On Wednesday 21 February 2007 21:25, Jeff Dike wrote:
> Add some locking to host_ldt_entries to prevent racing when reading
> LDT information from the host.
Please remove GFP_KERNEL allocation under spin_lock - simplest way is using a
mutex unless this can be important for performance.
> @@ -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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--
Inform me of my mistakes, so I can add them to my list!
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade
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