Michael McConville wrote:
> Maxim Pugachev wrote:
> > In a case when the shell name is not specified (i.e. just "#!" without
> > a path), don't run the heavy logic that checks shell, simply return
> > ENOENT.
>
> I'm not sure whether this is a reasonable thing to do. Someone with more
> kernel API experience will have to comment.
>
> > Also, as a tiny improvement: avoid a loop when calculating shell's
> > args length.
>
> It seems like there's a simpler solution to this: strlen. Also, the
> assignment that follows the for loop seems dead, as we know *cp will be
> NUL.
>
> The below diff makes that change, removes the useless if condition you
> noticed, and bumps a few variable initializations into the declaration
> block.
I just remembered that this was probably a perfomance concern as well.
In that case, we could assign shellarg and shellarglen earlier in the
function, right?
> Index: sys/kern/exec_script.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/exec_script.c,v
> retrieving revision 1.37
> diff -u -p -r1.37 exec_script.c
> --- sys/kern/exec_script.c 31 Dec 2015 18:55:33 -0000 1.37
> +++ sys/kern/exec_script.c 10 Jan 2016 01:41:55 -0000
> @@ -67,9 +67,9 @@
> int
> exec_script_makecmds(struct proc *p, struct exec_package *epp)
> {
> - int error, hdrlinelen, shellnamelen, shellarglen;
> + int error, hdrlinelen, shellnamelen, shellarglen = 0;
> char *hdrstr = epp->ep_hdr;
> - char *cp, *shellname, *shellarg, *oldpnbuf;
> + char *cp, *shellname = NULL, *shellarg = NULL, *oldpnbuf;
> char **shellargp = NULL, **tmpsap;
> struct vnode *scriptvp;
> uid_t script_uid = -1;
> @@ -110,10 +110,6 @@ exec_script_makecmds(struct proc *p, str
> if (cp >= hdrstr + hdrlinelen)
> return ENOEXEC;
>
> - shellname = NULL;
> - shellarg = NULL;
> - shellarglen = 0;
> -
> /* strip spaces before the shell name */
> for (cp = hdrstr + EXEC_SCRIPT_MAGICLEN; *cp == ' ' || *cp == '\t';
> cp++)
> @@ -122,8 +118,6 @@ exec_script_makecmds(struct proc *p, str
> /* collect the shell name; remember its length for later */
> shellname = cp;
> shellnamelen = 0;
> - if (*cp == '\0')
> - goto check_shell;
> for ( /* cp = cp */ ; *cp != '\0' && *cp != ' ' && *cp != '\t'; cp++)
> shellnamelen++;
> if (*cp == '\0')
> @@ -142,9 +136,8 @@ exec_script_makecmds(struct proc *p, str
> * behaviour.
> */
> shellarg = cp;
> - for ( /* cp = cp */ ; *cp != '\0'; cp++)
> - shellarglen++;
> - *cp++ = '\0';
> + shellarglen = strlen(shellarg);
> + cp += shellarglen + 1;
>
> check_shell:
> /*
>
