On Tue, Dec 15, 2015 at 11:25:36AM +0100, Paolo Bonzini wrote:
> set_exception_return forces exceptions handlers to return to a specific
> address instead of returning to the instruction address pushed by the
> CPU at the time of the exception. The unit tests apic.c and vmx.c use
> this functionality to recover from expected exceptions.
>
> When using set_exception_return one would have to be careful not to modify
> the stack (such as by doing a function call) as triggering the exception
> will likely jump us past the instructions which undo the stack manipulation
> (such as a ret). This is unnecessarily brittle, and C already has a
> mechanism to do non-local returns---setjmp. Now that libcflat includes
> an implementation of setjmp, replace set_exception_return with a wrapper
> that takes care of restoring the processor flags as well.
>
> Reported-by: David Matlack <dmatlack@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> lib/x86/desc.c | 15 +++++++++++----
> lib/x86/desc.h | 6 +++++-
> x86/apic.c | 8 ++++----
> x86/vmx.c | 18 +++++++++---------
> 4 files changed, 29 insertions(+), 18 deletions(-)
>
> diff --git a/lib/x86/desc.c b/lib/x86/desc.c
> index 4760026..acf29e3 100644
> --- a/lib/x86/desc.c
> +++ b/lib/x86/desc.c
> @@ -1,6 +1,7 @@
> #include "libcflat.h"
> #include "desc.h"
> #include "processor.h"
> +#include <setjmp.h>
>
> void set_idt_entry(int vec, void *addr, int dpl)
> {
> @@ -315,12 +316,18 @@ void setup_alt_stack(void)
> #endif
>
> static bool exception;
> -static void *exception_return;
> +static jmp_buf *exception_jmpbuf;
While changing this, how about making it per_cpu?
i.e. exception_jmpbuf[NR_CPUS]
drew
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