From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: In-Reply-To: <20050812050609.GA7355@krispykreme> References: <20050812050609.GA7355@krispykreme> Mime-Version: 1.0 (Apple Message framework v622) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: <3b9a91d3eebf79c9cc8a2b67cc5e3f84@us.ibm.com> From: Hollis Blanchard Date: Fri, 12 Aug 2005 08:58:32 -0500 To: Anton Blanchard Cc: PPC64-dev List , Linux PPC Dev Subject: Re: GDB backtrace and signal trampolines List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Aug 12, 2005, at 12:06 AM, Anton Blanchard wrote: > >> Would it make sense to limit the test to within a few hundred bytes of >> the stack pointer? Or some better way to detect that the PC is in a >> signal trampoline? > > With recent kernels we should be able to use the dwarf2 unwind > information in the vdso I think. I guess compatibility with older kernels will still need to be maintained, though. I see this note in arch/ppc64/mm/fault.c: /* * N.B. The POWER/Open ABI allows programs to access up to * 288 bytes below the stack pointer. * The kernel signal delivery code writes up to about 1.5kB * below the stack pointer (r1) before decrementing it. * The exec code can write slightly over 640kB to the stack * before setting the user r1. Thus we allow the stack to * expand to 1MB without further checks. */ So would 2KB be a reasonable limit to the signal frame check, as I described before? -- Hollis Blanchard IBM Linux Technology Center