x86-64, vdso: Do not allocate memory for the vDSO
Andy Lutomirski [Thu, 21 Jul 2011 19:47:10 +0000 (15:47 -0400)]
We can map the vDSO straight from kernel data, saving a few page
allocations.  As an added bonus, the deleted code contained a memory
leak.

Signed-off-by: Andy Lutomirski <luto@mit.edu>
Link: http://lkml.kernel.org/r/2c4ed5c2c2e93603790229e0c3403ae506ccc0cb.1311277573.git.luto@mit.edu
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/vdso/vdso.S
arch/x86/vdso/vma.c

index 1d3aa6b..1b979c1 100644 (file)
@@ -1,10 +1,21 @@
+#include <asm/page_types.h>
+#include <linux/linkage.h>
 #include <linux/init.h>
 
-__INITDATA
+__PAGE_ALIGNED_DATA
 
        .globl vdso_start, vdso_end
+       .align PAGE_SIZE
 vdso_start:
        .incbin "arch/x86/vdso/vdso.so"
 vdso_end:
 
-__FINIT
+.previous
+
+       .globl vdso_pages
+       .bss
+       .align 8
+       .type vdso_pages, @object
+vdso_pages:
+       .zero (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE * 8
+       .size vdso_pages, .-vdso_pages
index c39938d..316fbca 100644 (file)
 #include <asm/vgtod.h>
 #include <asm/proto.h>
 #include <asm/vdso.h>
+#include <asm/page.h>
 
 unsigned int __read_mostly vdso_enabled = 1;
 
 extern char vdso_start[], vdso_end[];
 extern unsigned short vdso_sync_cpuid;
 
-static struct page **vdso_pages;
+extern struct page *vdso_pages[];
 static unsigned vdso_size;
 
 static void __init patch_vdso(void *vdso, size_t len)
@@ -54,7 +55,7 @@ found:
        apply_alternatives(alt_data, alt_data + alt_sec->sh_size);
 }
 
-static int __init init_vdso_vars(void)
+static int __init init_vdso(void)
 {
        int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
        int i;
@@ -62,26 +63,12 @@ static int __init init_vdso_vars(void)
        patch_vdso(vdso_start, vdso_end - vdso_start);
 
        vdso_size = npages << PAGE_SHIFT;
-       vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL);
-       if (!vdso_pages)
-               goto oom;
-       for (i = 0; i < npages; i++) {
-               struct page *p;
-               p = alloc_page(GFP_KERNEL);
-               if (!p)
-                       goto oom;
-               vdso_pages[i] = p;
-               copy_page(page_address(p), vdso_start + i*PAGE_SIZE);
-       }
+       for (i = 0; i < npages; i++)
+               vdso_pages[i] = virt_to_page(vdso_start + i*PAGE_SIZE);
 
        return 0;
-
- oom:
-       printk("Cannot allocate vdso\n");
-       vdso_enabled = 0;
-       return -ENOMEM;
 }
-subsys_initcall(init_vdso_vars);
+subsys_initcall(init_vdso);
 
 struct linux_binprm;