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Date: Thu, 17 Jul 2008 14:49:33 -0700
From: Randy Dunlap <rdunlap@...otime.net>
To: Vegard Nossum <vegard.nossum@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>,
Pekka Enberg <penberg@...helsinki.fi>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/13] kmemcheck: add the kmemcheck core
On Wed, 16 Jul 2008 02:23:29 +0200 Vegard Nossum wrote:
> >From fcd8f514a8962ea22aafb831b9f22a2ea1a13870 Mon Sep 17 00:00:00 2001
eh?
> From: Vegard Nossum <vegard.nossum@...il.com>
> Date: Fri, 4 Apr 2008 00:51:41 +0200
> Subject: [PATCH 07/13] kmemcheck: add the kmemcheck core
>
> General description: kmemcheck is a patch to the linux kernel that
> detects use of uninitialized memory. It does this by trapping every
> read and write to memory that was allocated dynamically (e.g. using
> kmalloc()). If a memory address is read that has not previously been
> written to, a message is printed to the kernel log.
>
> (Thanks to Andi Kleen for the set_memory_4k() solution.)
>
> Signed-off-by: Vegard Nossum <vegardno@....uio.no>
> ---
> diff --git a/Documentation/kmemcheck.txt b/Documentation/kmemcheck.txt
> new file mode 100644
> index 0000000..843a63c
> --- /dev/null
> +++ b/Documentation/kmemcheck.txt
> @@ -0,0 +1,135 @@
Doc looks good. Thanks.
> diff --git a/arch/x86/mm/kmemcheck/error.h b/arch/x86/mm/kmemcheck/error.h
> new file mode 100644
> index 0000000..0efc2e8
> --- /dev/null
> +++ b/arch/x86/mm/kmemcheck/error.h
> @@ -0,0 +1,15 @@
> +#ifndef ARCH__X86__MM__KMEMCHECK__ERROR_H
> +#define ARCH__X86__MM__KMEMCHECK__ERROR_H
We don't usually use double __ here.
> +
> +#include <linux/ptrace.h>
> +
> +#include "shadow.h"
> +
> +void kmemcheck_error_save(enum kmemcheck_shadow state,
> + unsigned long address, unsigned int size, struct pt_regs *regs);
> +
> +void kmemcheck_error_save_bug(struct pt_regs *regs);
> +
> +void kmemcheck_error_recall(void);
> +
> +#endif
> diff --git a/arch/x86/mm/kmemcheck/string.c b/arch/x86/mm/kmemcheck/string.c
> new file mode 100644
> index 0000000..0d21d22
> --- /dev/null
> +++ b/arch/x86/mm/kmemcheck/string.c
> @@ -0,0 +1,91 @@
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/kmemcheck.h>
> +#include <linux/module.h>
> +#include <linux/string.h>
> +#include <linux/types.h>
> +
> +#include "shadow.h"
> +#include "smp.h"
> +
> +/*
> + * A faster implementation of memset() when tracking is enabled where the
> + * whole memory area is within a single page.
> + */
> +static void memset_one_page(void *s, int c, size_t n)
> +{
> + unsigned long addr;
> + void *x;
> + unsigned long flags;
> +
> + addr = (unsigned long) s;
> +
> + x = kmemcheck_shadow_lookup(addr);
> + if (!x) {
> + /* The page isn't being tracked. */
> + __memset(s, c, n);
> + return;
> + }
> +
> + /* While we are not guarding the page in question, nobody else
> + * should be able to change them. */
> + local_irq_save(flags);
> +
> + kmemcheck_pause_allbutself();
> + kmemcheck_show_addr(addr);
> + __memset(s, c, n);
> + __memset(x, KMEMCHECK_SHADOW_INITIALIZED, n);
> + if (kmemcheck_enabled)
> + kmemcheck_hide_addr(addr);
> + kmemcheck_resume();
> +
> + local_irq_restore(flags);
> +}
> +
> +/*
> + * A faster implementation of memset() when tracking is enabled. We cannot
> + * assume that all pages within the range are tracked, so copying has to be
> + * split into page-sized (or smaller, for the ends) chunks.
> + */
> +void *kmemcheck_memset(void *s, int c, size_t n)
> +{
> + unsigned long addr;
> + unsigned long start_page, start_offset;
> + unsigned long end_page, end_offset;
> + unsigned long i;
> +
> + if (!n)
> + return s;
> +
> + if (!slab_is_available()) {
> + __memset(s, c, n);
> + return s;
> + }
> +
> + addr = (unsigned long) s;
> +
> + start_page = addr & PAGE_MASK;
> + end_page = (addr + n) & PAGE_MASK;
> +
> + if (start_page == end_page) {
> + /* The entire area is within the same page. Good, we only
> + * need one memset(). */
> + memset_one_page(s, c, n);
> + return s;
> + }
> +
> + start_offset = addr & ~PAGE_MASK;
> + end_offset = (addr + n) & ~PAGE_MASK;
> +
> + /* Clear the head, body, and tail of the memory area. */
> + if (start_offset < PAGE_SIZE)
> + memset_one_page(s, c, PAGE_SIZE - start_offset);
> + for (i = start_page + PAGE_SIZE; i < end_page; i += PAGE_SIZE)
> + memset_one_page((void *) i, c, PAGE_SIZE);
> + if (end_offset > 0)
> + memset_one_page((void *) end_page, c, end_offset);
> +
> + return s;
> +}
> +
> +EXPORT_SYMBOL(kmemcheck_memset);
We would prefer to have kernel-doc on exported functions...
---
~Randy
Linux Plumbers Conference, 17-19 September 2008, Portland, Oregon USA
http://linuxplumbersconf.org/
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