Messages in this thread | | | Date | Mon, 7 Jul 2008 10:55:10 -0500 | From | Nathan Lynch <> | Subject | Re: [PATCH 1/2] elf loader support for auxvec base platform string |
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Mikael Pettersson wrote: > Nathan Lynch writes: > > Some IBM POWER-based platforms have the ability to run in a > > mode which mostly appears to the OS as a different processor from the > > actual hardware. For example, a Power6 system may appear to be a > > Power5+, which makes the AT_PLATFORM value "power5+". > > > > However, some applications (virtual machines, optimized libraries) can > > benefit from knowledge of the underlying CPU model. A new aux vector > > entry, AT_BASE_PLATFORM, will denote the actual hardware. For > > example, on a Power6 system in Power5+ compatibility mode, AT_PLATFORM > > will be "power5+" and AT_BASE_PLATFORM will be "power6". > > Why on earth would you ever want AT_PLATFORM to differ from AT_BASE_PLATFORM? > In cases that matter you admit that AT_BASE_PLATFORM takes precedence, > so why involve a fake lame not-quite-the-platform in the first place? > > Workaround for buggy software?
My apologies, I did not explain the motivation well.
The idea is that while AT_PLATFORM indicates the instruction set supported, AT_BASE_PLATFORM indicates the underlying microarchitecture. It's not a matter of buggy software, or of one value taking precedence over the other.
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