Failed to execute statically linked binaries

[imlk0]

A minimal test case:

echo 'int main(){return 0;}' | gcc -static -o rootfs/bin/test_static_linked -x c -
./target/debug/proot-rs --rootfs=./rootfs -- /bin/test_static_linked

output:

[imlk0]

Document the steps to solve this problem:

• First, in the source code of proot-rs, runing a executable without INTERP segment is not allowed currently. We need to remove some code snippet

  

• Now, we are able to execute a statically linked elf file. But in some case, we will got a SIGSEGV in loader.c:

  RUST_LOG=trace cargo run -- --rootfs=./rootfs -- /bin/test_execve_static 

  

  It was caused by a mmap() syscall, when the loader are mapping a PT_LOAD segment. In this case. the memory area being mapped was 0x401000 -- (0x401000+0x81000) , which is the second PT_LOAD segment of the executing elf file:

  

  By analysis the dumped core file, I found that the address of the current instruction (the value of rip register) is 0x401219, which is precisely within the mapping memory area.

  Then, I have a look at the program headers of our loader, and found that the PT_LOAD segment is conflict with the one in the executing elf file. That is why the issue occured.

  

• The original proot seems to be aware of this bug, and solve this by change the address of .text section. https://github.com/proot-me/proot/blob/a4db64532f4e8267bd37bcdc929daa4817f36ef5/src/GNUmakefile#L249

• Therefore, to fix this, we can use the -Wl,-Ttext=0xaddress option to set the address of the .text section when we compile the loader. This involves a change to build_loader.rs.

[imlk0]

Fixed in commit dcfd709