Subject: Re: crypto: sun4i-ss: error with kmap

From: Thomas Gleixner <[email-masked]>
Date: Tue, 01 Dec 2020 16:15:08 +0100

On Tue, Dec 01 2020 at 15:45, Corentin Labbe wrote:
> On Tue, Dec 01, 2020 at 03:16:36PM +0100, Thomas Gleixner wrote:
> In fact the warn was a bit later so I added:
>        preempt_disable();
>         idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
> -       WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
> +       if (WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx)))
> +               pr_err("kunmap_local: vaddr %lx\n", (unsigned long) vaddr);
>  
>         arch_kmap_local_pre_unmap(addr);
>         pte_clear(&init_mm, addr, kmap_pte - idx);
>
> and this give kunmap_local: vaddr ffefe000

which looks like a valid one.

Can you apply the patch below and add 'ftrace_dump_on_oops' on the
command line or enable it in /proc/sys/kernel/ftrace_dump_on_oops before
starting the test.

That should spill out the trace after crashing.

Thanks,

        tglx
---
diff --git a/mm/highmem.c b/mm/highmem.c
index b49364a306b8..461fe2c26107 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -485,6 +485,7 @@ static inline bool kmap_high_unmap_local(unsigned long vaddr)
 {
 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 	if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
+		trace_printk("kunmap_high: %lx\n", vaddr);
 		kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
 		return true;
 	}
@@ -520,6 +521,7 @@ void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
 	preempt_disable();
 	idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
 	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+	trace_printk("kmap_local_pfn: %d %lx\n", idx, (unsigned long) vaddr);
 	BUG_ON(!pte_none(*(kmap_pte - idx)));
 	pteval = pfn_pte(pfn, prot);
 	set_pte_at(&init_mm, vaddr, kmap_pte - idx, pteval);
@@ -545,8 +547,10 @@ void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
 
 	/* Try kmap_high_get() if architecture has it enabled */
 	kmap = arch_kmap_local_high_get(page);
-	if (kmap)
+	if (kmap) {
+		trace_printk("kmap_local_high_get: %lx\n", (unsigned long) kmap);
 		return kmap;
+	}
 
 	return __kmap_local_pfn_prot(page_to_pfn(page), prot);
 }
@@ -578,6 +582,7 @@ void kunmap_local_indexed(void *vaddr)
 
 	preempt_disable();
 	idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
+	trace_printk("kunmap_local: %i %lx\n", idx, (unsigned long) vaddr);
 	WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
 
 	arch_kmap_local_pre_unmap(addr);

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