[PATCH v3 20/23] arm64/vdso: Migrate native signals to generic vdso_base

[Dmitry Safonov <dima@arista.com>]

Generic way to track the land vma area.
As a bonus, after unmapping vdso, kernel won't try to land on its
previous position (due to UNMAPPED_VDSO_BASE check instead of
context.vdso ?= 0 check).

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 arch/arm64/include/asm/mmu.h |  1 -
 arch/arm64/kernel/signal.c   | 10 +++++++---
 arch/arm64/kernel/vdso.c     | 15 ++++++---------
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 434acd49dbc3..4432a2809e0d 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -19,7 +19,6 @@
 typedef struct {
 	atomic64_t	id;
 	refcount_t	pinned;
-	void		*vdso;
 	unsigned long	flags;
 } mm_context_t;
 
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 6237486ff6bb..5f6a8c0abc4c 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -723,9 +723,10 @@ static int get_sigframe(struct rt_sigframe_user_layout *user,
 	return 0;
 }
 
-static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
+static int setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 			 struct rt_sigframe_user_layout *user, int usig)
 {
+	unsigned long land = (unsigned long)current->mm->vdso_base;
 	__sigrestore_t sigtramp;
 
 	regs->regs[0] = usig;
@@ -754,10 +755,13 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 
 	if (ka->sa.sa_flags & SA_RESTORER)
 		sigtramp = ka->sa.sa_restorer;
+	else if (land != UNMAPPED_VDSO_BASE)
+		sigtramp = VDSO_SYMBOL(land, sigtramp);
 	else
-		sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
+		return 1;
 
 	regs->regs[30] = (unsigned long)sigtramp;
+	return 0;
 }
 
 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
@@ -780,7 +784,7 @@ static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 	err |= setup_sigframe(&user, regs, set);
 	if (err == 0) {
-		setup_return(regs, &ksig->ka, &user, usig);
+		err = setup_return(regs, &ksig->ka, &user, usig);
 		if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 			err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 			regs->regs[1] = (unsigned long)&frame->info;
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 3e9dd41abee0..4af29f89be37 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -78,12 +78,6 @@ static union {
 } vdso_data_store __page_aligned_data;
 struct vdso_data *vdso_data = vdso_data_store.data;
 
-static void vdso_mremap(const struct vm_special_mapping *sm,
-		struct vm_area_struct *new_vma)
-{
-	current->mm->context.vdso = (void *)new_vma->vm_start;
-}
-
 static int __init __vdso_init(enum vdso_abi abi)
 {
 	int i;
@@ -244,7 +238,12 @@ static int __setup_additional_pages(enum vdso_abi abi,
 	if (IS_ERR(ret))
 		return PTR_ERR(ret);
 
-	mm->context.vdso = (void *)vdso_base;
+	/*
+	 * 32-bit ABI is to land on sigpage (see aarch32_sigreturn_setup()),
+	 * 64-bit on vDSO.
+	 */
+	if (abi == VDSO_ABI_AA64)
+		mm->vdso_base = (void __user *)vdso_base;
 	*sysinfo_ehdr = vdso_base;
 
 	return 0;
@@ -279,7 +278,6 @@ static struct vm_special_mapping aarch32_vdso_maps[] = {
 	},
 	[AA32_MAP_VDSO] = {
 		.name = "[vdso]",
-		.mremap = vdso_mremap,
 	},
 };
 
@@ -426,7 +424,6 @@ static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
 	},
 	[AA64_MAP_VDSO] = {
 		.name	= "[vdso]",
-		.mremap = vdso_mremap,
 	},
 };
 
-- 
2.31.1