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Venkataraman" Message-ID: <9781011e-2d99-7f46-592c-621c66ea66c3@linux.microsoft.com> Date: Wed, 5 May 2021 13:48:21 -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: <20210505164648.GC4541@sirena.org.uk> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210505_114826_138146_E5C544CB X-CRM114-Status: GOOD ( 17.76 ) 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 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)) 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