Messages in this thread | | | Date | Mon, 9 Dec 2013 15:53:14 -0800 | Subject | Re: [PATCH] binfmt_elf: fix PIE load with randomization disabled | From | "H.J. Lu" <> |
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On Mon, Dec 9, 2013 at 3:35 PM, H. Peter Anvin <hpa@zytor.com> wrote: > On 12/09/2013 01:44 PM, H.J. Lu wrote: >> On Mon, Dec 9, 2013 at 1:39 PM, H. Peter Anvin <hpa@zytor.com> wrote: >>> On 12/09/2013 01:03 PM, H.J. Lu wrote: >>>> >>>> No, please don't do that. Normally, PIE has zero load address and kernel >>>> can load it anywhere. There are multiple reasons why PIE has non-zero >>>> load address. Saying you need to load a program above 4GB under x86-64, >>>> you can't do that with normal dynamic executable. PIE with non-zero load >>>> address is the only way to do that on x86-64. >>>> >>> >>> Why does it have to be PIE? >>> >> >> x86-64 small model is limited to 4GB in size. You can't build >> a dynamic executable in small model larger than 4GB. >> >> There are medium and large models. But they are slower than >> small models as well as small models in PIE. Also there are >> no glibc run-times for medium and large models. >> > > Compiling for the small PIC model shouldn't automatically mean > generating a PIE (ET_DYN) executable, though (and if those are > inherently linked, that is a fundamental bug IMNSHO.)
PIE uses PIC. But GCC has -fPIE and -fPIC. They aren't the same. You build PIE with
1. Compile with -fPIE. 2. Link with -pie.
-- H.J.
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