Re: [PATCH] prctl: implement PR_GET_ENDIAN for all architectures

Hi Andrew,

On 01.02.2017 01:26, Andrew Morton wrote:

On Sat, 28 Jan 2017 12:13:10 +0100 Helge Deller [off-list ref] wrote:

quoted

The prctl(PR_GET_ENDIAN) syscall was added to Kernel 2.6.18, but
implemented for PowerPC only.
This trivial patch adds support for this syscall for all other architectures.

Seems reasonable.  I guess.

Heck, I did forgot but I submitted a similar patch 8 years ago:
http://www.serverphorums.com/read.php?12,51902

Why is this needed?

It's not actually needed beside the trivial reason of providing an interface
not just for one single architecture.

After reading the discussion from 2009 again, I'm fine if 
you would simply drop the patch. The decision up to you.

The man page will need updating.  It says "PowerPC only".

In case you would include the patch I'd send patches to update
the manpage.

Thanks,
Helge

quoted

diff --git a/kernel/sys.c b/kernel/sys.c
index 842914e..5818e5e 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c

@@ -79,9 +79,6 @@
 #ifndef GET_FPEXC_CTL
 # define GET_FPEXC_CTL(a, b)	(-EINVAL)
 #endif
-#ifndef GET_ENDIAN
-# define GET_ENDIAN(a, b)	(-EINVAL)
-#endif
 #ifndef SET_ENDIAN
 # define SET_ENDIAN(a, b)	(-EINVAL)
 #endif

@@ -2136,7 +2133,13 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 			return -EFAULT;
 		break;
 	case PR_GET_ENDIAN:
+#ifdef GET_ENDIAN
 		error = GET_ENDIAN(me, arg2);
+#elif defined(__BIG_ENDIAN)
+		error = put_user(PR_ENDIAN_BIG, (unsigned int __user *)arg2);
+#else
+		error = put_user(PR_ENDIAN_LITTLE, (unsigned int __user *)arg2);
+#endif
 		break;
 	case PR_SET_ENDIAN:
 		error = SET_ENDIAN(me, arg2);