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Venkataraman" To: Mark Brown Cc: jpoimboe@redhat.com, mark.rutland@arm.com, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, pasha.tatashin@soleen.com, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org References: <65cf4dfbc439b010b50a0c46ec500432acde86d6> <20210503173615.21576-1-madvenka@linux.microsoft.com> <20210503173615.21576-3-madvenka@linux.microsoft.com> <20210504160508.GC7094@sirena.org.uk> <1bd2b177-509a-21d9-e349-9b2388db45eb@linux.microsoft.com> <0f72c4cb-25ef-ee23-49e4-986542be8673@linux.microsoft.com> <20210505164648.GC4541@sirena.org.uk> <9781011e-2d99-7f46-592c-621c66ea66c3@linux.microsoft.com> Message-ID: <8ea6a81a-2e19-f752-408c-21dea1078f9b@linux.microsoft.com> Date: Wed, 5 May 2021 13:50:23 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <9781011e-2d99-7f46-592c-621c66ea66c3@linux.microsoft.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210505_115025_211274_137064D4 X-CRM114-Status: GOOD ( 21.73 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 5/5/21 1:48 PM, Madhavan T. Venkataraman wrote: > > > On 5/5/21 11:46 AM, Mark Brown wrote: >> On Tue, May 04, 2021 at 02:32:35PM -0500, Madhavan T. Venkataraman wrote: >> >>> If you prefer, I could do something like this: >>> >>> check_pc: >>> if (!__kernel_text_address(frame->pc)) >>> frame->reliable = false; >>> >>> range = lookup_range(frame->pc); >>> >>> #ifdef CONFIG_FUNCTION_GRAPH_TRACER >>> if (tsk->ret_stack && >>> frame->pc == (unsigned long)return_to_handler) { >>> ... >>> frame->pc = ret_stack->ret; >>> frame->pc = ptrauth_strip_insn_pac(frame->pc); >>> goto check_pc; >>> } >>> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ >> >>> Is that acceptable? >> >> I think that works even if it's hard to love the goto, might want some >> defensiveness to ensure we can't somehow end up in an infinite loop with >> a sufficiently badly formed stack. >> > > I could do something like this: > > - Move all frame->pc checking code into a function called check_frame_pc(). > > bool check_frame_pc(frame) > { > Do all the checks including function graph > return frame->pc changed > } > > - Then, in unwind_frame() > > unwind_frame() > { > int i; > ... > > for (i = 0; i < MAX_CHECKS; i++) { > if (!check_frame(tsk, frame)) Small typo in the last statement - It should be check_frame_pc(). Sorry. Madhavan > break; > } > > if (i == MAX_CHECKS) > frame->reliable = false; > return 0; > } > > The above would take care of future cases like kretprobe_trampoline(). > > If this is acceptable, then the only question is - what should be the value of > MAX_CHECKS (I will rename it to something more appropriate)? > > Madhavan > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel