Re: Bug in #! processing - One More Time
From: Garance A Drosehn (gad_at_FreeBSD.org)
Date: 05/15/05
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Date: Sun, 15 May 2005 05:24:35 -0400 To: Maxim Sobolev <sobomax@FreeBSD.org>
At 7:05 PM +0300 5/13/05, Maxim Sobolev wrote:
>Attached please find patch which rips any special processing
>of command line arguments. It should put FreeBSD into the very
>same ship with the rest of unices and linuces out there.
>
>...This corresponds to the case (3) from the Garance's original
>message.
>
>I've run this change through buildworld.
Fwiw, this is the patch that I have been working with for the
same purpose. I might trim down the comments some more. This
includes a kludge to recognize '#!#<' as a way to trigger the
historical parsing behavior. I have another version which also
recognizes '#!#+' as a way to trigger a whole bunch of debug
messages, but that's probably of no interest to anyone but me.
This patch is also at:
http://people.freebsd.org/imgact_shell.diff
and the file you'd end up with by applying the patch is at:
http://people.freebsd.org/imgact_shell.c
This has installed and tested in i386 and powerpc, and sometime
on Sunday I'll have it installed on a sparc64 machine. (it's
building now, but my ultra10 machine is much much slower than my
i386 and my Mac-mini...).
Index: imgact_shell.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/imgact_shell.c,v
retrieving revision 1.32
diff -u -r1.32 imgact_shell.c
--- imgact_shell.c 25 Feb 2005 10:17:53 -0000 1.32
+++ imgact_shell.c 15 May 2005 09:07:13 -0000
@@ -36,6 +36,15 @@
#include <sys/imgact.h>
#include <sys/kernel.h>
+#define KEEP_OLDCODE 1
+#if BYTE_ORDER == LITTLE_ENDIAN /* temp for OLD_CODE kludge */
+#define DBG_MAGIC 0x2B23 /* #+ in "little-endian" */
+#define OLD_MAGIC 0x3C23 /* #< */
+#else
+#define DBG_MAGIC 0x232B /* #+ in big-endian */
+#define OLD_MAGIC 0x233C /* #< */
+#endif
+
#if BYTE_ORDER == LITTLE_ENDIAN
#define SHELLMAGIC 0x2123 /* #! */
#else
@@ -43,15 +52,66 @@
#endif
/*
- * Shell interpreter image activator. An interpreter name beginning
- * at imgp->args->begin_argv is the minimal successful exit requirement.
+ * At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE. This is
+ * significant because the caller has only mapped in one page of the
+ * file we're reading. This code should be changed to know how to
+ * read in the second page, but I'm not doing that just yet...
+ */
+#if MAXSHELLCMDLEN > PAGE_SIZE
+#error "MAXSHELLCMDLEN is larger than a single page!"
+#endif
+
+/**
+ * Shell interpreter image activator. An interpreter name beginning at
+ * imgp->args->begin_argv is the minimal successful exit requirement.
+ *
+ * If the given file is a shell-script, then the first line will start
+ * with the two characters `#!' (aka SHELLMAGIC), followed by the name
+ * of the shell-interpreter to run, followed by zero or more tokens.
+ *
+ * If there are *any* tokens, then we start up the interpreter such that
+ * it will see:
+ * arg[0] -> The name of interpreter as specified after `#!' in the
+ * first line of the script. The interpreter name must
+ * not be longer than MAXSHELLCMDLEN bytes.
+ * arg[1] -> *If* there are any additional tokens on the first line,
+ * then we add a new arg[1], which is a copy of the rest of
+ * that line. The copy starts at the first token after the
+ * interpreter name. We leave it to the interpreter to
+ * parse the tokens in that value.
+ * arg[x] -> the full pathname of the script. This will either be
+ * arg[2] or arg[1], depending on whether or not tokens
+ * were found after the interpreter name.
+ * arg[x+1] -> whatever arguments that were specified on the original
+ * command line (if the user had specified any).
+ *
+ * This processing is described in the execve(2) man page.
+ */
+
+/*
+ * HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as
+ * found on the first line of the script, and setup each token as a separate
+ * value in arg[]. This extra processing did not match the behavior of other
+ * OS's, and caused a few subtle problems. For one, it meant the kernel was
+ * deciding how those values should be parsed (wrt characters for quoting or
+ * comments, etc), while the interpreter might have other rules for parsing.
+ * It also meant the interpreter had no way of knowing which arguments came
+ * from the first line of the shell script, and which arguments were specified
+ * by the user on the command line.
+ *
+ * Luckily, only few things in the base system would notice that non-standard
+ * processing (mainly /bin/sh and /usr/bin/env). And for programs which are
+ * not in the base system, the "newer" behavior matches how NetBSD, OpenBSD,
+ * Linux, Solaris, AIX, IRIX, and some other Unixes have always setup the
+ * arg-list for the interpreter. So if a program can handle this behavior on
+ * any of those other OS's, it should be able to handle it for FreeBSD too.
*/
int
exec_shell_imgact(imgp)
struct image_params *imgp;
{
const char *image_header = imgp->image_header;
- const char *ihp;
+ const char *ihp, *interpb, *interpe, *maxp, *optb, *opte;
int error, offset;
size_t length, clength;
struct vattr vattr;
@@ -79,14 +139,34 @@
if (error)
return (error);
- clength = (vattr.va_size > MAXSHELLCMDLEN) ?
- MAXSHELLCMDLEN : vattr.va_size;
+ /*
+ * Copy shell name and arguments from image_header into a string
+ * buffer. Remember that the caller has mapped only the
+ * first page of the file into memory.
+ */
+ clength = (vattr.va_size > PAGE_SIZE) ? PAGE_SIZE : vattr.va_size;
+
+ maxp = &image_header[clength];
+ ihp = &image_header[2];
+#if KEEP_OLDCODE
+ /*
+ * XXX - Temporarily provide a quick-and-dirty way to get the
+ * older, non-standard option-parsing behavior, just in case
+ * someone finds themselves in an emergency where they need it.
+ * This will not be documented. It is only for initial testing.
+ */
+ if (*(const short *)ihp == OLD_MAGIC)
+ ihp += 2;
+ else
+ goto new_code;
+ interpb = ihp;
+
/*
* Figure out the number of bytes that need to be reserved in the
* argument string to copy the contents of the interpreter's command
* line into the argument string.
*/
- ihp = &image_header[2];
+ ihp = interpb;
offset = 0;
while (ihp < &image_header[clength]) {
/* Skip any whitespace */
@@ -152,7 +232,7 @@
* Loop through the interpreter name yet again, copying as
* we go.
*/
- ihp = &image_header[2];
+ ihp = interpb;
offset = 0;
while (ihp < &image_header[clength]) {
/* Skip whitespace */
@@ -174,8 +254,96 @@
imgp->args->begin_argv[offset++] = '\0';
imgp->args->argc++;
}
+ goto common_end;
+new_code:
+#endif
+ /*
+ * Find the beginning and end of the interpreter_name. If the
+ * line does not include any interpreter, or if the name which
+ * was found is too long, we bail out.
+ */
+ while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
+ ihp++;
+ interpb = ihp;
+ while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n')
+ && (*ihp != '\0')))
+ ihp++;
+ interpe = ihp;
+ if (interpb == interpe)
+ return (ENOEXEC);
+ if ((interpe - interpb) >= MAXSHELLCMDLEN)
+ return (ENAMETOOLONG);
+
+ /*
+ * Find the beginning of the options (if any), and the end-of-line.
+ * Then trim the trailing blanks off the value. Note that some
+ * other operating systems do *not* trim the trailing whitespace...
+ */
+ while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
+ ihp++;
+ optb = ihp;
+ while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0')))
+ ihp++;
+ opte = ihp;
+ while (--ihp > interpe && ((*ihp == ' ') || (*ihp == '\t')))
+ opte = ihp;
/*
+ * We need to "pop" (remove) the present value of arg[0], and "push"
+ * either two or three new values in the arg[] list. To do this,
+ * we first shift all the other values in the `begin_argv' area to
+ * provide the exact amount of room for the values added. Set up
+ * `offset' as the number of bytes to be added to the `begin_argv'
+ * area, and 'length' as the number of bytes being removed.
+ */
+ offset = interpe - interpb + 1; /* interpreter */
+ if (opte != optb) /* options (if any) */
+ offset += opte - optb + 1;
+ offset += strlen(imgp->args->fname) + 1; /* fname of script */
+ length = (imgp->args->argc == 0) ? 0 :
+ strlen(imgp->args->begin_argv) + 1; /* bytes to delete */
+
+ if (offset - length > imgp->args->stringspace)
+ return (E2BIG);
+
+ bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
+ imgp->args->endp - (imgp->args->begin_argv + length));
+
+ offset -= length; /* calculate actual adjustment */
+ imgp->args->begin_envv += offset;
+ imgp->args->endp += offset;
+ imgp->args->stringspace -= offset;
+
+ /*
+ * If there was no arg[0] when we started, then the interpreter_name
+ * is adding an argument (instead of replacing the arg[0] we started
+ * with). And we're always adding an argument when we include the
+ * full pathname of the original script.
+ */
+ if (imgp->args->argc == 0)
+ imgp->args->argc = 1;
+ imgp->args->argc++;
+
+ /*
+ * The original arg[] list has been shifted appropriately. Copy in
+ * the interpreter name and options-string.
+ */
+ length = interpe - interpb;
+ bcopy(interpb, imgp->args->buf, length);
+ *(imgp->args->buf + length) = '\0';
+ offset = length + 1;
+ if (opte != optb) {
+ length = opte - optb;
+ bcopy(optb, imgp->args->buf + offset, length);
+ *(imgp->args->buf + offset + length) = '\0';
+ offset += length + 1;
+ imgp->args->argc++;
+ }
+
+#if KEEP_OLDCODE
+common_end:
+#endif
+ /*
* Finally, add the filename onto the end for the interpreter to
* use and copy the interpreter's name to imgp->interpreter_name
* for exec to use.
-- Garance Alistair Drosehn = gad@gilead.netel.rpi.edu Senior Systems Programmer or gad@FreeBSD.org Rensselaer Polytechnic Institute; Troy, NY; USA _______________________________________________ freebsd-arch@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-arch To unsubscribe, send any mail to "freebsd-arch-unsubscribe@freebsd.org"
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