Hi Finn, thanks for your feedback! Am 29.04.2023 um 21:49 schrieb Finn Thain:
diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c index dfc7590abce8..75f4c4943231 100644 --- a/arch/m68k/kernel/signal.c +++ b/arch/m68k/kernel/signal.c @@ -858,11 +858,23 @@ static inline int rt_setup_ucontext(struct ucontext __user *uc, struct pt_regs * } static inline void __user * -get_sigframe(struct ksignal *ksig, size_t frame_size) +get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size) { - unsigned long usp = sigsp(rdusp(), ksig); + struct pt_regs *tregs = rte_regs(regs); + unsigned long usp = rdusp(); + unsigned long ssp = sigsp(usp, ksig); + + if (CPU_IS_020_OR_030 && ssp == usp && tregs->format == 0xb) { + struct frame *fmtbframe = (struct frame *) regs; + unsigned long fltp = (unsigned long) fmtbframe->un.fmtb.daddr; + + if (fltp < ssp && + (fltp >> PAGE_SHIFT) == (ssp >> PAGE_SHIFT)-1 && + (((fltp - frame_size) & -8UL) >> PAGE_SHIFT) == (fltp >> PAGE_SHIFT)) + ssp = fltp; + } - return (void __user *)((usp - frame_size) & -8UL); + return (void __user *)((ssp - frame_size) & -8UL); } static int setup_frame(struct ksignal *ksig, sigset_t *set,That seems over-complicated to me... I must be missing something. What I had in mind was something like this (untested): unsigned long usp; if (CPU_IS_020_OR_030 && tregs->format == 0xb) /* USP is unreliable so use the worst-case value. */ usp = sigsp(rdusp() - 256, ksig); else usp = sigsp(rdusp(), ksig); return (void __user *)((usp - frame_size) & -8UL);
sigsp() may return an address from the alternate signal stack. In that case, no adjustment to the signal stack address is advised.
The fault address may be on a different page than the normal signal stack address (should have tested that perhaps, instead of the second condition above). In that case we should not adjust the signal stack, either.
As to the rest, it's a matter of how detrimental indiscriminate use of the worst case gap size might be. Finding the 'best' adjustment may be more hassle than it's worth.
I'll run some stress testing on both versions Cheers, Michael
