Extend the file handle cache entries to include symbol tables as well. An
index is used to implement binary search by symbol value. Lookups by
name are comparatively rare and are thus still implemented with a linear
search, but support for a binary search by name would be straightforward
to add if needed.
libproc previously created a new handle for each symbol lookup, which
gives rather egregious performance for DTrace's ustack() action. With
this change libproc will cache the libelf descriptor upon access, making
lookups much faster in the common case.
This allows librtld_db to fetch the PID from a handle without calling into
libproc. Together with r303531, this means that librtld_db no longer
references symbols from libproc.
This is used by libdtrace to determine the data model of target processes.
This allows for the creation of pid provider probes in 32-bit processes on
amd64.
MFC after: 1 month
* Don't print any error messages to stderr unless DEBUG is defined.
* Add a DPRINTFX macro for use when errno isn't set.
* Print the error string from libelf when appropriate.
* breakpoint setup support
* register query
* symbol to address mapping and vice-versa
* more misc utility functions based on their Solaris counterpart
Also, I've written some test cases.
Sponsored by: The FreeBSD Foundation
These will be fleshed out as part of the DTrace userland tracing
development.
For now, the kernel tracing part of DTrace requires minimal functionality
for this library.
The API for this library is deliberately different from the libproc in
OpenSolaris due to licensing restrictions.
