kmemcheck: add the kmemcheck core

From fcd8f514a8962ea22aafb831b9f22a2ea1a13870 Mon Sep 17 00:00:00 2001

Quoted 1 line

From fcd8f514a8962ea22aafb831b9f22a2ea1a13870 Mon Sep 17 00:00:00 2001

arch/x86/mm/kmemcheck/error.h new file +13 -0

+
+#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

arch/x86/mm/kmemcheck/string.c new file +81 -0

new file mode 100644
index 0000000..0d21d22
@@ -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)

Quoted 1 line · On Wed, 16 Jul 2008 02:23:29 +0200 Vegard Nossum wrote:

Quoted 1 line

From fcd8f514a8962ea22aafb831b9f22a2ea1a13870 Mon Sep 17 00:00:00 2001

eh?

arch/x86/mm/kmemcheck/error.h line 2

Quoted 4 lines

+++ b/arch/x86/mm/kmemcheck/error.h

arch/x86/mm/kmemcheck/error.h new file +2 -0

@@ -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.

Quoted 36 lines

arch/x86/mm/kmemcheck/string.c new file +36 -0

+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)

arch/x86/mm/kmemcheck/string.c line 91

Quoted 6 lines

arch/x86/mm/kmemcheck/string.c new file +6 -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...

Quoted 5 lines · Randy Dunlap

Quoted 1 line · On Wed, 16 Jul 2008 02:23:29 +0200 Vegard Nossum wrote:

Quoted 1 line

From fcd8f514a8962ea22aafb831b9f22a2ea1a13870 Mon Sep 17 00:00:00 2001

eh?

Uhm, probably relative to my previous patch? About the date, I have no idea. All my "git format-patch" output looks like this.

Quoted 6 lines

arch/x86/mm/kmemcheck/error.h line 2

Quoted 4 lines

+++ b/arch/x86/mm/kmemcheck/error.h

arch/x86/mm/kmemcheck/error.h new file +2 -0

@@ -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.

But it's such a nice convention! How can we differentiate between mm/types.h and mm_types.h!

Quoted 36 lines

Quoted 36 lines

arch/x86/mm/kmemcheck/string.c new file +36 -0

+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)

Quoted 8 lines

arch/x86/mm/kmemcheck/string.c line 91

Quoted 6 lines

arch/x86/mm/kmemcheck/string.c new file +6 -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...

Oops. I will not add a kernel-doc, but I will add an explanation.

This function is a drop-in replacement for memset, and the reason for the EXPORT is that the real memset() in fact is just a macro that calls this function. And memset is needed in modules. This function should not actually have any users beside the memset() in x86 headers.

Thanks for mini-review! (Does this mean the rest was okay? :-D)