Messages in this thread | | | Date | Tue, 10 Dec 2013 14:47:06 -0800 | Subject | Re: RFC: binutils PATCH: Set e_type to ET_EXEC for -pie -Ttext-segment= | From | "H.J. Lu" <> |
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On Tue, Dec 10, 2013 at 2:36 PM, Alan Modra <amodra@gmail.com> wrote: > On Mon, Dec 09, 2013 at 07:10:23PM -0800, H.J. Lu wrote: >> Linker sets e_type in ELF header to ET_DYN for -pie -Ttext-segment=0xXXX. >> When I added -Ttext-segment=0xXXX, one goal was to load >> small model executable above 4GB on Linux/x86-64, which >> was done with -pie -Ttext-segment=0xXXX. But -pie sets >> e_type in ELF header to ET_DYN and kernel may ignore >> p_vaddr in ELF header to load ET_DYN binary at a random >> address. This patch changes ld to set e_type in ELF header >> to ET_EXEC if the first PT_LOAD segment has non-zero >> p_vaddr. If this is unacceptable as generic ELF change, >> I can make it specific to x86. > > Well, I suppose it's a hack to use ET_DYN for executables in the first > place, so one more hack in the linker hardly matters. Why not just > patch the kernel though? The kernel can look at the first PT_LOAD > header just as easily as the linker, and it's the kernel that is doing > the loading after all. >
Kernel should have some freedom on where to load ET_DYN object. But when -Ttext-segment= is used, programmer expects the executable will be loaded at the specified address. Setting ET_EXEC will guarantee that it will be loaded at that address.
-- H.J.
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