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Fri, 2 Feb 2024 16:31:23 -0500 (EST) Message-ID: <21ed604c-8607-43b7-853a-9bd1623bd918@flygoat.com> Date: Fri, 2 Feb 2024 21:31:22 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/3] Handle delay slot for extable lookup To: Linus Torvalds , Thomas Bogendoerfer Cc: Oleg Nesterov , Andrew Morton , Ben Hutchings , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, Xi Ruoyao References: <20240202-exception_ip-v2-0-e6894d5ce705@flygoat.com> Content-Language: en-US From: Jiaxun Yang Autocrypt: addr=jiaxun.yang@flygoat.com; keydata= xsFNBFnp/kwBEADEHKlSYJNLpFE1HPHfvsxjggAIK3ZtHTj5iLuRkEHDPiyyiLtmIgimmD3+ XN/uu2k1FFbrYiYgMjpGCXeRtdCLqkd+g9V4kYMlgi4MPHLt3XEuHcoKD1Yd2qYPT/OiQeGM 6bPtGUZlgfOpze1XuqHQ2VMWATL+kLYzk6FUUL715t8J5J9TgZBvSy8zc6gvpp3awsCwjFSv X3fiPMTC2dIiiMh4rKQKGboI1c7svgu6blHpy/Q5pXlEVqfLc7tFTGnvUp95jsK639GD8Ht3 0fSBxHGrTslrT775Aqi+1IsbJKBOmxIuU9eUGBUaZ00beGE09ovxiz2n2JKXKKZklNqhzifb 6uyVCOKdckR8uGqzRuohxDS7vlDZfFD5Z5OhplFY/9q+2IjCrWMmbHGSWYs9VV52XGM+wiEG sM5bup03N2q1kDXUWJ+zNNYowuOJKN9uxF3jBjdXSDi3uJu/ZUL/mBqI58SkHq5NTaHypRoE 5BxVmgDMCGQe93adKHUNmt4HK28R506S7019+umg1bq5vA/ncmh/J2k8MFGPXqO8t1xVI2O5 qrRheRKu1oST46ZJ7vKET1UwgcXTZ1iwqFlA26/iKxXoL7R7/AqWrapokEsUzRblGcutGZ/b 4lJVOxxAWaRcajpWvwqscI2mUF++O7DxYbhOJ/EFY2rv0i6+/QARAQABzSVKaWF4dW4gWWFu ZyA8amlheHVuLnlhbmdAZmx5Z29hdC5jb20+wsGRBBMBCAA7AhsjAh4BAheABQsJCAcCBhUK CQgLAgQWAgMBFiEEmAN5vv6/v0d+oE75wRGUkHP8D2cFAmKcjj8CGQEACgkQwRGUkHP8D2fx LxAAuNjknjfMBXIwEDpY+L2KMMU4V5rvTBATQ0dHZZzTlmTJuEduj/YdlVo0uTClRr9qkfEr Nfdr/YIS6BN6Am1x6nF2PAqHu/MkTNNFSAFiABh35hcm032jhrZVqLgAPLeydwQguIR8KXQB pP6S/jL3c7mUvVkoYy2g5PE1eH1MPeBwkg/r/ib9qNJSTuJH3SXnfZ4zoynvf3ipqnHsn2Sa 90Ta0Bux6ZgXIVlTL+LRDU88LISTpjBITyzn5F6fNEArxNDQFm4yrbPNbpWJXml50AWqsywp q9jRpu9Ly4qX2szkruJ/EnnAuS/FbEd4Agx2KZFb6LxxGAr4useXn6vab9p1bwRVBzfiXzqR WeTRAqwmJtdvzyo3tpkLmNC/jC3UsjqgfyBtiDSQzq0pSu7baOjvCGiRgeDCRSWq/T3HGZug 02QAi0Wwt/k5DX7jJS4Z5AAkfimXG3gq2nhiA6R995bYRyO8nIa+jmkMlYRFkwWdead3i/a0 zrtUyfZnIyWxUOsqHrfsN45rF2b0wHGpnFUfnR3Paa4my1uuwfp4BI6ZDVSVjz0oFBJ5y39A DCvFSpJkiJM/q71Erhyqn6c1weRnMok3hmG0rZ8RCSh5t7HllmyUUWe4OT97d5dhI7K/rnhc ze8vkrTNT6/fOvyPFqpSgYRDXGz2qboX/P6MG3zOOARlnqgjEgorBgEEAZdVAQUBAQdAUBqi bYcf0EGVya3wlwRABMwYsMimlsLEzvE4cKwoZzEDAQgHwsF2BBgBCAAgFiEEmAN5vv6/v0d+ oE75wRGUkHP8D2cFAmWeqCMCGwwACgkQwRGUkHP8D2dXlw/8CGKNXDloh1d7v/jDgcPPmlXd lQ4hssICgi6D+9aj3qYChIyuaNncRsUEOYvTmZoCHgQ6ymUUUBDuuog1KpuP3Ap8Pa3r5Tr6 TXtOl6Zi23ZWsrmthuYtJ8Yn5brxs6KQ5k4vCTkbF8ukue4Xl4O0RVlaIgJihJHZTfd9rUZy QugM8X98iLuUqYHCq2bAXHOq9h+mTLrhdy09dUalFyhOVejWMftULGfoXnRVz6OaHSBjTz5P HwZDAFChOUUR6vh31Lac2exTqtY/g+TjiUbXUPDEzN4mENACF/Aw+783v5CSEkSNYNxrCdt8 5+MRdhcj7y1wGfnSsKubHTOkBQJSanNr0cZZlPsJK0gxB2YTG6Nin13oX8mV7sAa3vBqqwfj ZtjNA+Up9IJY4Iz5upykUDAtCcvm82UnJoe5bMuoiyVccuqd5K/058AAxWv8fIvB4bSgmGMM aAN9l7GLyi4NhsKCCcAGSc2YAsxFrH6whVqY6JIF+08n1kur5ULrEKHpTTeffwajCgZPWpFc 7Mg2PDpoOwdpKLKlmIpyDexGVH0Lj/ycBL8ujDYZ2tA9HhEaO4dW6zsQyt1v6mZffpWK+ZXb Cs8oFeACbrtNFF0nhNI6LUPH3oaVOkUoRQUYDuX6mIc4VTwMA8EoZlueKEHfZIKrRf2QYbOZ HVO98ZmbMeg= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: p7fr6w5run3bmkwon9ttkegp3rwnb9jh X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 13A8C40020 X-HE-Tag: 1706909488-131198 X-HE-Meta: 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 GzH5HfZS 0SMuglxxDL/2tZmdBnKDRBj5u0rq6qnNyZ4F8cGhVaIZwUIepY8j9KDHyOT5yvFgTSG7rXLc7bsTSkXgTXZYXtp0gtJw++QfniqnB0JrJweDjdsKQM/RfluBRW361pXO27GgXvhkRiZT1YlUTbsgMPybq6mfkiAWgAcAWEXUMdwpNYGCGeiMlA4PGkvjAi4NI//qVeBcMm0il/nk0Khh7BwW7jshEHkHEn5jOTMrUeVKicfZb44RpOtNwo3u7350srqLU7hH/9+1liEPb90q3zbzi9oELQfQ3Ip2gw0dboIusgKgjawJVGU8Wqq+hwMQafaPfQstpUq/QP2qC2Jl6ANtt+BnuFnf4pfLR6DmeTpBl6EyOOs71pmyO8gev44YuSikY1lkh4A1vb9M= 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: 在 2024/2/2 18:39, Linus Torvalds 写道: > On Fri, 2 Feb 2024 at 04:30, Jiaxun Yang wrote: >> ptrace: Introduce exception_ip arch hook >> MIPS: Clear Cause.BD in instruction_pointer_set >> mm/memory: Use exception ip to search exception tables > Just to clarify: does that second patch fix the problem that > __isa_exception_epc() does a __get_user()? No it only covers an obvious case when I was playing around exception_ip with kgdb. There are still potential cases __isa_exception_epc may touch user space. > Because that mm/memory.c use of "exception_ip()" most definitely > cannot take a page fault. > > So if MIPS cannot do that whole exception IP thing without potentially > touching user space, I do worry that we might just have to add a > > #ifndef __MIPS__ > > around this all. It is possible to perform exception_ip() without touching user space by saving "BadInstr" in pt_regs at exception entries. For newer hardware it's as simple as saving an extra CP0 register, on older hardware we may have to read it from user space. + Thomas (MIPS maintainer), what's your opinion? Thanks > > Possibly somehow limited to just the microMIPS/MIPS16e case in Kconfig instead? > > Linus -- --- Jiaxun Yang