Brandon Williams <bmw...@google.com> writes:
> @@ -238,6 +238,12 @@ static void prepare_cmd(struct argv_array *out, const
> struct child_process *cmd)
> if (!cmd->argv[0])
> die("BUG: command is empty");
>
> + /*
> + * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
> + * attempt to interpret the command with 'sh'.
> + */
> + argv_array_push(out, SHELL_PATH);
> +
> if (cmd->git_cmd) {
> argv_array_push(out, "git");
> argv_array_pushv(out, cmd->argv);
So, given "cat-file", "-t", "HEAD" with cmd->git_cmd == TRUE, this
will now prepare ("/bin/sh", "git", "cat-file", "-t", "HEAD", NULL) in
the argv-array, and then ...
> @@ -246,6 +252,20 @@ static void prepare_cmd(struct argv_array *out, const
> struct child_process *cmd)
> } else {
> argv_array_pushv(out, cmd->argv);
> }
> +
> + /*
> + * If there are no '/' characters in the command then perform a path
> + * lookup and use the resolved path as the command to exec. If there
> + * are no '/' characters or if the command wasn't found in the path,
> + * have exec attempt to invoke the command directly.
> + */
> + if (!strchr(out->argv[1], '/')) {
> + char *program = locate_in_PATH(out->argv[1]);
> + if (program) {
> + free((char *)out->argv[1]);
> + out->argv[1] = program;
> + }
> + }
... turn the first element from "git" to "/usr/bin/git", i.e.
("/bin/sh", "/usr/bin/git", "cat-file", "-t", "HEAD", NULL)
which ...
> #endif
>
> @@ -445,7 +465,15 @@ int start_command(struct child_process *cmd)
> }
> }
>
> - sane_execvp(argv.argv[0], (char *const *) argv.argv);
> + /*
> + * Attempt to exec using the command and arguments starting at
> + * argv.argv[1]. argv.argv[0] contains SHELL_PATH which will
> + * be used in the event exec failed with ENOEXEC at which point
> + * we will try to interpret the command using 'sh'.
> + */
> + execv(argv.argv[1], (char *const *) argv.argv + 1);
... first is given without the leading "/bin/sh", as the end-user
intended (sort of), but if it fails
> + if (errno == ENOEXEC)
> + execv(argv.argv[0], (char *const *) argv.argv);
"/bin/sh" tries to run "/usr/bin/git" that was not executable (well,
the one in "usr/bin/" would have +x bit, but let's pretend that we
are trying to run one from bin-wrappers/ and somehow forgot +x bit)?
I think all of that is sensible, but there is one "huh?" I can't
figure out. Typically we do "sh -c git cat-file -t HEAD" but this
lacks the "-c" (cf. the original prepare_shell_cmd()); why do we not
need it in this case?
Thanks.
