Date: Wed, 24 Mar 2010 14:29:23 -0500 From: Nathan Whitehorn <nwhitehorn@freebsd.org> To: freebsd-hackers@freebsd.org Subject: Review/testing request: changing the detection of data_addr/text_addr Message-ID: <4BAA6813.7060604@freebsd.org>
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We currently detect the offical "text" and "data" addresses for ELF files in kern/imgact_elf.c by the heuristic of calling whichever section contains the executable's entry point the text section and everything else data. In general, both this concept and the very few things that use them are obsolete and rare. The data addresses are, however, used in obreak() to find the current break. On powerpc64, this logic fails, because the entry point points to a function descriptor in the data section, causing sbrk() to fail, which in turn breaks profiling. The patch at http://people.freebsd.org/~nwhitehorn/textseg.diff changes this algorithm to make the official text area be the largest executable segment, and all others data. The patch has been tested on sparc64, amd64, powerpc, and (of course) powerpc64, with no evident bad effects. I would appreciate any comments, as well as tests on other architectures. The main symptom of getting these values wrong is that sbrk() stops working correctly, so I have put a simple test program for sbrk() at http://people.freebsd.org/~nwhitehorn/sbrktest.c. -Nathan
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