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Tue, 19 Jan 2021 02:38:28 -0800 (PST) Received: from localhost ([2409:10:2e40:5100:6e29:95ff:fe2d:8f34]) by smtp.gmail.com with ESMTPSA id t8sm2753229pjm.45.2021.01.19.02.38.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jan 2021 02:38:27 -0800 (PST) Date: Tue, 19 Jan 2021 19:38:24 +0900 From: Sergey Senozhatsky To: Matthew Wilcox Cc: Sergey Senozhatsky , Timur Tabi , Andrew Morton , linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, Petr Mladek , roman.fietze@magna.com, keescook@chromium.org, Steven Rostedt , John Ogness , linux-mm@kvack.org, Akinobu Mita Subject: Re: [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps Message-ID: References: <20210116220950.47078-1-timur@kernel.org> <20210118182635.GD2260413@casper.infradead.org> <20210119014725.GH2260413@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210119014725.GH2260413@casper.infradead.org> 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: On (21/01/19 01:47), Matthew Wilcox wrote: [..] > > > So maybe DUMP_PREFIX_UNHASHED can do the unhashed dump only when > > CONFIG_DEBUG_KERNEL=y and fallback to DUMP_PREFIX_ADDRESS otherwise? > > Distros enable CONFIG_DEBUG_KERNEL. Oh, I see. > If you want to add CONFIG_DEBUG_LEAK_ADDRESSES, then that's great, > and you won't even have to change users, you can just change how %p > behaves. I like the name. config dependent behaviour of %p wouldn't be new, well, to some extent, e.g. XFS does something similar (see below). I don't think Linus will be sold on this, however. fs/xfs/xfs_linux.h: /* * Starting in Linux 4.15, the %p (raw pointer value) printk modifier * prints a hashed version of the pointer to avoid leaking kernel * pointers into dmesg. If we're trying to debug the kernel we want the * raw values, so override this behavior as best we can. */ #ifdef DEBUG # define PTR_FMT "%px" #else # define PTR_FMT "%p" #endif And then they just use it as xfs_alert(mp, "%s: bad inode magic number, dip = "ptr_fmt", dino bp = "ptr_fmt", ino = %ld", __func__, dip, bp, in_f->ilf_ino); -ss