From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Fri, 22 Feb 2002 19:54:27 +0000 Subject: [Linux-ia64] problem with unwind info for .init/.fini sections Message-Id: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org I mailed the attached article to libc-hacker yesterday, but forgot to cc the binutils list. I'd really appreciate hearing other people's ideas on how to fix this problem. While we found the problem with ia64 linux, I suspect other platforms that rely on unwind info are likely to be affected as well. Thanks, --david --- Today I noticed that the .init and .fini sections are lacking the info needed for reliably unwinding on ia64. This turns out to be a somewhat nasty problem to solve, because the section is generated at linktime. It's easy to fix up the unwind info for the init/fini prologues, but it's less clear what to do about the body of these sections. I can think of two approaches: (1) Change the linker so it updates the unwind info once the final .init/.fini section has been created. This shouldn't be all that hard: it requires updating the unwind table entry and adjusting the unwind descriptors so that the final body region is long enough to cover the entire section. (2) Require that each code fragment that goes into the .init/.fini section is wrapped like this: .proc whatever .prologue .vframe r32 .save rp, r33 .save ar.pfs, r34 .body : ACTUAL INIT CODE : .endp (2) might be somewhat easier to do, but is less efficient (the same unwind info gets duplicated over and over again for no good reason) and finding all code sequences that go into .init/.fini would be hard (e.g., it would require gcc, for sure). (1) doesn't strike me as a great solution as it would require building more special-section knowledge into the linker, but the solution would probably be more reliable and more localized than (2). Anybody else have a better idea or other comments? --david