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>

2 files changed, 18 insertions, 20 deletions

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 60ae12087d9f..24f2e8c62479 100644
--- 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 8154b8d1c826..beca249bc2f3 100644
--- 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*)