On August 22, 2016 3:23:06 PM PDT, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: >On Sun, Aug 21, 2016 at 10:52 AM, Linus Torvalds ><torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: >> On Sat, Aug 20, 2016 at 11:42 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> >wrote: >>> >>> It's not exactly setjmp/longjmp; what I had in mind was along the >lines of >> >> That ends up having all the exact same issues as setjmp, and >generally >> you *do* want the compiler to know about it. > >So just in case you wanted to play around with it, here's a kernel >implementation of 'setjmp/longjmp' for x86. > >It's very lightly tested (and I'll admit to editing it for some >cleanups after that light testing), but it does look largely sane. > >The whole interface choice may be debatable: maybe it would be better >to allocate the register buffer on the stack, and just hide a pointer >to it in the task struct. Things like that could be changed fairly >easily. But if you want to play around with this, this patch should >get you started. > >Of course, you'd want to wrap things up somehow, and I would *not* >want to see naked setjmp() calls in the kernel. > >And we'd need this for all other architectures too, but it's usually >not hard to do. It needs to save all the callee-saved registers and >the stack pointer and return address. That should generally be it. > >The 32-bit version has not been tested at all, but it compiled at some >point, and the code looks mostly sane. The 64-bit code I actually had >a stupid non-user-access test-case for. > > Linus The nice thing about using __builtin_ is that I believe gcc is aware of which registers need saving, and also know that the common path doesn't clobber registers at all. -- Sent from my Android device with K-9 Mail. Please excuse brevity and formatting. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
