ARM: allow alignment fault mode to be configured at kernel boot

Some glibc versions intentionally create lots of alignment faults in their gconv code, which if not fixed up, results in segfaults during boot. This can prevent systems booting properly. There is no clear hard-configurable default for this; the desired default depends on the nature of the userspace which is going to be booted. So, provide a way for the alignment fault handler to be configured via the kernel command line. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

ARM: allow alignment fault mode to be configured at kernel boot
Some glibc versions intentionally create lots of alignment faults in their gconv code, which if not fixed up, results in segfaults during boot. This can prevent systems booting properly. There is no clear hard-configurable default for this; the desired default depends on the nature of the userspace which is going to be booted. So, provide a way for the alignment fault handler to be configured via the kernel command line. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Russell King
1 parent 0fa11802e0
Showing 2 changed files with 8 additions and 0 deletions Side-by-side Diff
Documentation/kernel-parameters.txt
arch/arm/mm/alignment.c
@@ -315,6 +315,11 @@
 	aic79xx=	[HW,SCSI]
 			See Documentation/scsi/aic79xx.txt.
  
+	alignment=	[KNL,ARM]
+			Allow the default userspace alignment fault handler
+			behaviour to be specified.  Bit 0 enables warnings,
+			bit 1 enables fixups, and bit 2 sends a segfault.
+
 	amd_iommu=	[HW,X86-84]
 			Pass parameters to the AMD IOMMU driver in the system.
 			Possible values are:
@@ -11,6 +11,7 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
+#include <linux/moduleparam.h>
 #include <linux/compiler.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
@@ -76,6 +77,8 @@
 static unsigned long ai_dword;
 static unsigned long ai_multi;
 static int ai_usermode;
+
+core_param(alignment, ai_usermode, int, 0600);
  
 #define UM_WARN		(1 << 0)
 #define UM_FIXUP	(1 << 1)
...	...	@@ -315,6 +315,11 @@
315	315	aic79xx= [HW,SCSI]
316	316	See Documentation/scsi/aic79xx.txt.
317	317
	318	+ alignment= [KNL,ARM]
	319	+ Allow the default userspace alignment fault handler
	320	+ behaviour to be specified. Bit 0 enables warnings,
	321	+ bit 1 enables fixups, and bit 2 sends a segfault.
	322	+
318	323	amd_iommu= [HW,X86-84]
319	324	Pass parameters to the AMD IOMMU driver in the system.
320	325	Possible values are:
...	...	@@ -11,6 +11,7 @@
11	11	* it under the terms of the GNU General Public License version 2 as
12	12	* published by the Free Software Foundation.
13	13	*/
	14	+#include <linux/moduleparam.h>
14	15	#include <linux/compiler.h>
15	16	#include <linux/kernel.h>
16	17	#include <linux/errno.h>
...	...	@@ -76,6 +77,8 @@
76	77	static unsigned long ai_dword;
77	78	static unsigned long ai_multi;
78	79	static int ai_usermode;
	80	+
	81	+core_param(alignment, ai_usermode, int, 0600);
79	82
80	83	#define UM_WARN (1 << 0)
81	84	#define UM_FIXUP (1 << 1)