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Message-Id: <200702212025.l1LKPKRm006789@ccure.user-mode-linux.org>
Date: Wed, 21 Feb 2007 15:25:20 -0500
From: Jeff Dike <jdike@...toit.com>
To: akpm@...l.org
cc: linux-kernel@...r.kernel.org,
user-mode-linux-devel@...ts.sourceforge.net
Subject: [PATCH 4/4] UML - lock host ldt retrieval
Add some locking to host_ldt_entries to prevent racing when reading
LDT information from the host.
Also fixed some style violations.
Signed-off-by: Jeff Dike <jdike@...toit.com>
--
arch/um/sys-i386/ldt.c | 29 +++++++++++++++++++----------
1 file changed, 19 insertions(+), 10 deletions(-)
Index: linux-2.6.18-mm/arch/um/sys-i386/ldt.c
===================================================================
--- linux-2.6.18-mm.orig/arch/um/sys-i386/ldt.c 2007-01-14 17:29:35.000000000 +1100
+++ linux-2.6.18-mm/arch/um/sys-i386/ldt.c 2007-01-15 17:03:25.000000000 +1100
@@ -7,6 +7,7 @@
#include "linux/slab.h"
#include "linux/types.h"
#include "linux/errno.h"
+#include "linux/spinlock.h"
#include "asm/uaccess.h"
#include "asm/smp.h"
#include "asm/ldt.h"
@@ -386,15 +387,20 @@ static long do_modify_ldt_skas(int func,
return ret;
}
-short dummy_list[9] = {0, -1};
-short * host_ldt_entries = NULL;
+static DEFINE_SPINLOCK(host_ldt_lock);
+static short dummy_list[9] = {0, -1};
+static short * host_ldt_entries = NULL;
-void ldt_get_host_info(void)
+static void ldt_get_host_info(void)
{
long ret;
struct ldt_entry * ldt;
int i, size, k, order;
+ spin_lock(&host_ldt_lock);
+ if(host_ldt_entries != NULL)
+ goto out_unlock;
+
host_ldt_entries = dummy_list+1;
for(i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++);
@@ -402,8 +408,9 @@ void ldt_get_host_info(void)
ldt = (struct ldt_entry *)
__get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
if(ldt == NULL) {
- printk("ldt_get_host_info: couldn't allocate buffer for host ldt\n");
- return;
+ printk("ldt_get_host_info: couldn't allocate buffer for host "
+ "ldt\n");
+ goto out_unlock;
}
ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
@@ -428,7 +435,8 @@ void ldt_get_host_info(void)
size = (size + 1) * sizeof(dummy_list[0]);
host_ldt_entries = kmalloc(size, GFP_KERNEL);
if(host_ldt_entries == NULL) {
- printk("ldt_get_host_info: couldn't allocate host ldt list\n");
+ printk("ldt_get_host_info: couldn't allocate host ldt "
+ "list\n");
goto out_free;
}
}
@@ -442,6 +450,8 @@ void ldt_get_host_info(void)
out_free:
free_pages((unsigned long)ldt, order);
+out_unlock:
+ spin_unlock(&host_ldt_lock);
}
long init_new_ldt(struct mmu_context_skas * new_mm,
@@ -480,8 +490,7 @@ long init_new_ldt(struct mmu_context_ska
* inherited from the host. All ldt-entries found
* will be reset in the following loop
*/
- if(host_ldt_entries == NULL)
- ldt_get_host_info();
+ ldt_get_host_info();
for(num_p=host_ldt_entries; *num_p != -1; num_p++){
desc.entry_number = *num_p;
err = write_ldt_entry(&new_mm->id, 1, &desc,
@@ -560,6 +569,6 @@ void free_ldt(struct mmu_context_skas *
int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
{
- return(CHOOSE_MODE_PROC(do_modify_ldt_tt, do_modify_ldt_skas, func,
- ptr, bytecount));
+ return CHOOSE_MODE_PROC(do_modify_ldt_tt, do_modify_ldt_skas, func,
+ ptr, bytecount);
}
-
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