arm64: compat: Allow signal page to be remapped

For compatability with 32-bit Arm, allow the compat signal page to be
remapped via mremap().

Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20210318170738.7756-4-will@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 421411981dc3c316fc56df51e9b0debe93c40b10..16bf0b46fb70c0194b5d31d9a88e1d9fdbbf80c5 100644 (file)
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -271,6 +271,14 @@ enum aarch32_map {
 static struct page *aarch32_vectors_page __ro_after_init;
 static struct page *aarch32_sig_page __ro_after_init;
 
+static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
+                                 struct vm_area_struct *new_vma)
+{
+       current->mm->context.sigpage = (void *)new_vma->vm_start;
+
+       return 0;
+}
+
 static struct vm_special_mapping aarch32_vdso_maps[] = {
        [AA32_MAP_VECTORS] = {
                .name   = "[vectors]", /* ABI */
@@ -279,6 +287,7 @@ static struct vm_special_mapping aarch32_vdso_maps[] = {
        [AA32_MAP_SIGPAGE] = {
                .name   = "[sigpage]", /* ABI */
                .pages  = &aarch32_sig_page,
+               .mremap = aarch32_sigpage_mremap,
        },
        [AA32_MAP_VVAR] = {
                .name = "[vvar]",