Re: 2.6.8-rc3-mm2

[William Lee Irwin III <wli@holomorphy.com>]

On Sun, Aug 08, 2004 at 03:29:36PM -0700, Andrew Morton wrote:
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.8-rc3/2.6.8-rc3-mm2/
> - Added a little patch to the CPU scheduler which disables its array
>   switching.
[...]

During the kernel summit, some discussion was had about the support
requirements for a userspace program loader that loads executables
into hugetlb on behalf of a major application (Oracle). In order to
support this in a robust fashion, the cleanup of the hugetlb must be
robust in the presence of disorderly termination of the programs
(e.g. kill -9). Hence, the cleanup semantics are those of System V
shared memory, but Linux' System V shared memory needs one critical
extension for this use: executability.

The following microscopic patch enables this major application to
provide robust hugetlb cleanup.

Index: premm2-2.6.8-rc3/include/linux/shm.h
===================================================================
--- premm2-2.6.8-rc3.orig/include/linux/shm.h	2004-08-07 02:17:59.231816608 -0700
+++ premm2-2.6.8-rc3/include/linux/shm.h	2004-08-07 03:46:10.163472736 -0700
@@ -44,6 +44,7 @@
 #define	SHM_RDONLY	010000	/* read-only access */
 #define	SHM_RND		020000	/* round attach address to SHMLBA boundary */
 #define	SHM_REMAP	040000	/* take-over region on attach */
+#define	SHM_EXEC	0100000	/* execution access */
 
 /* super user shmctl commands */
 #define SHM_LOCK 	11
Index: premm2-2.6.8-rc3/ipc/shm.c
===================================================================
--- premm2-2.6.8-rc3.orig/ipc/shm.c	2004-08-07 02:17:59.395791680 -0700
+++ premm2-2.6.8-rc3/ipc/shm.c	2004-08-07 02:58:23.613254608 -0700
@@ -688,6 +688,10 @@
 		o_flags = O_RDWR;
 		acc_mode = S_IRUGO | S_IWUGO;
 	}
+	if (shmflg & SHM_EXEC) {
+		prot |= PROT_EXEC;
+		acc_mode |= S_IXUGO;
+	}
 
 	/*
 	 * We cannot rely on the fs check since SYSV IPC does have an