From a210f642592ce2a67b356953ca3993e90a00c39a Mon Sep 17 00:00:00 2001 From: Dmitry Safonov Date: Wed, 26 Jul 2017 20:07:37 +0300 Subject: [PATCH] arm64/vdso: Support mremap() for vDSO vDSO VMA address is saved in mm_context for the purpose of using restorer from vDSO page to return to userspace after signal handling. In Checkpoint Restore in Userspace (CRIU) project we place vDSO VMA on restore back to the place where it was on the dump. With the exception for x86 (where there is API to map vDSO with arch_prctl()), we move vDSO inherited from CRIU task to restoree position by mremap(). CRIU does support arm64 architecture, but kernel doesn't update context.vdso pointer after mremap(). Which results in translation fault after signal handling on restored application: https://github.com/xemul/criu/issues/288 Make vDSO code track the VMA address by supplying .mremap() fops the same way it's done for x86 and arm32 by: commit 6eb1736a6083 ("x86/vdso: Add mremap hook to vm_special_mapping") commit d486fb58fdce ("ARM: 8683/1: ARM32: Support mremap() for sigpage/vDSO"). Cc: Russell King Cc: linux-arm-kernel@lists.infradead.org Cc: Cyrill Gorcunov Cc: Pavel Emelyanov Cc: Christopher Covington Reviewed-by: Will Deacon Signed-off-by: Dmitry Safonov Signed-off-by: Catalin Marinas --- arch/arm64/kernel/vdso.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c index e8f759f764f21..2d419006ad433 100644 --- a/arch/arm64/kernel/vdso.c +++ b/arch/arm64/kernel/vdso.c @@ -110,12 +110,27 @@ int aarch32_setup_vectors_page(struct linux_binprm *bprm, int uses_interp) } #endif /* CONFIG_COMPAT */ +static int vdso_mremap(const struct vm_special_mapping *sm, + struct vm_area_struct *new_vma) +{ + unsigned long new_size = new_vma->vm_end - new_vma->vm_start; + unsigned long vdso_size = vdso_end - vdso_start; + + if (vdso_size != new_size) + return -EINVAL; + + current->mm->context.vdso = (void *)new_vma->vm_start; + + return 0; +} + static struct vm_special_mapping vdso_spec[2] __ro_after_init = { { .name = "[vvar]", }, { .name = "[vdso]", + .mremap = vdso_mremap, }, }; -- 2.39.5