lkml.org 
[lkml]   [2005]   [Aug]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH 3/6] i386 virtualization - Make ldt a desc struct
Chuck Ebbert wrote:

>
>>@@ -97,14 +96,16 @@
>>
>> void destroy_ldt(struct mm_struct *mm)
>> {
>>+ int pages = mm->context.ldt_pages;
>>+
>> if (mm == current->active_mm)
>> clear_LDT();
>>- ClearPagesLDT(mm->context.ldt, (mm->context.size * LDT_ENTRY_SIZE) / PAGE_SIZE);
>>- if (mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
>>+ ClearPagesLDT(mm->context.ldt, pages);
>>+ if (pages > 1)
>> vfree(mm->context.ldt);
>> else
>> kfree(mm->context.ldt);
>>- mm->context.size = 0;
>>+ mm->context.ldt_pages = 0; <====================
>> }
>>
>> static int read_ldt(void __user * ptr, unsigned long bytecount)
>>
>>
>
> destroy_ldt does not zero "ldt", just the size. Potential bug?
>
>

Not a bug, truly unnecessary at all.

Several reviewers noticed that initialization and destruction of the
mm->context is unnecessary, since the entire MM struct is zeroed on
allocation anyways.

Verified with BUG_ON(mm->context.ldt || mm->context.ldt_pages);
Signed-off-by: Zachary Amsden <zach@vmware.com>
Index: linux-2.6.13/include/asm-i386/mmu_context.h
===================================================================
--- linux-2.6.13.orig/include/asm-i386/mmu_context.h 2005-08-15 11:23:32.000000000 -0700
+++ linux-2.6.13/include/asm-i386/mmu_context.h 2005-08-16 11:35:11.000000000 -0700
@@ -16,7 +16,6 @@
struct mm_struct * old_mm;
int retval = 0;

- memset(&mm->context, 0, sizeof(mm->context));
init_MUTEX(&mm->context.sem);
old_mm = current->mm;
if (old_mm && unlikely(old_mm->context.ldt)) {
Index: linux-2.6.13/arch/i386/kernel/ldt.c
===================================================================
--- linux-2.6.13.orig/arch/i386/kernel/ldt.c 2005-08-15 11:23:32.000000000 -0700
+++ linux-2.6.13/arch/i386/kernel/ldt.c 2005-08-16 11:12:59.000000000 -0700
@@ -105,7 +105,6 @@
vfree(mm->context.ldt);
else
kfree(mm->context.ldt);
- mm->context.ldt_pages = 0;
}

static int read_ldt(void __user * ptr, unsigned long bytecount)
\
 
 \ /
  Last update: 2005-08-16 20:47    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site