Vegard Nossum wrote:
General description: kmemcheck will trap every read and write to
memory that was
allocated dynamically (ie. with kmalloc()). If a memory address is
read that has
not previously been written to, a message is printed to the kernel log.
<snip>
diff --git a/arch/x86/kernel/kmemcheck_32.c
b/arch/x86/kernel/kmemcheck_32.c
new file mode 100644
index 0000000..9d065b9
--- /dev/null
+++ b/arch/x86/kernel/kmemcheck_32.c
@@ -0,0 +1,290 @@
+#include <linux/kernel.h>
+#include <linux/kallsyms.h>
+#include <linux/mm.h>
+#include <asm/cacheflush.h>
+#include <asm/kmemcheck.h>
+#include <asm/tlbflush.h>
+
+static int
Not 'static bool'?
+page_is_tracked(struct page *page)
+{
+ struct page *head;
+
+ if (!page)
+ return 0;
+ head = compound_head(page);
+ if (!head)
+ return 0;
+ if (!(head->flags & (1 << PG_slab)))
+ return 0;
+ if (!head->slab)
+ return 0;
+ if (head->slab->flags & __GFP_NOTRACK)
+ return 0;
+ return 1;
Why not returning 'false' and 'true'?
+}
+
+static void
+show_addr(uint32_t addr)
+{
+ struct page *page;
+ pte_t *pte;
+
+ if (!addr)
+ return;
+ page = virt_to_page(addr);
+ if (!page_is_tracked(page))
+ return;
+
+ pte = lookup_address(addr);
+ change_page_attr(page, 1, __pgprot(pte->pte_low | _PAGE_VISIBLE));
+ __flush_tlb_one(addr);
+}
+
+static void
+hide_addr(uint32_t addr)
+{
+ struct page *page;
+ pte_t *pte;
+
+ if (!addr)
+ return;
+ page = virt_to_page(addr);
+ if (!page_is_tracked(page))
+ return;
+ pte = lookup_address(addr);
+ change_page_attr(page, 1, __pgprot(pte->pte_low & ~_PAGE_VISIBLE));
+ __flush_tlb_one(addr);
+}
+
+DEFINE_PER_CPU(uint32_t, kmemcheck_read_addr);
+DEFINE_PER_CPU(uint32_t, kmemcheck_write_addr);
+
+void
+kmemcheck_show(struct pt_regs *regs)
+{
+ show_addr(__get_cpu_var(kmemcheck_read_addr));
+ show_addr(__get_cpu_var(kmemcheck_write_addr));
+ regs->eflags |= TF_MASK;
+}
+
+void
+kmemcheck_hide(struct pt_regs *regs)
+{
+ hide_addr(__get_cpu_var(kmemcheck_read_addr));
+ hide_addr(__get_cpu_var(kmemcheck_write_addr));
+ regs->eflags &= ~TF_MASK;
+}
+
+void
+kmemcheck_hide_pages(struct page *p, unsigned int n)
+{
+ unsigned int i;
+
+ for(i = 0; i < n; ++i) {
+ unsigned long address = (unsigned long) page_address(&p[i]);
+ pte_t *pte = lookup_address(address);
+
+ change_page_attr(&p[i], 1,
+ __pgprot(pte->pte_low & ~_PAGE_VISIBLE));
+ __flush_tlb_one(address);
+ }
+}
+
+static int
'static bool'?
+opcode_is_prefix(uint8_t b)
+{
+ return
+ /* Group 1 */
+ b == 0xf0 || b == 0xf2 || b == 0xf3
+ /* Group 2 */
+ || b == 0x2e || b == 0x36 || b == 0x3e || b == 0x26
+ || b == 0x64 || b == 0x65 || b == 0x2e || b == 0x3e
+ /* Group 3 */
+ || b == 0x66
+ /* Group 4 */
+ || b == 0x67;
+}
+
+/* This is a VERY crude opcode decoder. We only need to find the size
of the
+ * load/store that caused our #PF and this should work for all the
opcodes
+ * that we care about. Moreover, the ones who invented this
instruction set
+ * should be shot. */
+static unsigned int
+opcode_get_size(const uint8_t *opcode)
Are we not using 'u8' in the kernel?
+{
+ const uint8_t *i;
and here. Also, I find the name 'i' a bit confusing in this context,
since it is not really a counter. What about 'cur', 'prefix_op' or
something of the sort?
+
+ /* Default operand size */
+ int operand_size_override = 32;
+
+ /* prefixes */
+ for (i = opcode; opcode_is_prefix(*i); ++i) {
+ if (*i == 0x66)
+ operand_size_override = 16;
+ }
+
+ /* escape opcode */
+ if (*i == 0x0f) {
+ ++i;
+
+ if(*i == 0xb6)
Please do, as the previous, 'if ()'. A good checker for these kind of
things is the 'scripts/checkpatch.pl'...
+ return operand_size_override >> 1;
+ if(*i == 0xb7)
+ return 16;
+ }
+
+ return (*i & 1) ? operand_size_override : 8;
+}
+
+static uint8_t
and here...
+opcode_get_primary(const uint8_t *opcode)
and here..
+{
+ const uint8_t *i;
and here. Also, I find the name 'i' a bit confusing in this context,
since it is not really a counter. What about 'cur', 'prim_op',
'prefix_op' or something of the sort?
+
+ /* skip prefixes */
+ for (i = opcode; opcode_is_prefix(*i); ++i);
+ return *i;
+}
+
+static void *address_get_shadow_slab(unsigned long address,
+ struct page *head)
+{
+ if (!head->slab)
+ return NULL;
+
+ if (head->slab->flags & __GFP_NOTRACK)
+ return NULL;
+
+ return (void *) address + (PAGE_SIZE << head->slab->order);
+}
+
+static void *address_get_shadow(unsigned long address)
+{
+ struct page *page = virt_to_page(address);
+ struct page *head = compound_head(page);
+
+ if (!head)
+ return NULL;
+
+ if (head->flags & (1 << PG_slab))
+ return address_get_shadow_slab(address, head);
+
+ return NULL;
+}
+
+static int
'static bool'?
+test(void *shadow, unsigned int size)
+{
+ switch (size) {
+ case 8:
+ return *(uint8_t *) shadow == 0xff;
+ case 16:
+ return *(uint16_t *) shadow == 0xffff;
+ case 32:
+ return *(uint32_t *) shadow == 0xffffffff;
+ }
+
+ BUG();
+ return 0;
'return false;'?
+}
+
<snip>
cu
Richard Knutsson
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