On 16 July 2016 at 15:54, Shi, Steven <steven....@intel.com> wrote: > Hi Ard, > > Sorry for my late response. For the PIC and PIE selection, my personal > opinion is to prefer the PIE rather than PIC, because PIE usually has even > smaller code size than PIC, although their difference is small (especially > if enable LTO). Below are some example data in my side. Also, like Andrew > mentioned, PIE is more secure than PIC, and more and more users use PIE > rather than PIC to generate the code. >
A PIE executable is built from PIC (*) objects, and simply contains a .rela section and a _DYNAMIC entry point that allows a runtime linker to load it at arbitrary offsets in memory. We already have this 'security' in EDK2 because we use relocatable PE/COFF executables, so PIE does not bring us anything in terms of features. (*) AARCH64 allows PIE executables to be built from non-PIC objects when using the small model From a code generation point of view, they are identical, and only differ in the linking step. > > > > I use your gcc-x64-opt and my llvm_v2 branches to collect the GCC49 and > GCC5 data > > Code size, > > Byte, > > the smaller the better > > GCC49 with hidden visibility > > (PIE = PIC) > > GCC49 with public visibility + my patch for new PIC/PIE relocation types > support in GenFw > > (PIC > PIE) > > GCC5 LTO > > (PIC > PIE) > > Shell X64 DEBUG PIC > > 1,138,048 > > 5,148,104 > > 899,136 > > Shell X64 DEBUG PIE > > 1,138,048 > > 5,130,464 > > 899,072 > > CpuDxe X64 DEBUG PIC > > 67,456 > > 68,608 > > 36,032 > > CpuDxe X64 DEBUG PIE > > 67,456 > > 67,456 > > 35,968 > > UsbKbDxe X64 DEBUG PIC > > 46,784 > > 47,296 > > 26,752 > > UsbKbDxe X64 DEBUG PIE > > 46,784 > > 46,784 > > 26,688 > You are changing several parameters at the same time, comparing non-PIE/hidden with PIE/default visibility. PIE is not an optimization. PIE is an executable format that can be understood by an ELF runtime linker, and so enabling PIE is not a goal in itself. We should only enable it if we must. -- Ard. _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
