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arm64: vdso: put vdso datapage in a separate vma 

The VDSO datapage doesn't need to be executable (no code there) or
CoW-able (the kernel writes the page, so a private copy is totally
useless).

This patch moves the datapage into its own VMA, identified as "[vvar]"
in /proc/<pid>/maps.

Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Will Deacon 2014-07-09 19:22:11 +01:00 committed by Catalin Marinas
parent b2f8c07bcb
commit 8715493852
1 changed files with 26 additions and 8 deletions
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34
arch/arm64/kernel/vdso.c
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@ -138,11 +138,12 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
int uses_interp) int uses_interp)
{ {
struct mm_struct *mm = current->mm; struct mm_struct *mm = current->mm;
unsigned long vdso_base, vdso_mapping_len; unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
int ret; int ret;
vdso_text_len = vdso_pages << PAGE_SHIFT;
/* Be sure to map the data page */ /* Be sure to map the data page */
vdso_mapping_len = (vdso_pages + 1) << PAGE_SHIFT; vdso_mapping_len = vdso_text_len + PAGE_SIZE;
down_write(&mm->mmap_sem); down_write(&mm->mmap_sem);
vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
@ -152,35 +153,52 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
} }
mm->context.vdso = (void *)vdso_base; mm->context.vdso = (void *)vdso_base;
ret = install_special_mapping(mm, vdso_base, vdso_mapping_len, ret = install_special_mapping(mm, vdso_base, vdso_text_len,
VM_READ|VM_EXEC| VM_READ|VM_EXEC|
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdso_pagelist); vdso_pagelist);
if (ret) { if (ret)
mm->context.vdso = NULL;
goto up_fail; goto up_fail;
}
vdso_base += vdso_text_len;
ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
VM_READ|VM_MAYREAD,
vdso_pagelist + vdso_pages);
if (ret)
goto up_fail;
up_write(&mm->mmap_sem);
return 0;
up_fail: up_fail:
mm->context.vdso = NULL;
up_write(&mm->mmap_sem); up_write(&mm->mmap_sem);
return ret; return ret;
} }
const char *arch_vma_name(struct vm_area_struct *vma) const char *arch_vma_name(struct vm_area_struct *vma)
{ {
unsigned long vdso_text;
if (!vma->vm_mm)
return NULL;
vdso_text = (unsigned long)vma->vm_mm->context.vdso;
/* /*
* We can re-use the vdso pointer in mm_context_t for identifying * We can re-use the vdso pointer in mm_context_t for identifying
* the vectors page for compat applications. The vDSO will always * the vectors page for compat applications. The vDSO will always
* sit above TASK_UNMAPPED_BASE and so we don't need to worry about * sit above TASK_UNMAPPED_BASE and so we don't need to worry about
* it conflicting with the vectors base. * it conflicting with the vectors base.
*/ */
if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso) { if (vma->vm_start == vdso_text) {
#ifdef CONFIG_COMPAT #ifdef CONFIG_COMPAT
if (vma->vm_start == AARCH32_VECTORS_BASE) if (vma->vm_start == AARCH32_VECTORS_BASE)
return "[vectors]"; return "[vectors]";
#endif #endif
return "[vdso]"; return "[vdso]";
} else if (vma->vm_start == (vdso_text + (vdso_pages << PAGE_SHIFT))) {
return "[vvar]";
} }
return NULL; return NULL;