Re: [PATCH 14/15] scripts: environment: Add --container option.

[Ludovic Courtès]

Hi!

I think I got it.  First, note that:

--8<---------------cut here---------------start------------->8---
$ guix build guile-bootstrap 
/gnu/store/aiz8db2gni401wc9fgidmcggxyb1czis-guile-bootstrap-2.0
$ cat /gnu/store/aiz8db2gni401wc9fgidmcggxyb1czis-guile-bootstrap-2.0/bin/guile 
#!/gnu/store/gvwf71vddp8c1d7ydqg02p43mgdjrx6s-bash
export 
GUILE_SYSTEM_PATH=/gnu/store/aiz8db2gni401wc9fgidmcggxyb1czis-guile-bootstrap-2.0/share/guile/2.0
export 
GUILE_SYSTEM_COMPILED_PATH=/gnu/store/aiz8db2gni401wc9fgidmcggxyb1czis-guile-bootstrap-2.0/lib/guile/2.0/ccache
exec -a "$0" 
/gnu/store/aiz8db2gni401wc9fgidmcggxyb1czis-guile-bootstrap-2.0/bin/.guile-real 
"$@"
--8<---------------cut here---------------end--------------->8---

So:

> [pid 32626] 
> execve("/home/dave/Code/guix/test-tmp/store/w8fsskwxr793yq6w3368x5k1p07syi3h-guile-bootstrap-2.0/bin/guile",
>  ["guile", "-c", "(exit 42)"], [/* 6 vars */]) = -1 ENOEXEC (Exec format 
> error)
> [pid 32626] 
> execve("/gnu/store/sybvv7vqvqqmijpn2ql1p6yk61cr5y3k-bash-static-4.3.39/bin/bash",
>  ["/gnu/store/sybvv7vqvqqmijpn2ql1p"..., 
> "/home/dave/Code/guix/test-tmp/st"..., "-c", "(exit 42)"], [/* 6 vars */]) = 
> -1 ENOENT (No such file or directory)
> [pid 32626] write(2, "In execvp of guile: No such file"..., 46In execvp of 
> guile: No such file or directory
> ) = 46

The first ‘execve’ fails.  The ‘execve’ comes from libc itself, which
notices ENOEXEC and thus falls back to interpreting the executable with
_PATH_BSHELL (see posix/execvpe.c.)

However, the _PATH_BSHELL that is taken here is the one from /gnu/store
rather than the one from /home/dave/Code/guix/test-tmp/…; this is
because that’s the _PATH_BSHELL value for the libc of the Guile that
runs ‘guix environment’.  (This is a problem in the test environment
because of the wrong _PATH_BSHELL, but it happens to work well out side
of the test environment.)

Now, I’m not sure why the first ‘execve’ shell; normally shebangs are
interpreted directly by the kernel, in fs/binfmt_script.c.

It seems that the file mentioned in the shebang of ‘guile’ is correctly
mapped:

> [pid 32625] 
> mount("/home/dave/Code/guix/test-tmp/store/xh177jawf1hl22wm1rzfq7dgn9iz67jy-bash",
>  
> "/tmp/guix-directory.Datz1K//home/dave/Code/guix/test-tmp/store/xh177jawf1hl22wm1rzfq7dgn9iz67jy-bash",
>  0x1d97b30, MS_RDONLY|MS_BIND, NULL) = 0
> [pid 32625] 
> mount("/home/dave/Code/guix/test-tmp/store/xh177jawf1hl22wm1rzfq7dgn9iz67jy-bash",
>  
> "/tmp/guix-directory.Datz1K//home/dave/Code/guix/test-tmp/store/xh177jawf1hl22wm1rzfq7dgn9iz67jy-bash",
>  0x13c3b30, MS_RDONLY|MS_REMOUNT|MS_BIND, NULL) = 0

Could it be that it lacks the executable bit?

Ludo’.