From: Andy Polyakov Date: Sat, 28 Dec 2013 12:20:14 +0000 (+0100) Subject: FAQ: why SIGILL? X-Git-Tag: master-post-reformat~1033 X-Git-Url: https://git.librecmc.org/?p=oweals%2Fopenssl.git;a=commitdiff_plain;h=e796666d34c24b96943ae653dc93371bcae19021 FAQ: why SIGILL? --- diff --git a/FAQ b/FAQ index 9543e4ab07..550a998e6f 100644 --- a/FAQ +++ b/FAQ @@ -76,6 +76,7 @@ OpenSSL - Frequently Asked Questions * Why does Valgrind complain about the use of uninitialized data? * Why doesn't a memory BIO work when a file does? * Where are the declarations and implementations of d2i_X509() etc? +* When debugging I observe SIGILL during OpenSSL initialization: why? =============================================================================== @@ -1069,5 +1070,20 @@ These are defined and implemented by macros of the form: The implementation passes an ASN1 "template" defining the structure into an ASN1 interpreter using generalised functions such as ASN1_item_d2i(). +* When debugging I observe SIGILL during OpenSSL initialization: why? + +OpenSSL adapts to processor it executes on and for this reason has to +query its capabilities. Unfortunately on some processors the only way +to achieve this for non-privileged code is to attempt instructions +that can cause Illegal Instruction exceptions. The initialization +procedure is coded to handle these exceptions to manipulate corresponding +bits in capabilities vector. This normally appears transparent, except +when you execute it under debugger, which stops prior delivering signal +to handler. Simply resuming execution does the trick, but when debugging +a lot it might feel counterproductive. Two options. Either set explicit +capability environment variable in order to bypass the capability query +(see corresponding crypto/*cap.c for details). Or configure debugger not +to stop upon SIGILL exception, e.g. in gdb case add 'handle SIGILL nostop' +to your .gdbinit. ===============================================================================