> I guess there is a mixup between interpreter and pathname. Do you mean that `interpreter' is supposed to be absolute, instead of `pathname'? The same example also disproves that, since argv[0] is relative: | interpreter [optional-arg] pathname arg... | | $ ./execve ./script | argv[0]: ./myecho | argv[1]: script-arg | argv[2]: ./script | argv[3]: hello | argv[4]: world > All this is only vaild if the > flag is set to P (P - preserve-argv[0]) when you add a new > setting in /proc/sys/fs/binfmt_misc/register I'm not sure how binfmt_misc is related to this. We are talking about the normal shebang mechanism (which doesn't preserve argv[0]), and the man page doesn't even mention binfmt_misc. Do you agree that the man page is in error? > (any way to get the current setting ?) You can see the active flags for a registered FORMAT by reading /proc/sys/fs/binfmt_misc/FORMAT. (Though I'm new to binfmt_misc, I usually keep it disabled.) > the original wording from the kernel says: > > Legacy behavior of binfmt_misc is to overwrite the original argv[0] with > the full path to the binary. When this flag is included, binfmt_misc will > add an argument to the argument vector for this purpose, thus preserving > the original argv[0]. e.g. If your interp is set to /bin/foo and you run > blah (which is in /usr/local/bin), then the kernel will execute /bin/foo > with argv[] set to ["/bin/foo", "/usr/local/bin/blah", "blah"]. The interp > has to be aware of this so it can execute /usr/local/bin/blah with argv[] > set to ["blah"]. According to my tests, no path is ever made absolute regardless of the P flag. Apparently where it says "the full path to the binary" it doesn't mean an absolute path, just a path that resolves to the actual file (and doesn't need to be searched in $PATH as it may be the case with the original argv[0]). # echo :myecho:M::1::./myecho: >/proc/sys/fs/binfmt_misc/register # echo :myechop:M::2::./myecho:P >/proc/sys/fs/binfmt_misc/register $ cat /proc/sys/fs/binfmt_misc/myecho enabled interpreter ./myecho flags: offset 0 magic 31 $ cat /proc/sys/fs/binfmt_misc/myechop enabled interpreter ./myecho flags: P offset 0 magic 32 $ echo 1 >script $ echo 2 >scriptp $ chmod a+x script scriptp $ ./execve ./script argv[0]: ./myecho argv[1]: ./script argv[2]: hello argv[3]: world $ ./execve ./scriptp argv[0]: ./myecho argv[1]: ./scriptp argv[2]: ./scriptp argv[3]: hello argv[4]: world As you can see, all the paths are relative regardless of the P flag.
