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Sat, 1 Jun 2024 20:48:54 +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 gqgkGjaJW2azTQAAD6G6ig (envelope-from ); Sat, 01 Jun 2024 20:48:54 +0000 Message-ID: <87a4928a-ea15-453c-b252-2da0b301cb7e@suse.cz> Date: Sat, 1 Jun 2024 22:48:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 0/4] static key support for error injection functions To: Mark Rutland Cc: Akinobu Mita , Christoph Lameter , David Rientjes , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" , Masami Hiramatsu , Steven Rostedt , Jiri Olsa , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org References: <20240531-fault-injection-statickeys-v1-0-a513fd0a9614@suse.cz> Content-Language: en-US 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-Stat-Signature: fqfsa5gezuujf4sh3jr4xuj3z6i1icux X-Rspamd-Queue-Id: 5C9D1120002 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1717274936-775922 X-HE-Meta: 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 SqMHPn96 BpDKf3r0gsM6LhzoWWy0i8kWTbt7kGY7eglxdfSJY4GAWadRLsmuR13UAnXpotlBApjFeTET0bTnDvLIzJPwlGSN02Pyg/5TQaqEZj/x77hhlZ2uKmZVgZ1TMMDaL7IdxZrOuQEK0SVHi3Pr62rtVtHWcnjKt9eqlJk7zM4UisFGpcHC9R8ivf2SnQrrFqMqDyYhJTu9jqICZ4796Cpjzmkd2Gypj+jWLGixGy0DKgKBqb57RxwVH9frTObLqCWYgCfL+30PV+6r+rpwMO5lL5tG9qt7ArCJdnW1W5vTydJE3FnZAG/g804YbmyOldAPwD188kL2YMbfoufkqvzFbfLSU6Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000005, 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 5/31/24 5:31 PM, Mark Rutland wrote: > Hi, > > On Fri, May 31, 2024 at 11:33:31AM +0200, Vlastimil Babka wrote: >> Incomplete, help needed from ftrace/kprobe and bpf folks. > >> - the generic error injection using kretprobes with >> override_function_with_return is handled in patch 2. The >> ALLOW_ERROR_INJECTION() annotation is extended so that static key >> address can be passed, and the framework controls it when error >> injection is enabled or disabled in debugfs for the function. >> >> There are two more users I know of but am not familiar enough to fix up >> myself. I hope people that are more familiar can help me here. >> >> - ftrace seems to be using override_function_with_return from >> #define ftrace_override_function_with_return but I found no place >> where the latter is used. I assume it might be hidden behind more >> macro magic? But the point is if ftrace can be instructed to act like >> an error injection, it would also have to use some form of metadata >> (from patch 2 presumably?) to get to the static key and control it. > > I don't think you've missed anything; nothing currently uses > ftrace_override_function_with_return(). I added that in commit: Ah, great, thanks for confirming that. > 94d095ffa0e16bb7 ("ftrace: abstract DYNAMIC_FTRACE_WITH_ARGS accesses") > > ... so that it was possible to do anything that was possible with > FTRACE_WITH_REGS and/or kprobes, under the expectation that we might > want to move fault injection and BPF probes over to fprobes in future, > as ftrace/fprobes is generally faster than kprobes (e.g. for > architectures that can't do KPROBES_ON_FTRACE or OPTPROBES). > > That's just the mechanism for the handler to use; I'd expect whatever > registered the handler to be responsible for flipping the static key, > and I don't think anything needs to change within ftrace itself. > >> If ftrace can only observe the function being called, maybe it >> wouldn't be wrong to just observe nothing if the static key isn't >> enabled because nobody is doing the fault injection? > > Yep, that sounds right to me. Good. > Mark.