arm64: vdso: move data page before code pages
authorWill Deacon <will.deacon@arm.com>
Wed, 9 Jul 2014 18:22:13 +0000 (19:22 +0100)
committerCatalin Marinas <catalin.marinas@arm.com>
Thu, 17 Jul 2014 15:18:57 +0000 (16:18 +0100)
Andy pointed out that binutils generates additional sections in the vdso
image (e.g. section string table) which, if our .text section gets big
enough, could cross a page boundary and end up screwing up the location
where the kernel expects to put the data page.

This patch solves the issue in the same manner as x86_32, by moving the
data page before the code pages.

Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arch/arm64/kernel/vdso.c
arch/arm64/kernel/vdso/vdso.lds.S

index 60ae12087d9f325e440a7e71b0ca793361221c9e..24f2e8c6247917ddc6dd7c7eeac3b979dbd5272c 100644 (file)
@@ -121,8 +121,8 @@ static int __init vdso_init(void)
        }
 
        vdso_pages = (&vdso_end - &vdso_start) >> PAGE_SHIFT;
-       pr_info("vdso: %ld pages (%ld code, %ld data) at base %p\n",
-               vdso_pages + 1, vdso_pages, 1L, &vdso_start);
+       pr_info("vdso: %ld pages (%ld code @ %p, %ld data @ %p)\n",
+               vdso_pages + 1, vdso_pages, &vdso_start, 1L, vdso_data);
 
        /* Allocate the vDSO pagelist, plus a page for the data. */
        vdso_pagelist = kcalloc(vdso_pages + 1, sizeof(struct page *),
@@ -130,22 +130,22 @@ static int __init vdso_init(void)
        if (vdso_pagelist == NULL)
                return -ENOMEM;
 
+       /* Grab the vDSO data page. */
+       vdso_pagelist[0] = virt_to_page(vdso_data);
+
        /* Grab the vDSO code pages. */
        for (i = 0; i < vdso_pages; i++)
-               vdso_pagelist[i] = virt_to_page(&vdso_start + i * PAGE_SIZE);
-
-       /* Grab the vDSO data page. */
-       vdso_pagelist[i] = virt_to_page(vdso_data);
+               vdso_pagelist[i + 1] = virt_to_page(&vdso_start + i * PAGE_SIZE);
 
        /* Populate the special mapping structures */
        vdso_spec[0] = (struct vm_special_mapping) {
-               .name   = "[vdso]",
+               .name   = "[vvar]",
                .pages  = vdso_pagelist,
        };
 
        vdso_spec[1] = (struct vm_special_mapping) {
-               .name   = "[vvar]",
-               .pages  = vdso_pagelist + vdso_pages,
+               .name   = "[vdso]",
+               .pages  = &vdso_pagelist[1],
        };
 
        return 0;
@@ -169,22 +169,22 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
                ret = ERR_PTR(vdso_base);
                goto up_fail;
        }
-       mm->context.vdso = (void *)vdso_base;
-
-       ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
-                                      VM_READ|VM_EXEC|
-                                      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
+       ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
+                                      VM_READ|VM_MAYREAD,
                                       &vdso_spec[0]);
        if (IS_ERR(ret))
                goto up_fail;
 
-       vdso_base += vdso_text_len;
-       ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
-                                      VM_READ|VM_MAYREAD,
+       vdso_base += PAGE_SIZE;
+       mm->context.vdso = (void *)vdso_base;
+       ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
+                                      VM_READ|VM_EXEC|
+                                      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
                                       &vdso_spec[1]);
        if (IS_ERR(ret))
                goto up_fail;
 
+
        up_write(&mm->mmap_sem);
        return 0;
 
index 8154b8d1c826b39d1a8fa527bf23f07496c1763d..beca249bc2f394ca3592a76d868b60ff275ddb5b 100644 (file)
@@ -28,6 +28,7 @@ OUTPUT_ARCH(aarch64)
 
 SECTIONS
 {
+       PROVIDE(_vdso_data = . - PAGE_SIZE);
        . = VDSO_LBASE + SIZEOF_HEADERS;
 
        .hash           : { *(.hash) }                  :text
@@ -57,9 +58,6 @@ SECTIONS
        _end = .;
        PROVIDE(end = .);
 
-       . = ALIGN(PAGE_SIZE);
-       PROVIDE(_vdso_data = .);
-
        /DISCARD/       : {
                *(.note.GNU-stack)
                *(.data .data.* .gnu.linkonce.d.* .sdata*)