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[209.132.183.28]) by mx.google.com with ESMTPS id r2si3053783qkd.62.2019.04.15.06.24.01 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 15 Apr 2019 06:24:01 -0700 (PDT) Received-SPF: pass (google.com: domain of jpoimboe@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jpoimboe@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jpoimboe@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9CBAB3092648; Mon, 15 Apr 2019 13:23:47 +0000 (UTC) Received: from treble (ovpn-120-105.rdu2.redhat.com [10.10.120.105]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9B92060150; Mon, 15 Apr 2019 13:23:43 +0000 (UTC) Date: Mon, 15 Apr 2019 08:23:39 -0500 From: Josh Poimboeuf To: Thomas Gleixner Cc: Andy Lutomirski , LKML , X86 ML , Sean Christopherson , Andrew Morton , Pekka Enberg , Linux-MM Subject: Re: [patch V4 01/32] mm/slab: Fix broken stack trace storage Message-ID: <20190415132339.wiqyzygqklliyml7@treble> References: <20190414155936.679808307@linutronix.de> <20190414160143.591255977@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Mon, 15 Apr 2019 13:23:52 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Apr 15, 2019 at 11:02:58AM +0200, Thomas Gleixner wrote: > kstack_end() is broken on interrupt stacks as they are not guaranteed to be > sized THREAD_SIZE and THREAD_SIZE aligned. > > Use the stack tracer instead. Remove the pointless pointer increment at the > end of the function while at it. > > Fixes: 98eb235b7feb ("[PATCH] page unmapping debug") - History tree > Signed-off-by: Thomas Gleixner > Cc: Andrew Morton > Cc: Pekka Enberg > Cc: linux-mm@kvack.org > --- > V4: Made the code simpler to understand (Andy) and make it actually compile > --- > mm/slab.c | 30 ++++++++++++++---------------- > 1 file changed, 14 insertions(+), 16 deletions(-) > > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -1470,33 +1470,31 @@ static bool is_debug_pagealloc_cache(str > static void store_stackinfo(struct kmem_cache *cachep, unsigned long *addr, > unsigned long caller) > { > - int size = cachep->object_size; > + int size = cachep->object_size / sizeof(unsigned long); > > addr = (unsigned long *)&((char *)addr)[obj_offset(cachep)]; > > - if (size < 5 * sizeof(unsigned long)) > + if (size < 5) > return; > > *addr++ = 0x12345678; > *addr++ = caller; > *addr++ = smp_processor_id(); > - size -= 3 * sizeof(unsigned long); > + size -= 3; > +#ifdef CONFIG_STACKTRACE > { > - unsigned long *sptr = &caller; > - unsigned long svalue; > - > - while (!kstack_end(sptr)) { > - svalue = *sptr++; > - if (kernel_text_address(svalue)) { > - *addr++ = svalue; > - size -= sizeof(unsigned long); > - if (size <= sizeof(unsigned long)) > - break; > - } > - } > + struct stack_trace trace = { > + /* Leave one for the end marker below */ > + .max_entries = size - 1, > + .entries = addr, > + .skip = 3, > + }; > > + save_stack_trace(&trace); > + addr += trace.nr_entries; > } > - *addr++ = 0x87654321; > +#endif > + *addr = 0x87654321; Looks like stack_trace.nr_entries isn't initialized? (though this code gets eventually replaced by a later patch) Who actually reads this stack trace? I couldn't find a consumer. -- Josh