On 07/09/2023 22:24, Guilherme G. Piccoli wrote: > Currently the kernel provides a symlink to the executable binary, in the > form of procfs file exe_file (/proc/self/exe_file for example). But what > happens in interpreted scenarios (like binfmt_misc) is that such link > always points to the *interpreter*. For cases of Linux binary emulators, > like FEX [0] for example, it's then necessary to somehow mask that and > emulate the true binary path. > > We hereby propose a way to expose such interpreted binary as exe_file if > the flag 'I' is selected on binfmt_misc. When that flag is set, the file > /proc/self/exe_file points to the *interpreted* file, be it ELF or not. > In order to allow users to distinguish if such flag is used or not without > checking the binfmt_misc filesystem, we propose also the /proc/self/interpreter > file, which always points to the *interpreter* in scenarios where > interpretation is set, like binfmt_misc. This file is empty / points to > nothing in the case of regular ELF execution, though we could consider > implementing a way to point to the LD preloader if that makes sense... > > This was sent as RFC because of course it's a very core change, affecting > multiple areas and there are design choices (and questions) in each patch > so we could discuss and check the best way to implement the solution as > well as the corner cases handling. This is a very useful feature for > emulators and such, like FEX and Wine, which usually need to circumvent > this kernel limitation in order to expose the true emulated file name > (more examples at [1][2][3]). > > This patchset is based on the currently v6.6-rc1 candidate (Linus tree > from yesterday) and was tested under QEMU as well as using FEX. > Thanks in advance for comments, any feedback is greatly appreciated! > Cheers, > > Guilherme > > > [0] https://github.com/FEX-Emu/FEX > > [1] Using an environment variable trick to override exe_file: > https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src/util/u_process.c#L209 > > [2] https://github.com/baldurk/renderdoc/pull/2694 > > [3] FEX handling of the exe_file parsing: > https://github.com/FEX-Emu/FEX/blob/main/Source/Tools/FEXLoader/LinuxSyscalls/FileManagement.cpp#L499 > > Hi folks, gentle monthly ping. Any opinions / suggestions on that? Thanks in advance, Guilherme
