[PATCH v3 19/23] arm64/vdso: Migrate compat signals to generic vdso_base

[Dmitry Safonov <dima@arista.com>]

Generic way to track the landing vma area.
As a bonus, after unmapping sigpage, 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/Kconfig           |  1 +
 arch/arm64/include/asm/mmu.h |  3 ---
 arch/arm64/kernel/signal32.c | 17 ++++++++++++-----
 arch/arm64/kernel/vdso.c     | 11 +----------
 4 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 385ef8d8ad9b..073d6c8aa195 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -43,6 +43,7 @@ config ARM64
 	select ARCH_HAS_SYSCALL_WRAPPER
 	select ARCH_HAS_TEARDOWN_DMA_OPS if IOMMU_SUPPORT
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
+	select ARCH_HAS_VDSO_BASE
 	select ARCH_HAVE_ELF_PROT
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_INLINE_READ_LOCK if !PREEMPTION
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 75beffe2ee8a..434acd49dbc3 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -18,9 +18,6 @@
 
 typedef struct {
 	atomic64_t	id;
-#ifdef CONFIG_COMPAT
-	void		*sigpage;
-#endif
 	refcount_t	pinned;
 	void		*vdso;
 	unsigned long	flags;
diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c
index 2f507f565c48..3d2ac8062e99 100644
--- a/arch/arm64/kernel/signal32.c
+++ b/arch/arm64/kernel/signal32.c
@@ -315,7 +315,7 @@ static void __user *compat_get_sigframe(struct ksignal *ksig,
 	return frame;
 }
 
-static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
+static int compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 				compat_ulong_t __user *rc, void __user *frame,
 				int usig)
 {
@@ -342,13 +342,16 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 		retcode = ptr_to_compat(ka->sa.sa_restorer);
 	} else {
 		/* Set up sigreturn pointer */
+		unsigned long land = (unsigned long)current->mm->vdso_base;
 		unsigned int idx = thumb << 1;
 
 		if (ka->sa.sa_flags & SA_SIGINFO)
 			idx += 3;
 
-		retcode = (unsigned long)current->mm->context.sigpage +
-			  (idx << 2) + thumb;
+		if (land == UNMAPPED_VDSO_BASE)
+			return 1;
+
+		retcode = land + (idx << 2) + thumb;
 	}
 
 	regs->regs[0]	= usig;
@@ -356,6 +359,8 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 	regs->compat_lr	= retcode;
 	regs->pc	= handler;
 	regs->pstate	= spsr;
+
+	return 0;
 }
 
 static int compat_setup_sigframe(struct compat_sigframe __user *sf,
@@ -425,7 +430,8 @@ int compat_setup_rt_frame(int usig, struct ksignal *ksig,
 	err |= compat_setup_sigframe(&frame->sig, regs, set);
 
 	if (err == 0) {
-		compat_setup_return(regs, &ksig->ka, frame->sig.retcode, frame, usig);
+		err = compat_setup_return(regs, &ksig->ka,
+					  frame->sig.retcode, frame, usig);
 		regs->regs[1] = (compat_ulong_t)(unsigned long)&frame->info;
 		regs->regs[2] = (compat_ulong_t)(unsigned long)&frame->sig.uc;
 	}
@@ -448,7 +454,8 @@ int compat_setup_frame(int usig, struct ksignal *ksig, sigset_t *set,
 
 	err |= compat_setup_sigframe(frame, regs, set);
 	if (err == 0)
-		compat_setup_return(regs, &ksig->ka, frame->retcode, frame, usig);
+		err = compat_setup_return(regs, &ksig->ka,
+					  frame->retcode, frame, usig);
 
 	return err;
 }
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 680415e0098c..3e9dd41abee0 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -264,14 +264,6 @@ 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 */
@@ -280,7 +272,6 @@ 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]",
@@ -398,7 +389,7 @@ static int aarch32_sigreturn_setup(struct mm_struct *mm)
 	if (IS_ERR(ret))
 		goto out;
 
-	mm->context.sigpage = (void *)addr;
+	mm->vdso_base = (void __user *)addr;
 
 out:
 	return PTR_ERR_OR_ZERO(ret);
-- 
2.31.1