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Sat, 18 Apr 2020 09:10:26 +0930 (ACST) Date: Sat, 18 Apr 2020 09:10:26 +0930 From: Alan Modra To: Nicholas Piggin Subject: Re: [RFC PATCH] powerpc/64/signal: balance return predictor stack in signal trampoline Message-ID: <20200417234026.GB29913@bubble.grove.modra.org> References: <20200417091747.316707-1-npiggin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200417091747.316707-1-npiggin@gmail.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, Anton Blanchard Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, Apr 17, 2020 at 07:17:47PM +1000, Nicholas Piggin wrote: > I don't know much about dwarf, gdb still seems to recognize the signal > frame and unwind properly if I break inside a signal handler. Yes, the dwarf unwind info still looks good. The commented out dwarf near the end of sigtramp.S should probably go. At least if you really can't take an async signal in the trampoline (a kernel question, not anything to do with gcc support of async signals as the comment wrongly says). If you *can* take an async signal at some point past the trampoline addi, then delete the comment and uncomment the code. Note that the advance_loc there bitrotted ever since the nop was added before the trampoline, so you'd need to change that to an advance_loc that moves from .Lsigrt_start to immediately after the addi, ie. 0x42. -- Alan Modra Australia Development Lab, IBM