[tip:x86/vdso] x86-64, vdso: Do not allocate memory for the vDSO

From: tip-bot for Andy Lutomirski
Date: Thu Jul 21 2011 - 16:52:46 EST


Commit-ID: aafade242ff24fac3aabf61c7861dfa44a3c2445
Gitweb: http://git.kernel.org/tip/aafade242ff24fac3aabf61c7861dfa44a3c2445
Author: Andy Lutomirski <luto@xxxxxxx>
AuthorDate: Thu, 21 Jul 2011 15:47:10 -0400
Committer: H. Peter Anvin <hpa@xxxxxxxxx>
CommitDate: Thu, 21 Jul 2011 13:41:53 -0700

x86-64, vdso: Do not allocate memory for the vDSO

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@xxxxxxx>
Link: http://lkml.kernel.org/r/2c4ed5c2c2e93603790229e0c3403ae506ccc0cb.1311277573.git.luto@xxxxxxx
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
---
arch/x86/vdso/vdso.S | 15 +++++++++++++--
arch/x86/vdso/vma.c | 25 ++++++-------------------
2 files changed, 19 insertions(+), 21 deletions(-)

diff --git a/arch/x86/vdso/vdso.S b/arch/x86/vdso/vdso.S
index 1d3aa6b..1b979c1 100644
--- a/arch/x86/vdso/vdso.S
+++ b/arch/x86/vdso/vdso.S
@@ -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
diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
index c39938d..316fbca 100644
--- a/arch/x86/vdso/vma.c
+++ b/arch/x86/vdso/vma.c
@@ -14,13 +14,14 @@
#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;

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