gcc creating a huge executable image (RedHat 2.6.18-8.el5, x86_64, Linux)
I'm trying to figure out the mystery of the 64-bit ELF image. I wrote a hello.c little program, compiled with
% gcc hello.c -o hello
No problem. Got a "hello" executable image of size 6668 bytes. So far so good.
I really want to understand the "-Ttext" linker parameter so I repeated the compilation, this time with a linker parameter:
% gcc -Xlinker -Ttext=0x2000 hello.c -o hello
Again, a "hello" executable gets created and even runs ok, but the size of the file is roughly 2MB (2102706 to be exact.) So I go looking inside the image for some clues:
% dd bs=4092 count=256 if=hello | od -Ax -tx1z -v
The image starts with the expected ELF header. Then I found out that the ".text" segment itself was placed in offset 0x2000 in the "hello" file. The ".text" segment was followed by almost 2MB of zeroes.
Main questions:
What is the meaning of the -Ttext= directive? (I thought it was supposed to tell the loader that I want the ".text" segment in that specific location in physical memory, not in the file itself. I really don't care where they place it in the file.)
Did I get this wrong? Does "-Ttext=" really indicate a file offset as opposed to a physical memory address?
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