x86: clean up text_poke()

Clean up the codepath, remove alignment restrictions and do sanity
checking of the end result, to make sure we patched the right site.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 18 insertions, 20 deletions

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 7ab3a977476..60299f61843 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -511,31 +511,29 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len)
         unsigned long flags;
         char *vaddr;
         int nr_pages = 2;
+        struct page *pages[2];
+        int i;
 
-        BUG_ON(len > sizeof(long));
-        BUG_ON((((long)addr + len - 1) & ~(sizeof(long) - 1))
-                - ((long)addr & ~(sizeof(long) - 1)));
-        if (core_kernel_text((unsigned long)addr)) {
-                struct page *pages[2] = { virt_to_page(addr),
-                        virt_to_page(addr + PAGE_SIZE) };
-                if (!pages[1])
-                        nr_pages = 1;
-                vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
-                BUG_ON(!vaddr);
-                local_irq_save(flags);
-                memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
-                local_irq_restore(flags);
-                vunmap(vaddr);
+        if (!core_kernel_text((unsigned long)addr)) {
+                pages[0] = vmalloc_to_page(addr);
+                pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
         } else {
-                /*
-                 * modules are in vmalloc'ed memory, always writable.
-                 */
-                local_irq_save(flags);
-                memcpy(addr, opcode, len);
-                local_irq_restore(flags);
+                pages[0] = virt_to_page(addr);
+                pages[1] = virt_to_page(addr + PAGE_SIZE);
         }
+        BUG_ON(!pages[0]);
+        if (!pages[1])
+                nr_pages = 1;
+        vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
+        BUG_ON(!vaddr);
+        local_irq_save(flags);
+        memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
+        local_irq_restore(flags);
+        vunmap(vaddr);
         sync_core();
         /* Could also do a CLFLUSH here to speed up CPU recovery; but
            that causes hangs on some VIA CPUs. */
+        for (i = 0; i < len; i++)
+                BUG_ON(((char *)addr)[i] != ((char *)opcode)[i]);
         return addr;
 }