, void*) (signum=11,
    Sergiy> arg3=0x1ffffffeeb0)
    Sergiy>     at libvm.C:209
    Sergiy> 209        return &((ucontext_t*)arg3)->uc_mcontext;
    Sergiy> (gdb) x/128xg arg3
    Sergiy> 0x1ffffffeeb0:  0x0000000000000000      0x0000000000000000
    Sergiy> 0x1ffffffeec0:  0x000001ffffffd628      0x0000000000000000
    Sergiy> ........................
    Sergiy> ........................
    Sergiy> ........................
    Sergiy> 0x1fffffff0e0:  0xffffffffffffffe8      0x0000000000200000

    Sergiy> Now the question is how do we extract it correctly?

I took a quick look, and it appears that the ucontext, sigcontext, and
ptrace .h files (the latter ultimately in /usr/include/asm-ppc64, but
"redirected" multiple levels) hold the key. I think that casting arg3
properly and following links / extracting fields in it properly will
work. And perhaps the get_context functions actually work and all now. Can
you dig into all that a little bit more?

-- Eliot