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Date: Mon, 25 Aug 2008 16:26:06 -0400 (EDT)
From: Vince Weaver <vince@csl.cornell.edu>
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Subject: [Qemu-devel] linux-user exception handling
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To: qemu-devel@nongnu.org

Hello

so I'm tracking down a problem on sparc32plus-linux-user.
SPARC has register windows, and when it tried to save another register 
context, but all available ones are full, it causes a TT_SPILL exception. 
In theory the OS would handle this and move some of the registers to RAM 
somewhere.

In any case, this doesn't seem to be working properly.  I've traced 
through the code, and I find in cpu-exec.c where userspace exceptions are 
handled.

The code involved in listed below.

Am I correct in reading that user-mode exceptions are only implemented for 
x86?  If so that makes me sad, because it means that pretty much any SPARC 
program that has more than 8 nested function calls won't work until a lot 
more code is implemented.

Vince



                } else if (env->user_mode_only) {
                     /* if user mode only, we simulate a fake exception
                        which will be handled outside the cpu execution
                        loop */
#if defined(TARGET_I386)
                     do_interrupt_user(env->exception_index,
                                       env->exception_is_int,
                                       env->error_code,
                                       env->exception_next_eip);
                     /* successfully delivered */
                     env->old_exception = -1;
#endif
                     ret = env->exception_index;
                     break;