https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113321
--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> --- (In reply to H. Peter Anvin from comment #0) > __attribute__((interrupt)) on x86 has two prototypes, and picking the wrong > type "probably will cause a system crash." It turns out that this is > unavoidable on i386, but on x86-64 we can do better: > > - On x86-64, an exception/interrupt carries an error code if and only if the > stack is 16-byte aligned (specifically, RSP[3] = 0) on exception entry. > > The proper stack pointer for using with IRET is therefore always given by: > > RSP |= 8 > > ... and the error code, if present, will be located at offset -8 from this > address. GCC always generates IRET for __attribute__((interrupt)). If there are 2 arguments (one of them is the error code), it is an exception handler. Otherwise, it is an interrupt handler.
