Re: [PATCH v7 3/4] vmalloc: Add debugfs modfraginfo

["Edgecombe, Rick P" <rick.p.edgecombe@intel.com>]

For a previous version before making asked for corrections, this was:

Reviewed-by: Kees Cook <keescook@chromium.org>

On Mon, 2018-10-01 at 14:38 -0700, Rick Edgecombe wrote:
> Add debugfs file "modfraginfo" for providing info on module space
> fragmentation.
> This can be used for determining if loadable module randomization is causing
> any
> problems for extreme module loading situations, like huge numbers of modules
> or
> extremely large modules.
> 
> Sample output when KASLR is enabled and X86_64 is configured:
> 	Largest free space:	897912 kB
> 	  Total free space:	1025424 kB
> Allocations in backup area:	0
> 
> Sample output when just X86_64:
> 	Largest free space:	897912 kB
> 	  Total free space:	1025424 kB
> 
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> ---
>  mm/vmalloc.c | 98
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 97 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 1954458..1b3c3da 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -18,6 +18,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/proc_fs.h>
>  #include <linux/seq_file.h>
> +#include <linux/debugfs.h>
>  #include <linux/debugobjects.h>
>  #include <linux/kallsyms.h>
>  #include <linux/list.h>
> @@ -36,6 +37,12 @@
>  #include <asm/tlbflush.h>
>  #include <asm/shmparam.h>
>  
> +#ifdef CONFIG_X86
> +#include <asm/page_types.h>
> +#include <asm/setup.h>
> +#include <asm/kaslr_modules.h>
> +#endif
> +
>  #include "internal.h"
>  
>  struct vfree_deferred {
> @@ -2919,7 +2926,96 @@ static int __init proc_vmalloc_init(void)
>  		proc_create_seq("vmallocinfo", 0400, NULL, &vmalloc_op);
>  	return 0;
>  }
> -module_init(proc_vmalloc_init);
> +#elif defined(CONFIG_DEBUG_FS)
> +static int __init proc_vmalloc_init(void)
> +{
> +	return 0;
> +}
> +#endif
>  
> +#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_RANDOMIZE_FINE_MODULE)
> +static inline unsigned long is_in_backup(unsigned long addr)
> +{
> +	return addr >= MODULES_VADDR + get_modules_rand_len();
> +}
> +
> +static int modulefraginfo_debug_show(struct seq_file *m, void *v)
> +{
> +	unsigned long last_end = MODULES_VADDR;
> +	unsigned long total_free = 0;
> +	unsigned long largest_free = 0;
> +	unsigned long backup_cnt = 0;
> +	unsigned long gap;
> +	struct vmap_area *prev, *cur = NULL;
> +
> +	spin_lock(&vmap_area_lock);
> +
> +	if (!pvm_find_next_prev(MODULES_VADDR, &cur, &prev) || !cur)
> +		goto done;
> +
> +	for (; cur->va_end <= MODULES_END; cur = list_next_entry(cur, list))
> {
> +		/* Don't count areas that are marked to be lazily freed */
> +		if (!(cur->flags & VM_LAZY_FREE)) {
> +			if (kaslr_mod_randomize_each_module())
> +				backup_cnt += is_in_backup(cur->va_start);
> +			gap = cur->va_start - last_end;
> +			if (gap > largest_free)
> +				largest_free = gap;
> +			total_free += gap;
> +			last_end = cur->va_end;
> +		}
> +
> +		if (list_is_last(&cur->list, &vmap_area_list))
> +			break;
> +	}
> +
> +done:
> +	gap = (MODULES_END - last_end);
> +	if (gap > largest_free)
> +		largest_free = gap;
> +	total_free += gap;
> +
> +	spin_unlock(&vmap_area_lock);
> +
> +	seq_printf(m, "\tLargest free space:\t%lu kB\n", largest_free /
> 1024);
> +	seq_printf(m, "\t  Total free space:\t%lu kB\n", total_free / 1024);
> +
> +	if (kaslr_mod_randomize_each_module())
> +		seq_printf(m, "Allocations in backup area:\t%lu\n",
> backup_cnt);
> +
> +	return 0;
> +}
> +
> +static int proc_module_frag_debug_open(struct inode *inode, struct file
> *file)
> +{
> +	return single_open(file, modulefraginfo_debug_show, NULL);
> +}
> +
> +static const struct file_operations debug_module_frag_operations = {
> +	.open       = proc_module_frag_debug_open,
> +	.read       = seq_read,
> +	.llseek     = seq_lseek,
> +	.release    = single_release,
> +};
> +
> +static void __init debug_modfrag_init(void)
> +{
> +	debugfs_create_file("modfraginfo", 0400, NULL, NULL,
> +			&debug_module_frag_operations);
> +}
> +#elif defined(CONFIG_DEBUG_FS) || defined(CONFIG_PROC_FS)
> +static void __init debug_modfrag_init(void)
> +{
> +}
>  #endif
>  
> +#if defined(CONFIG_DEBUG_FS) || defined(CONFIG_PROC_FS)
> +static int __init info_vmalloc_init(void)
> +{
> +	proc_vmalloc_init();
> +	debug_modfrag_init();
> +	return 0;
> +}
> +
> +module_init(info_vmalloc_init);
> +#endif