From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752876AbdAZWza (ORCPT ); Thu, 26 Jan 2017 17:55:30 -0500 Received: from merlin.infradead.org ([205.233.59.134]:58984 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752790AbdAZWz2 (ORCPT ); Thu, 26 Jan 2017 17:55:28 -0500 Date: Thu, 26 Jan 2017 23:15:08 +0100 From: Peter Zijlstra To: Andres Freund Cc: linux-kernel@vger.kernel.org, Stephane Eranian , acme@kernel.org, jolsa@redhat.com, mingo@elte.hu, anton@ozlabs.org, namhyung@kernel.org, Stephane Eranian Subject: Re: perf/jit doesn't cope well with mprotect() to jit containing pages Message-ID: <20170126221508.GF6536@twins.programming.kicks-ass.net> References: <20161210050218.jw4bak5jf766iqpb@alap3.anarazel.de> <20161212084903.GZ3124@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161212084903.GZ3124@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 12, 2016 at 09:49:03AM +0100, Peter Zijlstra wrote: > > BTW, it's also a bit weird that those MMAP2 records triggered by > > mprotect/mmap, have prot set to 0... > > Yes, mprotect() does: vma->vm_flags = newflags; before calling > perf_event_mmap(vma); which then looks at VM_{READ,WRITE,EXEC} bits in > that word to generate the prot value. > > So that being 0 is a bit weird. OK, that was a silly bug :/ With that fixed, the following proglet: #include #include #include #include #include #include #include void main(void) { void *ptr[5]; int i; for (i=0; i<5; i++) { ptr[i] = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); *(char *)ptr[i] = '\0'; mprotect(ptr[i], 4096, PROT_EXEC); } } Gives: root@ivb-ep:~# perf record -d ./mprot ... root@ivb-ep:~# perf report -D | grep MMAP2 ... 43805378481 0xc60 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0862000(0x1000) @ 0x7f6ec0862000 00:00 0 0]: --xp //anon 43805381755 0xcc0 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0861000(0x1000) @ 0x7f6ec0861000 00:00 0 0]: rw-p //anon 43805392374 0xd20 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0861000(0x2000) @ 0x7f6ec0861000 00:00 0 0]: --xp //anon 43805395093 0xd80 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0860000(0x1000) @ 0x7f6ec0860000 00:00 0 0]: rw-p //anon 43805402842 0xde0 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec0860000(0x3000) @ 0x7f6ec0860000 00:00 0 0]: --xp //anon 43805405388 0xe40 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec085f000(0x1000) @ 0x7f6ec085f000 00:00 0 0]: rw-p //anon 43805412605 0xea0 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec085f000(0x4000) @ 0x7f6ec085f000 00:00 0 0]: --xp //anon 43805415134 0xf00 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec085e000(0x1000) @ 0x7f6ec085e000 00:00 0 0]: rw-p //anon 43805422225 0xf60 [0x60]: PERF_RECORD_MMAP2 2073/2073: [0x7f6ec085e000(0x5000) @ 0x7f6ec085e000 00:00 0 0]: --xp //anon If you omit the mmap_data=1 thing, it looks like: 123087941779 0x500 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8bd000(0x1000) @ 0x7fca5a8bd000 00:00 0 0]: --xp //anon 123087953825 0x560 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8bc000(0x2000) @ 0x7fca5a8bc000 00:00 0 0]: --xp //anon 123087962944 0x5c0 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8bb000(0x3000) @ 0x7fca5a8bb000 00:00 0 0]: --xp //anon 123087971135 0x620 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8ba000(0x4000) @ 0x7fca5a8ba000 00:00 0 0]: --xp //anon 123087979360 0x680 [0x60]: PERF_RECORD_MMAP2 2084/2084: [0x7fca5a8b9000(0x5000) @ 0x7fca5a8b9000 00:00 0 0]: --xp //anon --- diff --git a/kernel/events/core.c b/kernel/events/core.c index 896aa53..e67c5ba 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6660,6 +6683,27 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) char *buf = NULL; char *name; + if (vma->vm_flags & VM_READ) + prot |= PROT_READ; + if (vma->vm_flags & VM_WRITE) + prot |= PROT_WRITE; + if (vma->vm_flags & VM_EXEC) + prot |= PROT_EXEC; + + if (vma->vm_flags & VM_MAYSHARE) + flags = MAP_SHARED; + else + flags = MAP_PRIVATE; + + if (vma->vm_flags & VM_DENYWRITE) + flags |= MAP_DENYWRITE; + if (vma->vm_flags & VM_MAYEXEC) + flags |= MAP_EXECUTABLE; + if (vma->vm_flags & VM_LOCKED) + flags |= MAP_LOCKED; + if (vma->vm_flags & VM_HUGETLB) + flags |= MAP_HUGETLB; + if (file) { struct inode *inode; dev_t dev; @@ -6686,27 +6730,6 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) maj = MAJOR(dev); min = MINOR(dev); - if (vma->vm_flags & VM_READ) - prot |= PROT_READ; - if (vma->vm_flags & VM_WRITE) - prot |= PROT_WRITE; - if (vma->vm_flags & VM_EXEC) - prot |= PROT_EXEC; - - if (vma->vm_flags & VM_MAYSHARE) - flags = MAP_SHARED; - else - flags = MAP_PRIVATE; - - if (vma->vm_flags & VM_DENYWRITE) - flags |= MAP_DENYWRITE; - if (vma->vm_flags & VM_MAYEXEC) - flags |= MAP_EXECUTABLE; - if (vma->vm_flags & VM_LOCKED) - flags |= MAP_LOCKED; - if (vma->vm_flags & VM_HUGETLB) - flags |= MAP_HUGETLB; - goto got_name; } else { if (vma->vm_ops && vma->vm_ops->name) {