Date: Thu, 28 Mar 2002 10:26:37 +0100 From: Thomas Quinot <thomas@cuivre.fr.eu.org> To: freebsd-audit@freebsd.org Subject: boot2.c deobfuscation Message-ID: <20020328102637.A842@melusine.cuivre.fr.eu.org>
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Could others please review the following patch (originally
PR i386/36015, diff updated to reflect the commit of 36016)?
Thanks,
Thomas.
>Fix:
The following patches clarifies the stream of control at
the beginning of main() by making autoboot a two-state
variable (instead of a 3-state), with no functional
change at all.
Magical numeric values for ioctrl are replaced with #define'd
macros.
Hard-coded tick values for calls to keyhit are replaced
by static expressions in terms of multiples of a SECOND
#define. This change introduces a functional difference:
the first time-out will be 1 tick shorter.
Index: boot2.c
===================================================================
RCS file: /home/ncvs/src/sys/boot/i386/boot2/boot2.c,v
retrieving revision 1.38
diff -u -r1.38 boot2.c
--- boot2.c 23 Mar 2002 19:40:27 -0000 1.38
+++ boot2.c 28 Mar 2002 09:25:42 -0000
@@ -37,6 +37,11 @@
#include "boot2.h"
#include "lib.h"
+#define IO_KEYBOARD 1
+#define IO_SERIAL 2
+
+#define SECOND 18 /* Circa that many ticks in a second. */
+
#define RBX_ASKNAME 0x0 /* -a */
#define RBX_SINGLE 0x1 /* -s */
#define RBX_DFLTROOT 0x5 /* -r */
@@ -138,7 +143,7 @@
static struct bootinfo bootinfo;
static int ls;
static uint32_t fs_off;
-static uint8_t ioctrl = 0x1;
+static uint8_t ioctrl = IO_KEYBOARD;
void exit(int);
static void load(const char *);
@@ -281,34 +286,39 @@
bootinfo.bi_memsizes_valid++;
for (i = 0; i < N_BIOS_GEOM; i++)
bootinfo.bi_bios_geom[i] = drvinfo(i);
- autoboot = 2;
+
+ /* Process configuration file */
+
+ autoboot = 1;
readfile(PATH_CONFIG, cmd, sizeof(cmd));
if (*cmd) {
printf("%s: %s", PATH_CONFIG, cmd);
if (parse(cmd))
autoboot = 0;
- *cmd = 0;
}
- if (autoboot && !*kname) {
- if (autoboot == 2) {
- memcpy(kname, PATH_BOOT3, sizeof(PATH_BOOT3));
- if (!keyhit(0x37)) {
- load(kname);
- autoboot = 1;
- }
- }
- if (autoboot == 1)
+
+ /* Try to exec stage 3 boot loader. If interrupted by a keypress, *
+ * or in case of failure, try to load a kernel directly instaed. */
+
+ if (autoboot) {
+ memcpy(kname, PATH_BOOT3, sizeof(PATH_BOOT3));
+ if (!keyhit(3 * SECOND)) {
+ load(kname);
memcpy(kname, PATH_KERNEL, sizeof(PATH_KERNEL));
+ }
}
+
+ /* Present the user with the boot2 prompt. */
+
for (;;) {
printf(" \n>> FreeBSD/i386 BOOT\n"
"Default: %u:%s(%u,%c)%s\n"
"boot: ",
dsk.drive & DRV_MASK, dev_nm[dsk.type], dsk.unit,
'a' + dsk.part, kname);
- if (ioctrl & 0x2)
+ if (ioctrl & IO_SERIAL)
sio_flush();
- if (!autoboot || keyhit(0x5a))
+ if (!autoboot || keyhit(5 * SECOND))
getstr(cmd, sizeof(cmd));
else
putchar('\n');
@@ -447,9 +457,9 @@
opts |= 1 << RBX_DUAL | 1 << RBX_SERIAL;
opts &= ~(1 << RBX_PROBEKBD);
}
- ioctrl = opts & 1 << RBX_DUAL ? 0x3 :
- opts & 1 << RBX_SERIAL ? 0x2 : 0x1;
- if (ioctrl & 0x2)
+ ioctrl = opts & 1 << RBX_DUAL ? (IO_SERIAL | IO_KEYBOARD) :
+ opts & 1 << RBX_SERIAL ? IO_SERIAL : IO_KEYBOARD;
+ if (ioctrl & IO_SERIAL)
sio_init();
} else {
for (q = arg--; *q && *q != '('; q++);
@@ -794,9 +804,9 @@
static int
xputc(int c)
{
- if (ioctrl & 0x1)
+ if (ioctrl & IO_KEYBOARD)
putc(c);
- if (ioctrl & 0x2)
+ if (ioctrl & IO_SERIAL)
sio_putc(c);
return c;
}
@@ -807,9 +817,9 @@
if (opts & 1 << RBX_NOINTR)
return 0;
for (;;) {
- if (ioctrl & 0x1 && getc(1))
+ if (ioctrl & IO_KEYBOARD && getc(1))
return fn ? 1 : getc(0);
- if (ioctrl & 0x2 && sio_ischar())
+ if (ioctrl & IO_SERIAL && sio_ischar())
return fn ? 1 : sio_getc();
if (fn)
return 0;
--
Thomas.Quinot@Cuivre.FR.EU.ORG
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