arm64: vdso: move data page before code pages

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>

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 60ae12087d9f325e440a7e71b0ca793361221c9e..24f2e8c6247917ddc6dd7c7eeac3b979dbd5272c 100644 (file)
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -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;
 

diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
index 8154b8d1c826b39d1a8fa527bf23f07496c1763d..beca249bc2f394ca3592a76d868b60ff275ddb5b 100644 (file)
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -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*)