On Sat, 11 Oct 2008, Yuri wrote:
Let's say I have signal(3) handler set.
And I know exactly what instruction caused SEGV and why.
Is there a way to access from signal handler CPU registers as they
were before signal, modify some of them, clear the signal and
continue from the instruction that caused SEGV initially?
Absolutely. Declare your signal handler as
void handler(int sig, int code, struct sigcontext *scp);
You will need to cast the pointer passed to signal(3). struct sigcontext
is defined in <machine/sysarch.h> I believe. struct sigcontext contains
the CPU registers as they were when the faulting instruction began to
execute. You can modify them and then return from the signal handler.
The program will resume the faulting instruction with the new registers.
You can also alter the copy of the instruction pointer in the struct
sigcontext if you want it to resume somewhere else.
There is also a libsigsegv which looks like it wraps some of this process
in a less machine-specific way.
Out of curiosity, what are you looking to achieve with this? And what
architecture are you on?
--
Nate Eldredge
[EMAIL PROTECTED]
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