m68k v4.4 backport fixes

CIP v4.4 backport patches for m68k. Basically everything needed to make v4.4 work on my Falcon. This includes my iounmap() fix, Al Viro's signal handling and uaccess page fault fixes, my 030 buserr_c fix for exception handling during page faults, and Finn's 030 signal frame fix.

Patch 1 should be applied to v4.4-cip, or else ioremap / iounmap has no chance to work on 030 processors.

Patches 2 and 3 have been applied to v4.4-cip.

Patches 4-6 are a prerequisite for patch 8, Finn Thain's 'm68k:
Move signal frame following exception on 68020/030' patch which had been applied but failed to compile (see error reported in
https://lore.kernel.org/oe-kbuild-all/[email protected]/
which has gone away with patches 4-6 in place).

Patch 7 is another page fault handling fix which should be applied (though I have found no test case for it, and cannot say how common that livelock issue is on m68k).

All patches as RFC version to give Geert and Al a chance to yell at me in case I got details of these patches wrong. I don't claim to understand signal handling in anywhere near the required level of detail.

Tested on my 68030 Atari Falcon.

Cheers,

Michael

If 020/030 support is enabled, get_io_area() leaves an IO_SIZE gap between mappings which is added to the vm_struct representing the mapping. __ioremap() uses the actual requested size (after alignment), while __iounmap() is passed the size from the vm_struct.

On 020/030, early termination descriptors are used to set up mappings of extent 'size', which are validated on unmapping. The unmapped gap of size IO_SIZE defeats the sanity check of the pmd tables, causing __iounmap() to loop forever on 030.

On 040/060, unmapping of page table entries does not check for a valid mapping, so the umapping loop always completes there.

Adjust size to be unmapped by the gap that had been added in the vm_struct prior.

This fixes the hang in atari_platform_init() reported a long time ago, and a similar one reported by Finn recently (addressed by removing ioremap() use from the SWIM driver.

Tested on my Falcon in 030 mode - untested but should work the same on 040/060 (the extra page tables cleared there would never have been set up anyway).

---
 arch/m68k/mm/kmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index 6e4955bc542b..fcd52cefee29 100644
@@ -88,7 +88,8 @@ static inline void free_io_area(void *addr)
 	for (p = &iolist ; (tmp = *p) ; p = &tmp->next) {
 		if (tmp->addr == addr) {
 			*p = tmp->next;
-			__iounmap(tmp->addr, tmp->size);
+			/* remove gap added in get_io_area() */
+			__iounmap(tmp->addr, tmp->size - IO_SIZE);
 			kfree(tmp);
 			return;
 		}

2.17.1

__get_kernel_nofault() does copy data in supervisor mode when forcing a task backtrace log through /proc/sysrq_trigger. This is expected cause a bus error exception on e.g. NULL pointer dereferencing when logging a kernel task has no workqueue associated. This bus error ought to be ignored.

Our 030 bus error handler is ill equipped to deal with this:

Whenever ssw indicates a kernel mode access on a data fault, we don't even attempt to handle the fault and instead always send a SEGV signal (or panic). As a result, the check for exception handling at the fault PC (buried in send_sig_fault() which gets called from do_page_fault() eventually) is never used.

In contrast, both 040 and 060 access error handlers do not care whether a fault happened on supervisor mode access, and will call do_page_fault() on those, ultimately honoring the exception table.

Add a check in bus_error030 to call do_page_fault() in case we do have an entry for the fault PC in our exception table.

I had attempted a fix for this earlier in 2019 that did rely on testing pagefault_disabled() (see link below) to achieve the same thing, but this patch should be more generic.

Tested on 030 Atari Falcon.

---
 arch/m68k/kernel/traps.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

index 6c9ca24830e9..c547140b8325 100644
@@ -29,6 +29,7 @@
 #include <linux/init.h>
 #include <linux/ptrace.h>
 #include <linux/kallsyms.h>
+#include <linux/extable.h>
 
 #include <asm/setup.h>
 #include <asm/fpu.h>

@@ -549,7 +550,8 @@ static inline void bus_error030 (struct frame *fp)
 			errorcode |= 2;
 
 		if (mmusr & (MMU_I | MMU_WP)) {
-			if (ssw & 4) {
+			/* We might have an exception table for this PC */
+			if (ssw & 4 && !search_exception_tables(fp->ptregs.pc)) {
 				pr_err("Data %s fault at %#010lx in %s (pc=%#lx)\n",
 				       ssw & RW ? "read" : "write",
 				       fp->un.fmtb.daddr,

2.17.1

Backporting commit 513138a14063760e (m68k: Only force 030 bus error if PC not in exception table) to v4.4 by the CIP project revealed a build error due to extable.h not yet available.

extable.h was split off module.h in v4.8 (commit 0ef7653797addea8) so amend 513138a14063760e accordingly.

---
 arch/m68k/kernel/traps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index c547140b8325..2209214cf91c 100644
@@ -29,7 +29,7 @@
 #include <linux/init.h>
 #include <linux/ptrace.h>
 #include <linux/kallsyms.h>
-#include <linux/extable.h>
+#include <linux/module.h>
 
 #include <asm/setup.h>
 #include <asm/fpu.h>

2.17.1

From: Al Viro <[email protected]>

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.

MSch: Minor v4.4 backport merge conflict fixes.

---
 arch/m68k/kernel/signal.c | 100 +++++++++++++++++---------------------
 1 file changed, 45 insertions(+), 55 deletions(-)

index af1c4f330aef..644c2ddc8aac 100644
@@ -465,7 +465,7 @@ 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 */

@@ -528,7 +528,7 @@ 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 */

@@ -788,18 +788,24 @@ 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);
 }

@@ -807,6 +813,7 @@ 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;
 

@@ -827,9 +834,9 @@ 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;
 }

@@ -846,15 +853,14 @@ 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) {
-#ifdef DEBUG
-		printk ("setup_frame: Unknown frame format %#x\n",
-			regs->format);
-#endif
+		pr_debug("setup_frame: Unknown frame format %#x\n",
+			 tregs->format);
 		return -EFAULT;
 	}
 

@@ -865,7 +871,7 @@ 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)

@@ -890,36 +896,28 @@ 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);
-#ifdef DEBUG
-		printk("Performing stackadjust=%04x\n", regs->stkadj);
-#endif
-		/* This must be copied with decreasing addresses to
-                   handle overlaps.  */
+		tregs = rte_regs(regs);
+		pr_debug("Performing stackadjust=%04lx\n", regs->stkadj);
 		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;
 }
 

@@ -927,7 +925,8 @@ 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) {

@@ -978,36 +977,27 @@ 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);
-#ifdef DEBUG
-		printk("Performing stackadjust=%04x\n", regs->stkadj);
-#endif
-		/* This must be copied with decreasing addresses to
-                   handle overlaps.  */
+		tregs = rte_regs(regs);
+		pr_debug("Performing stackadjust=%04lx\n", regs->stkadj);
 		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;
 }
 

2.17.1

Hi Michael,

Thanks for your patch!

When submitting a backport, please add lines like

    commit 4bb0bd81ce5e97092dfda6a106d414b703ec0ee8 upstream.

Please move this to "[MSch: ...] below...

... i.e. here.

Good.
Please add your SoB on all patches you handle, some lack it.

Thanks a lot for taking care of this!

Gr{oetje,eeting}s,

Geert

Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Hi Geert,

thanks for your feedback!

Am 05.02.2024 um 21:10 schrieb Geert Uytterhoeven:

Will do. I did wonder how the original commit could be found to prevent duplicates...

On that note - Uli: would you prefer the entire backport series, or only those you do not already have?

OK.

That would have been the ones that did not need any extra handling. But I take your point ...

No matter!

Cheers,

Michael

I'd prefer to only get what's missing.

CU
Uli

Ulrich, I imagine that you would normally receive fixes via the corresponding -stable trees. If Michael's series went into stable/linux-4.19.y you could cherry-pick from there for your v4.4.y tree and maybe avoid some merge conflicts that way. So perhaps we should ask the -stable maintainers to backport first (?)

Al, I see that the following commits are missing from stable/linux-v6.1 and older trees, despite the word "fix" in the subject. Reading the merge commit 1a8d05a726dc "Merge tag 'pull-fixes' of
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs" suggests to me that these are old bugs...

bd75497a77cc m68k: fix livelock in uaccess
d835eb3a57de riscv: fix livelock in uaccess
0b92ed09cb9f hexagon: fix livelock in uaccess
15261678a8c2 parisc: fix livelock in uaccess
dce45493aff3 alpha: fix livelock in uaccess
79c54c97c773 sparc: fix livelock in uaccess
d088af1e221c ia64: fix livelock in uaccess
a1179ac743e8 microblaze: fix livelock in uaccess
e902e508c5b2 nios2: fix livelock in uaccess
caa82ae7ef52 openrisc: fix livelock in uaccess

In addition, stable/linux-v5.10 and the older trees lack the following commit, despite the Fixes tag.

50e43a573344 m68k: Update ->thread.esp0 before calling syscall_trace() in ret_from_signal

Only

bd75497a77cc m68k: fix livelock in uaccess, and

0d20abde987b m68k: Leave stack mangling to asm wrapper of sigreturn()

need changes to apply to v4.19. Only compile tested so far.

Happy to submit the adjusted patches to stable, and ask the stable maintainers to pick up the missing bits from Linus' or Geert's tree.

Would that be good enough?

Cheers,

Michael

That would work for me.

CU
Uli

[Cc: stable]

OK. Here's the relevant commit. It fixes bd6f56a75bb2 which first appeared in v2.6.38-rc1. I believe this can be cherry-picked without any conflicts.

50e43a573344 m68k: Update ->thread.esp0 before calling syscall_trace() in ret_from_signal

From: Al Viro <[email protected]>

We get there when sigreturn has performed obscene acts on kernel stack; in particular, the location of pt_regs has shifted. We are about to call syscall_trace(), which might stop for tracer. If that happens, we'd better have task_pt_regs() returning correct result...

---
 arch/m68k/kernel/entry.S | 2 ++
 1 file changed, 2 insertions(+)

index b54ac7aba850..dbeba043b703 100644
@@ -173,6 +173,8 @@ ENTRY(ret_from_signal)
 	movel	%curptr@(TASK_STACK),%a1
 	tstb	%a1@(TINFO_FLAGS+2)
 	jge	1f
+	lea	%sp@(SWITCH_STACK_SIZE),%a1
+	movel	%a1,%curptr@(TASK_THREAD+THREAD_ESP0)
 	jbsr	syscall_trace
 1:	RESTORE_SWITCH_STACK
 	addql	#4,%sp

2.17.1

From: Al Viro <[email protected]>

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.

MSch: Minor v4.4 backport merge conflict and compile errors fixed.

---
 arch/m68k/68000/entry.S       |   3 -
 arch/m68k/coldfire/entry.S    |   3 -
 arch/m68k/include/asm/traps.h |   4 ++
 arch/m68k/kernel/entry.S      |  49 +++++++-------
 arch/m68k/kernel/signal.c     | 118 ++++++++++++----------------------
 5 files changed, 72 insertions(+), 105 deletions(-)

index 259b3661b614..cce465e850fe 100644
@@ -25,7 +25,6 @@
 .globl system_call
 .globl resume
 .globl ret_from_exception
-.globl ret_from_signal
 .globl sys_call_table
 .globl bad_interrupt
 .globl inthandler1

@@ -59,8 +58,6 @@ do_trace:
 	subql	#4,%sp			/* dummy return address */
 	SAVE_SWITCH_STACK
 	jbsr	syscall_trace_leave
-
-ret_from_signal:
 	RESTORE_SWITCH_STACK
 	addql	#4,%sp
 	jra	ret_from_exception

index 52d312d5b4d4..1a75c1015847 100644
@@ -51,7 +51,6 @@ sw_usp:
 .globl system_call
 .globl resume
 .globl ret_from_exception
-.globl ret_from_signal
 .globl sys_call_table
 .globl inthandler
 

@@ -98,8 +97,6 @@ ENTRY(system_call)
 	subql	#4,%sp			/* dummy return address */
 	SAVE_SWITCH_STACK
 	jbsr	syscall_trace_leave
-
-ret_from_signal:
 	RESTORE_SWITCH_STACK
 	addql	#4,%sp
 

index 4aff3358fbaf..a9d5c1c870d3 100644
@@ -267,6 +267,10 @@ struct frame {
     } un;
 };
 
+#ifdef CONFIG_M68040
+asmlinkage void berr_040cleanup(struct frame *fp);
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _M68K_TRAPS_H */

2.17.1

From: Al Viro <[email protected]>

m68k equivalent of 26178ec11ef3 "x86: mm: consolidate VM_FAULT_RETRY handling" If e.g. get_user() triggers a page fault and a fatal signal is caught, we might end up with handle_mm_fault() returning VM_FAULT_RETRY and not doing anything to page tables. In such case we must *not* return to the faulting insn - that would repeat the entire thing without making any progress; what we need instead is to treat that as failed (user) memory access.

MSch: v4.4 backport compile errors fixes.

---
 arch/m68k/mm/fault.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

index 6a94cdd0c830..f94df64c3784 100644
@@ -139,8 +139,11 @@ good_area:
 	fault = handle_mm_fault(mm, vma, address, flags);
 	pr_debug("handle_mm_fault returns %d\n", fault);
 
-	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
+		if (!user_mode(regs))
+			goto no_context;
 		return 0;
+	}
 
 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		if (fault & VM_FAULT_OOM)

2.17.1

From: Finn Thain <[email protected]>

On 68030/020, an instruction such as, moveml %a2-%a3/%a5,%sp@- may cause a stack page fault during instruction execution (i.e. not at an instruction boundary) and produce a format 0xB exception frame.

In this situation, the value of USP will be unreliable. If a signal is to be delivered following the exception, this USP value is used to calculate the location for a signal frame. This can result in a corrupted user stack.

The corruption was detected in dash (actually in glibc) where it showed up as an intermittent "stack smashing detected" message and crash following signal delivery for SIGCHLD.

It was hard to reproduce that failure because delivery of the signal raced with the page fault and because the kernel places an unpredictable gap of up to 7 bytes between the USP and the signal frame.

A format 0xB exception frame can be produced by a bus error or an address error. The 68030 Users Manual says that address errors occur immediately upon detection during instruction prefetch. The instruction pipeline allows prefetch to overlap with other instructions, which means an address error can arise during the execution of a different instruction. So it seems likely that this patch may help in the address error case also.

---
 arch/m68k/kernel/signal.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

index 8fb8ee804b3a..de7c1bde62bc 100644
@@ -808,11 +808,17 @@ 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 *tregs, size_t frame_size)
 {
 	unsigned long usp = sigsp(rdusp(), ksig);
+	unsigned long gap = 0;
 
-	return (void __user *)((usp - frame_size) & -8UL);
+	if (CPU_IS_020_OR_030 && tregs->format == 0xb) {
+		/* USP is unreliable so use worst-case value */
+		gap = 256;
+	}
+
+	return (void __user *)((usp - gap - frame_size) & -8UL);
 }
 
 static int setup_frame(struct ksignal *ksig, sigset_t *set,

@@ -830,7 +836,7 @@ static int setup_frame(struct ksignal *ksig, sigset_t *set,
 		return -EFAULT;
 	}
 
-	frame = get_sigframe(ksig, sizeof(*frame) + fsize);
+	frame = get_sigframe(ksig, tregs, sizeof(*frame) + fsize);
 
 	if (fsize)
 		err |= copy_to_user (frame + 1, regs + 1, fsize);

@@ -903,7 +909,7 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 		return -EFAULT;
 	}
 
-	frame = get_sigframe(ksig, sizeof(*frame));
+	frame = get_sigframe(ksig, tregs, sizeof(*frame));
 
 	if (fsize)
 		err |= copy_to_user (&frame->uc.uc_extra, regs + 1, fsize);

2.17.1