Date: Tue, 10 Dec 2002 11:10:03 -0800 (PST) From: "Peter Edwards" <pmedwards@eircom.net> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/45994: Pages marked read-only via mprotect are zeroed in core files Message-ID: <200212101910.gBAJA3AC010009@freefall.freebsd.org>
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The following reply was made to PR kern/45994; it has been noted by GNATS. From: "Peter Edwards" <pmedwards@eircom.net> To: Archie Cobbs <archie@packetdesign.com>, Peter Edwards <pmedwards@eircom.net> Cc: freebsd-gnats-submit@freebsd.org Subject: Re: kern/45994: Pages marked read-only via mprotect are zeroed in core files Date: Tue, 10 Dec 2002 18:58:30 +0000 This is a multi-part message in MIME format. ---------O55DF2D7B4YK0IC6O5NW1WAD Content-Type: text/plain Content-Transfer-Encoding: 7bit Ok. I had a quick look, and it was easier than I thought. The following patch (which should be applied _instead_ of the noddy one I previously posted) Does the following 1: Update rtld_elf's map_object to set MAP_NOCORE when mmap()ing readonly sections. 2: Causes elf_load_section (kern/imgact_elf.c) to do the same (by passing MAP_DISABLE_COREDUMP to the "COW" flags of vm_map_insert()) 3: Reverses the polarity of the sysctl from the old patch, so, by default the corefiles _include_ readonly pages. A quick test shows that both a static and dynamic executable produce corefiles of the same size, irrespective of the setting of this flag, and a simple program that mmaps a chunk of anonymous readonly data is grows and shrinks by the size of the extra mmaped data, depending on the setting of the sysctl. Archie, I'd appreciate any feedback if you install this patch. I'll be running a kernel with it here, anyway. Reviews from any VM hackers would be probably an idea, before committing :-) Cheers, Peter. ---------O55DF2D7B4YK0IC6O5NW1WAD Content-Type: application/octet-stream Content-Disposition: attachment; filename="coredump.diff" Content-Transfer-Encoding: base64 SW5kZXg6IGxpYmV4ZWMvcnRsZC1lbGYvbWFwX29iamVjdC5jCj09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT0KUkNTIGZpbGU6IC9wdWIvRnJlZUJTRC9kZXZlbG9w bWVudC9GcmVlQlNELUNWUy9zcmMvbGliZXhlYy9ydGxkLWVsZi9tYXBfb2Jq ZWN0LmMsdgpyZXRyaWV2aW5nIHJldmlzaW9uIDEuNy4yLjEKZGlmZiAtdSAt cjEuNy4yLjEgbWFwX29iamVjdC5jCi0tLSBsaWJleGVjL3J0bGQtZWxmL21h cF9vYmplY3QuYwkyOSBOb3YgMjAwMiAxNjowNToxNCAtMDAwMAkxLjcuMi4x CisrKyBsaWJleGVjL3J0bGQtZWxmL21hcF9vYmplY3QuYwkxMCBEZWMgMjAw MiAxNTowMjo1OSAtMDAwMApAQCAtMzcsNyArMzcsOCBAQAogCiAjaW5jbHVk ZSAicnRsZC5oIgogCi1zdGF0aWMgaW50IHByb3RmbGFncyhpbnQpOwkvKiBF bGYgZmxhZ3MgLT4gbW1hcCBwcm90ZWN0aW9uICovCitzdGF0aWMgaW50IGNv bnZlcnRfcHJvdChpbnQpOwkvKiBFbGYgZmxhZ3MgLT4gbW1hcCBwcm90ZWN0 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