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Thu, 5 Dec 2024 20:43:09 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id fkkuLl0QUmfZUQAAD6G6ig (envelope-from ); Thu, 05 Dec 2024 20:43:09 +0000 Message-ID: <01514d6a-5b8f-4a38-8c08-7cacede47f67@suse.cz> Date: Thu, 5 Dec 2024 21:43:09 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH man-pages v4] madvise.2: add MADV_GUARD_INSTALL, MADV_GUARD_REMOVE description Content-Language: en-US To: Lorenzo Stoakes Cc: Alejandro Colomar , linux-man@vger.kernel.org, Suren Baghdasaryan , "Liam R . Howlett" , Matthew Wilcox , Jann Horn , linux-mm@kvack.org References: <20241205104125.67518-1-lorenzo.stoakes@oracle.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Stat-Signature: 4o7tkafkcgkpt6k97hnid71y4ry3me7z X-Rspamd-Queue-Id: 7C91A4001E X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1733431375-772775 X-HE-Meta: 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 xdIIOQKL ctYNtN+BkZYF0LAq45RXVMbucs0lgllKoNl95QwLMcRM+Jm5JkYqgA57gnFbZ9xjZSkfDlZonkUfyqtMvIoDbRGKd83fbRy6lfKEyQkAT1+OC7wUX7NLs+SsrWyphKm4wUjzblftXegAB/uZTXrBLe2mm3+3ECugC4jX6zDg4ER6LEo6v0lGa60mrmD8b2A2OJRrjlH4k0y+qcB0d5qgk97WITNBGd7rfzuR8foaKgNA+g33x+IyVtGnjkBWLGqy1nvdouoWBUpzkygcSOjfSLaQ1OwwNIIwoQYY54y8lqhOnPG2vWXCd0IamUWkLXSjkT+m2hungOHpLaY1FwCuixKwK+igw58xLKet8T4sFDeBl3AwgOyHmlj701pQxlzTuQKy8z7a9jFFAdKuQzTKUt2HP+g== 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: List-Subscribe: List-Unsubscribe: On 12/5/24 19:09, Lorenzo Stoakes wrote: > On Thu, Dec 05, 2024 at 06:50:09PM +0100, Vlastimil Babka wrote: >> On 12/5/24 11:41, Lorenzo Stoakes wrote: >> > Lightweight guard region support has been added to Linux 6.13, which adds >> > MADV_GUARD_INSTALL and MADV_GUARD_REMOVE flags to the madvise() system >> > call. Therefore, update the manpage for madvise() and describe these >> > operations. >> > >> > Reviewed-by: Jann Horn >> > Signed-off-by: Lorenzo Stoakes >> > --- >> > v4: >> > * Reference function chapters as per Alejandro. >> > * Minor rewording as per Alejandro. >> > >> > v3: >> > * Don't describe SIGSEGV as a fatal signal as per Jann. >> > https://lore.kernel.org/all/20241202165829.72121-1-lorenzo.stoakes@oracle.com >> > >> > v2: >> > * Updated to use semantic newlines as suggested by Alejandro. >> > * Avoided emboldening parens as suggested by Alejandro. >> > * One very minor grammatical fix. >> > https://lore.kernel.org/all/20241129155943.85215-1-lorenzo.stoakes@oracle.com >> > >> > v1: >> > https://lore.kernel.org/all/20241129093205.8664-1-lorenzo.stoakes@oracle.com >> > >> > man/man2/madvise.2 | 93 ++++++++++++++++++++++++++++++++++++++++++++++ >> > 1 file changed, 93 insertions(+) >> > >> > diff --git a/man/man2/madvise.2 b/man/man2/madvise.2 >> > index 4f2210ee2..7d682fa40 100644 >> > --- a/man/man2/madvise.2 >> > +++ b/man/man2/madvise.2 >> > @@ -676,6 +676,91 @@ or secret memory regions created using >> > Note that with >> > .BR MADV_POPULATE_WRITE , >> > the process can be killed at any moment when the system runs out of memory. >> > +.TP >> > +.BR MADV_GUARD_INSTALL " (since Linux 6.13)" >> > +Install a lightweight guard region into the range specified by >> > +.I addr >> > +and >> > +.IR size , >> > +causing any read or write in the range to result in a >> > +.B SIGSEGV >> > +signal being raised. >> > +.IP >> > +If the region maps memory pages they will be cleared as part of the operation, >> > +though if >> >> Hm this reads a bit ambiguous. One could read it as the memory pages are >> being cleared, but it's the page tables. > > This was really hard to word, because you don't want to say unmapped, and saying > 'clearing page tables' or 'zapping' is clear to us but not necessarily to a > reader. 'Clearing mapping' makes it ambiguous vs. munmap(), etc. etc. Maybe saying "removed" instead of "cleared" would be better? Anyway, I don't want to cause bikeshedding, so in any case: Reviewed-by: Vlastimil Babka > But you want to make it clear (no pun intended) that anon pages, if there's any > data, it's probably lost. So I think this is a distinction that doesn't matter. > > Will revisit once we support file-backed mappings. >