Messages in this thread Patch in this message |  | | | Date | Tue, 16 Aug 2005 11:44:15 -0700 | | From | Zachary Amsden <> | | Subject | Re: [PATCH 3/6] i386 virtualization - Make ldt a desc struct |
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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) |  |