[2.4][TRIVIAL] Use of uninitialized vars in arch/i386/kernel/process.c

[2.4][TRIVIAL] Use of uninitialized vars in arch/i386/kernel/process.c

[Disconnect]

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Sorry for the longish To list, not sure who's responsible for this
particular piece. (And if I got it wrong even after all that, please let
me know..)

This is for 2.4; in 2.5 reboot.c has identical code with an identical
problem. (I'll send a separate patch after getting feedback on this
one.)

If you don't pass reboot=, reboot_mode and reboot_thru_bios are used
uninitialized and (in the case of reboot_mode) written directly to
memory for the bios.

This patch sets reboot_mode to 0x1234 by default, and reboot_thru_bios
(used in "if(!reboot_thru_bios)") to 1.

void machine_restart(char * __unused)
{
..[smp shutdown]..
  if(!reboot_thru_bios) {
        /* rebooting needs to touch the page at absolute addr 0 */
        *((unsigned short *)__va(0x472)) = reboot_mode;
...
        machine_real_restart(jump_to_bios, sizeof(jump_to_bios));
}

void machine_real_restart(unsigned char *code, int length)
{
.....
  /* Write 0x1234 to absolute memory location 0x472.  The BIOS reads
     this on booting to tell it to "Bypass memory test (also warm
     boot)".  This seems like a fairly standard thing that gets set by
     REBOOT.COM programs, and the previous reset routine did this
     too. */

  *((unsigned short *)0x472) = reboot_mode;
...
}


-- 
Disconnect <lkml@sigkill.net>

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# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
#	           ChangeSet	1.1042  -> 1.1043 
#	arch/i386/kernel/process.c	1.14    -> 1.15   
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/07/07	dis@slappy.(none)	1.1043
# Initialize reboot_mode to defaults (according to comments) even if reboot= is lacking.  Ditto for reboot_thru_bios. 
# (Warm boot, use bios.) 
# --------------------------------------------
#
diff -Nru a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
--- a/arch/i386/kernel/process.c	Mon Jul  7 11:42:50 2003
+++ b/arch/i386/kernel/process.c	Mon Jul  7 11:42:50 2003
@@ -152,8 +152,8 @@
 __setup("idle=", idle_setup);
 
 static long no_idt[2];
-static int reboot_mode;
-int reboot_thru_bios;
+static int reboot_mode=0x1234;
+int reboot_thru_bios=1;
 
 #ifdef CONFIG_SMP
 int reboot_smp = 0;

Re: [2.4][TRIVIAL] Use of uninitialized vars in arch/i386/kernel/process.c

[Alan Cox]

On Llu, 2003-07-07 at 17:01, Disconnect wrote:
> If you don't pass reboot=, reboot_mode and reboot_thru_bios are used
> uninitialized and (in the case of reboot_mode) written directly to
> memory for the bios.

reboot_mode is static so defaults to zero.