On Thu, 2012-10-04 at 13:22 +0100, Al Viro wrote: > On Thu, Oct 04, 2012 at 11:02:16AM +0100, James Bottomley wrote: > > > It's plausible. I just verified the theory that the branch is redundant > > by successfully booting with this patch applied. > > Somewhat related question: does CONFIG_HPUX work at all? I don't believe so. It's been bitrotting for some time. > What we have there > is this: > mfctl %cr30,%r1 > xor %r1,%r30,%r30 /* ye olde xor trick */ > xor %r1,%r30,%r1 > xor %r1,%r30,%r30 > ldo TASK_SZ_ALGN+FRAME_SIZE(%r30),%r30 /* set up kernel stack */ > followed by saving registers into &((struct task_struct *)cr30)->thread.regs. > cr30 contains something very different, though - struct thread_info *. > Had been that way since 2002 or so. And after we'd been finished with > syscall, we'll get to hpux_syscall_exit, tweak r22/r28 a bit and > sod off to syscall_exit. Which does > mfctl %cr30, %r1 > LDREG TI_TASK(%r1),%r1 > and eventually restores the values of registers saved in > &(struct task_struct)r1->thread.regs. Except that here the value of r1 is > ((struct thread_info *)cr30)->task, not cr30 itself. Which matches what we > have in current.h (and do_fork(), etc.), but not what we'd done when we > entered the syscall. IOW, the values we restore will have nothing to do > with what we saved. > > Unless I'm missing something really subtle, it looks like HPUX compat had > been very noticably broken since at least 2002. Comments? I think it probably has. I don't believe there's anyone left with hpux binaries actually checking it. James -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
