From 4bb0bd81ce5e97092dfda6a106d414b703ec0ee8 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 25 Jul 2021 17:19:00 +0000 Subject: m68k: Handle arrivals of multiple signals correctly When we have several pending signals, have entered with the kernel with large exception frame *and* have already built at least one sigframe, regs->stkadj is going to be non-zero and regs->format/sr/pc are going to be junk - the real values are in shifted exception stack frame we'd built when putting together the first sigframe. If that happens, subsequent sigframes are going to be garbage. Not hard to fix - just need to find the "adjusted" frame first and look for format/vector/sr/pc in it. Signed-off-by: Al Viro Tested-by: Michael Schmitz Reviewed-by: Michael Schmitz Tested-by: Finn Thain Link: https://lore.kernel.org/r/YP2dBIAPTaVvHiZ6@zeniv-ca.linux.org.uk Signed-off-by: Geert Uytterhoeven --- arch/m68k/kernel/signal.c | 88 ++++++++++++++++++++++------------------------- 1 file changed, 42 insertions(+), 46 deletions(-) (limited to 'arch/m68k/kernel/signal.c') diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c index 8f215e79e70e..cd11eb101eac 100644 --- a/arch/m68k/kernel/signal.c +++ b/arch/m68k/kernel/signal.c @@ -447,7 +447,7 @@ static inline void save_fpu_state(struct sigcontext *sc, struct pt_regs *regs) if (CPU_IS_060 ? sc->sc_fpstate[2] : sc->sc_fpstate[0]) { fpu_version = sc->sc_fpstate[0]; - if (CPU_IS_020_OR_030 && + if (CPU_IS_020_OR_030 && !regs->stkadj && regs->vector >= (VEC_FPBRUC * 4) && regs->vector <= (VEC_FPNAN * 4)) { /* Clear pending exception in 68882 idle frame */ @@ -510,7 +510,7 @@ static inline int rt_save_fpu_state(struct ucontext __user *uc, struct pt_regs * if (!(CPU_IS_060 || CPU_IS_COLDFIRE)) context_size = fpstate[1]; fpu_version = fpstate[0]; - if (CPU_IS_020_OR_030 && + if (CPU_IS_020_OR_030 && !regs->stkadj && regs->vector >= (VEC_FPBRUC * 4) && regs->vector <= (VEC_FPNAN * 4)) { /* Clear pending exception in 68882 idle frame */ @@ -832,18 +832,24 @@ badframe: return 0; } +static inline struct pt_regs *rte_regs(struct pt_regs *regs) +{ + return (void *)regs + regs->stkadj; +} + static void setup_sigcontext(struct sigcontext *sc, struct pt_regs *regs, unsigned long mask) { + struct pt_regs *tregs = rte_regs(regs); sc->sc_mask = mask; sc->sc_usp = rdusp(); sc->sc_d0 = regs->d0; sc->sc_d1 = regs->d1; sc->sc_a0 = regs->a0; sc->sc_a1 = regs->a1; - sc->sc_sr = regs->sr; - sc->sc_pc = regs->pc; - sc->sc_formatvec = regs->format << 12 | regs->vector; + sc->sc_sr = tregs->sr; + sc->sc_pc = tregs->pc; + sc->sc_formatvec = tregs->format << 12 | tregs->vector; save_a5_state(sc, regs); save_fpu_state(sc, regs); } @@ -851,6 +857,7 @@ static void setup_sigcontext(struct sigcontext *sc, struct pt_regs *regs, static inline int rt_setup_ucontext(struct ucontext __user *uc, struct pt_regs *regs) { struct switch_stack *sw = (struct switch_stack *)regs - 1; + struct pt_regs *tregs = rte_regs(regs); greg_t __user *gregs = uc->uc_mcontext.gregs; int err = 0; @@ -871,9 +878,9 @@ static inline int rt_setup_ucontext(struct ucontext __user *uc, struct pt_regs * err |= __put_user(sw->a5, &gregs[13]); err |= __put_user(sw->a6, &gregs[14]); err |= __put_user(rdusp(), &gregs[15]); - err |= __put_user(regs->pc, &gregs[16]); - err |= __put_user(regs->sr, &gregs[17]); - err |= __put_user((regs->format << 12) | regs->vector, &uc->uc_formatvec); + err |= __put_user(tregs->pc, &gregs[16]); + err |= __put_user(tregs->sr, &gregs[17]); + err |= __put_user((tregs->format << 12) | tregs->vector, &uc->uc_formatvec); err |= rt_save_fpu_state(uc, regs); return err; } @@ -890,13 +897,14 @@ static int setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) { struct sigframe __user *frame; - int fsize = frame_extra_sizes(regs->format); + struct pt_regs *tregs = rte_regs(regs); + int fsize = frame_extra_sizes(tregs->format); struct sigcontext context; int err = 0, sig = ksig->sig; if (fsize < 0) { pr_debug("setup_frame: Unknown frame format %#x\n", - regs->format); + tregs->format); return -EFAULT; } @@ -907,7 +915,7 @@ static int setup_frame(struct ksignal *ksig, sigset_t *set, err |= __put_user(sig, &frame->sig); - err |= __put_user(regs->vector, &frame->code); + err |= __put_user(tregs->vector, &frame->code); err |= __put_user(&frame->sc, &frame->psc); if (_NSIG_WORDS > 1) @@ -933,34 +941,28 @@ static int setup_frame(struct ksignal *ksig, sigset_t *set, push_cache ((unsigned long) &frame->retcode); - /* - * Set up registers for signal handler. All the state we are about - * to destroy is successfully copied to sigframe. - */ - wrusp ((unsigned long) frame); - regs->pc = (unsigned long) ksig->ka.sa.sa_handler; - adjustformat(regs); - /* * This is subtle; if we build more than one sigframe, all but the * first one will see frame format 0 and have fsize == 0, so we won't * screw stkadj. */ - if (fsize) + if (fsize) { regs->stkadj = fsize; - - /* Prepare to skip over the extra stuff in the exception frame. */ - if (regs->stkadj) { - struct pt_regs *tregs = - (struct pt_regs *)((ulong)regs + regs->stkadj); + tregs = rte_regs(regs); pr_debug("Performing stackadjust=%04lx\n", regs->stkadj); - /* This must be copied with decreasing addresses to - handle overlaps. */ tregs->vector = 0; tregs->format = 0; - tregs->pc = regs->pc; tregs->sr = regs->sr; } + + /* + * Set up registers for signal handler. All the state we are about + * to destroy is successfully copied to sigframe. + */ + wrusp ((unsigned long) frame); + tregs->pc = (unsigned long) ksig->ka.sa.sa_handler; + adjustformat(regs); + return 0; } @@ -968,7 +970,8 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) { struct rt_sigframe __user *frame; - int fsize = frame_extra_sizes(regs->format); + struct pt_regs *tregs = rte_regs(regs); + int fsize = frame_extra_sizes(tregs->format); int err = 0, sig = ksig->sig; if (fsize < 0) { @@ -1018,34 +1021,27 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set, push_cache ((unsigned long) &frame->retcode); - /* - * Set up registers for signal handler. All the state we are about - * to destroy is successfully copied to sigframe. - */ - wrusp ((unsigned long) frame); - regs->pc = (unsigned long) ksig->ka.sa.sa_handler; - adjustformat(regs); - /* * This is subtle; if we build more than one sigframe, all but the * first one will see frame format 0 and have fsize == 0, so we won't * screw stkadj. */ - if (fsize) + if (fsize) { regs->stkadj = fsize; - - /* Prepare to skip over the extra stuff in the exception frame. */ - if (regs->stkadj) { - struct pt_regs *tregs = - (struct pt_regs *)((ulong)regs + regs->stkadj); + tregs = rte_regs(regs); pr_debug("Performing stackadjust=%04lx\n", regs->stkadj); - /* This must be copied with decreasing addresses to - handle overlaps. */ tregs->vector = 0; tregs->format = 0; - tregs->pc = regs->pc; tregs->sr = regs->sr; } + + /* + * Set up registers for signal handler. All the state we are about + * to destroy is successfully copied to sigframe. + */ + wrusp ((unsigned long) frame); + tregs->pc = (unsigned long) ksig->ka.sa.sa_handler; + adjustformat(regs); return 0; } -- cgit v1.2.3 From 0d20abde987bed05a8963c8aa4276019d54ff9e7 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 25 Jul 2021 17:20:13 +0000 Subject: m68k: Leave stack mangling to asm wrapper of sigreturn() sigreturn has to deal with an unpleasant problem - exception stack frames have different sizes, depending upon the exception (and processor model, as well) and variable-sized part of exception frame may contain information needed for instruction restart. So when signal handler terminates and calls sigreturn to resume the execution at the place where we'd been when we caught the signal, it has to rearrange the frame at the bottom of kernel stack. Worse, it might need to open a gap in the kernel stack, shifting pt_regs towards lower addresses. Doing that from C is insane - we'd need to shift stack frames (return addresses, local variables, etc.) of C call chain, right under the nose of compiler and hope it won't fall apart horribly. What had been actually done is only slightly less insane - an inline asm in mangle_kernel_stack() moved the stuff around, then reset stack pointer and jumped to label in asm glue. However, we can avoid all that mess if the asm wrapper we have to use anyway would reserve some space on the stack between switch_stack and the C stack frame of do_{rt_,}sigreturn(). Then C part can simply memmove() pt_regs + switch_stack, memcpy() the variable part of exception frame into the opened gap - all of that without inline asm, buggering C call chain, magical jumps to asm labels, etc. Asm wrapper would need to know where the moved switch_stack has ended up - it might have been shifted into the gap we'd reserved before do_rt_sigreturn() call. That's where it needs to set the stack pointer to. So let the C part return just that and be done with that. While we are at it, the call of berr_040cleanup() we need to do when returning via 68040 bus error exception frame can be moved into C part as well. Signed-off-by: Al Viro Tested-by: Michael Schmitz Reviewed-by: Michael Schmitz Tested-by: Finn Thain Link: https://lore.kernel.org/r/YP2dTQPm1wGPWFgD@zeniv-ca.linux.org.uk Signed-off-by: Geert Uytterhoeven --- arch/m68k/kernel/signal.c | 111 +++++++++++++++++----------------------------- 1 file changed, 41 insertions(+), 70 deletions(-) (limited to 'arch/m68k/kernel/signal.c') diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c index cd11eb101eac..338817d0cb3f 100644 --- a/arch/m68k/kernel/signal.c +++ b/arch/m68k/kernel/signal.c @@ -641,56 +641,35 @@ static inline void siginfo_build_tests(void) static int mangle_kernel_stack(struct pt_regs *regs, int formatvec, void __user *fp) { - int fsize = frame_extra_sizes(formatvec >> 12); - if (fsize < 0) { + int extra = frame_extra_sizes(formatvec >> 12); + char buf[sizeof_field(struct frame, un)]; + + if (extra < 0) { /* * user process trying to return with weird frame format */ pr_debug("user process returning with weird frame format\n"); - return 1; + return -1; } - if (!fsize) { - regs->format = formatvec >> 12; - regs->vector = formatvec & 0xfff; - } else { - struct switch_stack *sw = (struct switch_stack *)regs - 1; - /* yes, twice as much as max(sizeof(frame.un.fmt)) */ - unsigned long buf[sizeof_field(struct frame, un) / 2]; - - /* that'll make sure that expansion won't crap over data */ - if (copy_from_user(buf + fsize / 4, fp, fsize)) - return 1; - - /* point of no return */ - regs->format = formatvec >> 12; - regs->vector = formatvec & 0xfff; -#define frame_offset (sizeof(struct pt_regs)+sizeof(struct switch_stack)) - __asm__ __volatile__ ( -#ifdef CONFIG_COLDFIRE - " movel %0,%/sp\n\t" - " bra ret_from_signal\n" -#else - " movel %0,%/a0\n\t" - " subl %1,%/a0\n\t" /* make room on stack */ - " movel %/a0,%/sp\n\t" /* set stack pointer */ - /* move switch_stack and pt_regs */ - "1: movel %0@+,%/a0@+\n\t" - " dbra %2,1b\n\t" - " lea %/sp@(%c3),%/a0\n\t" /* add offset of fmt */ - " lsrl #2,%1\n\t" - " subql #1,%1\n\t" - /* copy to the gap we'd made */ - "2: movel %4@+,%/a0@+\n\t" - " dbra %1,2b\n\t" - " bral ret_from_signal\n" + if (extra && copy_from_user(buf, fp, extra)) + return -1; + regs->format = formatvec >> 12; + regs->vector = formatvec & 0xfff; + if (extra) { + void *p = (struct switch_stack *)regs - 1; + struct frame *new = (void *)regs - extra; + int size = sizeof(struct pt_regs)+sizeof(struct switch_stack); + + memmove(p - extra, p, size); + memcpy(p - extra + size, buf, extra); + current->thread.esp0 = (unsigned long)&new->ptregs; +#ifdef CONFIG_M68040 + /* on 68040 complete pending writebacks if any */ + if (new->ptregs.format == 7) // bus error frame + berr_040cleanup(new); #endif - : /* no outputs, it doesn't ever return */ - : "a" (sw), "d" (fsize), "d" (frame_offset/4-1), - "n" (frame_offset), "a" (buf + fsize/4) - : "a0"); -#undef frame_offset } - return 0; + return extra; } static inline int @@ -698,7 +677,6 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *usc, void __u { int formatvec; struct sigcontext context; - int err = 0; siginfo_build_tests(); @@ -707,7 +685,7 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *usc, void __u /* get previous context */ if (copy_from_user(&context, usc, sizeof(context))) - goto badframe; + return -1; /* restore passed registers */ regs->d0 = context.sc_d0; @@ -720,15 +698,10 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *usc, void __u wrusp(context.sc_usp); formatvec = context.sc_formatvec; - err = restore_fpu_state(&context); - - if (err || mangle_kernel_stack(regs, formatvec, fp)) - goto badframe; - - return 0; + if (restore_fpu_state(&context)) + return -1; -badframe: - return 1; + return mangle_kernel_stack(regs, formatvec, fp); } static inline int @@ -745,7 +718,7 @@ rt_restore_ucontext(struct pt_regs *regs, struct switch_stack *sw, err = __get_user(temp, &uc->uc_mcontext.version); if (temp != MCONTEXT_VERSION) - goto badframe; + return -1; /* restore passed registers */ err |= __get_user(regs->d0, &gregs[0]); err |= __get_user(regs->d1, &gregs[1]); @@ -774,22 +747,17 @@ rt_restore_ucontext(struct pt_regs *regs, struct switch_stack *sw, err |= restore_altstack(&uc->uc_stack); if (err) - goto badframe; - - if (mangle_kernel_stack(regs, temp, &uc->uc_extra)) - goto badframe; + return -1; - return 0; - -badframe: - return 1; + return mangle_kernel_stack(regs, temp, &uc->uc_extra); } -asmlinkage int do_sigreturn(struct pt_regs *regs, struct switch_stack *sw) +asmlinkage void *do_sigreturn(struct pt_regs *regs, struct switch_stack *sw) { unsigned long usp = rdusp(); struct sigframe __user *frame = (struct sigframe __user *)(usp - 4); sigset_t set; + int size; if (!access_ok(frame, sizeof(*frame))) goto badframe; @@ -801,20 +769,22 @@ asmlinkage int do_sigreturn(struct pt_regs *regs, struct switch_stack *sw) set_current_blocked(&set); - if (restore_sigcontext(regs, &frame->sc, frame + 1)) + size = restore_sigcontext(regs, &frame->sc, frame + 1); + if (size < 0) goto badframe; - return regs->d0; + return (void *)sw - size; badframe: force_sig(SIGSEGV); - return 0; + return sw; } -asmlinkage int do_rt_sigreturn(struct pt_regs *regs, struct switch_stack *sw) +asmlinkage void *do_rt_sigreturn(struct pt_regs *regs, struct switch_stack *sw) { unsigned long usp = rdusp(); struct rt_sigframe __user *frame = (struct rt_sigframe __user *)(usp - 4); sigset_t set; + int size; if (!access_ok(frame, sizeof(*frame))) goto badframe; @@ -823,13 +793,14 @@ asmlinkage int do_rt_sigreturn(struct pt_regs *regs, struct switch_stack *sw) set_current_blocked(&set); - if (rt_restore_ucontext(regs, sw, &frame->uc)) + size = rt_restore_ucontext(regs, sw, &frame->uc); + if (size < 0) goto badframe; - return regs->d0; + return (void *)sw - size; badframe: force_sig(SIGSEGV); - return 0; + return sw; } static inline struct pt_regs *rte_regs(struct pt_regs *regs) -- cgit v1.2.3