From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergey Senozhatsky Subject: Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor dereference Date: Tue, 19 Sep 2017 19:31:54 +0900 Message-ID: <20170919103154.GC401@jagdpanzerIV.localdomain> References: <20170916035347.19705-1-sergey.senozhatsky@gmail.com> <20170916035347.19705-4-sergey.senozhatsky@gmail.com> <20170916094345.d332z3odceqiyrll@naverao1-tp.localdomain> <87shfjkmxe.fsf@concordia.ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Naveen N. Rao" , Sergey Senozhatsky , Tony Luck , Fenghua Yu , Benjamin Herrenschmidt , Paul Mackerras , "James E . J . Bottomley" , Helge Deller , Petr Mladek , linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, Alexei Starovoitov , Steven Rostedt , linux-kernel@vger.kernel.org, Jessica Yu , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Nicholas Piggin To: Michael Ellerman Return-path: In-Reply-To: <87shfjkmxe.fsf@concordia.ellerman.id.au> List-ID: List-Id: linux-parisc.vger.kernel.org On (09/19/17 20:22), Michael Ellerman wrote: > > On 2017/09/16 12:53PM, Sergey Senozhatsky wrote: > >> We are moving towards separate kernel and module function descriptor > >> dereference callbacks. This patch enables it for powerpc64. > >> > >> For pointers that belong to the kernel > >> - Added __start_opd and __end_opd pointers, to track the kernel > >> .opd section address range; > >> > >> - Added dereference_kernel_function_descriptor(). Now we > >> will dereference only function pointers that are within > >> [__start_opd, __end_opd]; > >> > >> For pointers that belong to a module > >> - Added dereference_module_function_descriptor() to handle module > >> function descriptor dereference. Now we will dereference only > >> pointers that are within [module->opd.start, module->opd.end]. > > > > Would it be simpler to just use kernel_text_address() and dereference > > everything else? See commit 83e840c770f2c5 ("powerpc64/elfv1: Only > > dereference function descriptor for non-text symbols") for a related > > patch. > > Yeah that would be a lot simpler and probably work perfectly well. unlike ppc_function_entry(), printk() can get called on any symbol, not just function pointers. for example, cat /proc/kallsyms | grep shrinker_rwsem ffffffff81a4b1e0 d shrinker_rwsem or cat /proc/kallsyms | grep vm_total_pages ffffffff81dcd418 B vm_total_pages and so on. -ss From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergey Senozhatsky Date: Tue, 19 Sep 2017 10:31:54 +0000 Subject: Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor dereference Message-Id: <20170919103154.GC401@jagdpanzerIV.localdomain> List-Id: References: <20170916035347.19705-1-sergey.senozhatsky@gmail.com> <20170916035347.19705-4-sergey.senozhatsky@gmail.com> <20170916094345.d332z3odceqiyrll@naverao1-tp.localdomain> <87shfjkmxe.fsf@concordia.ellerman.id.au> In-Reply-To: <87shfjkmxe.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Michael Ellerman Cc: "Naveen N. Rao" , Sergey Senozhatsky , Tony Luck , Fenghua Yu , Benjamin Herrenschmidt , Paul Mackerras , "James E . J . Bottomley" , Helge Deller , Petr Mladek , linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, Alexei Starovoitov , Steven Rostedt , linux-kernel@vger.kernel.org, Jessica Yu , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Nicholas Piggin On (09/19/17 20:22), Michael Ellerman wrote: > > On 2017/09/16 12:53PM, Sergey Senozhatsky wrote: > >> We are moving towards separate kernel and module function descriptor > >> dereference callbacks. This patch enables it for powerpc64. > >> > >> For pointers that belong to the kernel > >> - Added __start_opd and __end_opd pointers, to track the kernel > >> .opd section address range; > >> > >> - Added dereference_kernel_function_descriptor(). Now we > >> will dereference only function pointers that are within > >> [__start_opd, __end_opd]; > >> > >> For pointers that belong to a module > >> - Added dereference_module_function_descriptor() to handle module > >> function descriptor dereference. Now we will dereference only > >> pointers that are within [module->opd.start, module->opd.end]. > > > > Would it be simpler to just use kernel_text_address() and dereference > > everything else? See commit 83e840c770f2c5 ("powerpc64/elfv1: Only > > dereference function descriptor for non-text symbols") for a related > > patch. > > Yeah that would be a lot simpler and probably work perfectly well. unlike ppc_function_entry(), printk() can get called on any symbol, not just function pointers. for example, cat /proc/kallsyms | grep shrinker_rwsem ffffffff81a4b1e0 d shrinker_rwsem or cat /proc/kallsyms | grep vm_total_pages ffffffff81dcd418 B vm_total_pages and so on. -ss