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FAQ: why SIGILL?

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Andy Polyakov 2013-12-28 13:20:14 +01:00
parent 2218c296b4
commit e796666d34
1 changed files with 16 additions and 0 deletions
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FAQ
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@ -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?
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@ -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.
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