Commit d2b176ed authored by Jes Sorensen's avatar Jes Sorensen Committed by Tony Luck
Browse files

[IA64] sysctl option to silence unaligned trap warnings 



Allow sysadmin to disable all warnings about userland apps
making unaligned accesses by using:
 # echo 1 > /proc/sys/kernel/ignore-unaligned-usertrap
Rather than having to use prctl on a process by process basis.

Default behaivour leaves the warnings enabled.

Signed-off-by: default avatarJes Sorensen <jes@sgi.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent c8c1635f

arch/ia64/kernel/unaligned.c

+28 −3
Original line number Diff line number Diff line
@@ -52,6 +52,15 @@ dump (const char *str, void *vp, size_t len) 
#define IA64_FIRST_ROTATING_FR	32

#define SIGN_EXT9		0xffffffffffffff00ul



/*

 *  sysctl settable hook which tells the kernel whether to honor the

 *  IA64_THREAD_UAC_NOPRINT prctl.  Because this is user settable, we want

 *  to allow the super user to enable/disable this for security reasons

 *  (i.e. don't allow attacker to fill up logs with unaligned accesses).

 */

int no_unaligned_warning;

static int noprint_warning;



/*

 * For M-unit:

 *
@@ -1324,8 +1333,9 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs) 
		if ((current->thread.flags & IA64_THREAD_UAC_SIGBUS) != 0)

			goto force_sigbus;



		if (!(current->thread.flags & IA64_THREAD_UAC_NOPRINT)

		    && within_logging_rate_limit())

		if (!no_unaligned_warning &&

		    !(current->thread.flags & IA64_THREAD_UAC_NOPRINT) &&

		    within_logging_rate_limit())

		{

			char buf[200];	/* comm[] is at most 16 bytes... */

			size_t len;
@@ -1340,7 +1350,22 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs) 
			if (user_mode(regs))

				tty_write_message(current->signal->tty, buf);

			buf[len-1] = '\0';	/* drop '\r' */

			printk(KERN_WARNING "%s", buf);	/* watch for command names containing %s */

			/* watch for command names containing %s */

			printk(KERN_WARNING "%s", buf);

		} else {

			if (no_unaligned_warning && !noprint_warning) {

				noprint_warning = 1;

				printk(KERN_WARNING "%s(%d) encountered an "

				       "unaligned exception which required\n"

				       "kernel assistance, which degrades "

				       "the performance of the application.\n"

				       "Unaligned exception warnings have "

				       "been disabled by the system "

				       "administrator\n"

				       "echo 0 > /proc/sys/kernel/ignore-"

				       "unaligned-usertrap to re-enable\n",

				       current->comm, current->pid);

			}

		}

	} else {

		if (within_logging_rate_limit())

include/linux/sysctl.h

+1 −0
Original line number Diff line number Diff line
@@ -147,6 +147,7 @@ enum 
	KERN_SETUID_DUMPABLE=69, /* int: behaviour of dumps for setuid core */

	KERN_SPIN_RETRY=70,	/* int: number of spinlock retries */

	KERN_ACPI_VIDEO_FLAGS=71, /* int: flags for setting up video after ACPI sleep */

	KERN_IA64_UNALIGNED=72, /* int: ia64 unaligned userland trap enable */

};

kernel/sysctl.c

+14 −0
Original line number Diff line number Diff line
@@ -124,6 +124,10 @@ extern int sysctl_hz_timer; 
extern int acct_parm[];

#endif



#ifdef CONFIG_IA64

extern int no_unaligned_warning;

#endif



static int parse_table(int __user *, int, void __user *, size_t __user *, void __user *, size_t,

		       ctl_table *, void **);

static int proc_doutsstring(ctl_table *table, int write, struct file *filp,
@@ -665,6 +669,16 @@ static ctl_table kern_table[] = { 
		.mode		= 0644,

		.proc_handler	= &proc_dointvec,

	},

#endif

#ifdef CONFIG_IA64

	{

		.ctl_name	= KERN_IA64_UNALIGNED,

		.procname	= "ignore-unaligned-usertrap",

		.data		= &no_unaligned_warning,

		.maxlen		= sizeof (int),

	 	.mode		= 0644,

		.proc_handler	= &proc_dointvec,

	},

#endif

	{ .ctl_name = 0 }

};