Date: Wed, 24 Mar 2010 16:42:00 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: Nathan Whitehorn <nwhitehorn@freebsd.org> Subject: Re: Review/testing request: changing the detection of data_addr/text_addr Message-ID: <201003241642.00246.jhb@freebsd.org> In-Reply-To: <4BAA6813.7060604@freebsd.org> References: <4BAA6813.7060604@freebsd.org>
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On Wednesday 24 March 2010 3:29:23 pm Nathan Whitehorn wrote: > 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. My only comment is that I would keep the existing language about obreak() as it describes multiple data segments, etc. Instead, I would just use the first sentence of your new comment to replace the first paragraph in the old comment. -- John Baldwin
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